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TRANSCRIPT
ITAECL-5802
ATOMIC ENERGY | W A L'ÉNERGIE ATOMIQUEOF CANADA UMITED Y & J r DU CANADA LIMITÉE
PROGRESS REPORT
PHYSICS DIVISION
January I to March 31,1977
PR-P-113
Chalk River Nuclear Laboratories
Chalk River, Ontario
April \977
ATOMIC ENERGY OF CANADA LIMITED
Chalk River Nuclear Laboratories
PROGRESS REPORT
January 1 to March 31, 1977
PHYSICS DIVISION
PR-P-113
The results and conclusions given here are not classifiedor restricted in any way; however, some of the informationis of a preliminary nature. Readers interested in usingthe information in their own research are invited to consultwith the contributors for further details. Copies of AECLpublications referred to in this report may be obtained bywriting to the Scientific Document Distribution Office,Chalk River Nuclear Laboratories.
Chalk River, Ontario
April 1977
AECL-5802
PROGRESS REPORT
January 1 to March 31, 1977
PHYSICS DIVISION
Research Director - G.A. Bartholomew
Secretary - J.M. Jones
CONTENTSPage
1. Summary - G.A. Bartholomew 1
2. Nuclear Physics Branch - J.C.D. Milton 8
3. Neutron and Solid State Physics Branch - A.D.B. Woods 49
4. Theoretical Physics Branch - G.E. Lee-Whiting 69
5. Mathematics and Computation Branch - D. McPherson 79
6. Accelerator Physics Branch - P.R. Tunnicliffe 102
RECENT REPORTS IN THIS SERIES
PR-P-109 1 January to 31 March, 1976 AECL-5508
PR-P-110 1 April to 30 June, 1976 AECL-5546
PR-P-111 1 July to 30 September, 1976 AECL-5614
PR-P-112 1 October to 31 December, 1976 AECL-5696
- 1 -
PHYSICS DIVISION SUMMARY
G.A. Bartholomew
1.1 Nuclear Physics Research
MP Tandem Operation
Transmission of beams through the accelerator has
now been markedly improved. Failures of the high voltage
isolation transformer supplying three-phase power to the ion
source and leak of SFg gas from the tank into the accelerating
tubes contributed to unscheduled shutdown time during the
quarter.
Experiments running
Scheduled shutdowns
Unscheduled shutdowns
All major components of the on-line isotope separator
are now on hand and assembly is proceeding. A gas scintillation
detector system that will selectively count recoiling nuclei
from heavy ion reactions in the presence of much more numerous
and energetic charged particles from the primary beam neutrons,
y-rays, and other reaction products has been built.
Twelve experiments were performed involving CRNL and
10 visiting scientists. The visiting scientists were involved
in experiments occupying 85% of the beam time and their
participation averaged 48%.
Research Activities
A new technique based on a measurement of the polarization
of y-rays was used to investigate the strength of parity non-93
conserving interactions between two close-lying states in Tc.
The program to measure magnetic moments (g-factors)
of excited states has produced many new results in nuclei near
neutron number 50 and in several heavier nuclei. These measure-
ments help elucidate the shell structure in these nuclei.
986744
4532184
.7
.0
.3
.0
hourshours
hourshours
45.34.
20.loo.
2%1%
7%0%
- 2 -
The new gas scintillation recoil detector is being
used in experiments to isolate and identify decay y-rays in
competition with fission in excited states in the highly
neutron deficient nucleus l^Hg formed by chlorine ion
bombardment of europium nuclei.
Preliminary experiments to deduce beta-neutrino
angular correlations in the decay of delayed-particle precursors
have been carried out.
High energy alpha particles following excitation of
238u with 9 MeV photons provided by a Ni(n,y) source have been
detected. This measurement and others planned may shed light
on the strength of an electric quadrupole giant resonance at
this energy.
1.2 Accelerator and Applied Physics
Research Applications
The Fast Intense Neutron Source has been operated
reliably with beam currents up to 25% of the design value.
Peripheral systems are operating satisfactorily. The beam
spot on target appears uniform, circular and of the correct
size.
The heavy ion cyclotron modelling program included
the following developments:
- The effects on particle orbits of the radial ripple
in the magnetic field caused by trim rods have been
calculated and found to be not as serious as previously
suspected.
The design of both the vacuum cryostat and helium cans
is complete and quotations have been requested for
their fabrication.
The design of the flutter poles and skirt is complete
and out for quotation.
Fabrication of the steel yoke is complete except for
drilling the trim-rod holes.
- 3 -
- All the superconductor for the main coils has been
received and short sample tests have shown that the
critical current exceeds specifications in every
piece. Eight double pancakes have been wound.
- Design of the magnetic field mapping equipment is in
progress and experiments have begun on flip-coils.
Fabrication of the full-scale radiofrequency structure
is half complete and delivery is scheduled for late
this year.
The computer for the cyclotron-tandem computer-aided
control system has been installed and some software
. provided by Hahn-Meitner Institute is being tested.
Nuclear Power Applications
The electrode apertures of the injector accelerating
column of the High Current Test Facility have been increased and
the column reassembled in preparation for tests. The output
power limitation of the rf supply has been traced to the triode
grid circuit but the specific cause is as yet unidentified.
Work has continued on improvement of the instrumentation
for the Model 3 structure of the Electron Test Accelerator to
permit start-up under computer control. The temperature/
regulation system now relies on an active computer link to
control a valve in the heat exchanger. Testing of klystrons
has commenced in the new test stand.
In the fertile-to-fissile conversion experiments,
seven irradiations of various target assemblies including reruns
of some anomalous experiments were done. Much of the effort has
been spent on analyzing results obtained to date and preliminary
values for neutron leakage from ten types of target have been
obtained.
- 4 -
1. 3 Solid State Physics
Neutron powder diffraction experiments on plastic SFg
just above the 95 K phase transition indicate a tendency for
the S-P bonds to align along certain crystallographic directions
about which the SF6 molecules execute librational notion.
In collaboration with scientists at University of Toronto
elastic neutron scattering measurements on K2OSCJI6 have been
analysed. Evidence is found that the crystal undergoes a
rotational phase transition (ferro-rotative) analogous to
transitions in ferromagnetic and ferroelectric materials.
Analysis of neutron scattering in liquid ^He shows
the surprising result that any two atoms in the liquid, beyond
a certain distance, seem to repel rather than attract one
another. It would appear that other nearby helium atoms modify
the force between the pair in a stronger way than previously
understood.
Measurements of phonon dispersion curves have been
carried out in four materials:
- RbCoF3. The results are primarily being used to obtain
a better understanding of the magnetic properties.
- TiS2. The properties of this material show features
characteristic of two-dimensional systems.
- Coo.92Feo.08- T n e phonon dispersion relation has been
determined in the principal symmetry directions.
- Nucleic acid 1-methylthymine (1-MT). One branch of the
dispersion relation differs markedly from its counterpart
in cytosine monohydrate which differs structurally from
1-MT mainly by the addition of water.
A study of the stability of the Wigner solid at
finite temperatures has been extended to include cubic
corrections to the force constants used in the self-consistent
harmonic model.
- 5 -
1.4 Detectors
One of the CdTe crystal growing systems has been
improved by careful attention to vibrations in the supporting
structure. A new furnace is being installed in the other
system.
A time-of-flight spectrometer for charged particle
reaction products has been built for use on the MP Tandem.
1.5 Applied Mathematics and Computation
Work continued on the inertial analysis of the
steam mains network for Gentilly-1, and the acoustical
analysis of the network is being re-examined to determine
the feasibility of including damping effects.
A technique for handling discontinuities that avoids
excessive time delays in the integration of ordinary
differential equations (ODE's) has been developed. In this
method, the discontinuities (or retarded functions) are
themselves represented as additional ODE's, and this permits
more efficient integration than methods used previously.
A further revision to the MARC stress analysis program
was received and installed during the quarter. Another
application of MARC, now in progress, is the determination of
strains in the liquid helium cans for the superconducting
cyclotron, and exploration of changes in structural dimensions
which will reduce deflections to acceptable amounts.
Miscellaneous programs and subroutines developed or
modified during the quarter include:
- Extension of the statistical analyses of results
of burst tests of Zr-Nb pressure tubas.
Extension to the program management code PROD.
Completion of a new version of the program DATPAK
for the efficient storage and retrieval of numerical
data.
- 6 -
Improvements to the major non-linear least squares
fitting routines in the CRNL library.
Routines for the calculation of Bickley functions
Kin(x) for 1 < n < 10 and x > 0 to 12 or more
significant digits.
The FORTRAN compiler was updated -to include memory
management features, and a revision of the mathematical program
library which added thirteen new routines was completed.
The handling of local print files by the CDC 3300
input/output system has been modified - print files can now
be handled directly from disc instead of being first "spooled"
to the 3300 drum. Also added to the 3300 system was the ability
to obtain queue status displays from both the CDC 6600 and the
C Y B E R 170, although file transfer still takes place between the
3300 and only one of the 6600 or 170.
Equipment added to the Computing Centre during the
quarter included a new magnetic tape subsystem, shared by the
6600 and 170, and an automatic exchange which eventually will
provide the interface between the computer communication ports
and telephone lines in place of the dedicated ports (one per
telephone line) was used.
The total workload of 86,736 jobs for the 6600/170
system originated as follows :
- 7 -
Percentage ofNumber of Jobs
27.46
15.08
3.43
2.64
3.04
3.80
5.53
Percentage ofTotal Utilization
6.08
35.46
6.29
0.62
1.36
5.77
5.77
Computing Centre
Power ProjectsWNRE
Technical Information &University Relations
Biology and Health Physics
Chemistry & Materials
Physics
Electronics, Instrument & n ,K n ,.-
Control °'75 °-16
Advanced Projects & n OK OI A?Reactor Physics 1 1 # " *J..«J
Fuels & Materials 13.67 12.08
Administration 0.82 0.14
Medical 0.22 0.01
Finance 2.41 0.73
Operations 4.20 1.95
General Services 0.24 0.04
Plant Design 0.84 0.50
Special Projects 2.92 0.67
Contracts 1.70 2.80
Others 0.02 0.00
- 8 -
NUCLEAR PHYSICS BRANCH
J.C.D. Milton
2.1 Staff
2.2 Upper Limit on Parity Mixing in the 3Tc 17/2"Isomer
2.3 g-factors of 8+ States in N = 48: Onset of MixingBetween Proton and Neutron Orbitals
94 91 90g-factors in Ru, Mo and Nb
g-f actor for the K = 6, J17 = 6+ Isomer in 1 7 8Hf
Knight-shift of Rn in Hg212
High-spin Isomers in Rn
Search for Static Perturbation of the 5/2 Statein Hied During Recoil in Vacuum
182Search for HgAccurate Determination of the Lifetime of the 3.35 MeV,4+ Level in 22Ne
40Gamma Decay of the Lowest T = 2 Level of K
Isospin Forbidden Particle Decay of the LowestT = 2 Level of 1 60
A Search for a Highly Excited Rotational Band in8Be Arising from Excited Alpha Clusters
Beta-Neutrino Correlations from the KinematicShift of Beta-Delayed Particles
A Review Article on Short Nuclear LifetimeMeasurements
Computer Aided Contrcl System for the SuperconductingCyclotron and MP Tandem
Design of the Beam Transport Svstem for theSuperconducting Cyclotron
Construction and Use of a Compton Polarimeter
Polarization Sensitivity of a Ge(Li) Planar Diode
Development of a Gas Scintillator System forDetecting Recoils Following (HI,xny) Reactions
Time-of-Flight Spectrometer Using Channel ElectronMultiplier Arrays (CEMA's)
Assembly of the On-line Isotope Separator
22
2
2
2
22.
2.
2.
2.
2.
2 .
2 .
2 .
2 .
2 .
2 .
2 .
2.
. 4
. 5
.6
.7
.8
.9.10
.11
.12
,13
14
15
16
17
18
19
20
21
.22
22
2
2
2
2
2,
2,
2.
2.
2.2 .
2.2.2 .
2 .
2 .
2 .
. 2 3
.24
. 25
.26
.27
.28
.29
.30
,31
,32
,33
34
.35
36
37
38
3940
- 9 -
Progress on the QD3 Focal Plane Counter System
Cryogenic Differentially Pumped Gas Target
Status of Ge(Li) Gamma Detectors
Target Preparation
Tandem Electronics
Computers and Instrumentation
MP Tandem Operation
Monte Carlo Calculation of Neutron Production inSpallation Targets
Participation in BIPM Calibration Comparisons
The Half-life of 1 9 8Au
Recalibration of the Any Icn Chamber for *98Au
Pile-up Test for Gamma-ray Spectrometry
Standards Issued
Miscellaneous Services
Sharing of KK Vacancies for [Is ] Configurations
Superconducting Cyclotron - MP Tandem AcceleratorControl System
The H(n,yy)D Experiment at NRU
Publications and Lectures
2.1 Staff
- 10 -
Branch Head: J.C.D. Milton
Professional Staff
SECTION I
J.C.D. Milton
Technical Staff
Accelerator Group
T.GW,
A,J.J.
K.A.
.K.
.C.
.G.T..J..S..C.0.D.P.B.D.
AlexanderBallDaviesFaestermannFergusonForsterHardy (2)HausserHorn (1)Jackson (3)McDonaldWard
SECTION II
R.H.J.
L.R.S.
GrahamAndrewsGeiger (4)
(1)
J.AN.C.R.L.L.H.J.L.J,J.R.E.
A.S.C.K.T.
J.P.D.A.R.F.J.R.A.R.B.E.C.D.J.
BarsczewskiBrayBrownBucholtzGallantHillHowardHydeMcKeeO'DacreRutledgeSharpSuretteTomlinsonWai toYaraskavitch
Beta Ray Croup
W.L. PerryL.V. SmithR.B. Walker
SECTION III Radioisotope Standardization Group
J.S. Merritt F.H. Gibson
Students & Visitors
E.T.H. Clifford (5)
Laboratory Services & Workshop
G.M. BoireM. DesrochersC. Johnson
Secretarial Staff
J • R» H•S.M.
BowesCarlos
- 11 -
(1) NRC Postdoctoral Fellow.
(2) On leave of absence at CERN, Geneva, Switzerland.
(3) Visiting research associate from University of Toronto.
(4) On leave of absence at the University of Rochester.
(5) Graduate Student attached from the University of Toronto.
- 12 -
93 -2.2 Upper Limit on Parity Mixing in the Tc 17/2 Isoroer
O. Hausser, B.A. Brown (Michigan State University),T. Faestermann, D. Ward, H.R. Andrews and O. Horn
93Recently, Brown et al. found a doublet in Tc with
spin J = 17/2 and opposite parity, separated by 440 eV (Phys.
Rev. C13 (1976) 1194). The higher member of the doublet is
isomeric (T1/2 = 10.1 ± 0.3 ys, see PR-P-112: 2.2, AECL-5696)
and decays by three possible branches (39.7 keV E2 -»• 13/2~,
74%; 750.78 keV E2/M2/E3 •*• 13/2+, 26%; and -\- 0.4 keV El •* 17/2+,
< 7%; Brown et al. loc. cit.). Assuming that the 750.78 keV
gamma ray results entirely from a parity-forbidden E2 transi-
tion, Brown et al. derived an upper limit, |cx'_<_7.4 x 10~ for
the admixture of the parity-forbidden component in the wave
function and |<17/2+|H v|l7/2~>\<0.34 eV for the parity-vio-
lating matrix element.
In the present work we have measured the angular
distribution and linear polarization of the 750.78 keV gamma
ray, allowing us to determine the partial widths, r(E2)/r,
T(M2)/r and r(E3)/r, and have substantially lowered the previous
limit on a parity-violating admixture. A new limit for the
17/2~ •* 17/2+ El branch was also obtained.
The 93Tc 17/2~ isomer was populated by the 6 5Cu( 3 2S,
2p2n)93Tc reaction at E(32S) = 120 MeV on 1.8 mg/cm2 thick
targets of Cu. Long-range evaporation residues were stopped
in 64 mg/cm thick Pb backings to maintain the nuclear align-
ment over several half-lives. The de-excitation of isomeric
states was observed during 1.2 ys time intervals between 0.15 ys
beam pulses spaced by 2 ys. The gamma-ray angular distributions
were measured with a Ge(Li) detector placed 12.2 cm from the
target, and the linear polarizations of delayed gamma rays
with a three Ge(Li) detector Compton polarimeter placed at
6 = 90° (see PR-P-113: 2.18, AECL-5802). The angular dis-
tributions were normalized to gamma-ray intensities in the
scattering crystal of the polarimeter or to the beam charge
measured in a carefully suppressed Faraday cup. Both procedures
yielded nearly identical results. Consistency checks of the
- 13 -
angular distributions were performed with isotropic gamma rays
following beta decay and nonisotropic, prompt gamma rays from
Coulomb excitation of thick, natural Ge, whose angular distri-
butions were compared to first order Coulex calculations. In
all cases extremely good agreement with expectations was observed,
The polarization sensitivity of the polarimeter was calculated
with Coulex gamma rays as described in a succeeding section
(PR-P-113: 2.18, AECL-5802).
The data from isoraeric decays had to be corrected
for the effects of a magnetic field of 140 pT which was
measured at the target position. The resulting integral spin
rotation effects (|ut J = 7 for the Tc isomer) were cal-
culated exactly for both angular distributions and linear
polarizations.
A summary of angular distribution coefficients (a~ and
a. at t = 0) and linear polarizations, P =(W(9=90 ,i|)=0°) -
W(e=90o,<p=90o))7<W@=90°,i|/=0o) + W(e=90°,i//=90°}), for prominent
delayed gamma rays is given in Table 2.2.1.
The following properties of the 750.78 keV gamma ray
and of the initial 17/2* state have been deduced: r(E2)/r =
0.032 ± 0.032, T(M2)/r = 0.35 ± 0.10, r(E3)/r = 0.62 + 0.10,
mixing ratio ô(E3/M2) = 1.33+«*,f (sign convention of Rose and
Brink), parity violating admixture |a| = (1.3 ± 1.3) x 10~ ,
parity violating matrix element |<17/2+|H |17/2~>|= (0.06 ±
0.06) eV. The 17/2~ •+ 17/2+ El branching ratio was obtained
from the centroid shift of the 751 keV gamma peak, which is a7m 7ii +
mixture of the strong 17/2 — ' «13/2 component and a weak,unresolved 17/2" °'4 k e V. 17/2+ .751-34 keV 1 3 / 2+ l o w e r e n e r g y
component. The centroid of the unresolved gamma rays is angle
dependent because of strong differences in the angular distri-
butions of each constituent. We obtain r(17/2~ •* 17/2+)/r(17/2
-»• 13/2+) = 0.023 ± 0.030, assuming a separation of 440 eV be-
tween the two 17/2 levels. It is obvious that the observed
T(E2)/r = 0.032 ± 0.032 could result entirely from the 17/2+ -*•
13/2+ E2 transition following a 17/2~ f 17/2+ El decay, rather
than from genuine parity mixing.
Properties
ENucleus (keJ,
93Tc a ) 629.
711.
750.
1434.
1515.
90Mo 809.
947.
1054.
44
11
78
52
8
56
98
2
Ji
13/2
13/2
17/2
13/2
11/2
6
2A
of some
oi
* Jf
% l l / 2 +
% 1 3 / 2 +
% 1 3 / 2 +
+-> 9/2+
++ 9/2+
+ - 4 +
: +-K) +
+->-2+
Table 2.2.1
delayed gamma rays
: 6 5 C u with
MX
El
EÏ
E2/M2/E3
E2
M1/E2
E2
E2
B2
120 MeV
a2(t=0)
-0.185+0.
0.312+0.
-0.191+0.
0.247+0.
-0.086+0.
0.18010.
0.18410.
0.180+0.
from
3 2s
a)
008
006
008
006
011b)
006
.005
.006
the
0.
0.
-0.
-0.
0.
-0.
-0.
-0.
bombardment
a4(t=0)a)
01910.
002±0.
262+0.
043+0.
155+0.
03910.
030+0.
03110.
014
010
013
010
017b)
007
007
008
0
-0
0
0
0
0
0
0
exp
.231+0,
.479+0.
.233+0.
.37210.
089+0.
.31210.
.28210.
.31010.
033
031
041
054
081b)
035
040
068
0.
-0.
0.
0.
0.
0.
0.
Pcalc
215+0.
453+0.
•
010
010
see text
327+0.
075+0.
27410.
28710.
27910.
013
010
009
008
009
a)
b)
93The Tc results quoted assume estimated spin-lattice relaxation times, t(k= 2) = 85 ys
and T(k = 4) = 4 5 ys; the calculated linear polarization, P a l cf deduced mixing-ratios
and partial gamma-decay widthsare extremely insensitive to this choice.
Results imply 6(E2/M1) = 16.6^*?..
- 15 -
Further improvements in the limit on the parity mixing93
in Tc should come from different experiments probing either
the circular polarization of the 17/2~ •+ 13/2+ gamma ray or
its asymmetry, provided the 17/2~ isomer can be polarized.,
The present results on the partial widths of the 17/2" state
are essential for planning such future experiments.
2.3 g-factors of 8 + States in N = 48: Onset of Mixing Between
Proton and Neutron Orbitals
T. Faestermann, 0. Hausser, T.K. Alexander, H.R. Andrews,D. Horn and D. Ward
The g-factors of 8 states in N = 50 isotones can be
well reproduced (PR-P-112: 2.3, AECL-5696) if the single
particle values of pure proton configurations are corrected
for core polarization in first order. For the 8 states in
N = 48 nuclei however, neutron as well as proton excitations
are generally possible. In order to determine the structure
of these states we measured their g-factors, which are very
sensitive to admixtures.
Pulsed beams were used to produce the 8 isomers in86Sr, 88Zr and 90Mo with the reactions 84Kr(ct,2n)86Sr, 86Sr
(ct,2n)88Zr, 78Se(16O,a2n)88Zr and 78Se (16O,4n) 90Mo on gaseous
natural Kr, heated (390°C) 86Sr and lead-backed 78Se targets
respectively. The spin rotation of the nuclei in an external
magnetic field of ^ 1 T was measured by observing the time
dependence of gamma-ray intensities with two Ge(Li) detectors.
The data did not show a significant relaxation of the alignment,op
except for Zr in Sr, where we observed a relaxation time of
T (k = 2) = 800 ns. The results are listed in Table 2.3.1. We
applied corrections for diamagnetism (F.D. Feiock and W.R.
Johnson, Phys. Rev. 187 (1969) 39) and, in the case of a metallicenvironment, for an estimated Knight shift of K = (0.6 + 0.3)%.
+ 86 —2For the 8 state in Sr we expect a pure g g / 2 neutron
structure because of the pronounced p. ,_ proton subshell closure
- 16 -
at Z = 38. Its g-factor agrees with the one for the vg a /,
state in Sr (g = -0.2429), showing that the addivity of g-
factors holds well in this case. With the addition of protons
the g-f actor increases from an admixture of a [ir(ggy2 '
••'- N~f] component. Neglecting effects of a change in the
core polarization we obtain for the intensity of the admixture
(1.0 ± 0.3)% and (4.0 + 0.3)% for 88£r and 90Mo respectively
Table 2.3.1
g-factors of 8 states
Nucleus Host T, (ns)
86Sr88
90Mo
*uncorrected
Kr 457 ± 7 -0.240 ± 0.003
Zr Sr 1320 ± 25 -0.2274 ± 0.0026
Pb -0.2268 ± 0.0017
Pb 1140 ± 50 -0.1744 + 0.0017
gcorrected
-0.241 ± 0.003
-0.227 + 0.003
-0.2265 ± 0.0024
-0.1742 + 0.0022
94 91 902.4 g-factors in Ru, Mo and Nb
0. Hausser, T. Faestermann, D. Ward, T.K. Alexander,H.R. Andrews, D. Horn and I.S. Towner (Theoretical PhysicsBranch)
The study of magnetic properties of low-lying isomeric
states in the region of the neutron shell closure at N = 50
has been continued.92 4 94
The Mo( He,2n) Ru reaction was used to measure the
g-factor of the lowest 6 state in Ru for the first time at4 +
E( He) = 26 MeV. At this bombarding energy the long-lived 8isomer (t, ,,. = 68 ps), which feeds the 6+ isomer, is only
' 94 +
weakly populated. The spin rotation of Ru (6 ) was observed
in an external magnetic field of 2.29 T with two Ge(Li) de-
tectors at 9 = ± 135° to detect delayed de-excitation gamma
rays. The results obtained from a fit of the time-differential
- 17 -
data are: t±/2 = 64.5 ± 1.5 ns, S u n c o r r e cted( 6 + ) = x- 3 5 7 *
0.002. The g-factor is significantly lower than that for the
8 + state, g(8+) = 1.388 + 0.004 (see PR-P-112: 2.3, AECL-5696),
allowing for possible uncertainties in solid state shifts. A
convincing theoretical explanation of this difference has not
yet been found.
Nuclei with a nearly closed neutron shell (N < 49)78 16
have been produced in the bombardment of Se with 68 MeV O.
The evaporation residues recoiled out of the target into a
thick Pb backing. The energies, lifetimes, and g-factors
associated with several delayed gamma rays have been obtained
by standard pulsed beam methods. The results for isomers in38 90
Zr and Mo are reported in the previous section (PR-P-113:
2.3, AECL-5802). We have also observed three delayed gamma
rays from 91Mo (199, 654 and 1414 keV) populated by the Se
(160,3n)91Mo reaction. The half-life, t 1 / 2 = 46.7 ±0.6 ns,
and g-factor, 9 u n c o r r e ct ed = 0 - 8 5 3 ± °-°07, is in excellent
agreement with our previous result (PR-P-109: 2.8, AECL-5508).
We associate the half-life and g-factor with a 21/2 state at
E v = 2267 keV in 91Mo and a structure of 74%|Trg- ._28+;vg_/_~
1>, 2 + -1 *f£ *fz
+ 26%|7rg9/2^6 ; vgg/2 x>.
Five delayed gamma rays have been found that originate
from a new isomer with t 1 / 2 = 477 + 10 ns and 9 u n c o r r e c t e d =
0.8005 + 0.0006. The gamma-ray energies, half-lives, intensities,
angular distribution coefficients (a_) and g-factors are given
in Table 2.4.1. We tentatively assign the isomer to a state in
*uNb with J >_ 13 populated by the Se(xoO,3n) uNb reaction.
:ay properties
Ey(keV)
813.
996.
1067.
1809.
1880.
.5
.0
.0
1
6
fcl/485
462
477
481
477
of
2<!
±
±
±
±
+
a
is)
8
7
8
41
16
- 18 -
Table 2.
new isomer
Zrel
100
35
80
34
11
4 .1
, te
-0
0
0
-0
0
nta
a2
.28
.34
.43
.26
.52
90Nb
^uncorrected
0.8008 ± 0.0008
0.8009 ± 0.0013
0.8005 ± 0.0006
0.798 ± 0.003
0.8007 ± 0.0010
2.5 g-factor for the K = 6, J* = 6+ Isomer in Hf
T. Faestermann, 0. Hausser, D. Ward, H.R. Andrews,T.K. Alexander, D. Horn and T.L. Khoo (MichiganState University)
High-K isomers are prevalent towards the end of the
rare-earth deformed region where the valence particles fill
high Ù orbitals. Very little is known about the g-factors
for these isomers, mainly because in the half-life range en-
countered, 50 ns - 50 us, quadrupole and paramagnetic relax-
ation effects can destroy the nuclear alignment very rapidly.
The K = 6, J* = 6+ state in 1 7 8Hf at 1554 keV decays predomin-
antly to the ground band (K = 0) 6 and 4 levels with gamma
rays of 921.8 keV and 1247.3 keV respectively and its half-
life has previously been measured (T.L. Khoo and G. L0vhjrfiden,
preprint 1977) as 78 + 1 ns. According to Khoo and L0vh0iden
(ibid) its structure is a mixture of two quasi-partiele proton
[404]7/2 9 [514]5/2 and neutron [514]7/2 ® [512]5/2 states.
We measured the g-factor by the method of spin rotation,
populating the state with the reaction 176Yb(4He,2n)178Hf at
27 MeV by using the pulsed beam facility at the Chalk River MP
tandem. Beam bursts were of 2 ns duration spaced by 0.8 ps.
Hafnium lies outside the rare-earth region proper in that the
4f atomic shell is closed,' consequently there should be no para-
- 19 -
magnetic relaxation or paramagnetic enhancement of the applied
field. Ytterbium metal has an fee crystal structure and at
elevated temperatures, quadrupcie relaxation should not be too
severe despite the large moment expected for the isomer. The
target was heated to a temperature of 505°C during the experi-
ment. The external magnetic field was measured by an NMR probe
to be 0.97856 T. Analysis of the time differential data gave
g = 0.96 ± 0.01.
Analysis of the branching ratios within the K = 6 band
(ibid) according to the usual rotational model expressions gives
(gK-gR)/Qo = 0.067 i 0.0025 b"1 . Assuming ,GO is the same for this
band as for the ground band, namely Q = 6.69 b, then g^-g- =O J\ R
0.448 ± 0.017. For antiparallel spin coupling in a two quasi-
particle state we have (Khoo et al., Can. J. Phys. 51 (1973)
2307) y = [1/(1+1)]{KgR+gR}, where gR is expected to be 1 for
protons and 0 for neutrons. Combining the two results for g
and gR we find gR = 1.02 ± 0.01 and gR = 0.57 + 0.02.
Clearly the isomer is a rather pure two-proton con-
figuration. A surprising feature of the result is the large
value for g R compared to that for the ground band (gR = 0.24
± 0.014). It is well known that the addition of an odd proton
to a paired system typically raises gD by 0.05 - 0.10 and we
might expect a somewhat larger effect for two unpaired protons.
The observed relaxation time, T(K=2) 'V- 200 ns, is too
short to enable measurement of longer-lived high K isomers in
Hf isotopes; however this might be improved by further increasing
the target temperature.
2.6 Knight-shift of Rn in Hg
T. Faestermann, T.K. Alexander, O. Hausser, D. Horn,A.B. McDonald, A.S.C. Hyde,and N.C. Bray
An external magnetic field applied to a metal causes
a polarization of the conduction electrons and therefore the
*1 barn = 10~ 2 8 m 2
- 20 -
field at a nuclear site in the metal is slightly altered. If
the magnitude of this effect, the Knight shift K, is unknown
the accuracy of g-factor measurements is limited (to ^ ± 2%
for Z <\» 80) .+ 212
The g-factor of the 8. state in Rn has previously
been measured in a metallic Hg environment (PR-P-111, 2.2,
AECL-5614). We have now measured the same g-factor in Hg204 12 212
vapour using the Hg( C,4n) Rn reaction. Forty milligrams204
of Hg were placed in an evacuated Ta cell. The cell was
heated to a temperature of 360°C, corresponding to a vapour12
pressure for Hg of 106.7 kPa (800 Torr), The C beam entered2
the cell through a 7 mg/cm thick Ta foil sealed with a Cu gas-212
ket and ^ 85% of the Rn recoils were stopped in the Hg vapour.
When the target cell was placed in an external magnetic
field of 0.9787 T, we were able to observe the spin rotation212 +
of Rn(8 ). The analysis of the data is still in progress,
but it is certain that we have found a suitable method of
measuring the Knight shift K(RnHg_) in spite of the technological
problems of handling a hot Hg vapour target.
2122.7 High-spin Isomers in Rn
D. Horn, 0. Hausser, T.K. Alexander, A.B. McDonaldand T. Faestermann
204 13 212Previous studies of the Hg( C,5n) Rn reaction
(see PR-P- 111:2.3, AECL-5614 for table of early measurements
and PR-P-112: 2.5, AECL-5696 for proposed decay scheme) have212
demonstrated the existence of high-spin isomers in Rn.
The present experiment was performed to measure the g-fsctors
of the highest-lying isomers and to obtain more precise values
for the half-lives of several previously observed lower-lying
states. In the course of the experiment an improved energy
calibration was performed giving more accurate values for the
energies of the gamma transitions. The g-factors were measured
- 21 -
by the perturbed angular correlation technique with a magnetic
field of 2.2389 T and a pulsed beam of 84 MeV 1 3C from the CRNL
tandem. Analysis is still in progress, but some preliminary
values have already been determined and are shown in Table 2.7.1.
Results support our earlier J* assignments and suggest tentative
assignments for the uppermost observed isomer:
27"[ir(17")v(~1i13y2i11/2)10+] and for the next isomer:
2 5 " [ » ( 1 7 " ) v 1 +
Table 2,7.1
Rn g-factors
E (keV) g-factor t1/2(ns) A 2
701.0 0.645 ± 0.002 154 ± 14 0.50 ± 0.07
736.1 0.64 + 0.05 1 4 + 4 0.28 ± 0.04967.7 0.68 ± 0.02 18.0 ± 0.6 0.52 ± 0.04
1360.6 0.708 ± 0.011 128 ± 10 -0.72 ± 0.4
708.7 1.034 ± 0.016 16 ± 4
Search for Static Perturbation of the 5/2"*" State in 111Cd
During Recoil in Vacuum
H.R. Andrews, R.L. Graham, O. Hausser, D. Horn and 0. Ward
A further attempt (see PR-P-112: 2.7, AECL-5696) has
been made to study the vacuum deorientation of the 5/2+, 247
keV isomeric state in Cd. This data, obtained at the same
recoil velocity of 0.01 c extends our previous work on the
21/2+ and 11/2" states in 107Cd (ibid). The level was Coulomb
excited with 40 MeV O ions. Gamma rays were detected with
two Ge(Li) detectors, each operated in coincidence with an
annular particle detector centred at 180° to the beam direction.
- 22 -
One gamma counter was fixed at 90° for normalization purposes
and the other alternated between 0° and 90°. The target con-2 111 2
sisted of one foil of 960 yg/cm Cd evaporated on 400 ug/cm
natural Cu, spaced about 1.6 mm in front of a 0.025 mm thick
piece of natural Ag, which was centred with respect to the
correlation tabls. The target assembly was inclined at 50
to the beam direction resulting in a flight time for the Cd
ions between target and stopper of about 800 ps. To test for
instrumental isotropy the beam energy was raised to 60 MeV
and activity was produced in the Ag foil at the same place
that the Cd recoils had come to rest.
The hard core prediction of G2 for a nuclear spin of
5/2 and atomic spin of 7/2 is 0.24 and it remains essentially
at this value for higher atomic spins. A value of 1.36 was
found previously for the 0°/90° anisotropy of the 247 keVgamma ray, corresponding to an A_ of 0.21 since A, 2i 0-
hard core value of G_ predicts a 0°/90° ratio of 1.08. The
experimental value is 1.04 ± 0.04, including a 2% correction
for instrumental asymmetry. This result, which is not con-
clusive, appears to lie below the hard core. The accuracy is
however limited by counting statistics since the Coulomb
excitation probability of the level is small and the beam
current had to be kept low to avoid destruction of the targets.
2.9 Search for 182Hg
D. Ward, H.R. Andrews, 0. Hausser, R.L. Graham, R.B. WalkerD. Horn, T. Faestermann and P. Skensved (Queen's University)
We have performed experiments with the gas scintil-
lation recoil detector described in PR-P-113: 2.20, AECL-5802,
partly to test it and partly to search for in-beam gamma rays
in Hg. Beams of Cl and Cl in the range 160-175 MeV were
used on targets of Eu and Eu. The 4n reactions expected
at these energies would lead to 1 8 6 » 1 8 4 ' 1 8 2H g > T n e isotopes
- 23 -
Hg and Hg have been studied previously (D. Proetel,
R.M. Diamond, P. Kienle, J.R. Leigh, K.H. Maier and F.S.
Stephens, Phys. Rev. Lett. 31. (1973) 896; N. Rud, D. Ward,
H.R. Andrews, R.L. Graham and J.S. Geiger, Phys. Rev. Lett.182
31 (1975) 1421); however a previous attempt to observe Hg
was not successful (P. Taras, H.R. Andrews, R.L. Graham, W.
McLatchie, H. Schmeing and D. Ward, PR-P-103: 2.8, AECL-4931).182
The isotope Hg is so neutron-deficient that one might ex-
pect charged particle evaporation to deplete seriously the
cross section. This effect can not be improved by recoil2
detection; however the systematics of the Z /A dependence of
fission cross sections suggest that fission will add a large
contribution to the background, an effect that may be reduced
by recoil detection.
Gamma spectra for Hg and Hg in coincidence with
recoils were found to be very clean compared to the direct
gamma spectra. Only the well-known Hg and Hg yrast
sequences were observed in the recoil-coincidence gamma spectra;
in the case of Cl + Eu, we observed only three strong
transitions. The energies and relative intensities of these
transitions parallel the lowest transitions in Hg, and on
the basis of systematics are good candidates for the assignments
given in Table 2.9.1. Furthermore in a y~Y coincidence experi-
ment performed simultaneously with the recoil gamma experiment
they were shown to be in cascade. Experiments are being planned
to verify the assignments.
An interesting feature of the reaction systemacics
shown by the recoil-coincidence technique was the strong de-
crease (factor of 2 to 3) in the intensity of compound nuclear
recoils between the reactions 37Cl + 1 5 1Eu and 35C1 + 1 5 1Eu at
165 MeV. Since the target was common, we conclude that this
represents a decrease in the fusion-residue cross section, pre-
sumably caused by the rapid onset of fission competition in
these highly neutron deficient systems.
- 24 -
Table 2.9.1
Systematics in Light Mercur" "•"i topes Gamma-ray Energies in keV
1 8 6Hg l> 1 8 4Hg 2) 1 8 2Hg
2 + 0 405.8 366.7 [351.2]
4 ->• 2 402.6 287.9 [261.9]
6 + 4 356.7 340.1 [332.9]
1) D. Proetel, R.M. Diamond, P. Kienle, J.R. Leigh/ K.H. Maierand F.S. Stephens, Phys. Rev. Lett. ^î. (1973) 896.
2) N. Rud, D. Ward, H.R. Andrews, R.L. Graham and J.S. GeigerPhys. Rev. Lett. 31 (1975) 1421.
2.10 Accurate Determination of the Lifetime of the 3.35 Me'v,
4 + Level in 2 2Ne
J.S. Forster, T.K. Alexander, G.C. Ball and W.G. Davies
The thorough study of derived lifetime of the 3.35+ 22MeV, 4 level in Ne as a function of stopping material by
Broude et al. (C. Broude, P. Engelstein, M. Popp and P.N.
Tandon, Phys. Lett. 39B (1972) 185) highlighted the problem
of obtaining consistent lifetime values from low initial re-
coil velocity (v - 1% the velocity of light) DSAM* experiment
when theoretical stopping powers are used. More recently,
Toulemonde and Haas (Phys. Rev. C15 (1977) 49) made similar
measurements using three new stopping materials (Li, Na and
Sr) as well as twelve of the 39 materials used by Broude et
al.; even larger variations in apparent lifetime were ob-
served when these three new materials were included.22
In order to determine an absolute value for the Ne,4 + lifetime we used the 4He(19F,p) Ne reaction to produce
4recoils with velocities of <\» 4%c. Implanted targets of He(to a concentration of <\» 6 x 10 atoms/cm ) in ^ 25 um foils
of Cu and Au were bombarded with beams of 27.8 MeV i 9 F 4 + ions
from the Chalk River MP tandem. The beam and heavy ion re-
coils stopped in the foils but light reaction products passed
doppler shift attenuation method
- 25 -
through and were detected in a counter telescope at 0 to
the beam. A gamma-ray detector, also at 0 to the beam, de-
tected gamma rays in coincidence with the AE counter of the
telescope. The AE and B data provided mass identification of
the light reaction products by means of conventional range
table lookup procedures. Doppler broadened gamma-ray line-
shapes of the 4 -*• 2 transition were generated with appropri-
ate gates on the time, mass and proton spectra. Mean life-
times were determined by least squares fitting of lineshapes
calculated by a PDP 10 computer program to the experimental
lineshapes. The electronic stopping powers of J.S. Forster,
D. Ward, H.R. Andrews, G.C. Ball, G.J. Costa, W.G. Davies and
I.V. Mitchell (Nucl. Instr. & Meth. 136 (1976) 349) were used
in these calculations.
Mean life values of 0.333 ± 0.020 ps and 0.315 ± 0.020
ps were obtained for the 3.35 MeV, 4 + lifetime in Ne for Cu
and Au backings respectively, giving an average value of 0.324
± 0.014 ps. This value can help to resolve uncertainties in
stopping powers used in low velocity OSAM calculations.
402.11 Gamma Decay of the Lowest T = 2 Level of K
A.B. McDonald, G.C. Ball, W.G. Davies, D. Horn, D. Martin(Queen's University) and P.G. Ikossi (McMaster University)
An attempt has been made to measure the gamma decay
properties of the 4378 ± 16 keV, Jïï = 0+, T = 2 level of 4 0K,41 3 40
by using the K( He,a) K reaction. Coincidences were re-
corded between a 70 cm long multiwire proportional counter
(PR-P-109: 2.21, AECL-5508) in the focal plane of the QD3 magnetic
spectrometer and a 12.5 cm diameter by 15 cm Nal detector near
the target. Targets consisting of 'v. 250 yg/cm2 of 41KI on 102
jig/cm carbon foils were bombarded with * 100 particle nanoamperes3 2+
of He at 12.5 MeV. The high counting rate in the Nal detector
limited the incident beam intensity and was dominated by reactions
in the target with little contribution from the tantalum beam
- 26 -
stop ^ 0.7 m from the target. The time resolution At/t
was found to be ^ 15% FWHM*(^ 40 ns) as expected for the
path length difference in the magnet at full solid angle
(J.C.D. Milton et al. AECL-3563).
Excitation energies were determined for the observed40
energy levels of K by comparison with well known levels in3 8 2
K, by using a thin (^> 80 pg/cm ) target containing equal39 41
parts of KI and KI. Three partially resolved levels
(energy resolution ^ 20 keV FWHM) were observed near the
excitation energy of the T = 2 level. Data analysis is
currently in progress, but further measurements will be re-
quired to identify the T = 2 level and determine its decay
properties.
2.12 Isospin Forbidden Particle Decay of the Lowest
T = 2 Level of 1 6O
A.B. McDonald; S.J. Freedman, M.A. Oothoudt, R.G.H. Robertsonand F.J. Zutavern (Princeton University) and E.G. Adelberger(University of Washington)
Data analysis has been completed for the measurements
(PR-P-109: 2.3, AECL-5508) performed at the Princeton cyclotron
to determine branching ratios for the isospin forbidden particle
decay of the 22.72 MeV, Ju = 0+, T = 2 level of 1 6O. In this
experiment, charged decay particles were detected in a three18
detector telescope in coincidence with tritons from the o
(p,t) o reaction (E = 42 MeV), observed in the Princeton3 P
QD magnetic spectrometer with an energy resolution of 25 keV
FWHM. Neutrons were detected in a 5 cm x 12 cm diameter plastic
scintillator at a distance of 0.7 m. Branching ratios (%) of
Po = 7 ± 2, p L + p 2 = 11 ± 2, p 3 = 5 ± 2, dQ = 2.1 ± 1.2, aQ =
1.6 + 0.7, a1 = 1.9 ± 0.7, a2 = 14 + 2, n Q < 15 and n 2 + n 2 =
2 3 + 1 5 were determined. The present result for p is signifi-*full width at half maximum
- 27 -
cantly smaller than that previously reported, p = 25 ± 6%
(T.K. Koh et al., Phys. Rev. C7 (1973) 50). This explains
the null result obtained in a high resolution search for this
level in the N(p,p ) N reaction, which was performed at
Chalk River with the differentially pumped gas target during
the course of the recent high resolution resonance studies
(see PR-P-110: 2.2, AECL-5546 and PR-P-111: 2.10, AECL-5614).
2.13 A Search for a Highly Excited Rotational Band in Be Arising
from Excited Alpha Clusters
R.E. Warner (Obeilin College), G.C. Ball, W.G. Davies,A.J. Ferguson and J.S. Forster
Recently, Hackenbroich et al. (Phys. Lett. 62B (1976)
121) predicted the existence of a rotational band in Be whose
structure is a. + a*, a* being the 0 first excited state of
the alpha particle. The 0 member of the band is expected toQ
lie near 20 MeV in Be, corresponding to the excitation of a*
relative to its ground state. We have searched for this band
by measuring an excitation function for the reaction d( Li,a)6 2+
a*. Beams of 10-31 MeV Li ions were used to bombard a
deuterium gas target. Two independent counter telescopes
positioned at angles near +12 and -18° were used to measure the
cross sections for the d( Li,a)a* and d( Li,a)a reaction chan-
nels, respectively at 0_M = 30 . No new resonances were ob-
served in Be in the region of excitation from 24.8 to 30.0
MeV. However, the known level at 25.2 MeV was found to decay
strongly by a + a*. Analysis of these data is in progress.
- 28 -
2.14 Beta-Neutrino Correlations from the Kinematic Shift
of Beta-Delayed Particles
E.T.H. Clifford, H. Schmeing (Neutron and Solid StatePhysics Branch), T. Faestermann, K.P. Jackson, R.E. Azuma(University of Toronto) and J.C. Hardy
Preliminary experiments in a program to deduce the
beta-neutrino angular correlations in the decays of delayed-
particle precursors have been carried out (PR-P-112: 2.14,
AECL-5696).
In a first attempt to measure this correlation,
exploiting beta-delayed proton emission as a probe, the
precursor Si(T,/o = 220 ms) was produced by the ( He,2n)2 24
reaction at 32 MeV incident energy in a 1.2 mg/cm Mg
target. The helium jet and skimmer system (Nucl. Instr. &
Meth. 139 (1976) 335) was employed to transport the reaction
products from the target area to a counting chamber where the
activity was deposited on an aluminum foil. The protons from25
Si were detected in an annular silicon counter with a de-
pletion depth of 300 ym and subtending 0.6 sr. Two plastic
scintillators, one subtending 1.5 sr situated at 90° with
respect to the silicon counter, and the other subtending 2.3
sr at 180°, were used to detect betas in coincidence with the
protons. The coincidence data contain <v 2 x 10 e /ents in
the most prominent peak of the proton spectrum and indicate
a proton energy resolution of ^ 20 keV. The statistical ac-
curacy of the data is sufficient to obtain the kinematic shift
in the proton energy as a function of beta energy with a pre-
cision adequate to obtain useful estimates of the beta-neutrino
angular correlation.
Data of similar quality have been obtained for the20 3
delayed alpha emitter Na, produced in the ( He,p2n) reaction
on neon gas. Analysis of the existing data should reveal the
limitations imposed by systematic errors. Future experiments
are planned.
- 29 -
2.15 A Review Article on Short Nuclear Lifetime Measurements
T.K. Alexander and J.S. Forster
The first draft of a manuscript entitled "Lifetime
Measurements of Excited Nuclear Levels by Doppler Shift
Methods" has been written for Advances in Nuclear Physics.
The article reviews the Doppler-shift attenuation and recoil-
distance methods in detail and summarizes the complementary
techniques, some of which are well established, while others
are specialized or under development. The methods are dis-
cussed and compared in the light of published data. An exten-
sive bibliography is included.
2.16 Computer Aided Control System for the Superconducting
Cyclotron and MP Tandem
R.L. Graham, L.D. Eansen (Mathematics and ComputationBranch) and R.B. Walker
The PDP 11/34 computer (cf. PR-P-112: 2.22, AECL-
5696) became operational in January. Aside from one de-
fective disk pack (out of three) all hardware is performing
satisfactorily. Delivery of the CA-11C CAMAC interface unit
from Digital Equipment Corporation's (DEC) special products
group in.Munich, Germany has been delayed; DEC now promises
delivery before the end of March. The RSX-11D version 6B
software operating system purchased from DEC could not be
made to operate properly on this computer because of minor
hardware differences between the /34 model and earlier models
such as the /40 and /45. As an interim solution DEC has pro-
vided us with a pre-release version of the next operating
system.
The status of software development is discussed in
detail elsewhere in this report by Hansen et al.(PR-P-113:5.5,
AECL-5802). The software obtained from the VICKSI project
at the Hahn-Meitner Institute in Berlin has been successfully
- 30 -
installed and those portions compatible with our existing
hardware appear to function satisfactorily.
A communications link to the computing centre has
been established. Extensive tests have shown that reliable
communication is not possible with existing software. A
reliable 'high-speed' link will be needed during periods of
cyclotron beam development; the link should operate at a
rate of 9600 baud ( 960 characters per second). Changes in
the asynchronous conventions for the CDC 3300 computer have
been recommended .
Almost all the CAMAC equipment ordered last November
has arrived. Quotations for the next set of modules has
been received and orders are now being processed.
2.17 Design of the Beam Transport System for the
Superconducting Cyclotron
W.G. Davies and A.R. Rutledge
Further investigation of the use of a chopper to pro-
vide phase control of the buncher (PR-P-112: 2.25, AECL-5696)
showed that such an approach was not feasible because a chopper
introduces a large momentum spread that is not correlated with
buncher phase. This uncorrelated momentum component arises
from coupling of the transverse size and the longitudinal
momentum components of the beam phase space in the fringe
fields of the chopper. Consequently it was necessary to in-
vestigate other methods of controlling the buncher phase and
removing the leading and trailing edges of the beam burst.
During the course of these studies it was realized that
operating the high energy buncher in front of the analyzing
magnet seriously interfered: with the control of the tandem
voltage. Moving the buncher required a complete redesign of
the injection line.
- 31 -
In the new design, control of the tandem energy and
buncher phase are completely separated by using two achromatic
pairs of dipole magnets. Energy analysis is done between the
two elements of the first pair with the buncher placed at a
double waist after the second element. Isochronism is required
at the buncher because the correlation between phase and momentum
must be nearly perfect (r > 0.97) if the phase width at the
injection point in the cyclotron is to be < ± 1.5°. Phase
analysis and removal of most of the unwanted tails of the beam
burst occur between the elements of the second doublet. The
use of an analyzer to control the phase of the buncher is
similar to that used in the VICKSI project at the Hahn-Meitner
Institute. A double waist following the second achromatic
doublet serves as a boundary between the system that matches
the cyclotron to this section. Adjustment of the injection
system up to this boundary is independent of beam phase
space, energy and ion species.
Matching of the beam properties to the acceptance
requirements of the cyclotron is achieved with two dipoles
and about six quadrupoles. Considerable freedom is required
here because the properties of the cyclotron are a strong
function of both ion species and energy. The design has been
optimized from the tandem stripper through to the end of the
second achromatic pair. Optimization of the matching section
to the cyclotron is in progress. All calculations now include
explicitly the effects of the energy straggling in the terminal
stripper (see PR-P-112; 2.24 and 2.25, AECL-5696) as well as
the latest values for the beam emittance (ibid; 2.20). This
new design gives an injection system that not only solves the
before-mentioned problems but is less sensitive to the beam
phase spa^e, and easier to set up than the earlier design.
- 32 -
Construction and Use of a Compton Polarimeter
0. Hausser, T. Faestermann, D. Ward, D. Horn
H.R. Andrews and L.V. Smith
A polarimeter, which is sensitive to linear polari-
zation of gamma rays, has been set up and successfully used93
in an attempt to measure parity mixing in Tc (see PR-P-113:
2.2, AECL-5802). We used the method described by P.A. Butler
et al. (Nucl. Instr. & Meth. 108 (1973) 497), which is based
on the dependence of the Compton scattering cross section on
th« angle ty between the scattering plane and the plane of the
polarization.
The polarimeter consists of three Ge(Li) detectors.
One at an angle 0 (in our case 90°) to the beam direction
serves as a scatterer for the incident radiation. The other
two are shielded from direct radiation by 7.5 cm of lead and
view the scatterer at an angle of 90° to the primary radiation,
one in the plane of beam and scatterer, the other one perpendi-
cular to it. The pulse heights of coincident events between
the scatterer and either of the other detectors are recorded
on magnetic tape. The spectra produced from the sums of coin-
cident pulse heights have only slightly worse energy resolution
than those from the scattering detector alone. The photopeak
efficiency of a coincident pair compared to the singles efficiency
was 4.4% at 661 keV and 6.0% at 1836 keV.
The sensitivity of the apparatus was measured with32
gamma rays produced by Coulomb excitation of S on natural Ge.
The observed sensitivity for linear polarization (expressed as
P = [I(e,i|>=0°) -1(6,4» =90°)]/[I(6,^=0°) + I(6,i//=90°)]) decreases
with increasing gamma energy from 0.44 at 400 keV to 0.20 at
1400 keV. This is 59% of the sensitivity one would expect for
infinitely small solid angles.
Combined with the results of angular distribution
measurements the polarimeter enables us to make unambiguous
spin and parity assignments.
- 33 -
2.19 Polarization Sensitivity of a Ge(Li) Planar Diode
A.J. Ferguson
Over the past five years a CDC 6600 program has been
developed to compute the polarization sensitivity of planar
Ge(Li) diodes (PR-P-106: 2.16, AECL-5226; PR-P-101: 2.17,
AECL-4773). The program is valid for the energy range 1 to
5 MeV where Compton scattering is the dominant process. In
response to an enquiry from Professor Martin Johns of McMaster
University, the program has been upgraded to' extend the energy
range, particularly to lower energies, by including other pro-
cesses such as photoelectric and pair production. Stokes
parameters for each process are introduced, weighted by cross
sections taken from the table of Storm and Israel (Nuclear
Data Tables A7 (1970) 565).
Preliminary calculations for low energies indicate a
peak sensitivity at ^ 0-4 MeV, below which the sensitivity
falls rapidly because of the increasing strength of the photo-
electric process. Provision has been made for the easy sub-
stitution of cross sections for other detector materials. It
is expected that Si planar diodes will retain their sensitivity
to. lower energies than Ge(Li) diodes.
2.20 Development of a Gas Scintillator System for Detecting
Recoils Following (HI,xny) Reactions
D. Ward, H.R. Andrews and R.B. Walker
A system of gas scintillation counters that detects
recoils from (HI,xny) reactions in the angular range 7°-16°
has been developed. The system, which is a natural extension
of an earlier device utilizing one chamber which necessitated
pulsing the beam (PR-P-109: 2.11, AECL-5508), consists of two
chambers separated by a window of aluminized mylar ^ 800 pg/cm .
Recoils enter the first chamber through a pressure window of2
500 yg/cm and are stopped there. Scattered beam particles
- 34 -
pass through both chambers. Scintillations in the gas volume
are observed by four photomultipliers, two to each chamber.
Pulses in the first chamber are vetoed if accompanied by events
in the back chamber, so that the high counting rate from the
scattered beam is reduced to a manageable level. The device
operates in coincidence with Ge(Li) detectors and considerably
improves the gamma-ray spectrum for systems in which fusion-
evaporation is not the predominant channel. ;
Performance figures measured during a recent experi-
ment (PR-P-113: 2.9, AECL-5802) are reproduced below.
In this particular experiment the pulse height in
the front chamber from beam particles was appreciably greater
than that from recoils so that an additional constraint on
the amplitudes could be imposed (cf last entry in Table 2.20.1).
It will be seen that the overall effect of the procedure was to5-1 3 -1 '
reduce a particle rate of 8 x 10 s down to 27 x 10 s before
entering the recoil-gamma time to amplitude converter. The time
resolution obtained was sufficient to separate peaks arising
from Coulomb excited target recoils and fission fragments from
compound nuclear recoils.
The overall efficiency for detecting recoils was
measured to be 11% in the reaction Eu( Cl,4n) Hg. This
figure is compatible with the fraction of compound nuclei re-
coiling in the polar angle range 7° -16°. Further improvements to
the efficiency count rate capability are being considered.
Table 2.20.1
Typical Performance Figures
Target 1.5 mg-cm Eu
Beam 2 nA (electrical) 35cl
165 MeV (charge 15)
Tube 1, 2 singles rate = 800 x 10 s
Tube 1-2 coincidence
Tube 3 or Tube 4anticoincidence rate
Output rate: 1-2 in coincidencevetoed by either 3 or 4
After amplitude discrimination
= 530
= 750
= 77
= 27
x
x
X
X
103
103
103
103i
s"1
s-1
s-l
-1
- 35 -
2.21 Time-of-Flight Spectrometer Using Channel Electron
Multiplier Arrays (CEMA's)
D. Ward and R.B. Walker
Construction of a simple time-of-flight spectrometer
has been completed. Start and stop signals are each provided
by two channel electron multiplier assemblies (CEMA) arranged
as a chevron. Ionizing particles passing through a thin foil
generate electrons which are quickly accelerated by a potential
of 2 kV onto the chevron CEMA. Each of the systems, foil,
accelerating grid and CEMA, are mounted in modules that can be
plugged into standard beam tubing. Voltage holding and time
resolution tests are currently in progress.
2.22 Assembly of the On-line Isotope Separator
H. Schmeing (Neutron and Solid State Physics Branch),W.L. Perry and N.C. Bray
All major components of the on-line isotope separator,
which is being built with the assistance of Dr. J. Camplan from
the Laboratoire Rene Bernas, Orsay (PR-P-108: 2.18, AECL-5315)
have arrived now at CRNL from France, except for the ion sources
and most power supplies. The assembly of the system in its
final position in target room 1 is well under way. As planned,
a number of modifications are being made, e.g. to structural
support elements (with the assistance of the Plant Design
Branch). Installation, modifications, and projects being
tackled locally, such as the completion of the trim coils, are
proceeding according to schedule. We expect the instrument to
work in its off-line mode at the end of the summer.
- 36 -
2.23 Progress on the QD Focal Plane Counter System
G.C. Ball, J.J. Hill and W.G. Davies
Having successfully conditioned a new 704 wire front
counter module with pure CO, to 3300 V (cf. PR-P-112: 2.15,
AECL-5696) we carried out preliminary testing with 13.5 MeV
He ions scattered from a thin Au foil and analyzed with the
QD spectrometer operating at 0.5 T. Adequate gain was
achieved at 1900 volts using a 65% isobutane, 35% argon gas
mixture. When the address computer was set to accept all 1
to 6 wire events the counter efficiency was 'v» 95%. However,
in several regions of the counter the differential linearity
was poor, leading to a counter resolution of only 1-1.5 mm.
Whether this effect arises from variations in amplifier gains
and/or thresholds, or to variations in the computer geometry
has not yet been determined. At present, a complete front-
back counter module is being assembled for testing.
2.24 Cryogenic Differentially Pumped Gas Target
A.B. McDonald, R.A. Suretta and K.T. McKee
In order to perform experiments with rare isotope gas
targets, the differentially pumped gas target has been equip-
ped with a cryopump based on an Air Products Corp. liquid
helium cooling system. The cryopump can be used instead of
the Rootes blowers for the first state pumping. Tests have
been completed which indicate that adequate pressures, < 1 mPa
in the first stage of differential pumping can be maintained
for argon target pressures up to 200 Pa. Liquid helium con-
sumption is typically 0.5 £/h. At the target pressures of
36,15 Pa to be used in future studies of the Ar(a,ot) and
Ar(a,y) reactions, gas consumption rates of *v< 1 9. per day
are expected, with > 90% recovery after a 30-minute warm-up
and recovery cycle.
- 37 -
2.25 Status of Ge(Li) Gamma Detectors
L.V. Smith
The properties of the Ge(Li) gamma-ray detectors
available in the Nuclear Physics Branch as of March 1st
1977 are summarized in Table 2.25.1
During the past year, two detectors, Ortec III and
Nuclear Diodes I, which had suffered from neutron damage,
have been successfully rehabilitated by the manufacturers.
The reprocessed detectors are designated by the suffix A in
the table. A new Ge(Li) detector, PGT IX, with a 50 cm long
end cap was purchased to be used with an existing Nal(Tl)
counter for suppressing Compton scattered events in a desire
to improve the peak-to-background ratio in the energy region
of 0.1-5 MeV. Detector PGT V has been returned for remounting
in a special cryostate designed to allow the measurement of
linear polarization of gamma rays while doing angular distri-
butions (cf. PR-P-113: 2.18, AECL-5802).
Name
Table 2.25.1
Type Efficiency Resolution Neutron Volumeat 25 cm at 1.333 MeV Damage cc
xl07n/cm2
PGT VIII
ORTEC IIIA
PGT IX
PGT VII
PGT VI
PGT V
NUCLEAR DIODES 1A
PGT II
HARSHAW
ORTEC II
TC
TC
TC
TC
TC
C
C
TC
C
TC
20.2%
17.3%
16.2%
16.0%
15.0%
15.0%
9.5%
8.0%
6.7%
5.6%
2-2.
2.
2.
1.
2.
2.
1.•-
2.
oy2
1
1
86
2
0
95n
75
keV
kev
keV
kevkeV
keV
keV
keV
keV
keV
1.—
0.
12.
31.
12.
—
10.
3.
2.
.9
8
4
4
5
85
82
0
100.
86.
85.
80.
75.
75.
50.
45.
39.
30.
0
5
0
0
0
0
6
0
8
6
- 38 -
2.26 Target Preparation
J.L. Gallant
The following targets were prepared for experiments
performed during the quarter: Cu on lead, Cu on mercury,
C on copper, C on nickel, Be on copper, Be on nickel,
LiF and Li on 10 yg/cm carbon, KI and n a tKI on 10 yg/cm
carbon, Cd self supporting and on copper and aluminum,1 ft 7fl 92Se and Se on lead, and self supporting targets of Mo,
1 7 4Yb, 1 7 6Yb, 2 0 5Tl, 86Sr, 24Mg, 26Mg, Au and Al. In addi-2
tion 225 carbon foils (2 yg/cm ) for the terminal stripper2
and 65 carbon foils (10 yg/cm ) for the high energy stripper
were mounted.
Large area cadmium foils needed for plunger targets
used in experiments on the vacuum deorientation of states in
Cd were prepared by a new method. Since the existing
method by which cadmium is reduced with thorium and the metal
evaporated on a substrate proved unsatisfactory, a method was
developed starting from the oxide. Cadmium oxide is dissolved
in 4 N sulfuric acid and metallic cadmium is collected on the
cathode of an electrolytic cell. The metal is then evaporated
onto a glass plate previously coated with a thin film of
cadmium chloride. The cadmium salt is used because the metal
and the salt are both hexagonal in structure. Matching crystal
structure facilitates condensation. The film is removed from
its substrate by complete immersion in methanol.
Potassium-41 iodide was prepsred by reacting potassium-
41 carbonate with hydriodic acid, and metallic films of Sr,
Yb, Yh were fabricated by reducing the oxide of these
metals with thorium, prior to evaporation.
Work done for other branches1 2
Evaporated gold and aluminum (2 yg/cm on polished
carbon discs) for stopping power measurements by helium ion
back-scattering were prepared on request from Dr. D.C. Santry
of Solid State Science Branch.
- 39 -
For Dr. Peter Martel of the Neutron and Solid State
Physics Branch a metallic disc was coated with thymine covered
by a conductive film of copper.2
Uranium fluoride films, each 1 mg/cm thick were eva-
porated on both sides of twelve thin mica plates to be used
as fission targets and neutron counters. This work was re-
quested by Dr. Aslam Lone of Neutron and Solid State Physics
Branch.
Work done for universities
Several large area gold windows used in an alpha
spectrometer were prepared for Dr. J.S. Geiger, Laboratory
for Laser Energetics, University of Rochester.
2.27 Tandem Electronics
J.P.D. O'Dacre
Thirty-one analog channels covering various accelerator
parameters - including twenty in the ion source - are now being
logged through the PDP 10 scanner, with the results displayed
on the teletype immediately adjacent to the operator's console.
The system is compatible with the CAMAC input modules associ-
ated with the PDP 11 computer control system.
In addition fourteen CAMAC compatible control channels
employing fibre optic signalling to the ion source are now oper-
ational. One of these controls and reads out the extraction
power supply. Accuracy here and for the inflection magnet is
necessary in order to differentiate between the many various
beams emitted. In practise to date, setting and reading voltage
to one part in 10 has been possible routinely,* however some
initial voltage drift occurs for perhaps 30 minutes after power
switch on. This is believed to be caused by thermal drift in
the voltage divider string, and a lower temperature coefficient
. unit has been ordered.
- 40 -
The prototype charge balancing generating voltmeter
designed for terminal voltage control of the MP accelerator
has been mechanically refined with improved results. Step
changes of one part in 20,000 can be detected. The unit has
reached the stage where it can be considered a usable device
but further refinement is necessary to reach the goal of orçe
part in 10 . The accompanying electronics are still at the
prototype stage.
2.28 Computers and Instrumentation
F.J. Sharp
Since the beginning of March inadequate air con-
ditioning in the Memory Room (Room 49) has caused overheating
with resultant failures in the Intel Memories. During one
week of warm weather it was necessary to shut down the second
64 K of Intel Memory (#104), which had just been installed
in January, thus reducing the available memory from 208 K to
144 K.
The new display is in full service under the control
of PDP 10 software. At a later date it is intended to install
an 8080 microprocessor system to take over control of some of
the more mundane functions at present under the control of the
PDP 10.
Two satellite calendar clocks have been built and
installed in the control room, controlled via a daisy chain
bus from the master clock.
A microprocessor EROM (Erasable Read Only Memory)
programmer has been built and tested. The unit will allow
programming of the 1702A type EROM via the PDP 10 for future
8080 microprocessor.systems.
A data Multiplexer has been built which will allow
the PDP 10 to monitor the field settings of the magnetic com-
ponents of the beam transport system.
- 41 -
2.29 MP Tandem Operation
J.C.D. Milton
The availability of the tandem, though better than
last quarter, was still poor (see Table 2.29.1) largely be-
cause of two failures of the high voltage isolation trans-
former supplying three-phase power to the ion source. After
the second failure, the transformer was rebuilt in an attempt
to improve -the mechanical interface between the primary and
the core. The tank was entered twice, once to install a new
housing for the second stripper and to replenish the stripping
foils and the Ti-ball pumps. New foils may now be inserted
without letting the accelerating tubes up to air. The second
entry was required to remove a source of gas in the tubes; an
O-ring on the new stripper housing was being struck by back
streaming electrons.
Efforts continued to understand the transmission (see
PR-P-J.12: 2.15, AECL-5696). After re-installation of the
electrostatic quadrupole (in a slightly modified form) im-
mediately in front of the gridded lens (PR-P-106: 2.19, AECL-
5226) the transmissions shown in Table 2.29.2 were obtained
at a cage voltage of 25 kv corresponding to an injection
energy of approximately 50 keV.
During the quarter, 12 experiments were performed
involving CRNL and 10 visiting scientists. Non-CRNL scientists
collaborated pn experiments occupying 85% of the beam time
during which their average participation was 48%.
Table 2.29.1
Beam available
Scheduled shutdown
Unscheduled shutdown
Total
hours
986.7
744.0
453.3
2184.0
%
45.2
34.1
20.7
100.0
- 42 -
Table 2.29.2
MP Tandem Beam Transmission
Beam Transmission Stripper Source
Protons 85% foil Heinicke-Penning
Oxygen (all charge states) 41 gas Heinicke-Penning
Oxygen (all charge states) 51 gas Heinicke-Penning
Li (all charge states) 35 foil Purser
Monte Carlo Calculation of Neutron Production
in Spallation Targets
J.C.D. Milton
The conversion of MC74 to MC76 described in PR-P-112:
2.6, AECL-5696 is progressing. At the present time the modi-
fication required for loose packed cylinders has been success-
fully completed. However problems still exist with multiple
zones. In making the modifications, several small faults were
uncovered and cured in the old version of the program. None
of these was serious, but in one case a fortunately very rare
event in which a proton interacted in the first few millimetres
of the target, transferring most of its energy to excitation
of the struck nucleus, resulted in a fatal fault.
Participation in BIPM Calibration Comparisons
J.S. Merritt and F.H. Gibson
Concerning the program "International Reference
System for Measuring Activity of Gamma-ray Emitting Nuclides",
- 43 -
the Bureau International des Poids et Mesures (BIPM) has
informed us fiat the results from a Sc standard submitted
by CRNL in 1976 (PR-P-112: 2.27, AECL-5696) agree with those
of a Sc standard submitted by another laboratory. The
agreement is within the statistical uncertainty of the BIPM's
comparison of the two standards and well within the uncertainty
quoted by each laboratory for its standard.
2.32 The Half-life of 1 9 8Au
J.S. Merritt and F.H. Gibson
198The decay of a sample of Au produced by a short
irradiation in the NRU rabbit was followed for approximately
14 half-lifes by measuring it versus a radium reference source
in the 4 IT y ion chamber. No impurities were detectable by
Ge(Li) spectrometry either initially or after 14 half-lives
had elapsed. A least-squares analysis of the data gave a
preliminary half-life value of 2.6937 days with a standard
deviation of ± 0.0002 day. It is estimated that the effect• • 1 9 9
on the apparent half-life of a small but undetected Au
impurity is 0.0001 day. This effect and other possible
sources of error will be examined further, because gold is
an important neutron-capture standard and this preliminary198
value is low compared with the accepted Au half-lifeof 2.696 ± 0.002 days (ORNL-5114, 1976).
1982.33 Recalibration of the 4TTY Ion Chamber for Au
J.S. Merritt and F.H. Gibson
198A solution of Au was standardized by the 4ir3-y
coincidence method. Samples of it were measured in the 4ity
ion chamber -versus a radium reference source to effect a
- 44 -
198recalibration for Au. The results agree within 0.1% with
the previous calibration (PR-P-102: 2.20, AECL-4841).
Pile-up Test for Gamma-ray Spectrometry
J.S. Merritt and F.H. Gibson
The International Committee for Radionuclide
Metrology (ICRM) recommended a test for the validity of
corrections for dead-time and pile-up effects in Ge(Li)
spectrometry (Report ICRM-S-1, 1976). The test consists
of (1) preparing a set of sources by delivering accurately
determined masses of Cs and Co solutions to each source
mount (each source contains approximately the same quantity
of Cs but the Co activity range is > 10), (2) preparing
some sources containing Cs only, (3) counting each source
at a fixed distance from the Ge(Li) detector and (4) deter-
mining the 662-keV peak area corrected for dead-time and
pile-up; the 662-keV peak area for each mixed source is
divided by the peak area for a Cs-only source; finally
this experimentally obtained ratio is compared with the true137
ratio deduced from the known masses of Cs delivered to
the sources.
This test was done by counting the sources at 10 cm
from the detector, and used the reference-peak method for
determining the dead-time and pile-up correction with pulses
from a constant frequency puiser introduced at the preamplifier
input (H.H. Solotin et al., Nucl. Instr. & Meth. 83_ (1970) 1).
For the range of counting rates normally encountered in this
laboratory with corrections up to % 10%, no difference was
observed between the experimentally obtained Cs ratio
and the true ratio; for corrections of 20 to 30%, a dis-
crepancy of £ 1.5% was observed.
- 45 -
2.35 Standards Issued
J.S. Merritt and F.H. Gibson
H - Commercial Products
Co - Fuel Materials60,Co - Solid State Science3
198
90Sr - Radiation and Industrial SafetyAu - Environmental Research
2.36 Miscellaneous Services
J.S. Merritt and F.H. Gibson
Seven counter windows were made for the Nuclear Physics
Branch by laminating thin VYNS layers.88
Four sources of Y were prepared for the Nuclear88
Physics Branch, one of Y for the Reactor Loops Branch, fivean 241
of Sr for the Health Physics Branch and one of Am for the
Solid State Science Branch.
2.37 Sharing of KK Vacancies for [ls~ ] Configurations
J.S. Porster et al.
See PR-CMa-40: 1.2.1
2.38 Superconducting Cyclotron - MP Tandem Accelerator Control System
L.D. Hansen, R.L. Graham and R.B. Walker
See PR-P-113: 5.5 (i)
2.39 The H(n,Yy)D Experiment at NRU
A.B.. McDonald et al.
See PR-P-1Ï3: 3.16
- 46 -
2.40 Publications and Lectures
a) Publications
ISOSPIN FORBIDDEN PARTICLE DECAYS IN LIGHT NUCLEI (I):T = 3/2 LEVELS IN 9Be, 9BA.B. McDonald, T.K. Alexander, O. Hausser, D.L. Disdier,E.G. Adelberger, H.B. Mak, A.P. Shùkla and A.V. NeroNucl. Phys. A273 (1976) 451.
ISOSPIN FORBIDDEN PARTICLE DECAYS IN LIGHT NUCLEI (II):WIDTHS OF T = 3/2 LEVELS IN 1 7OA.B. McDonald, T.K. Alexander and O. HausserNucl. Phys. A273 (1976) 464.
ISOSPIN FORBIDDEN PARTICLE DECAYS IN LIGHT NUCLEI (III):DECAY WIDTHS OF THE LOWEST T = 3/2 LEVELS IN 2lNeA.B. McDonald, H.B. Mak, H.C. Evans, G.T. Ewan andH.B. TrautvetterNucl. P.hys. A273 (1976) 477.
MAGNETIC MOMENTS AND HALFLIVES OF ISOMERIC STATES INPOLONIUM ISOTOPESO. Hausser, T.K. Alexander, J.R. Beene, E.D. Earle,A.B. McDonald, F.C. Khanna and I.S. TownerNucl. Phys.. A273 (1976) 253.
THE CHALK RIVER, HELIUM JET AND SKIMMER SYSTEMH. Schmeing, V..Koslowsky, M. Wightman, J.C. Hardy,J.A. Macdonald', T. Faestermann, H.R. Andrews, J.S. Geigerand R.L. GrahamNucl. Instr. & Meth. 139 (1976) 331.
A FAST TAPE TRANSPORT SYSTEM FOR USE WITH ON-LINESEPARATORSJ.A. Macdonald, J.C. Hardy, H. Schmeing, N.C. Bray,W.L. Perry, R.B. Walker and M. WightmanNucl. Instr. & Meth. 139 (1976) 355
PROPERTIES OF YRAST STATESD. WardProc. of INS International Symposium on Collectivity ofMedium and Heavy Nuclei. 23-25 September 1976, Tokyo,Japan p.282.
GAMMA DECAY OF THE T = 3/2 STATES IN 25A1D.W.O. Rogers, N. Anyas-Weiss, S.P. Dolan, N.A. Jelleyand T.K. AlexanderCan. J. Phys. 55 (1977) 206.
- 47 -
MAGNETIC MOMENT IN N = 126 ISOTONES AND COREPOLARIZATION BLOCKINGI.S. Towner, F.C. Khanna and O. HausserNucl. Phys. A277 (1977) 285.
b) Lectures
BETA DELAYED PROTONS AND THE MEASUREMENT OF NUCLEARLIFETIMES IN THE REGION OF 10"16 SJ.C. Hardya seminar at GSI Darmstadt on 11 January 77.
SUPERALLOWED NUCLEAR BETA-DECAY: A NUCLEAR VIEW OF THEZ-VECTOR BOSON AND SYMMETRY RESTORATION IN HIGH ELECTRO-MAGNETIC FIELDSJ.C. Hardya colloquium at CERN, Geneva, Switzerland on 13 January 77.
BETA-DECAY STRENGTH FUNCTIONS : ON THE FRONTIERS OFPANDEMONIUMJ.C. Hardyat the Hirschegg International Workshop V, Hirschegg,Austria, 17-22 January 77.
ISOSPIN FORBIDDEN PARTICLE DECAYS IN LIGHT NUCLEI:EVIDENCE FOR ISOTENSOR MIXINGA.B. McDonalda seminar at the University of Toronto on 27 January 77.
The following two papers were presented at the XV WinterSchool on Nuclear Physics in Zakopane, Poland 6-19 February 77.
BETA DELAYED PROTONS, STRENGTH FUNCTIONS AND NUCLEAR LIFETIMEMEASUREMENTS IN THE REGION OF ÎO"1^ s.J.C. Hardy
SUPERALLOWED NUCLEAR BETA DECAY: A NUCLEAR VIEW OF THE ZVECTOR BOSON AND SYMMETRY RESTORATION IN HIGH ELECTROMAGNETICFIELDSJ.C. Hardy
LIFETIMES OF COMPOUND NUCLEI PRECEDING FISSION BYCRYSTAL BLOCKING TECHNIQUESJ.S. ForsterColloquia presented to McGill University (February 23)and Université de Montreal (February 24).
HOW DO NUCLEI SPIN?H.R. AndrewsLectures sponsored by CAP to the University of Ottawa (March 2)and Université de Montreal (March 3)
- 48 -
RECENT EXPERIMENTS AT CHALK RIVER USING HEAVY ION BEAMSFROM THE UPGRADED MP TANDEMJ.S. Forsterat Aarhus University, Aarhus, Denmark, 16 March 77.
THE EXCITED NUCLEUS AS A PROBE IN BEAM FOIL SPECTROSCOPYH.R. AndrewsSeminar presented to the University of Western Ontario23 March 77.
The following papers were presented at the XXVII NationalConference on Nuclear Spectroscopy and Structure of theAtomic Nucleus at Tashkent, USSR 22-25 March 1977
ACCURATE DSAM LIFETIME MEASUREMENTS OF THE 3.35 MeV4+ LEVEL IN 22NeJ.S. Forster, T.K. Alexander, G.C. Ball and W.G. Davies
GAMMA-RAY SPECTROSCOPY OF (HI,xnY) REACTIONS WITHDETECTION OF RECOILSD. Ward, H.R. Andrews, 0. Hausser, R.L. Graham, R.B. Walker,D. Horn, T. Faestermann, P. Skensved and J.R. Beene
THE USE OF EXOTIC HEAVY ION TRANSFER REACTIONS TO STUDYLIGHT n-EXCESS NUCLEIG.C. Ball, W.G. Davies, J.S. Forster, H.R. Andrews,W. McLatchie and R.E. Warner
3
3
3
3
3
3
3
3,
3,
3.
3.
3 .
3 .
3 .
3 .
3 .
3 .
3 .
3 .
3 .
. 1
. 2
. 3
. 4
. 5
.6
.7
.8
.9
.10
.11
,12
.13
,14
15
16
17
18
19
20
- 49 -
NEUTRON AND SOLID STATE PHYSICS BRANCH
A.D.B. WOODS
Staff
Amplitudes of Librational Motion in Plastic SF,
Phonon Dispersion Relation of Uranium Nitride Aboveand Below the Néel Temperature
Phonons in TiS,
Phonon Dispersion in fee CoQ 9 2F eo 08
Ferro-rotative Transition in K_OsClc
z o
Transverse Phonons in 1-Methylthymine (1-MT)
Phonon Dispersion in RbCoF3
Anisotropic Exchange in RbCoF,
Magnetic Structure of TbRhA
The Atomic Kinetic Energy in Liquid HeA
The Effective Pair Potential in Liquid HeThe Temperature Dependence of Positron Annihilationin Iron
N4 Thermal Neutron Facility
The Au y~ray Strength Function Below 9 MeV
The H(n,YY)D Experiment at NRU
238High Energy Alpha Decay in U
Improved Operation of the Compton Monochromator
Reactor Beam Hole Use
Supply and Servicing of Detector Systems
- 50 -
3.21 CdTe Crystal Growth
3.22 Glassblowing
3.23 Beta-neutrino Correlations from the Kinematic Shiftof Beta-delayed Particles
3.24 Assembly of the On-line Isotope Separator
3.25 Response of a -y—ray Spectrometer
3.26 Publications and Lectures
- 51 -
3.1 Staff
SECTION I
A.D.B. WoodsW.J.L. BuyersG. DollingT.M. HoldenS.M. KimP. MartelB.M. PowellE.C. Svensson
BRANCH HEAD: A.D.B. Woods
SOLID STATE PHYSICS TECHNICAL STAFF
R.S. CampbellH.F. NiemanM.M. PotterD.C. Tennant
SECTION II
J.W. KnowlesE.D. EarleS.T. Lim (1)M.A. Lone
NEUTRON NUCLEAR PHYSICS
W.M. InglisR.N. KingW.F. Mills
SECTION III
J.G.V. TaylorH. Schmeing
COUNTER DEVELOPMENT
M.A. GulickMs. M.M.L. RacicotW.F. SlaterR.J. Toone
GLASSBLOWING
J.G. Wesanko
WORKSHOPS
R.R. MacLandersH.C. Spenceley
A.H. Hewitt
DESIGN
W. McAlpinK. Tait (2)
SECRETARIAL STAFF
Mrs. Dianne Mitchell
(1) NRC Post-doctoral Fellow from University of BritishColumbia, Vancouver, B.C.
(2) Seconded from Design Engineering.
- 52 -
3.2 Amplitudes of Librational Motion in Plastic SFg
G. Dolling and B.M. Powell
We have previously reported (PR-P-112:3.3,
AECL-5696) an analysis of neutron powder diffraction
experiments on plastic SF,, just above the 95 K phase
transition, in terms of an expansion in cubic harmonics
of the neutron scattering cross section. Further diffrac-
tion measurements have now been made with the L3 spectro-
meter on different powder specimens, and analysis of these
results provides more precise estimates of the coefficients
of higher order harmonics, as follows: L = 4,6,8 coefficients
are 0.58 ± 0.02, 0.27 ± 0.02 and 0.26 ± 0.03 respectively;
the L = 10 coefficient was not significant, and the root-
mean-square translational displacement <u2>^ was found to
be 0.016 ± 0.001 nm. These results indicate a strong ten-
dency for the S-F bonds to align along [100] crystallographic
directions. If we assume that the (rigid) SFg molecules are
librating about such a [100] mean orientation, the diffraction
results may be reanalysed in terms of a rotational as well
as a translational Debye-Waller factor. The best least-squares
fit in this case is significantly poorer than for the cubic
harmonic analysis, but it suggests nevertheless a root-mean-
square librational amplitude of 12.7 ± 0.4 degrees away from
the [100] directions, in conjunction with a value
0.018 ± 0.001 nm for <u2>^.
3.3 Phonon Dispersion Relation of Uranium Nitride Above and
Below the Néel Temperature
G. Dolling, T.M. Holden, E.C. Svensson and W.J.L. Buyers
We have carried out a detailed neutron scatter-
ing study of the phonon dispersion relation in UN, above
- 53 -
and below T N = 53 K, using the C5 triple-axis spectrometer.
At 4.2 K, two acoustic and two optic branches
have been determined for each of the [001], [110] and [111]
directions. The optic mode measurements revealed (a) a 20%
variation in frequency across the Brillouin zone and (b) an
interesting disposition of the longitudinal (LO) and trans-
verse (TO) modes, such that vL_ > v T Q along [001] and [110],
while the reverse is true along the [111] direction. The
LO and TO modes appear to be degenerate near q = 0, indicating
either strong covalent effects or conduction electron screen-
ing of the ionic charges. Indeed, in the [001] direction
the LO branch rises sharply above the TO with increasing q,
in a manner reminiscent of the screening effects charac-
teristic of degenerate semiconductors. However, along [110]
the LO branch is almost q-independent for the first half of
the zone.
Certain selected normal modes were also studied
at 45 K, 57 K, 77 K and 293 K. Within the precision of our
measurements no significant changes were observed as a
function of temperature other than those arising from popu-
lation factor changes and a small stiffening of the lattice
as the temperature decreases. No definite evidence was
found for any influence of the magnetic structure and dynamics
on the vibrational properties. A number of constant-^ and
constant-E scans were made at 4.2 K and 293 K, over wide
ranges of Q and E (E up to 20 THz), but no scattering was
observed other than that attributable to phonons, in agree-
ment with our earlier measurements (PR-P-108:3.11, AECL-5315) .
3.4 Phonons in
B.M. Powell with J.L. Brebner (Université de Montréal)
and S. Jandl (Université de Sherbrooke)
Measurements of the low-frequency phonons propa-
gating along the [001] and [100] directions have been made
- 54 -
in the hexagonal layer compound TiS~. The TiS2 crystal
had a volume of -0.06 cms and the measurements were made
on the N5 and L3 spectrometers at 296 K. The observed
lattice parameters (a - 0.3415 nm, c = 0.5715 nm) showed
that the crystal is non-stoichiometric, and indicated that
the actual chemical composition is Ti. -Si o* M a n v °^ t n e
scattered-neutron distributions showed, in the frequency
range up to 3 THz, four intense well-defined peaks which
were tentatively interpreted as peaks in the density of
states seen through the incoherent cross section. It
will, however, be necessary to carry out Raman scattering
measurements in order to confirm this interpretation.
Other, much weaker, peaks were interpreted as coherent
scattering from the acoustic phonons belonging to the
[001]L and T branches and the low frequency [100]T franch.
From the limiting slopes of these dispersion curves the
elastic constants C,, and C.. were determined to be
48.6 ± 5.0 GN-m"2 and 16.8 ± 2.0 GN-m"2 respectively.
3.5 Phonon Dispersion in fee CoQ -^Fe» 0 8
E.C. Svensson, B.M. Powell and A.D.B. Woods
Further measurements (PR-P-112:3.6, AECL-5696)
of phonons in fee Co- «2Feo 08 n a v e keen carried out with
the N5 triple-axis crystal spectrometer. By means of the
constant-E technique, che [00c]L branch has now been deter-
mined up to v = 7.50 THz and the [ççO]T2 branch up to
v = 7.75 THz. By scaling and subtracting the incoherent
scattering observed in a constant-Q scan at the (113)
reciprocal-lattice point, where there is no coherent in-
elastic scattering, we have corrected the scattering
observed in constant-Q scans at (114), i.e. the fOOç]L
zone-boundary (Z.B.) position, and at (3/2,3/2,7/2),
i.e. the [ççç]L Z.B. position, for the distortion by the
- 55 -
high-frequency (v ~ 7.6 THz) density-of-states peak in the
incoherent scattering. This procedure has enabled us to
determine the [00c]L and [ççç]L zone-boundary frequencies
as 8.1 ± 0.4 and 8.1 ± 0.3 THz respectively.
Higher-resolution measurements have also been
carried out in order to determine the low frequency part
of the dispersion relation more accurately. The transverse
branches have been determined down to v < 1.5 THz, but few
reliable results have been obtained below v - 2.0 THz for
the longitudinal branches because the phonon scattering by
longitudinal modes in this region is badly distorted by the
raagnon scattering (R.N. Sinclair and B.N. Brockhouse,
Phys. Rev. 120, (1960) 1638, AECL-1114).
3.6 Ferro-rotative Transition in K_OsCl,
B.M. Powell and W.J.L. Buyers with D. Mintz and
R.L. Armstrong (University of Toronto)
Analysis of the elastic neutron scattering
measurements from potassium hexachloro-osmate (PR-P-111:3.5,
AECL-5614) has been continued. The crystal structure at
4.6 K has been determined for the first time and is described
by the parameters in the table. The comparison of the high-
and low-temperature structures shows that the crystal under-
goes a rotational phase transition. The structural change
occurs at 44.5 ± 0.4 K, leaves the cell dimensions unchanged
and corresponds to a collective in-phase rotation of rigid
OsClg octahedra. It is described as ferro-rotative in
analogy with similar transitions in ferromagnetic and ferro-
electric materials. The order parameter is the static
rotation angle of the octahedra about the cubic axis. The
temperature dependence of the rotation angle near T has
the form (Tc - T) p with an exponent, g = 0.35 ± 0.06, which
is characteristic of three-dimensional transitions.
1 ,.--.-. . .
- 56 -
Crystal Structure of K^OsClg at 4.6 K
Lattice parameter 0.969 ±0.002 nm
Rotation angle of OsClg 3.65° ±0.24°
Os-Cl bond length 0.2330 4 0.0012 nm
RMS librational amplitude of Cl 1.7° ±0.5°
RMS translational displacement of OsCl, 19 ±1 nmo
RMS translational displacement of K 19 ± 2 nm
3.7 Transverse Phonons in 1-Methylthymine (1-MT)
P. Martel and B.M. Powell
The observation of transverse acoustic phonons in
cytosine monohydrate (CMH) was reported previously
(PR-P-112:3.7, AECL-5696). These transverse modes propagate
in the molecular planes, perpendicular to the diad axis,
and their frequencies are determined principally by the
intraplanar hydrogen bonds. Measurements of the correspond-
ing transverse acoustic branch in 1-MT, which could not be
observed in the previous experimental configuration
(PP-P-106:3.5, AECL-5226), have been carried out at the L3
spectrometer on a newly grown crystal. In CMH this branch
showed little dispersion, but in 1-MT considerable upward
curvature has been observed. The frequency at the zone
boundary is 0.98±0.04 THz. The observed frequencies have
been fitted to an expression containing terms linear and
quadratic in wave vector. A good fit is obtained and, from
the limiting slope at the zone centre, the effective elastic
constant is found to be 0.48 ± 0.05 GN-m . In CMH the
corresponding value is 3.0 ± 0.5 GN-m . Lattice dynamical cal-
culations are being carried out to determine if the water
molecule in CMH is responsible for this large difference in
the effective elastic constants.
- 57 -
3.8 Phonon Dispersion in RbCoF.
E.C. Svensson, T.M. Holden and W.J.L. Buyers
A study of phonon excitations in RbCoF- at
T = 296 K is being carried out with the C5 triple-axis
spectrometer. The aim is to study those phonons which in-
teract with the magnons (PR-P-104:3.4, AECL-5032) or which
can affect the interpretation of the magnon scattering.
Several phonon branches in the range 1 < v < 7 THz have
been determined for each of the [OOç], [ççO] and [çççj
symmetry directions, and also along zone boundaries where,
at 4.2 K, strong interactions with the magnons were ob-
served .
3.9 Anisotropic Exchange in RbCoF3
T.M. Holden, W.J.L. Buyers and E.C. Svensson
For ions such as Co that possess orbital angular
momentum, Copland and Levy (Phys. Rev. Bl (1970) 3043) have
suggested an effective exchange nantiltonian which contains,
in addition to isotropic exchange, anisotropic terms that
depend on the orbital states of the interacting ions. This
model, with an anisotropic exchange which is 43% of the iso-
tropic exchange, gives a better overall description of the
RbCoF3 spin waves (PR-P-104.-3.4, AECL-5032) than does a
purely isotropic model (PR-P-105:3.7, AECL-5121) but the
Davydov splitting of the longitudinal modes and the band-
width of the second transverse (S+) branch are still seriously
overestimated. We conclude that anisotropic effects of this
type, although large, are not sufficiently general to give a
completely satisfactory description of the spin waves in this
material. The possibility that the magnon frequencies are
affected by as yet unobserved phonons is currently being in-
vestigated (section 3.8 of this report).
- 58 -
3.10 Magnetic Structure of TbRh
T.M. Holden and H. Nieman with R. Chamard-Bois
(Université Jean-Bedel Borassa, Bangui, République
Centre-Africaine)
TbRh is a ferromagnetic compound (T = 19 K)
with the CsCl structure at T = 296 K. Powder diffraction
measurements were made at 296, 77 and 4.2 K with the object
of determining the magnetic structure and the magnitude
of the magnetic moments on the Tb and Rh sites. The
measurements were made with the C4 spectrometer operated
as a twin-axis diffractometer with an incident wavelength
of 0.1176 ran from the (331) planes of a Ge monochromator.
At 296 and 77 K TbRh was found to have the CsCl structure
and the Debye-Wallsr factors measured at the two tempera-
tures were consistent with the Debye temperature, 245 K,
deduced from specific heat measurements. At 4.2 K the
Bragg peak positions were found, unexpectedly, to be in-
consistent with the CsCl structure and extra weak lines
appeared in the diffraction pattern. Present efforts are
directed to finding the new crystal structure as a pre-
liminary to determining the magnetic structure.
A
3.11 The Atomic Kinetic Energy in Liquid He
A.D.B. Woods
Previously published measurements of the
scattered-neutron energy distributions for liquid He
(PR-P-76:4.6, AECL-3009, and R.A. Cowley and A.D.B. Woods,
Can. J. Phys. 4£ (1971) 177, AECL-375S) have been re-
analysed by treating the zeroeth and first frequency
moments of the dynamic structure factor, S(Q,u), as con-
straints which must be satisfied. The resultant
resolution-broadened S(Q,u>), for 60 nm < Q < 80 nm ,
- 59 -
were used to derive values of the average kinetic energies
of the helium atoms with the aid of the high-Q limits of
the expressions for other frequency moments (V.F. Sears,
PR-P-113:4.4, AECL-5802). The average kinetic energy was
found to be 13.5 ± 1.2 K at 1.1 K and 14.1 ± 1.0 K at 4.2 K.
While these results are reasonably close to theoretical and
previous, less direct, experimental estimates the difference
between the values at 1.1 K and 4.2 K is less than expected.
The increase in the kinetic energy arising from the in-
creased temperature is presumably compensated by a decrease
in the zero-point contribution to the kinetic energy arising
from the increased volume/atom as the temperature is raised.
4
3.12 The Effective Pair Potential in Liquid He
V.F. Sears (Theoretical Physics Branch) with A.D.B. Woods,
E.C. Svensson and P. Martel
See PR-P-113:4.3 .
3.13 The Temperature Dependence of Positron Annihilation in Iron
S.M. Kim
Measurements of the temperature dependence of peak
coincidence rate in iron (PR-P-112:3.12, AECL-5696) are
continuing in order to improve the statistical accuracy of
the results and to understand the cause of an apparent
specimen-history dependence of the peak coincidence rate
in y-Phase iron (T > 910°C).
3.14 N4 Thermal Neutron Facility
M.A. Lone and W.M. Inglis
In order to optimize the thickness of the Y~ray
attenuator, the spectral distributions of the y~rays from
- 60 -
the N4 through tube in the thermal column at NRU were
measured with a Ge(Li) detector. In addition to the
resolved y-ray peaks from C (graphite reflector at the
centre of the tube), Fe (collimator walls) and Nj (air),
a relatively strong continuum extending to 9 MeV was
observed.
From the intensity of the C y-rays, the neutron
flux at the centre of the beam tube was calculated and
found to be consistent with the earlier measurements
(PR-P-111-.3.19, AECL-5614) of 10 1 3 n-cm"2^"1 made with
In and Cu foil activation.
Installation of the beam tube and collimators
is in progress.
1983.15 The Au Y-ray Strength Function Below 9 MeV
E.D. Earle with I. Bergqvist (University of Lund, Sweden)
and L. Nilsson (Tandem Accel. Lab., Uppsala, Sweden)
The y-ray spectra following capture of 0.03,
0.56, 1.2, 1.5, 2.0 and 2.5 MeV neutrons in Au
(PR-P-104:3.12, AECL-5032) have been fitted to intensity
distributions derived from a single y-ray strength func-
tion according to the spectrum fitting method described by
Bartholomew et al. (Advances in Nuclear Physics, eds.
M. Baranger and E.W. Vogt (Plenum Press, New York, 1973)
Vol. 7, p. 229, AECL-5729).
The shape of the y-ray spectra at various
neutron energies can be described by the statistical model.
A y-ray strength function was found which gives calculated
spectra in good agreement with all measured spectra.
However, the Lorentz line shape which is frequently used
to fit the experimental Y-ray absorption cross section
- 61 -
in the giant dipole resonance region does not provide an
appropriate description of the average strength in gold
at lower y-ray energies. The observed strength is signi-
ficantly lower than that estimated from the Lorentzian
tail and furthermore does not decrease monotonically with198
decreasing y-ray energy. However, the Au strength197function is consistent in magnitude with that for Au
above 8 MeV as deduced from (y,n) measurements by
Veyssière et al. (Nucl. Phys. A159_ (1970) 561).
3.16 The H(n,yy)D Experiment at NRU
E.D. Earle and S.T. Lim with A.B. McDonald (Nuclear
Physics Branch)
Preparation of the C4 experimental area for an
attempt to reduce the uncertainty in the H(n,yy)D cross
section (PR-P-112:3.13, AECL-5696) is in progress. The
neutron flux has been increased by more than an order of
magnitude by inserting a graphite scatterer in the reactor
through tube, by realigning the exit channel and by in-
creasing the acceptance angle seen by the target. The
neutron background in the vicinity of the Nal detectors
has been significantly reduced by the systematic placement
of boron-loaded wax and LiF.
Tests with the Nal detectors have demonstrated
that good time resolution (1.6 ns FWHM per detector) can
be obtained and that modified photomultiplier bases can
handle the high counting rate. Presses to make a LiD
flight tube have been constructed. The PDP-8 data
acquisition system has been installed and is being tested.
- 62 -
2 o g3.17 High Energy Alpha Decay in U
S.T. Lim, J.W. Knowles and E.D. Earle
Recent measurements (E. Wolynec et al., Phys.
Rev. Lett. 37 (1976) 585) of the production rate of J Th— 238
following the irradiation of U with 10-25 MeV electronsindicate an enhancement in the cross section for the238
U(e,e'a) reaction near 9 MeV excitation. This result
was interpreted as an indication of E2 strength at this
energy.We have attempted to excite this resonance with
9.0 MeV y~raYs an<3 to observe the 13 MeV ct-particles which238 234
should follow from the reaction U(y,a) Th. For this
purpose we used the 9.0 MeV y-r&ys from a nickel source
located in the Cl through tube in the thermal column of
the NRU reactor. These y-rays were incident on a 500 ug/cm
target of UF. placed inside a multiwire gas counter. A2
4 mg/cm aluminum foil placed between the target and the
counter gas completely absorbed the fission particles and
the 4 MeV a-particles from spontaneous decay and the fission
particles from the (y,f) reaction. With this arrangement
we measured a pulse-height distribution of events in the
gas counter, which we interpreted as arising from highly
penetrating a-particles of energy >8 MeV. The observed
counting rate corresponds to a (y,a) cross section of about2
4 mb (0.4 fm ) in agreement with the photo-cross section
calculated from results of the U(e,e'a) Th measurement.
We plan to carry out energy and angular distri-
bution measurements of these penetrating particles using
solid-state charged-particle detectors.
- 63 -
3.18 Improved Operation of the Compton Monochromator
J.W. Knowles, S.T. Lim, W.F. Mills and M.A. Lone
The background in the vicinity of the target
caused by stray radiation transmitted by the scattering
chamber of the Compton monochromator at hole C-l, NRU,
has been reduced by a factor of 5 by increasing the
thickness of the lead shielding wall of the scattering
chamber from 5 to 10 cm.
3.19 Reactor Beam Hole Use
A.D.B. Woods
The McMaster University double-monochromator
triple-axis spectrometer and the Guelph University
spectrometer were in operation during the period. The
N5 spectrometer was out of commission for about two
months for the installation of new shielding.
The following table summarizes utilization of
operating CRNL facilities at NRU beam holes.
Beam Hole No. of No. of No. of EfficiencyExperiments Participating Participating (% of available
CRNL non-CRNL reactor operatingscientists scientists time used for
experiments)
Cl
C2
C4
C5
L3
N5
3
1
2
2
3
4
4
1
3
4
3
4
0
0
1
0
0
4
98%
75%
99%
90%
95%
30%
Total reactor operating time was 76 days.
- 64 -
3.20 Supply and Servicing of Detector Systems
R.J. Toone, W.F. Slater, M.M.L. Racicot and M.A. Gulick
Tests on the second double high-purity Ge detector
system for Reactor Control Branch (PR-P-111:3.25, AECL-5614)
were completed and the system has been delivered.
A "windowless" high-purity Ge diode (PR-P-106:3.21,
AECL-5226) was successfully restored by washing it in Freon
to remove a surface layer of vacuum-pump oil. This system
will be used by personnel of Section II of this Branch in
photofission experiments at the University of Illinois.
A Pickering-type feeder-scanner detector system
(PR-P-98:3.17, AECL-4595) from Reactor Control Branch was
repumped to prepare it for use in neutron nuclear physics
experiments at NRU.
A cryostat was repumped for Chemical Engineering
Branch.
Five BP-9D counters were supplied to Section II
of this Branch.
3.21 CdTe Crystal Growth
H. Schmeing, R.J. Toone, W.F. Slater, M.M.L. Racicot,
R.R. MacLanders and J.G.V. Taylor
The period under review has been devoted to
expansion and further improvements in the CdTe crystal-
growing systems.
It is known that even very low-level vibrations
may limit the size and quality of solution-grown single
crystals. Recent measurements have shown that the concrete
pier supporting the CdTe crystal-growing furnaces is not as
vibration-free as had been assumed. Consequently a new
furnace mount consisting of a heavy base plate supporting
- 65 -
the rigid furnace assemblies has been designed and built.
This base plate rests on a softly inflated inner tube that
in turn lies on the concrete pier. Two identical furnaces
are counterbalanced on opposite sides of the base plate.
The second (new) furnace will provide a second slow-cooling
crystal-growing station. A load of lead bricks (currently
70 kg), adjusted to give accurate leveling, helps to reduce
the natural oscillation frequency of the system to <1 Hz.
While the new mount was being assembled, all cabling and
water lines were relocated to minimize vibration trans-
mission and the risk of accidental disturbances. We esti-
mate that the level of vibrations has been reduced by at
least an order of magnitude. Crystal growth has been
resumed.
In order to increase the temperature gradient in
crystals grown by the travelling heater method a new furnace,
basically similar to our previous furnace (PR-P-112:3.21,
AECL-5696), has been designed and built. The principal modi-
fication consisted of a new arrangement of thermal-insulation
that was developed after extensive tests with commercially
available insulating material. This new arrangement consists
of layers, 1 mm thick, of ceramic paper separated by heat-
reflecting platinum foils, 2 ym thick. The furnace is now
ready for testing. Compared to the earlier model this fur-
nace is expected to maintain a substantially higher tempera-
ture gradient perpendicular to the layers (i.e. parallel to
the axis of the ampoule). In addition, the temperature
stability should be improved and the heat losses reduced.
3.22 Glassblowing
J.G. Wesanko and M.A. Gulick
A i m water-jacketed column for hydrogen-water
exchange catalyst lifetime studies was constructed for
Physical Chemistry Branch. Glass apparatus has been
- 66 -
supplied to Health Physics Branch for tritium-in-air
monitors to be used at Bruce and Pickering. A three-metre
long tube for a 30-watt continuous-wave CO^ laser has been
constructed and installed, together with a gas-flow-control
system, for Physical Chemistry Branch. Numerous small
pieces of glass and quartz apparatus have been made for
various branches.
3.23 Beta-neutrino Correlations from the Kinematic Shift of
Beta-delaved Particles
H. Schmeing et al.
See PR-P-113:2.14 .
3.24 Assembly of the On-line Isotope Separator
H. Schmeing et al.
See PR-P-113:2.22 .
3.25 Response of a y-ray Spectrometer
M.A. Lone et al.
See PR-P-113:4.11 .
3.26 Publications and Lectures
Publications
A NEW DETERMINATION OF THE ROTON ENERGY IN SUPERFLUIDLIQUID HELIUMA.D.B. Woods, P.A. Hilton, R. Scherm and W.G. StirlingJ. Phys. C 1£ (1977) L45Atomic Energy of Canada Limited publication AECL-5642
- 67 -
MAGNETIC MOMENTS AND HALF-LIVES OF ISOMERIC STATES INPOLONIUM ISOTOPESO. Hausser, T.K. Alexander, J.R. Beene, E.D. Earle,A.B. McDonald, F.C. Khanna and I.S. TownerNucl. Phys. A 273 (1976) 253Atomic Energy of Canada Limited publication AECL-5581
MEASUREMENTS OF ACCURATE g-FACTORS IN TRANSLEAD NUCLEIWITH HEAVY-ION INDUCED REACTIONSO. Hausser, T.K. Alexander, J.R. Beene, E.D. Earle,A.B. McDonald, F.C. Khanna and I.S. TownerHyperfine Interactions 2_ (1976) 334Atomic Energy of Canada Limited publication AECL-5372
DOUBLY RADIATIVE NEUTRON CAPTURE BY 2H, 3He, 1 6O AND 2 0 8PbH.C. Lee, F.C. Khanna, M.A. Lone and A.B. McDonaldPhys. Lett. 6_5B (1976) 201Atomic Energy of Canada Limited publication AECL-5593
THE CHALK RIVER HELIUM JET AND SKIMMER SYSTEMH. Schmeing, V. Koslowsky» M. Wightman, J.C. Hardy,J.A. Macdonald, T. Faestermann, H.R. Andrews, J.S. Geigerand R.L. GrahamNucl. Instr. and Meths. 139_ (1976) 335Atomic Energy of Canada Limited publication AECL-5596
A FAST TAPE TRANSPORT SYSTEM FOR USE WITH ON-LINE SEPARATORSJ.A. Macdonald, J.C. Hardy, H. Schmeing, N.C. Bray,W. Perry, R.B. Walker and M. WightmanNucl. Instr. and Meths. 139 (1976) 355Atomic Energy of Canada Limited publication AECL-5595
CONSTRUCTION OF A THREE-COMPARTMENT CELL TO STUDY THEELECTROLYTIC HYDROGEN-DEUTERIUM SEPARATION FACTORJ.G. WesankoProceedings - The Twenty-first Symposium on the Art ofGlassblowing, (The American Scientific GlassblowersSociety, Wilmington, 1976) p. 44
- 68 -
Lectures
MAGNETIC NEUTRON SCATTERING: SPIN WAVES AND IMPURITYEFFECTS, PERCOLATION PHENOMENA, AND THE EXCITATIONS OFSMALL CLUSTERSE.C. SvenssonNational Research Council, Ottawa, OntarioJanuary 19, 1977
THE DYNAMIC STRUCTURE OF LIQUID 4HeE.C. SvenssonNational Research Council, Ottawa, OntarioJanuary 20, 1977
MAGNETIC NEUTRON SCATTERING: SPIN WAVES AND IMPURITYEFFECTS, PERCOLATION PHENOMENA, AND THE EXCITATIONS OFSMALL CLUSTERSE.C. SvenssonClarkson College of Technology, Potsdam, New YorkJanuary 21, 1977
STRUCTURE OF 1-METHYLTHYMINE DIMERS BY MONOCHROMATIC(254 nm) AND SOLAR IRRADIATIONP. Martel and B.M. PowellBiophysical Society Annual Meeting, New OrleansFebruary 15-18, 1977
ORIENTATIONAL STRUCTURE OF PLASTIC SFG. Dolling and B.M. PowellA.P.S. Meeting, San Diego, CaliforniaMarch 21-24, 1977
OBSERVATION OF QUASI-FREE pn SCATTERING IN CARBONAT TRIUMFA.J. James, W.J. McDonald, J.M. Cameron, P. Kitching,C.A. Miller, D.A. Hutcheon, G.C. Neilson, W.C. Olsen,J.T. Sample, A.W. Stetz, G.M. Stinson and E.D. EarleBritish Institute of Physics Conference on NuclearPhysics, Guildford, Surrey, U.K.March 23-25, 1977
NEUTRON YIELDS FROM 7Li(^,n) AND 9Be(!?,n) REACTIONS vM.A. Lone p p
International Specialists Symposium on Neutron Standardsand Applications, N.B.S., Gaithersburg, MarylandMarch 28-31, 1977
- 69 -
THEORETICAL PHYSICS BRANCH
G.E. Lee-Whiting
4.1 Staff
4.2 Neutron Calculations for a Fusion-Reactor Blanket
4.3 The Effective Pair Potential in Liquid 4He
4.4 The Atomic Kinetic Energy in Liquid He
4.5 Elementary Excitations in Liquid He
4.6 Charge-State Fluctuations in Electronic Stopping
4.7 Penetration of Heavy Jons in Solids
4.8 Collective Renormalization in the Spherical Shell Model
4.9 Exchange Currents and the Quenching of the Gamow-Teller Operator
4.10 g-Factors in 94Ru, 91Mo and 90Nb
4.11 Response of a Y-Ray Spectrometer
4.12 Electromagnetic Fields in the Nucleus and the Salam-Strathdee Phase Transition
4.13 Reports, Publications, and Lectures
- 70 -
4.1 Staff
Branch Head:
M.F.C.S.A.H.C.V.F.I.S.
G.E. Lee-
HarveyKhannaKushneriukLeeSearsTowner
K.B. Winterbon
Secretarial Staff
M.E. Carey
- 71 -
4.2 Neutron Calculations for a Fusion-Reactor Blanket
S.A. Kushneriuk with P.Y. Wong (Math. & Computation Branch)
The extensions mentioned in PR-P-110:4.2
(AECL-5546) of the neutronics calculations to systems
(natural uranium and lithium metal assemblies) for which
experimental data on neutron activations and multiplication
are available have been completed. A report summarizing
the results of our calculations on fusion reactor blankets
to date, giving the comparisons made with measured values
as well as the calculated results obtained at other labora-
tories, has been written.
Preparations are now underway for the neutronics
evaluations of fusion-reactor blankets that contain thorium
and uranium metal, as well as lithium and the associated
coolant and structural materials. The purpose is to assess
the system potential for the combined breeding of fissileoil jiq
materials r J J u and/or Pu) and tritium.
4.3 The Effective Pair Potential in Liquid He
V.F. Sears with A.D.B. Woods, E.C. Svensson, and P. Martel
(N.S.S.P. Branch)
We have shown that the iterative method pro-
posed by Rahman (Phys. Rev. A 11^ 2191 (1975)) for the direct
determination of the effective pair potential, <b(r), in a
monatomic liquid from neutron-inelastic-scattering data is
equivalent to solving the integral equation
with the conditions
<|>'(r) = - /" f (r')dr1, * (r) = - / f (r')dr1.r r
72 -
The inhomogeneous term, <f>j!(r), is determined by the low-
order frequency moments of the dynamic structure factor,
S(Q,a>), and the kernel, K(r,r'), by the pair correlation
function, g(r).
The above integral equation has been solved
by numerical iteration for liquid He at T = 4.2 K with the
help of neutron data for S(Q,u>) and X-ray results for g(r).
We find that the shape of $(r) differs radically from that
expected for the potential of an isolated pair of He atoms
by having a double minimum and being positive at large r.
After excluding the possibility that the unusual qualitative
behaviour of 4> (r) might be due to some error in the data
analysis or in the theoretical assumptions, we are led to
attribute it to the effect of many-body interactions in the
liquid. We conclude that these interactions are either
larger than previously estimated or else their effect on the
effective potential is somehow greatly enhanced.
4.4 The Atomic Kinetic Energy in Liquid He
V.F. Sears
We have shown that the average kinetic energy
per atom in a monatomic liquid with velocity-independent
interatomic forces can be expressed rigorously in the form
<KE> - li. S H J J { - 5 £ _ - .J. I.- 1.2.3....)
where <ojn> denotes the n-th frequency moment of the dynamic
structure factor, S(Q,w), and "fiw = ("RQ) /2m is the average
recoil energy of an atom of mass m.
The use of the above expression to determine
<KE> from neutron-scattering data for S(Q,u) at large Q has
- 73 -
a number of advantages over the conventional method of fit-
ting a theoretical model for S(Q,to) to the data:
- The value obtained for <KE> is model-independent.
- The redundancy with respect to n provides a useful check
on the consistency of the data and also allows one to
obtain a good estimate of the accuracy of the result.
- The quantities <un>, unlike S(Q,o>) itself, can be correc-
ted for effects of instrumental resolution in a particu-
larly simple way.
- The value obtained for <KE> is independent of the normali-
zation of the neutron-scattering data.
The above method has been applied to liquid
He at temperatures above and below the A-point and the
results are described in PR-P-113:3.11 (AECL-5802).
4.5 Elementary Excitations in Liquid He
P.C. Khanna with H.R. Glyde (University of Ottawa)
Recent studies with a phenomenological extension
of the Landau theory of Fermi liquids to finite momentum
transfers, finite energy transfers and finite temperature
(T) indicate that a well-defined zero-sound mode exists in
liquid 3He at T = 15 mK but not at T = 0.63K. At present we
are attempting a completely microscopic calculation, starting
with a bare two-body interaction (say Lennard-Jones potential),
in order to seek a justification of the phenomenological
description. A computer program (PR-P-111:4.3 (AECL-5614))
that calculates two-body ^-matrix elements is being utilized
to investigate excitations in liquid He within the Random-
Phase approximation. Also, a computer program is being set
up to calculate the width of the zero-sound mode in pertur-
bation theory.
•* 74
4.6 Charge-State Fluctuations in Electronic Stopping
K.B. Winterbon
This work has been written up and submitted
to Nuclear Instruments and Methods for publication.
4.7 Penetration of Heavy Ions in Solids
K.B. Winterbon
Exact calculation of path-length distributions
(PR-P-112:4.5 (AECL-5696)) is continuing. A draft of the
equal-mass work has been written. The unequal-mass version
of the program appears to be correct now; this work is also
being prepared for publication.
Calculations for distributions in a non-uniform
medium (PR-P-112:4.5 (AECL-5696)) have been started. One
obtains for the moments a two-variable difference equation.
This has been solved analytically for positive integer
values of the first variable, and arbitrary positive values
of the second; a formal solution has been obtained for
general values of the first variable. It has not yet been
possible to relate the two solutions, nor to extend the
first solution to negative integer values of the argument.
However, the positive integer values correspond to the usual
moments, and these are being used to try to reproduce the
distribution. The distribution has in general an unknown
step discontinuity where the target changes, and this causes
some difficulty.
Doppler shift attenuation (DSA) measurements
for one reaction in several backings, giving F ( T ) values,
(M. Toulemonde and F. Haas, Phys. Rev. C L5, 49 (1977)),
and a heavy-ion DSA measurement by Forster et al. (PR-P-113:
2.10 (AECL-5802)) giving a lifetime for the 3.34 MeV state of
- 75 -
00 22
Ne, have been used to deduce stopping powers for Ne in
15 backings. The results differ by factors of ^1-3 from
the Lindhard-Scharff values; although they bear some resem-
blance to the stopping powers calculated by Latta and
Scanlon (Phys. Rev. A L3, 1370 (1976)), there is no overall
agreement.
4.8 Collective Renormalization in the Spherical Shell Model
M. Harvey and I.S. Towner
The renormalization of the nuclear spherical
shell model for collective motion, which had previously
been formulated in terms of transition fields (PR-P-108:4.6
(AECL-5315)) has been reformulated in terms of transition
densities. We can now show that the summation of the set
of perturbation terms found to be important in a schematic
model (M. Harvey, Ann. Phys. 9£, 47 (1975)) is equivalent
to the iterative solution of a set of equations defining
the transition densities. As long as we work in the
Hartree-Fock representation for the shell-model core, the
instabilities in the iterative solutions which plagued our
earlier calculations do not appear. A computer program has
been written which calculates the transition densities in
the open-shell random-phase approximation (RPA) with polari-
zation of both the core and valence orbitals taken into
account. In the case of A=17 we find the enhancements to
the quadrupole matrix elements to be smaller than required
by experiment, in agreement with other calculations and our
understanding (from the schematic model) of the role of RPA
in collective renormalization. We are at present including
in the program higher-order terms which should increase the
quadrupole enhancements.
- 76 -
4.9 Exchange Currents and the Quenching of the Gamow-Teller Operator
I.S.Towner, H.C. Lee and F.C. Khanna
The study of meson-exchange-current effects
(PR-P-112:4.10 (AECL-5696)) is being extended to investigate
systematically the effect on the Gamow-Teller (G-T) operator.
Initially the study will be restricted to closed shell-plus
(minus)-one nuclei and to one-pion exchange processes. By
summing explicitly over core orbits the two-body meson-
exchange current operator can be replaced by an equivalent
one-body operator parameterised as: g L + g o + g [Y- xol +
gT_[L x or]. For the GT operator g_ is zero. The term in gT_
represents a non-hermitian component, which is zero in closed-
shell-plus (minus) -one nuclei but can be non-zero in other
situations. Our aim is to study systematically the effective
axial-vector coupling constant, g.., and to examine the sugges-
tion (M. Rho, Nucl. Phys. A 231^, 493 (1974)) that gft will be
progressively quenched, i.e. g •*• 1, for heavy nuclei, andA
that in the case of infinite nuclear matter g^ = l.
QA qi an
4.10 g-factors in aftRu, Mo and Nb
0. Hausser, T. Faestermann, D. Ward, T.K. Alexander,
H.R. Andrews, D. Horn with I.S. Towner (Theoretical Physics Branch)
See PR-P-113:2.4 (AECL-5802).
4.11 Response of a y~Ray Spectrometer
H.C. Lee with M.A. Lone (N.S.S.P. Branch)
A Monte Carlo computer code (PR-P-106:4.9 (AECL-
5226)) is being modified and expanded for the purpose of esti-
mating the characteristics of a "y-ray spectrometer based on
coincidences between the pulses generated by the Y~rays in
one detector and those generated by backward scattered y-rays
in a second detector placed annularly about the incident beam.
- 77 -
4.12 Electromagnetic Fields in the Nucleus and the Salam-Strathdee
Phase Transition
H.C. Lee and F.C. Khanna
In continuation of an earlier study (PR-P-107:4.8
' (AECL-5256)) the invariant electromagnetic field strength,
3'= B - E /c , inside members of the baryon octet and inside the
nucleus have been calculated. For the baryons the static quark
model was used, and for the structure of the nucleus the single-
particle shell model was used. The results are relevant to the
Salam-Strathdee (A. Salam and J. Strathdee, Nature, 252, 569
(1974)) phase transition in connection with the possible vanish-
ing of the Cabibbo angle, 8 , in the weak interaction.
Studies on several nuclei (ignoring the internal
structure of the nucléon) across the periodic table indicate
that only in a very small region near the centre of the nucleus
(r £ 0.4 fm, but usually <<0.4 fm) is the quantity &(r) small
and positive. Near the surface of the nucleus &(r) is large and
negative. Inside charged baryons 5^(r) is large and positive
over a relatively much larger region of space, while inside neu-
tral baryons 3>(r) is positive everywhere.
In the theory of Salam and Strathdee a normal
value for 31 is such that it will not cause 6 to deviate from
its normal value (^15°). In order to delineate a range of normal
values f o r ^ the field inside a nucléon (A-particle) within a
weak-decaying nucleus (hypernucleus) was calculated. Combining
the present results and data on superallowed B-decays it has
been concluded that the minimal region of normalcy for & is
-5 x 10 2 4 <# £ 30 x io 2 4 Tesla2.
Very interestingly, the values of 3" for almost all A-hyper-
nuclei are outside this normal region.
- 78 -
4.13 Reports, Publications, and Lectures
Publications
TRANSVERSE SPREADING OF IMPLANTED-ION COLLISION CASCADESK.B. WinterbonRad. Effects 30(1976)75
NEUTRON SCATTERING FROM LIQUID 3HeH.R. Glyde and F.C. KhannaPhys. Rev. Lett. 37(1976)1692
MAGNETIC MOMENTS IN N=126 ISOTONES AND CORE POLARISATION BLOCKINGI.S. Towner, F.C. Khanna and O. HausserNucl. Phys. A277(1977)285
DOUBLY RADIATIVE NEUTRON CAPTURE BY 2H, 3He, 1 6O and 2 0 8PbH.C. Lee, F.C. Khanna, M.A. Lone and A.B. McDonaldPhys. Lett. 65B(1976)201
MEASUREMENT OF ACCURATE g-FACTORS IN TRANSLEAD NUCLEI WITHHEAVY ION INDUCED REACTIONSO. Hausser, T.K. Alexander, J.R. Beene, E.D. Earle, A.B. McDonald,F.C. Khanna and I.S. TownerHyperfine Interactions 2(1976)334
MAGNETIC MOMENTS AND HALF-LIVES OF ISOMERIC STATES INPOLONIUM ISOTOPESO. Hausser, T.K. Alexander, J.R. Beene, E.D. Earle, A.B. McDonald,F.C. Khanna and I.S. TownerNucl. Phys. A273(1976)253
Lectures
EXCITATIONS IN NORMAL LIQUID 3HeH.R. Glyde and F.C. KhannaInt. Symp. on Quantum Fluids and Solids, Sanibel Island, Florida,Jan. 24-27, 1977
COLLECTIVE RENORMALIZATION IN THE SPHERICAL SHELL MODELM. Harveygiven at Univ. of Minnesota and Univ. of Iowa, March 2 and 4, 1977
NEUTRAL CURRENT EXPERIMENT WITH REACTOR ANTINEUTRINOSH.C. Leegiven at McGill University, January 20, 1977
ESTIMATION OF THE PROPERTIES OF NUCLEAR EXCITED STATES WITHSIMPLE COLLECTIVE CRITERIAM. -Harveygiven at Michigan State University, January 6, 1977
THE EFFECTIVE PAIR POTENTIAL IN LIQUID 4HeV.F. Sears, A.D.B. Woods, E.C. Svensson and P. MartelCAP Congress, Univ. of Saskatchewan, March 11, 1977
- 79 -
MATHEMATICS AND COMPUTATION BRANCH
D. McPherson
5.1 Staff
5.2 CDC CYBER 170/6600 System
5.3 CDC 3300 System
5.4 DECsystem-10
5.5 Superconducting Cyclotron/MP Tandem AcceleratorControl System
5.6 Analysis of Acoustic Phenomena in a System ofSteam Mains
5.7 Inertial Analysis of the Gentilly-1 ModifiedSteam Mains Network
5.8 The Wigner Solid
5.9 Integration
5.10 Stress Analysis Programs
5.11 Statistical Analysis of Slotted Burst Tests OnCold-Worked Zr-2.5 wt % Nb Pressure Tubes
5.12 Information Handling Programs
5.13 Neutron Calculations for a Fusion-ReactorBlanket
5.14 Miscellaneous Programs and Subroutines
5.15 Operations
5.16 Publications, Reports and Lectures
~ 80
5.1 Staff
Branch Head: D. McPherson
Section I; Systems
Head:D. McPherson
Programmer/Analysts :J.A. EdgecombeL.D.J. HansenJ.F. SteljesC.J. Tanner
Programmer :Mrs. E.A. Okazaki
System Librarian:Mrs. K.M. Haddon
Section II: Operations
Head:G.N. Williams
Programmer/Analyst :B.B. Ostrom
Programmer:C D . Price
Operator Supervisor:Mrs. V.L. Tomlinson
Section III: MathematicalServices and Applications
Head:J.M. Blair
Mathematical Analysts:G.H. KeechW.N. Selander
Programmer/Analysts:M.B. CarverMrs. L.E. EvansP.Y. Wong
Programmers :K.R. ChaplinMiss P.A. ChristieE.G. LongMrs. B.E. PurcellB.V RiffD.G. Stewart
Secretarial Staff
Mrs. K.F. Barnard
(3)
Computer Operators:Miss K.M. BjarboMrs. M.H. Burke (1)Mrs.MissMrs.Mrs.Mrs.Mrs.Mrs.
L.P.M.E.CM.A.A.E.S.
L. CybulskiEdwardsHepburnLarocheMorin (2
T. SpearL.J. Sutton
Mrs. N.M. Ward
(1) Joined Branch 11 February 1977(2) Transferred to General Services Division 14 February
1977(3) Waterloo co-op student; joined Branch 3 January 1977
- 81 -
5.2 CDC CYBER 170/6600 System
(i) Operating System - General
D. McPherson and C.J. Tanner
A number of minor improvements and modifications to
eliminate inconsistencies or to correct errors have been made
to the operating system. Chief amongst these was the ident-
ification and modification of critically-timed instruction
sequences in the 6638 disc driver so that the CYBER 170
peripheral processor system can now operate at its full speed
with a 500 nanosecond cycle time. (This work was carried out
by W.J. Irving and M. Montaigne of Control Data Canada, Ltd.)
The accounting formulae used for the CYBER 170 and
6600 have been re-normalized to reflect both the changes in
the CRNL system and changes in the rate structure of equivalent
commercial systems by N. Abush of Power Projects. The revised
accounting formulae will be used for assigning resource
utilization costs after 1 April.
The design of a job scheduling system whose principal
function is to select the most appropriate mix of jobs for
concurrent execution has begun. This system will incorporate
the recipes that evolved through experience with earlier ver-
sions of the 6600 operating system, expanded to recognize the
existence of two computers with quite different central pro-
cessor to input/output speed ratios.
(ii) FORTRAN Compiler
M.B. Carver and D.G. Stewart
Extensive testing of the field length management
version of the FORTRAN compiler (see PR-P-112; 5.2(ii);
AECL-5696) has revealed no problems peculiar to this version.
To avoid the problem of maintaining two compilers, this
compiler has replaced the unmodified CDC compiler. At the
same time changes to correct some inconsistencies in
- 82 -
selection of print density, page length, and to improve
handling of error conditions encountered in reading magnetic
tapes have been made. Programs compiled by the new version
of FORTRAN require slightly more field length (^250g words)
for execution.
A routine FLCHEK has been written to permit an
executing program to determine memory sizes (both central
memory and extended core storage) established by job card
parameters.
(iii) FORTRAN-Callabls Subroutine Libraries
L.E. Evans and B.E. Purcell
Complete testing of the NOS/BE version of AELIB
(CRNL Subroutine Library) was carried out and no new prob-
lems were encountered.
Since the FTN compiler at level 406 (the version
prior to the current NOS/BE compiler) produced many opti-
mization problems in AELIB and IMSLIB (International Math-
ematical and Statistical Library) subroutines as well as in
user programs, these libraries were both installed for
NOS/BE without optimization. This quarter, the AELIB and
IMSLIB routines which had not been optimized correctly with
the previous compiler were tested with the new compiler.
The results were encouraging. Ten out of eleven previous
optimization problems were solved. The subroutine libraries
AELIB and IMS'. IB will remain installed without optimization
but may be used as a convenient test base to evaluate future
compiler optimization changes.
The error message handling for all recently in-
stalled AELIB routines is performed by a routine AELERR
which retrieves the text of error messages from another
system library. To facilitate the use of some AELIB rou-
tines at other installations, a stand-alone version of
AELERR was written and made available to users.
r> 83 -
A major AELIB installation was performed on
21 March 1977. The following routines were added:
CADRE Integration by Extrapolative Romberg Method
AGAUSS Integration by Adaptive Gauss Method.
QUAD Integration by Adaptive Newton Cotes Method
SPLINT Integration of Tabular Functions
MFID Hardware Mainframe Identification Subroutine
The following routines were modified:
COSIMP Integration by Adaptive Simpson's Rule
FILON Filon Integration
GALA Gauss-Laguerre Integration
GAHER Gauss-Hermite Integration
GAJAC Gauss-Jacobi Integration
DUBLINT Double Integral Using the Gaussian Method
The following routines were removed:
ITABLK Table Look-Up Functions
SORTF Sorting Records with SORT/MERGE
In addition, library statistics calls were added
to another group of AELIB routines, to expand the monitoring
of AELIB usage.
(iv) Utility Programs
H. Keech
Binary files in which information is in the format
of number representation on CDC computers, cannot generally
be read by other computers since their form for arithmetic
operations is different. Although it would be possible to
translate directly from one internal form to another, it is
much better to write the information in standard external
BCD format, thus making use of the BCD to internal repre-
sentation conversion programs which already exist.
- 84 -
A program EXPORTB has been written to block large
arrays of binary information (generated by FORTRAN unfor-
matted writes), and write it to "stranger" tapes in blocks
of 5120 external BCD characters or less.
A second program READS has been written to reverse
this translation. READS checks various key words written by
EXPORTB to see that they are correct.
5.3 CDC 3300 System
(i) Handling of Local Print Files
E.A. Okazaki
A change was made in the method of handling files
which are printed at the central site. Files in the 6600/
175 output queue are processed directly via the satellite
coupler, using a double buffer system with editing being
done by interrupt-enabled overlay programs. Print, files
generated by the 3300 are printed directly from the drum
unless a printer is not available, in which case they are
sent to the 6600/175 to gain the rescue/recovery advantages
of the output queue.
The previous method of transferring and editing an
entire print file on to the 3300 drum before sending the
file to the printer, had a weakness in the area of column-1-
format procesring in certain rare but possible circum-
stances. This weakness has been eliminated.
The removal of print file transfers from the
3300's stream of batch-job tasks to hardware-interrupt-
driven tasks means that there is a smaller average delay in
transferring input files from the 3300 to the 6600/175.
A 3300 console command has been provided so that
the operator can send a specific print file from the 6600/
175 output queue to a free printer.
- 85 -
» The previous method of transferring files to the
drum before printing is still available. This will allow
printing to continue when the other machines are unavail-
able, as long as there is time for the file transfers to the
3300 to take place before the other machines are discon-
nected.
(ii) File Status Displays at Terminals
E.A. Okazaki
An "I" command was added to the repertoire of
commands which the 3300 can accept from terminals. This
command, together with the H and J commands, enables a
terminal operator to display file status for each of the
three computers at the central site. A limited queuing
mechanism for these commands was also installed in the 3300
system. This allows access to the file status displays with
little delay during normal operation, at the same time
decreasing the system resources required to provide these
displays.
(iii) Private Automatic Exchange
J.F. Steljes
CRNL terminals are now connected to the 3300
Computer via a Gandalf PACX II automatic exchange. This
means that a large number of terminals may share a smaller
number of computer ports. Ports will have a 'class* as-
signed to them (largely a function of the baud rate only)
and users will be able to access any idle port of a class
compatible with their terminal until all ports of that class
are used up. Users will be automatically disconnected after
10 minutes of disuse of their terminal if they do not dis-
connect themselves (by switching off their modem).
- 86 -
All users will have to log in using a suitable
password and they will be able to select any special char-
acteristics of their terminal at this time so that they will
not lose any advantages of having dedicated ports.
5.4 DECsystegt- \C_
J.A« 6vJQf;N"Oiflbe
(i) Monitor
The monitor was upgraded to remove some problems.
There remain two known problems, one of which has a cor-
rection, not yet installed.
(ii) New Hardware Support
The second display unit, reported on in previous
progress reports, is completed and in use. Preliminary
discussions on replacing the old display unit because of the
age of the components have begun.
The second 64K bank of memory from INTEL has
arrived and been installed. Problems are being observed,
due to either (or both) cable length or air-conditioning
problems.
(iii) Micro-Processor Support
Cross assemblers for the INTEL 8080A and Zilog Z80
have been developed and tested. The interface between the
cross-assembler and PL/M outputs and a PROM programmer have
been developed and tested.
(iv) System Software Updates
Updated versions of the following have been
installed: TECO text editor, LINK-10 loader, MACRO as-
sembler, COMPIL command decoder, and BATCON batch control-
ler.
- 87 -
5.5 Superconducting Cyclotron/MP TandemAccelerator Control System *
(i) Software
L.D. Hansen with R.L. Graham and R.B. Walker,Nuclear Physics Branch
The software for this system consists of:
(1} RSX-llD
The RSX-llD operating system provides the real
time operating environment for the control system software.
The RSX-llD version 6.2 is expected to arrive in
May of this year. In the meantime, an inr te "pre-
release" of that system is being used satisfactorily. L
complete "pre-release" of that system is expected within two
weeks.
(2) Intermediate Control System Software
Source code software of approximately 800,000
bytes was obtained from the Hahn-Meitner Institute in Berlin
and has been successfully installed on the PDP 11/34. This
code provides an interface between control system tasks and
the elements of the control system that the tasks need to
manipulate. The interface consists of data bases, CAMAC
interrupt service routines, tasks and subroutines which can
be interrogated and/or influenced by control system tasks.
The software includes code in the following areas:
(a) MUMTI Interpreter System
This code provides a BASIC-like interpreter
language and access to CAMAC functions in a straight forward
manner.
- 88 -
(b) System Variable Data Base Management
A system variable data base exists which provides
for the functioning of the CAMAC system through the refer-
encing of system variables; i.e. the data base includes the
information describing the CAMAC address and function
(CNAF), which corresponds to a character string representing
the system variable. Data base management code for this
data base has been installed. The mechanics of that system
are being studied with the aim of creating a system variable
data base for the parameters, controlling the ion source and
MP tandem.
(c) System Variable Data Base Access
Code for the system variable data base access
system has been installed. This code is accessible from
FORTRAN, MUMTI or MACRO assembler. It, together with the
system variable data base, provides the mechanism with which
CAMAC operations are initiated by referencing a system
variable. Thus the programmer need not be aware of the CNAF
associated with the operation.
(d) CAMAC Interrupt Service Routines
Code is provided for handling interrupts from the
CAMAC system. \ This code provides the link between the
physical control operations, e.g. turning a knob, touching a
sensitive spot: on a touch panel, etc., and code specific to
the physical operation.J
(e) Color TV, Touch Panel and Knob Drivers
This code is currently being produced by the Hahn-
Meitner Group and we have only one incomplete portion of it.
It is believed that the touch panel and color TV drivers are
"data base driven" in much the same way as is the system
variable data base access system. All these drivers are
intimately associated with the CAMAC interrupt service
routine.
- 89 -
(3) Control System Tasks
Control system tasks are those written in FORTRAN,
MUMTI or MACRO which use the previously described inter-
mediate control system software and RSX-11D operating system
as "tools" to manipulate control parameters. Efforts to-
wards a clear understanding of these tools are continuing so
that a high level of consulting can be given to the control
system task writers.
(ii) Communications Software forRSX-llD Operating System
L.D. Hansen
Experience with PDP11 RSX-llD operating system
indicates that the existing software for file/terminal
handling cannot communicate files successfully with the CDC
3300. An asynchronous communications adapter software
handler is being written which will overcome the diffi-
culties inherent in the RSX-llD terminal handler which
precludes successful communications. In addition the
feasibility of an additional mode of interchange of binary
data in the 3300 communications system is being explored
with J.F. Steljes.
(iii) Computer-Aided Control System for the
Superconducting Cyclotron and MP Tandem
L.D. Hansen et al.
See PR-P-113; 2.16; AECL-5802.
- 90 -
5.6 Analysis of Acoustic Phenomenain a System of Steam Mains
W.N. Selander and P.Y. Wong
The results described last quarter have been dis-
cussed with Power Projects staff. A report is being writ-
ten. Preliminary calculations are underway to determine the
feasibility of computing the frequency response of the G-l
system, using the acoustic model with damping and Doppler
effects included.
5.7 inertial Analysis of the Gentilly-1Modified Steam Mains Network
P.Y. Wong with E.O. Moeck, Reactor Control Branch
A revised version of the inertial analysis of the
G-l modified steam mains network (PR-P-109; 5.10, AECL-5508)
has been examined for programming. The analysis is now
characterized by a 20 x 20 matrix whose eigenvalues would
provide the natural frequencies of the network and the
corresponding modes of pressure oscillations.
A computer program has been written to provide the
steady-state calculation of the network on which the eigen-
values of the matrix can be evaluated. Preliminary results
indicated that the network is stable as expected and that,
depending on operating conditions, a total of seven modes of
pressure oscillations (all damped) can be identified. These
results have been discussed with Power Projects staff at a
meeting held at Sheridan Park on 24 February 1977.
An attempt is being made to describe the behaviour
of the oscillation modes with respect to operating condi-
tions and network parameters. Results so far indicate that
at full power, natural frequencies are not sensitive to the
amount of steam in each steam vessel (steam drums, reheaters
- 91 -
and reboilers), but the treatment of the extra piping
volumes (deemed necessary due to network simplification) may
have a significant effect on natural frequencies and hence
the corresponding modes of oscillations.
The Wigner Solid
H. Keech with H. Glyde, University of Ottawa
A study of the stability of the Wigner solid at
finite temperatures has been made for the self-consistent
harmonic (SCH) model both with and without the cubic cor-
rection to the force constants included in the SCH iteration
procedure. Observation of a breakdown in the calculation of
the lattice frequencies of the solid (square of a frequency
going negative) is used to signify a transition to the
liquid state.
This criterion does not provide a sharp definition
of the melting curve for all values of the model parameters,
temperature T and ion-sphere radius Rs. For the SCH and
cubic case, and Rs values between 175 (where the solid
breaks up at 0 K) and ^600, the curve is broadened into a
band of values. Although the frequency "imaginary" cri-
terion works better for the SCH case, the mean-square ion
displacements are often uncomfortably large before the
transition occurs.
In the classical region, we have compared our SCH
and cubic results with the Monte Carlo free energy calcula-
tion results of Pollock and Hansen (Phys. Rev. A $_, 3110
(1973)). For Rs = 104, we find T » 3 K, whereas the Monte
Carlo value is T « .2 K.
- 92 -
5.9 integration
(i) Quadrature
M.B. Carver
The reassessment of the quadrature section of the
library as reported in PR-P-112; 5.5(iii); AECL-5696, is now
complete. The quadrature section now consists of ten rou-
tines, newly written or extensively revised, all of which
have been proven by extensive testing.
A report, AECL-5605 "An Evaluation of Available
Quadrature Algorithms and Selection for the AECL FORTRAN
Mathematical Library", has been prepared.
(ii) Discontinuities in ODE's
M.B. Carver
The study of discontinuity detection and handling
in ODE's is now complete. Basically the problem is that the
type of sophisticated implicit algorithm, necessary to
integrate efficiently large sets of ODE's can get into
difficulties when the system is subject to a discontinuity
or switch in the equation definition. In such cases the
algorithm can waste a large fraction of its time attempting
to locate and overcome this discontinuity.
A new technique was developed to describe the
governing equation of the discontinuity as a differential
equation itself. This permits the occurrence of the dis-
continuity to be accurately predicted. One can then inte-
grate neatly to this point and then merely restart the new
problem. A paper "Efficient Integration Over Discontin-
uities in Ordinary Differential Equations" was presented at
the IMACS 'Simulation of Differential Equations' Conference
in Blacksburg, Virginia, 9-11 March 1977.
- 93 -
(iii) Time and Transport Delays in ODE's
M.B. Carver
The approach of (ii) above has also been used in a
new fast method of handling time and transport delays in
simulations. Normally delays are treated by storing previous
values and obtaining "delayed values" by interpolation. The
need for constant revision of the table of stored values as
the integration proceeds is costly in time, and no really
satisfactory scheme has yet been developed. However, by
applying a similar philosophy to time delays as to discontin-
uities, i.e. treat the delayed functions as additional
ODE's, one can obtain a high order approximation to the time
delay in a negligible time without any auxiliary storage
requirements. A routine is currently being written to apply
this principle.
(iv) FORSIM and OOE/PDE Simulation Package
M.B. Carver and D.G. Stewart
A new manual for FORSIM is being prepared. It
will describe the new version of FORSIM, which now conforms
to ANSI FORTRAN standards except for the use of a few local
features (overlays, memory management, etc.) for the sake of
efficiency. New features added in this version include the
discontinuity routine discussed above.
A study of various methods of handling the logis-
tics of two- and three-dimensional systems is under way,
with the intention of developing a routine to automate the
solution of PDE's in three dimensions.
Requests for FORSIM have been received from the
University of New Brunswick, the University of Calgary,
Bishops University, and Multiple Access Limited. The University
of British Columbia, Lehigh University and Siemens AG have
reported that FORSi:: is now in use at their installations.
- 94 -
5.10 Stress Analysis Programs
(i) MARC - General
B.V. Riff
A new release, Revision G, Release 4, of MARC was
received and installed after the modifications necessary to
adapt it to our system were made. A check of the demon-
stration problems provided by MARC revealed the following
problems :
(a) Some differences were found in the stresses produced by
G.3 and G.4 for one demonstration problem, and also
between G.4 and the demonstration problem results sent
with the release.
(b) A difficulty with MARC-MESH3D hidden line plotting.
(c) The gap element is not handled any better than it was
in G.3 (see PR-P-112, 5.7, AECL-5696).
These problems have been reported to MARC, and we
have been informed that the gap element problem will be
fixed in Revision G, Release 5, in the near future.
(ii) MARC - Subroutine for Mesh Optimization
B.V. Riff
A program for H. Hatton, Applied Mathematics
Branch, was converted into a subroutine which can be used
for any mesh or element type. The subroutine optimizes the
mesh using a method similar to that of the Cuthill-McKee
algorithm. Each attempt uses a different starting node and
then arranges the connecting nodes in ascending order of
their connectivity. The maximum difference between node
numbers in an element is determined for each attempt and the
minimum of all the maximum differences is found. The sub-
routine returns the new node numbering for this minimum
half-bandwidth.
- 95 -
(iii) Liquid Helium Cans of Cryostat for SCC
B.V. Riff and J.M. Blair
The purpose of this study, undertaken for
J.A. Hulbert, Accelerator Physics Branch, is to determine
the amount of deflection of the buttom plate of the liquid
helium cans, and to find out how much the top plate or outer
wall thickness must be increased to give a maximum deflec-
tion of 0.05 mm.
The structure is modelled by the axi-symmetric
isoparametric two-dimensional element 28 of MARC. The
support can be treated as a point, so that the boundary
condition is zero deflection at the outer bottom edge. The
load is 45,000 N applied uniformly to the inside face of
the bottom plate. An analysis of the bottom plate, ignoring
the rest of the structure, was done first. The maximum
deflection found was 8.75 mm.
The entire structure was then modelled and the
maximum deflection was found to be 0.32 mm. An attempt will
now be made to reduce the deflection to the desired maximum
by:
(1) Increasing the outer wall thickness
(2) Increasing the top plate thickness
(3) Both of the above.
5.11 Statistical Analysis of Slotted Burst TestsOn Cold-Worked Zr-2.5 wt % Nb Pressure Tubes
J.M. Blair
The original data (PR-P-112, 5.7(iii), AECL-5696)
were modified by the elimination of six data points which
correspond to non-propagating cracks, and by the addition of
four new experimental measurements for sharp cracks at
300°c. The form of the regression equation was altered,
- 96 -
following a reconunendation of J.G. Kalbfleisch, University
of Waterloo, and the stepwise regression analysis was
repeated. The resulting equations are:
Una = 6.916 - 0.1819*10"1c - 0.2762*10"4(T-157)2
+ 0.1425*10"2(T-157)f - 0.3172f
var(£na) = 5.426*10"2 - 0.1533*10~3c - 0.3426*10~6(T-157)2
- 2.396*10"6(T-157)f - 4.024*10"4f + 2.431*10~6c2
- 0.3096*10~9(T-157)2c + 0.3623*10~7(T-157)fc
+ 0.2960*10"4fc + 2.252*10"i:L(T-157)4
+ 0.3081*10"9(T-157)3f + 1.495*10"7(T-157)2f
where a(MPa), c(mm) and T(°C) denote stress, crack length
and temperature respectively, and f is 0 for a blunt crack
and 1 for a sharp crack. These equations may be used to
predict critical cracks lengths and confidence limits at
reactor operating conditions.
Further experimental measurements will be made by
Metallurgical Engineering Branch to determine whether the
temperature variation in these equations is a real effect,
or is due to the sparsity of the data.
5.12 information Handling Programs
(i) Pickering Pressure Tube Data Base
G.N. Williams
Final results were derived and incorporated in the
report that was issued during the period.
(ii) PROD
C D . Price
An additional interrogation mode was incorporated
into the Project Management Design code (PROD) to allow
retrieval of data by specifying a system code, for J. Moore
of Design and Technical Service Branch. The system code may
- 97 -
be an experiment number assigned to a set of drawings, or
may be used to distinguish a particular series of drawings
involved in a design job.
(iii) DATPAK Version 2
C D . Price and G.N. Williams
The report "DATPAK: A Data Management Package,
Version 2" (Atomic Energy of Canada Limited report AECL-
5562) has been completed. The DATPAK system of FORTRAN
Extended subroutines allows users to store sequentially data
and associated comments onto an indexed magnetic tape file
and retrieve these data. The report outlines the design
philosophy and briefly describes the various subroutine
calls. A stand-alone utility program, DPUTILITY, is also
outlined. A DATPAK User's Guide is being prepared with
suitable examples for the use of DATPAK and DPUTILITY at the
CRNL Computing Centre. A utility program, COPY, has been
written to enable Version 1 DATPAK tapes to be converted to
the improved Version 2 format.
(iv) Leave Reporting System
C.J. Tanner
During this quarter the Daily Attendance Form was
produced by a computer program for a few days. This was
discontinued because of the problems encountered, but with
the experience gained from this trial run, the system will
be modified and the Daily Attendance Forms should be pro-
duced regularly by computer before the end of this quarter.
5.13 Neutron Calculations for a Fusion-Reactor Blanket
S.A. Kushneriuk (Theoretical Physics Branch) and P.Y. Wong
See PR-P-113; 4.2; AECL-5802.
- 98 -
5.14 Miscellaneous Programs and Subroutines
(i) Superconducting Accelerator Codes
K.R. Chaplin
Work continued on a quadratic programming field
fitting routine for Accelerator Physics Branch. Work was
completed on a routine which removed first harmonic com-
ponents of the radial and z-field from the superconducting
cyclotron. An established routine, TRIUMF, is being modified
for greater size and accuracy. Also investigated was the
behaviour of the ion beam in a critical region of the
cyclotron.
(ii) Non-linear Least Squares Fitting Software
L.E. Evans and E.G. Long
Revisions were made to the non-linear least
squares fitting routine, LSQQ, and a new version of this
routine was made available to users. Improvements included:
(1) A revised error matrix calculation for weighted and
unweighted fits.
(2) More sophisticated error handling and informative
diagnostics.
(3) Addition of parameters to improve flexibility of usage.
Parallel modifications were also made to MLSQQ,
the version of LSQQ which allows the user of more than one
independent variable.
Preliminary versions of routines to provide
standard deviation estimates for the fitted function values
were prepared.
(iii) Bickley Functions
P. Christie
Rational chebyshev approximations have been gen-
erated for the Bickley function Ki 3(x), x ^ 6 using the
REMES2 program (programmed by J.M. Blair and J.H. Johnson)
with accuracy to 23D.
- 99 -
Two functions and one subroutine have been written
for AELIB to evaluate the Bickley functions Ki n(x), n=l,2,...,10
for x >_ 0. The functions AKI1 and AKI3 evaluate Ki^l) and
Ki,(x) respectively for x > 0 to a minimum precision of 13
significant figures. The subroutine KIN evaluates K i ( x ) ,
n=l,2,...,10 for x > 0 to a minimum precision of 12 signif-
icant figures.
5.15 Operations
(i) New Equipment installation
B.B. Ostrom
During this period the 66x magnetic tape subsystem
was delivered and installed, replacing four of the eight 657
tape drives used formerly.
Work continued on:
(1) The motor generator vault and associated electrical
modifications to the building.
(2) The installation of the building sprinker system.
(3) The consolidation by Bell Canada of their data and
voice lines within Building 508.
(ii) Dayfile Analysis for Two-Computer Configuration
C D . Price
DEMERGE, a system dayfile pre-processor was writ-
ten to merge mainframe dayfiles for the CDC 6600 and CYBER
175 Computer systems. The host identifier is included with
each dayfile time field and incorporated into each accounting
record. The resulting merged file, OLDDAYFILE, is made
available to other programs as well as the DAYFILEANALYZER
program. Modifications were required to all report gen-
erating programs to incorporate the host identifier field.
- 100 -
(iii) Computer Use by Division
The following table is an analysis of the jobs
processed during the quarter.
Power ProjectsWNRE
CBNL:
Computing Centre
Technical Information& University Relations
Biology and HealthPhysics
Chemistry & Materials
Physics
Electronics, Instru-ment and Control
Advanced Projects &Reactor Physics
Fuels & MaterialsAdministration
Medical
Finance
Operations
Genetal Services
Plant Design
Special Projects
Contracts
Others
TOTAL
Number
13,083
2,972
23,813
2,286
2,635
3,292
4,799
650
9,754
11,858
712
193
2,090
3,642
208
724
2,534
1,477
14
86,736
Of :
(15
(3
(27
(2
(3
(3
(5
(0
(11
(13
(0,
(0.
(2.
(4.
(0.
(0.
(2.
(1.
(0.
Jobs
.08%)
.43%)
.46%)
.64%)
.04%)
.80%)
.53%)
.75%)
.25%)
.67%)
.82%)
.22%)
.41%)
.20%)
,24%)
,84%)
92%)
70%)
02%)
2,
UtilizationSystem Seconds
730
129
125
12
28
80,
118,
3,
441,
248,
2,
15,40,
10,
13,57,
059,
,102
,471
,190
,750
,092
,384
,854,
,212,
.260.
,733.
,935.
230.
074.
131.
897.
257.
698.
740.
46.
063.
.43
.35
.75
.44
.44
.46
.12
.30
,22
,35
,95
45
06
21
0502
52
18
85
13
(35
(6
(6
(0
(1
(5
(5,(0
(21,
(12.
(0.
(0.
(0.
(1.(0.
(0.
(0.
(2.
(0.
.46%)
.29%)
.08%)
.62%)
.36%)
.77%)
.77%)
.16%)
.43%)
.08%)
.14%)
,01%)
,73%)
,95%)
04%)
50%)
67%)
80%)
00%)
- 101 ~
5.16 Publications, Reports and Lectures
Publications
EFFICIENT INTEGRATION OVER DISCONTINUITIES IN ORDINARYDIFFERENTIAL EQUATIONSM.B. CarverIMACS International Symposium on Simulation Software andNumerical Methods for Differential Equations, Blacksburg,Virginia, 9-11 March 1977.
COMPUTING CENTRE NEWSLETTER, Vol. 4, Nos. 1, 2, and 3,Edited by L.E. Evans.
Reports
f* f(x)dx: AN EVALUATION OF AVAILABLE QUADRATUREALGORITHMS AND SELECTION FOR THE AECL FORTRAN MATHEMATICALLIBRARYM.B. Carver and V.J. JonesAECL-5605, March 1977
Lectures
THERMODYNAMICSM.B. CarverAlgonquin College of Applied Arts & Technology, AdvancedTechnical Evening Course Series, 1 October 1976 to 28 Feb-ruary 1977, CRNL.
ANS COBOL PROGRAMMINGC D . PriceAlgonquin College of Applied Arts & Technology, ContinuingEducation Course, 1 March to 3 June 1977, CRNL.
FORTRAN IVJ.M. BlairAlgonquin College of Applied Arts & Technology, ContinuingEducation Course, 28 February to 3 June 1977, CPNL.
WHY SOME TUBES IN PICKERING WERE MORE SUSCEPTIBLE TO CRACKINGTHAN OTHERSB.A. Cheadle (Metallurgical Engineering Branch) andG.N. Williams, 9 February 1977, CRNL.
- 102 -
ACCELERATOR PHYSICS BRANCH
P.R. Tunnicliffe
6.1 Staff
6.2 Nuclear Power Applications
6.2.1 High Current Test Facility6.2.2 Electron Test Accelerator6*2.3 Fertile-to-Fissile Conversion Experiments
at TRIUMF
6.3 Research Applications
6.3.1 Fast Intense Neutron Source6.3.2 Heavy-Ion Superconducting Cyclotron
6.4 Mechanical Laboratory
6.4.1 High Current Test Facility6.4.2 Electron Test Accelerator6.4.3 Fast Intense Neutron Source6.4.4 Heavy-Ion Superconducting Cyclotron6.4.5 Reactor Physics6.4.6 Mechanical Laboratory
6.5 Publications, Reports, Papers, Lectures and Patents
- 103 -
6.1 Staff
BRANCH HEAD:
Professional Staff
P.R. Tunnicliffe
Technical Staff
cJKB.J,L.E.J.
.B.
.C.
.C.>G..S..W..A..D.
S.B.C.J.R.P.
G.J.H.S.H.
,R..A..M.,W.J.E.H.R.0.R.J.
BighamBrownChan (1)ChidleyFraserFunkHeighwayHepburnHodge
J, HoffmannHulbertHutcheonJames (2)McKeownMcMichaelOrmrodSchneiderSchriberShubalyUngrin
Mechanical Laboratory
J. E. AnderchekR.J. BakewellR.J. KellyN.I.G. LabrieD.W. WarrenJ.F. Weaver
(1) NRC Post Doctorate Fellow.(2) NRC Post Doctorate Fellow.(3) Arrived 3 January, 1977.
B.J.R.T.L.F.H.F.M.R.K.A.L.E.B.A.K.J.A.B.J.C.S.H.P.J.W.L.R.A.A.E.
ArdielF. BirdBirneyCampbellCoxDobbsGeoffreyGilliesHohbanHoodJonesKidnerMetivierMichelVokesWeeden
Laboratory Services
J.K.J.J.
HewittMurphy
Secretarial Staff
Mrs. M.A. Trecartin
Waterloo Student
E.P. Keyes (3)
- 104 -
6.2 Nuclear Power Applications
6.2.1 High Current Test Facility
B.G. Chidley
Work continues on assembly and testing of the 3 MeV
100% duty factor proton linear accelerator to study problems
in the initial section of an accelerator suitable for a
spallation neutron factory.
a) Injector
J. Ungrin
The injector has been operated during the present
quarter with beams up to 30 mA. The addition of stress
relieving hoops to two electrodes which was reported last
quarter (PR-P-112, 6.2.1 a), AECL-5696) has made no appreciable
effect on the overall accelerator reliability. Arcdown rates
at 20 mA remain at ^ 2 per hour.
The spacing between the extraction electrode and
the ion source container was reduced from 20.8 to 16.8 mm to
investigate the effects of geometry on beam focusing and
reliability. Apart from a corresponding 25% reduction in the
voltage required for optimum focusing no changes in behaviour
of the accelerating column at 20 mA were observed.
Examinations of the Ti6A14V column electrodes
during past inspections have revealed spark damage mainly in
the region within 3-5 mm of the beam aperture. Titanium and
many of its alloys are known to be excellent pumping agents
for hydrogen. Hydrogen and titanium atomic ratios in the
range 1-1.5 have been reported for titanium metals at 300°C
in hydrogen atmospheres at pressures ^ 10 - 10 Pa
(Iwanovski and Schirjeev, UCRL-trans-10665). The adsorption
and desorption rates are highly temperature dependent and
outgassing bursts may occur from the electrodes when small
amounts of beam are intercepted. The column has therefore
- 105 -
been dismantled and the apertures of the downstream electrodes
wh' *-v show the most spark damage have been increased to 40 mm
diameter from 26 mm to decrease the probability of beam inter-
ception and to investigate the effect of this change on
accelerator arcdown rates. The column has been reassembled
but has not yet been operated with beam. A 100 kV test
column with two titanium electrodes has been assembled and is
being used in an auxiliary experiment to investigate this
outgassing problem.
One of the two 1000 Z/s titanium ion pumps in the
high voltage dome failed just prior to the column disassembly.
It was dismantled and has been rebuilt.
b) Beam Emittance Studies
M.R. Shubaly
A shot -. series of emittance measurements was made
on a 20 mA total current beam using the pepper-pot plate
described previously (PR-P-112, 6.2.1 b), AECL-5696). The
normalized emittance of the main part of the beam is much
greater than the previously reported measurements (4.03 ir
mm*mrad as compared to 1.8 IT mm-mrad (PR-P-111, 6.2.1 b),
AECL-5614). The emittance tails are less pronounced than
previously and are, to some extent, masked by the emittance
increase in the main beam. A check using the old pepper-pot
plate showed that this change was not caused by changing the
plate. Measurements made while moving the plate vertically
through the beam show that the beam is very asymmetrical and
non-uniform. A new pepper-pot plate with an 11 by 17
rectangular array of 0.10 mm holes on 7.62 mm centres has
been fabricated to permit simultaneous measurements over the
entire beam.
A proposed explanation of the emittance growth is
that the high-frequency oscillations present on the beam
disturb pace charge neutralization, producing non-linear
- 106 -
space charge blowup. An experiment to test this hypothesis
gave Inconclusive results.
The light output from the p-Quaterphenyl coated
detector screen was too low for accurate measurements so the
NE102 scintillator will continue to be used.
c) Ion Source Development
M.R. Shubaly
Development of the duoPIGatron source continues.
Experiments are now being carried out on a source with a
4.5 mm diameter plasma aperture. For a given arc current,
the beam current and proton fraction increase as the source
pressure is decreased. Minimum operating pressure is currently
limited by the voltage available from the arc supply.
Shortening the reflex-arc section of the duoPIGatron
has given increased current and has improved the proton
fraction. The long source gave 40 mA ('v- 12% H.. ) with a 10 A
arc and 60 mA with an 11 A arc. The shortened source (Fig.
6.2.1.1) gave 40 mA (30-35% H ^ at 20 Pa, 25% H ^ at 22.6 Pa)
with an 8 A arc and 63 mA with a 9.2 A arc. Because this
source is capable of 1 A beam current, and because the proton
fraction generally increases with beam current, these per-
centages at low beam currents are encouraging. At 40 mA, the
beam quality is very good, with a normalized emittance of
0.79 TT mm*mrad for 99% of the beam. Figure 6.2.1.2 shows a
plot of current density as a function of divergence angle for
a central beamlet of a 40 mA beam from the short duoPIGatron
and a corresponding plot for a duoplasmatron. The duoPIGatron
has a much lower total divergence and is free of the triple
peaked distribution of the duoplasmatron which indicates a
beam halo.
The high current density ( 400 mA/cm ) gives
extreme growth in the beam diameter with the present extractor
ANODE #1
FILAMENT
COMPRESSORCOIL
I [ COPPER
CERAMIC
IRON
INTERMEDIATEELECTRODE
PLASMAAPERTURE-PLATE
V////////A
MOLYBDENUMTUBE ANODE #2-
MYLAR-INSULATION
i
o
J
Fig. 6.2.1.1 Short DuoPIGatron Source
- 108 -
as
8EAMLET
OUOPIGATIONDIVERGENCE (ARBITRARY UNITS)
DUOPLASMATION
Fig. 6.2.1.2 Current density vs. beamlet divergencefor 40 mA beam.
system. Higher current runs are halted until new electrodescan be designed and built.
Extraction and output current optimization forduoplasmatron sources were studied. Because of the problems
- 109 -
caused by extractor sparking, a number of low voltage or
passive electrodes mounted close to the plasma surface were
tested. The only arrangement giving any success was the
copper focus plate used on the FINS source (section 6.3.1).
However the beam diameter and quality were strongly dependent
on the beam current. The study of output current optimization
established a) the intermediate electrode canal diameter - as
small as possible consistent with reasonable starting,
currently 2.36 mm; b) the width of the land on the anode
aperture (the parallel portion of the hole) - as small as
possible. The effects of intermediate electrode to anode
spacing are still unresolved.
Operation of the arc and coil supplies has been
improved. Damage from spark-generated transients has been
almost eliminated by enclosing the voltage regulator integrated
circuits in copper shielding boxes. The series-limiting
resistors in the 150 kV supply failed because of spark damage
and have been temporarily replaced by wire-wound resistors.
d) Alvarez Linac
B.G. Chidley and J.C. Brown
High power commissioning of the triode amplifier
of the rf power supply continues. The double stub tuner was
modified for installation in the main 23 cm line but performance
evaluation with improved plate loading was delayed pending
repairs to the rf load and investigation of a fading phenomenon
recently observed during high power operation.
The rf match of the high power rf load had
deteriorated due to water leaking into the load interior.
Temporary repairs have been made.
During subsequent high power operation of the triode
amplifier slow fading of the rf output was observed similar to
that experienced before the tube vacuum repair. At the time of
- 110 -
tube repair, this fade was attributed to loss of filament
emission due to poisoning or ion-bombardment damage of that
portion of the filament which faces the plate because of a
high residual gas level. The manufacturer confirmed the
presence of a high internal gas level although after
dismantling the tube, he could not find a leak source in any
of the sub-assemblies.
After being rebuilt, the tube exhibited excellent
performance during the manufacturer's tests under pulse
operation. Since delivery it has maintained an excellent
vacuum. The initial high power tests under continuous
operation indicated good performance although the lower power
output and rf gain for equivalent dc and rf drive conditions
were attributed to a high plate load impedance.
During power runs at somewhat higher drive power
levels, the output power and dc plate current faded by 20-30
percent over a 5 to 10 minute period. The rate and amount
of fade increase with drive power level.
Operation with a detuned plate resonant circuit
and higher dc plate voltage indicates that larger rf plate
voltages, as would be produced by a high plate load impedance,
do not contribute to fading. More recent tests suggest
an emission deterioration of grid-filament or input circuit
origin. Large dc grid currents (greater than that encountered
in operation to date) do not produce detectable internal gas,
whereas a sizeable release of gas occurs with rf grid currents
of the same average values with no plate voltage on the tube.
Measurements indicate that gas is evolved during operation
with plate voltage as well but much of this gas is driven
into the grid and filament surfaces resulting in a loss of
emission due to poisoning so that only a small increase in
gas level is detectable immediately after. The investigation
is continuing.
- Ill -
The Alvarez tank magnet circuit was electrically
tested up to 380 A, the present current limit of the dc power
supply. New transistors are being installed in the power
supply regulators to allow operation up to 800 A.
Fabrication of the high power beam scop was com-
pleted and it has been positioned in the beam line. The
cooling system interconnections were completed and flow
tested.
6.2.2 Electron Test Accelerator
J.S. Fraser
This two-tank experimental 4 MeV 100% duty factor
electron accelerator is intended to study problems associated
with the main portion of a spallation neutron factory based
on a proton linear accelerator.
a) g=l Tank High Power Commissioning
J. McKeown
The tank (Model 3) was run routinely at 50 kW rf
dissipation during the period. Work continues to improve the
instrumentation for start-up under computer control.
The voltage-controlled slave oscillator used for
tank start-up did not have sufficient output power to drive
the klystron with the varactor phase shifter in the circuit.
An rf amplifier has been used to overcome this problem but
the match it presented to the oscillator pulled the
oscillator frequency outside the accelerator operating
range. A tuned stub has been used to pull the frequency of
the oscillator to within that tuning range of the tank.
Improvements are being made to the amplitude and
resonance control modules to permit the computer to scan the
oscillator frequency across the tank resonance at 2 kW forward
power before locking the resonance loop. Work has been done
to make the phase controller less sensitive to changes in
- 112 -
signal amplitude. This is necessary for beam experiments at
different tank power levels. The present detector shows a
1.5° shift for a 3 dB input power change. A nuclear physics
instrument of recent design, the Canberra discriminator
Model 1428, was tested to evaluate the effect of pulse
amplitude variation at 10 MHz which is the intermediate
frequency of our phase detector. The instrument gave a 3°
variation for a 10 dB input power change. As this represents
the timing resolution in present nuclear physics experiments
it indicates that our phase detector approaches the limit of
gain/bandwidth product that can be achieved at present. A
somewhat related problem is the cross talk which exists
between the two rf channels in our detector. This becomes
important when the amplitude difference between channels is
large. Work has begun to repackage the detectors to reduce
this effect.
The rf field monitoring has been rearranged so that
field-monitoring signals from the accelerating cells are
multiplexed by the computer and sensed by a single crystal.
This eliminates drifts from temperature effects and the
gradual degradation of crystal sensitivity with age.
Calibration of the calorimetry with electrical
heaters showed that a plumbing error had routed the bridge
coolant through one of the two accelerating sections; this
was corrected. Window and tuner cooling has now been incor-
porated into the bridge cooling circuit with appropriate
interlocks.
The temperature-control system used in the graded-6
tank (Model 4) was transferred to the klystron cooling system
to reduce thermally generated phase shifts across the
klystron. The system monitors the secondary circuit water
temperature with a gas bulb thermometer and a controller
sends a signal to a control valve in the primary flow to the
heat exchanger. So far the control loop is not working
- 113 -
satisfactorily. With the range of pneumatic control signals
available it is thought that the control valve is unable to
give an adequate reduction in primary flow. The temperature-
control systems for both the tanks are now based on thermistor
tempera*. • ore sensors and computer control links both using a
software algorithm which controls valves in the heat
exchangers.
b) Bi-modal Cavity
J. McKeown
This cavity, designed as a non-destructive beam
position monitor, has been machined to 14.897 cm I.D. to
resonate at 2.4143 GHz under vacuum. After correction of
some problems, the cavity and its tuners have been satis-
factorily assembled and are leak-tight.
Tests on mode orientation show that the modes are
orthogonal along the desired axes provided proper contact is
maintained by the tuning plungers. The position and orienta-
tion of the pick-up probes have been adjusted to give strong
coupling to a 50 ft termination which is necessariy to excite
the cavity externally when it is in place in the beam line.
The cavity is now tuned to the third harmonic of the
accelerator frequency and ready for beam tests.
c) Klystron Test Stand in Bldg. 467
J. McKeown
Fabrication of the test stand is complete and crow-
bar testing has begun. The cooling system has been run and service
interlocks have been tested. The rf drive system is in place
and the fast trips are ready for calibration. The electro-
magnet has been energized and one of the U.S. Air Force
klystrons has been prepared for tests. Over a period of
four days the klystron electron gun has been brought to full
- 114 -
filament power without the pressure exceeding 10 Pa. Once
crowbar tests are complete, high power rf tests will begin.
d) Computer Data Acquisition and Control System
J.S. Fraser, J. McKeown and G.E. McMichael
(i) Hardware
Work on relocating the transport control modules
from the control desk to the computer cabinet is about 50%
complete. When finished there will be facilities for com-
puter control of 40 beam transport magnets and 20 other
voltage set points.
(ii) System Software
Integration of the second disk drive into the
system has led to a significant increase in throughput for
program development jobs. Recoding of parts of the FORTRAN
library has corrected known errors and decreased execution
time of certain programs by 50% or more. A free-format input
routine has been added to the FORTRAN library to handle
numeric or Hollerith input using commas as field delimiters.
(iii) Data Acquisition and Accelerator Control
The RFLOG program has been rewritten to read and
display analog data from a single scan of the whole accelerator.
The operator may also select a summary of the important beam
parameters or the parameters of any one of the structures.
The program complements the SCAN/PLTPTS system which displays
data from a few variables taken from several scans. The raw
data is converted to engineering units using scaling factors
which are read from a disk file each time the program is
called. Polynomial fits have been made for the non-linear
sensors used in the calculation of temperature and rf field
level.
- 115 -
e) Beam Profile Wire Scanner Calculations
P.W. James and J.S. Fraser
Further calculations of the power déposition in
wire scanners have led to the choice of a 0.5 mm diameter
stainless steel wire scanner. This material was chosen on
the basis of a compromise between a low Z value, a reasonably
high melting point, good thermal capacity and tensile strength.
Operation of the scanner in the Electron Test Accelerator will2
be limited to electron beams of less than 100 mA/cm (a few
mA for a 2 mm diameter beam).
A scanner using a water-cooled tube has been
rejected because it does not significantly increase the limits
of current operation and because the scanner-tubing could
rupture in the vacuum system.
6.2.3 Fertile-to-Fissile Conversion Experiments at TRIUMF
B.D. Pate, I.M. Thorson and F.M. Kiely (Simon Fraser
University) with J.S. Fraser
This work is intended to provide experimental
measurements of neutron and fissile material production in
spallation targets for a neutron factory and to provide a
verified base for calculations of yields.
a) Experimental
A total of seven irradiations were performed during
this period. The uranium oxide target was repeated because
of indications (negative signal on the self-powered detector)
that beam focusing was poor in the previous irradiations.
The 7-element thorium and uranium assemblies were also
repeated, with a larger complément of gold foils. In
addition, several gold foils were located inside the target
cans, to aid interpretation. The residual radiation fields
of these targets were monitored -\s a function of time.
- 116 -
The neutron leakage measurements analyzed to date
are listed in Table 6.2.3.1; these are only preliminary
results. The data are currently being examined in some detail
to determine, if possible, the origins of certain anomalies
seen in the neutron flux maps.
Table 6.2.3.1 Neutron leakage measurements (neutrons/
proton). Numbers in parentheses indicate
number of determinations. Uncertainties
are maximum deviations from the mean. A
target designation of e.g. Th-7 indicates
a seven-element thorium array.
^^^^^ Incident Proton^Energy(MeV)
Target ^^~*»^^
Th-1
Th-7
Th-19
U-l
U-7
U-19
U-37
UO--372
Pb-1
Pb-7
(4.19 cm)
(3.25 cm)(depleted)
(2.54 cm)(natural)
(10.16 cm)
(3.84 cm)
8.
10.
10.
10.
19.
9.
7.
90
89
16
16
2
18
95
480
±
±
±
11
±
±
±
8.
0.
0.
0.
1.
0
0.
0.
0.
30
3
4
5
4
8
6
3
(3)
(5)
(2)
(2)
(1)
(2)
(3)
(5)
(1)
6
6
10
7.00
11
5
5.39
6
350
.23
.40
.10
± 0.3
.0
.44
± 0.5
.93
(1)
(1)
(1)
(2)
(1)
(1)
(2)
(2)
- 117 -
b) Equipment
(i) Computer System
The NOVA computer systems, for use in the conversion
measurements, have been installed at TRIUMF. Software for
CPU-CPU communication is currently undergoing final testing.
A CAMAC interface is now being installed. This will provide
communication between the NOVA and the automatic sample
changer.
(ii) Sample Changer
Construction of the mechanical elements is proceeding
well in the Simon Fraser University (SFU) machine shop. The
electronic components have been submitted to the SFU electronics
shop and construction is expected to commence shortly.
The planned mode of operation relies primarily
upon the NOVA software. The changer itself will provide two
pieces of information to the computer: (a) that a sample
is in place and ready for counting; and (b) the identification
number (position in the stack) of the sample. The computer,
having this information, can then determine how long the
sample is to be counted (or if it is to be counted at all),
the starting time-of-day, etc. This and other information
is made part of an identification label written on the
magnetic tape with the spectrum collected. Once the computer
is finished with a particular sample, it will issue a
command to the changer to move to the next sample.
6.3 Research Applications
6.3.1 Fast Intense Neutron Source (FINS)
J.D. Hepburn, B.G. Chidley, J. Ungrin and M.R. Shubaly
12Development of the 4 x 10 14 MeV neutrons/s
source for the Biology Division continues.
- 118 -
Proton beam trials on the complete accelerator-
target system continued, with the largest beams obtained
being 25 mA total (17 mA on target) at 275 kV. Reliability
decreased with increasing beam current to about 6 trips per
hour at 25 mA.
It was found that the source and column imposed
conflicting criteria on choice of the extraction electrode
potential that gave the most reliable accelerator performance.
The source required a high potential to prevent the plasma
surface from jumping to the extractor aperture from the
plasma aperture. However, the optimum extractor setting
for column reliability (giving minimum intercepted current
and radiation) was much lower. These effects, together with
a power supply output maximum of 30 kV, prevented reliable
operation above 12 mA total beam ( 6 mA on target).
Experiments showed that the biased extraction
electrode could be replaced by a suitably shaped passive
focus electrode fastened directly to the ion source can, thus
eliminating problems with the extraction electrode and its
power supply. However the passive electrode has changed the
field distribution in the column and reshaping the other
electrodes will be necessary to eliminate regions of excessive
gradient before significantly improved performance can be
expected.
Two types of ion source have been used - one with
a 6 mm plasma aperture which gives between 2 mA and 20 mA
total current, and one with a 10 mm plasma aperture which
gives between 10 mA and 40 mA. At a given current, the
6 mm source is more reliable in the accelerator than the
10 mm one.
The high voltage power supply and auxiliary power
supply reliability has been good, with only one minor repair
to the arc supply required during this quarter.
- 119 -
The target assembly was operated satisfactorily
with up to 17 mA incident on a bare copper drum.
In the present configuration using an ion source
with a passive focus electrode, the unit operates very
satisfactorily in conditions which should produce at least
10 n/s. Typically 3-4 interruptions of about 2 minutas
duration occur during an 8-hour operating day. The beam
spot on the drum is, by visual inspection, round, uniform,
and of an acceptable diameter.
6.3.2 Heavy-Ion Superconducting Cyclotron
J.H. Ormrod
Design and development on a superconducting
cyclotron for a post-tandem accelerator continues. Field
mapping is scheduled for late this fall.
a) Code Development
E.A. Heighway
TRIUMF: A version of this static orbit code has
been developed which includes constraints imposed on v and
v . This was attempted earlier (PR-P-110, 6.3.2 b), AFCL-5546)z
but with limited success. The new version which has been used
successfully for 50 MeV/u carbon 6 (constraining v ) and for
3 MeV/u uranium 21 (constraining v ) uses constrained
optimization routines available from the Harwell Subroutine
Library.
TRIUMF is being enlarged to accept a greater number
of radial intervals in the magnetic field. This will allow
better resolution and improved fitting to the isochronous
field.
- 120 -
b) Cryogenic- Systems
J.A. Hulbert
During the current isport period 3380 litres of
liquid helium were produced for short sample tests on the
magnet conductor.
Additional pressure monitors have been fitted to
the liquéfier and pressure drop surveys carried out on the
heat exchanger before and during liquefaction runs. It is
clear that the fall-off in performance can be attributed to
flow restrictions due to impurities in the helium and no
further refrigeration measurements will be attempted until
the metal-walled low pressure buffer is installed and the
helium high pressure storage is cleaned up.
The liquéfier required mechanical servicing on two
occasions, for replacement of the seals on both pistons and
because of failure of a pressure switch on compressor No. 2.
The seals were replaced in four working hours using stock
spares. Because this was a premature failure (800 hours opera-
tion instead of 6000) the vendor has supplied an improved seal
which we will fit at the next service. The compressor was
out of action for two weeks awaiting delivery of the replace-
ment part.
Room temperature tests on a prototype 2500 A magnet
lead indicate a satisfactory pressure drop and heat exchange
coefficient and a matching lead is under construction for low
temperature tests.
Surface finishing of the prototype cryopump is
complete and the components are awaiting assembly.
Construction of the metal-walled gas holder is
awaiting delivery of the aluminum end shells.
Work orders have been raised for the helium tank
shells and bridge components and for the main vacuum tank
for the cryostat.
- 121 -
An extensive computer analysis is being carried
out on the deflection modes of the helium tank with the aid
of the Mathematics and Computation Branch to ensure that mid-
plane radial field components arising from misalignments
caused by tank distortion under the coil weight and vacuum
loading are acceptable (see section 5.10 (iii)).
c) Magnet
(i) Orbit Dynamics
E.A. Heighway
It was reported (PR-P-112, 6.3.2 c), AECL-5696) that
the presence of *v holes' in the magnetic fields for some low
specific-energy heavy-ions did not influence radial stability.
To clearly understand this, radial phase space in the neigh-
bourhood of a 'hole' was examined in detail using the static
orbit code TRIUMF to locate the fixed points. Figure 6.3.2.1
shows the resulting phase space diagrams. While v < 1,
eight new fixed points exist enclosing a smaller stable region
with v < 1. These fixed points are associated with orbits
enclosing maximum flux by including or excluding flux from
the trim rod field perturbation. This inner region is still
large (20 mm per side) compared with the beam (2 mm radial
width). Only at the two crossings of v = 1 is the stable
region comparable with the beam and then only for 0.1 turn
which explains the negligible beam distortion.
It seems possible that for a brief period between
the radii where 3<B >/3r = 0 and v = 1 a phase space diagram
of the form shown in Fig. 6.3.2.2 may exist. All the inner
stable fixed points would have v > 1. Detailed construction
of the phase space diagram using the accelerated orbit code
GOBLIN has so far not revealed the existence of this type
of diagrair..
vr = 0.997 vr =1.009
-100 -50 50 100 -50 0
X (mm)50 100 -50 50 100
toI
Pig. 6.3.2.1 Behaviour of phase space in the neighbourhood of a 'v hole'. While
vr < 1 eight new fixed points exist. The outer fixed points are undisturbed.
- 123 -
Fig. 6.3.2.2 Possible phase space configuration between
3<B >/3r =z 0 and v
points would have v
= 1. All stable fixed
> 1.
- 124 -
(ii) Yoke
Q.A. Walker (Civil & Mechanical Design Branch)
1) Yoke
Delivery of the yoke has been delayed due to
problems in fabrication techniques. As of 12th March the
status was:
Yoke Wall; This 81 Mg structure was assembled
for measurement and proved satisfactory.
A mishap during subsequent handling
required realignment and machining which
should be complete by the end of March.
End Rings: These are essentially complete requiring
only the dowel brackets to be welded in
place.
Poles: The critical path item is the drilling of
the 104 trim rod holes. The manufacturer
has completed deep drilling tasts which
exposed problems of surface finish in
the bores. To achieve the specified
finish three separate operations are
required and this will extend the time
to complete the poles to mid-April.
2) Trim Rods
The first 40 mm rod driver is complete and ready
for testing. The design of the 60 mm driver is complete; a
work order for its fabrication is being prepared.
3) Hills and Hill PlateEnquiries for steel prices for these items brought
only one quotation, with delivery time of 12 weeks; a purchaseorder is being prepared. The detailed drawings are completeand quotations on fabrication are due March 21st.
4) Lower Pole Jacking System
All hardware has been received or fabricated and
installation started.
- 125 -
(iii) Superconducting Coils
H.R. Schneider
1) Superconductor
All the superconductor for the magnet is now on hand
and short sample critical current tests on all lengths have
been completed.
Figure 6.3.2.3 summarizes the critical current
measurements as a function of transverse magnetic induction,
for the conductor oriented with the broad dimension both
parallel and perpendicular to the magnetic field. The
specification of 3400 A at 4 T with the field parallel to the
broad conductor dimension is exceeded by at least 7% for all
conductor lengths. The perpendicular field specification of
3400 A at 3 T is exceeded by more than 16%.
2) Coil WindingEight double pancake coils have been completed.
3) Solder Joint Resistance Measurements
Electrical connections to the superconducting coil,
and interconnections between pancake windings are made
through non-superconducting soldered joints. These joints
must have low resistance (< 10 fi) to minimize power
dissipation in the liquid helium.
To evaluate the proposed joints, resistances of
Indaloy 2 solder joints have been measured at 4.2 K. Test
specimens were incorporated into the secondary circuit of
the superconducting transformer of the short sample test
apparatus. Resistance measurements were made by inducing a
large current in the secondary (3000 A - 4000 A) and measuring
the potential drop across the solder joint with a micro-
voltmeter. The current was measured with a pickup coil and
integrator in the same way as for the critical current
measurements. Because the secondary current decays with a
time constant of about 15 seconds all measurements were
recorded with an oscilloscope and camera.
- 126 -
4.
cece
3.5
3.0
2.53.0
i i rSCC CONDUCTOR CRITICAL CURRENT AS A FUNCTIONOF TRANSVERSE MAGNETIC INDUCTION
CONDUCTOR BROAD DIMENSIONPARALLEL TO MAGNETIC FIELD
CONDUCTOR BROAD
DIMENSION PERPENDICULAR
TO MAGNETIC FIELD
I I3.5 4.0
TRANSVERSE MAGNETIC INDUCTION TESLA4.5
Pig. 6.3.2.3 Cyclotron superconductor critical current asa function of transverse magnetic induction.
- 127 -
Resistance measurements were made on three joints
of different areas and in magnetic fields up to 4.3 T.
Representing the solder joint resistance R as a function of
joint area A by R = R /A, it was found for the Indaloy 2-12 2
solder joints that R = 3.8 x 10 Çl-m in low magnetic-12 2
fields (<v 0.3 T) and increases to 5.8 x 10 n«m at 4.3 T.
This means the total resistance of all electrical connections
in the coils should be less than 500 nft and the power
dissipation then should be less than 2.6 w.
(iv) Field Measurements
K.C. Chan
The mapping system will use flip coils and be4
capable of an accuracy of 1 part in 10 . Forty flip coils
are distributed along an I-beam with one end pivoted at the
centre of the cyclotron. A stepping motor rotates this beam
in one degree steps in the midplane of the cyclotron and the
coils are flipped at each step. The possibility of automating
and controlling the operation through an HP9830 calculator
is being investigated. The time needed to obtain one field
map, i.e. 360 azimuthal positions at 1° apart, is estimated
to be 3 hours.
The flip coils are 10 mm in diameter and 7 mm high,
and have 1200 turns of 0.114 mm diameter insulated wire.
The dimensions of the coil are chosen to rive no second order
field gradient errors. Several coils and one integrator
have been built for testing. Results show a sensitivity of
1.6 V/T with an error of 0.03 mT/s coming mainly from the
integrator drift.
d) Accelerating Structure
C.B. Bigham
Construction of the full-sized rf structure is half-
finished. Design of the dummy vacuum chamber for out-of-magnet
tests is complete and construction has started.
- 128 -
Response to the first round of quotations for the
main 100 kW rf power amplifier was not satisfactory. Requotes
based on revised specifications are now due.
New power tubes have been installed in the Collins
205-G 20 kW amplifier. Characteristics of the output stage
operating into a resistive load are shown in Fig. 6.3.2.4.
These are close to the characteristics of an ideal class B
amplifier.
The automatic resonator tuner circuit for the full-
scale model tests has been wired and those tests possible will
be run with the Collins 205-G driving the single A/4 resonator
used in earlier work.
e) Injection
(i) Injection Dipole
K.C. Chan
The mechanical design of the injection dipole is
finished. Further calculations have confirmed that the beam
spread introduced at the stripper foil because of the
inhomogeneity of the dipole field is negligible compared to
the original width of the beam.
(ii) Foil Changer
D.L. Beaulieu (Civil & Mechanical Design Branch)
Detailed design of the foil magazine is almost
complete. The foil holder geometry has been tested for foil
mounting (foils prepared by J. Gallant, Nuclear Physics Branch)
and for stacking density.
Foil bulging limits the stacking density to about
one foil per mm of magazine length. Detailed design of the
chain drive is currently underway.
- 129 -
P(rf) = 20 kW
1.0
P(dc)/PB(rf)
0.5
Fig. 6.3.2.4
Vp(rf)/Vp(dc)
Characteristics of the Collins 205-G 20 kWamplifier output stage operating at 46.5 MHz.This stage consists of two grid driven RCA6166A/7007 tubes in parallel. The curves showinput power P(dc), output power P(rf) and platedissipation P(Plate) normalized to Pm(rf) = 25kW plotted against the ratio of plate rf voltageVp(rf) to plate dc voltage Vp(dc). These resultsare typical for class B operation of these tubes.
- 130 -
f) Extraction
C.R.J. Hoffmann
The dimensions of the second segment of the split
magnetic channel have been scaled up to increase its beam
aperture by ^ 30%. Also the leading edge hill lens, which
immediately follows the electrostatic deflector, has been
doubled in length to make it identical with the trailing
edge lens. This improves the orientations of the enclosing
radial and axial emittance diagrams at the magnetic channel
entrance and also contributes to beam deflection.
Calculations have been done to explore methods of
reducing the effects of unwanted fields in the accelerating
region from the extraction system magnetic elements. The
iron components contribute fixed fields. Their first harmonics
are removed by adding iron in diametrically opposite locations.
The unwanted fields from the superconducting elements are
variable. Much of their effects can be removed by adding
compensating superconducting windings, but the trim rods will
probably be needed to get adequate compensation.
6.4 Mechanical Laboratory
J.E. Anderchek
The Mechanical Laboratory operates the machine shop
and furnaces in Bldg. 145 and carries out mechanical con-
struction, assembly, repairs and vacuum testing for the
Accelerator Physics Branch and the Reactor Physics Branch.
Total laboratory time breakdown in the quarter is
as follows:
Accelerator Physics Branch - 99.4%
Reactor Physics Branch - 0.6%
- 131 -
6.4.1 High Current Test Facility
Assistance was provided in the repair of the 400 kW
rf load. A temporary cooling air distribution ring was
fabricated to alleviate an overheating problem on the input
end. Later this was replaced with a more permanent arrange-
ment. For the latter an air supply header was fabricated and
air distribution holes were drilled in the input end
plate. Other components were made to improve the rf match.
All of the bolts used inside the vacuum envelope
of the Alvarez tank were modified to improve evacuation and
an adapter was made to permit electrical tests of the drift-
tube guadrupole magnets with one of the magnet windings shorted.
Parts were fabricated for a gravity operated
grounding switch, and other safety devices for the dc power
supplies which feed the rf po» jr source were made.
A section of the injector beam line through two
quadrupole doublets was modified to allow for improved cooling.
Several special sized crumflat gaskets and two alignment posts
were made and a bending magnet chamber was modified.
A new aperture plate was fabricated for the
emittance measuring unit and a stand was made for the
travelling microscope used to view the emittance photographs.
Two test electrode holders were made for a materials
testing high voltage column and modifications were made to
additional column electrodes.
The cover for the high voltage dome on the test
stand was hinged to ease access to the dome interior and
aluminum sheet was fastened to the top of the dome to improve
electrostatic shielding.
Two new furnace brazed anodes were fabricated for
the FINS-type source; four damaged anodes were replated and
two intermediate electrodes were repaired. A water cooled
plasma aperture plate and a filament holder for a multipole
source were made for ion source development.
- 132 -
6.4.2 Electron Test Accelerator
Major modifications and repairs were made to the
bi-modal non-intercepting beam position monitor, and small
hardware was fabricated for the rf line.
6.4.3 Fast Intense Neutron Source
Much of the shop work involved ion source extraction
and focus electrodes; a stainless steel extractor was
modified and a copper extractor made; one focus electrode was
made and another modified.
A spare ion source can and associated hardware was
fabricated, two anodes were remachined, and some ceramic
stand-offs and copper gaskets were made.
6.4.4 Heavy-Ion Superconducting Cyclotron
Various small coil components and tooling for the
winding line have been made. These include insulator packing
strips, electrical connectors, a drill jig and a radial
clamp sander.
A number of superconductor test specimens were
prepared for short sample critical current measurements.
Some repair work was done as well on the short sample test
apparatus.
Development work for coil electrical connections
required fabrication of a soldering jig and several copper
test pieces.
For the cryogenics a liquid helium transfer tube
was fabricated, several new transfer tube components were
developed and a cryostat and liquéfier regulator were
modified.
Miscellaneous jobs included making a differential
screw prototype for magnet suspension, fabricating several
stripper foil holders and components for sliding seals on rf
- 133 -
structures to prove out designs and manufacturing several
flip coils for magnetic field measurements.
6.4.5 Reactor Physics
ZED-II Reactor
Two lattices spacing bars were modified and a
detector calibration rig was manufactured.
6.4.6 Mechanical Laboratory
A totally metric lathe with a swing capacity of
390 mm and distance between centres of 1250 mm has been
installed.
A linear digital readout system has also been added
to the Bridgeport milling machine so that it can now work
either completely in metric units with 0.01 mm increments
or inches with 0.0005 inch increments. Components can now
be fabricated directly to metric dimensions without con-
version of units.
6.5 Publications, Reports, Papers, Lectures and Patents
Publications
HIGH CURRENT PROTON LINEAR ACCELERATORS AND NUCLEAR POWERP.R. Tunnicliffe, B.G.Chidley and J.S. FraserProceedings of the 1976 Proton Linear Accelerator Conference,September 14 to 17, 1976, Atomic Energy of Canada Limited,Report No. AECL-5677, p. 36 (November 1976).
OPERATION OF THE GRADED-3 ELECTRON TEST ACCELERATORJ.S. Fraser, J. McKeown, G.E. McMichael and W.T. Diamondibid., p. lcf.
CHALK RIVER EXPERIENCE IN THE OPERATION OF HIGH CURRENT 100%DUTY FACTOR ACCELERATING COLUMNSJ. Ungrin, J.D. Hepburn, M.R. Shubaly, B.G. Chidley andJ.H. Ormrodibid., p. 171.
- 134 -
FIELD CONTROL IN A STANDING WAVE STRUCTURE AT HIGH AVERAGEBEAM POWERJ. McKeown, J.S. Fraser and G.E. McMichaelibid., p. 291.
A HIGH POWER RF SUPPLY FOR THE CHALK RIVER 100% DUTY FACTORALVAREZ LINACJ.C. Brown and B.G. Chidleyibid., p. 296.
AN EMITTANCE MEASURING UNIT FOR 100% DUTY FACTOR LINACINJECTORM.R. Shubaly, J. Pachner, Jr., J.H. Ormrod and J. Ungrinibid., p. 313.
EFFECTIVE SHUNT IMPEDANCE COMPARISON BETWEEN S-BAND STANDINGWAVE ACCELERATORS WITH ON-AXIS AND OFF-AXIS COUPLERSS.O. Schriber, L.W. Funk and R.M. Hutcheonibid., p. 338.
MECHANICAL DESIGN CONSIDERATIONS OF A STANDING WAVE S-BANDACCELERATOR WITH ON-AXIS COUPLERSS.B.Hodge, L.W. Funk and S.O. Schriberibid., p. 344.
PRELIMINARY DESIGN STUDY OF A 60 MeV CW ELECTRON ACCELERATORUSING A CONVENTIONAL STANDING WAVE LINACS.O. Schriberibid., p. 405.
Reports
PROCEEDINGS OF THE 1976 PROTON LINEAR ACCELERATOR CONFERENCESEPTEMBER 14 TO 17, 1976S.O. Schriber, editorAECL-5677, November 1976.
Papers
The following papers were presented at the ERDA InformationMeeting of Accelerator Breeding, Brookhaven NationalLaboratory, 18-19 January, 1977.
SOME ACCELERATOR PHYSICS PROBLEMS OF A HIGH CURRENT LINACB.G. Chidley.
HIGH CURRENT PROTON ACCELERATORS AND NUCLEAR POWERP.R. Tunnicliffe.
SPALLATION TARGET PHYSICS AND TECHNOLOGYJ.S. Fraser.
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The following papers were presented at the IEEE ParticleAccelerator Conference Accelerator Engineering and Technology,Chicago, Illinois, 16-18 March, 1977.
COUNTERSTREAMING ELECTRON BEAM PROFILE AND POSITION MONITORS.O. Schriber and K.J. Hohban.
EXPERIMENTAL MEASUREMENTS ON A 25 MeV REFLEXOTRONS.O. Schriber, L.W. Funk, S.B. Hodge and R.M. Hutcheon.
EXTRACTION SYSTEM FOR THE CHALK RIVER SUPERCONDUCTINGHEAVY-ION CYCLOTRONC.R. Hoffmann.
MODELLING OF THE CHALK RIVER SUPERCONDUCTING HEAVY-ION RFSTRUCTUREC.B. Bigham.
STATUS OF THE CHALK RIVER SUPERCONDUCTING HEAVY-ION CYCLOTRONJ.H. Ormrod, C.B. Bigham, J.S. Fraser, E.A. Heighway,C.R. Hoffmann, J.A. Hulbert, P.W. James, H.R. Schneider andQ.A. Walker.
MOVABLE STEEL TRIM RODS AND THE ORBIT DYNAMICS OF THE CHALKRIVER SUPERCONDUCTING HEAVY-ION CYCLOTRONE.A. Heighway.
AN IMPROVED REFERENCE CAVITY DESIGN FOR FREQUENCY TRACKINGOF RF ACCELERATING STRUCTURESR.M. Hutcheon and P.J. Metivier.
HIGH POWER ACCELERATORS FOR SPALLATION BREEDERS OF FISSILEMATERIALJ.S. Fraser.
Lectures
THE CHALK RIVER SUPERCONDUCTING HEAVY-ION CYCLOTRONJ.H. OrmrodPresented at McGill University, Montreal, P.Q.,February 8, 1977.
ACCELERATOR PHYSICSJ.S. FraserPresented at Graduate Seminar, McMaster University,Department of Engineering Physics, Hamilton, Ontario,February 10, 1977.
ACCELERATORS AND SPALLATION TARGETS FOR ELECTRICAL BREEDINGJ.S. FraserPresented at Graduate Seminar, McMaster University,Department of Engineering Physics, Hamilton, Ontario,February 11, 1977.
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THE SPALLATION BREEDERJ.S. FraserPresented at McGill University Physical Society, Montreal, P.Q.,March 25, 1977.
Patents
UNITED STATES PATENT NO. 3,999,096LAYERED, MULTI-ELEMENT ELECTRON-BREMSSTRAHLUNG PHOTONCONVERTER TARGETL.W. Funk and S.O. SchriberIssued 21 December, 1976.
UNITED STATES PATENT NO. 4,006,361X-RAY BEAM FLATTENERS.O. SchriberIssued 1 February, 1977.
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