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Simulations on “Energy plus
Transmutation” setup, 1.5 GeV
Mitja Majerle
The document about simulations of EPT setup can be downloaded in form of report at :
http://ojs.ujf.cas.cz/~mitja/articles/ept.pdf
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Outline Cluster of computers (linux) MCNPX 2.4.0 First tests with PVM (in Třešt) Simulations of PHASOTRON
experiment (presented in Pavia, Avignon)
Simulations of ENERGY PLUS TRANSMUTATION setup (Dubna, Jaipur)
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Cluster
1 server (the slowest machine) Hosts boot through DHCP,
filesystem through NFS – extendable to many hosts
Connections through SSH PVM (Parallel Virtual Machine) PVM works also on li1 and li2.
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Parallel processing
The use of parallel processing (PVM) speeds up our calculations significantly.
A very powerful tool – where to use it ?
2000
4000
6000
8000
0
10
20
30
40
50
60
70
80
90
0 2000 4000 6000 8000 10000
Accumulated processor power [MHz]H
isto
ries
sim
ula
ted
in 1
s
nps=2000k
nps=50k
?
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Simulations, how/what
we calculate
MCNPX code v. 2.4.0 (on Linux, parallel computing)
Input : setup geometry starting conditions
Output 1: neutron
distribution Cross-section libraries
(Au, Al - ENDF; Bi - experimental; Iodine - ?)
Output 2: masses of
produced elements or B-values
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Influence of the setup parts
Concrete walls : Neutrons are
moderated and reflected back
197Au(n,g)198Au
1E-8
1E-7
1E-6
1E-5
1E-4
0 5 10 15 20 25 30 35 40 45
Distance along the target [cm]
B [g
-1 p
roto
n-1
]
experimentalno wallsHTAPE3XFM
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ENERGY + TRANSMUTATION INFLUENCE OF THE SETUP PARTS
simplifications of the setup description different parts of the setup
SYSTEMATIC ERROR (not accurately known exp. conditions)
beam geometry reactions with protons inserted detectors
ACCURACY OF SIMULATION intra-nuclear cascade model used in calculations
PARAMETERS OF THE SETUP the number of produced neutrons (spallation,
fission, ..) k (criticality)
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Control detectors for studying the setup
- with (n,g) we study LE neutrons (flat part) – odd numbers
-(n,4n) threshold is 23 MeV – even numbers
1E-07
1E-06
1E-05
1E-04
1E-03
1E-02
1E-01
1E+00
1E-10 1E-08 1E-06 1E-04 1E-02 1E+00 1E+02 1E+04
Energy [MeV]
Nne
utro
ns
on the target
under Cd
outside box
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The influence of setup parts
We cannot remove some things from the setup and measure.
Simulations help us understand what would happen if we did that.
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The simplifications of the blanket
No influence on high energy neutrons (even numbers)
Box has no influence on HE neutrons !
Box blurs differences.
40%, 10%
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Polyethylene, Cd layer
The spectra were taken inside the 1st and 3rd gap.
No influence on HE neutrons.
1st gap, 3cm from axis
1E-06
1E-05
1E-04
1E-03
1E-02
1E-01
1E-10 1E-08 1E-06 1E-04 1E-02 1E+00 1E+02 1E+04
without Cd
without box
whole_setup
3rd gap, 3 cm from axis
1E-07
1E-06
1E-05
1E-04
1E-03
1E-02
1E-01
1E-10 1E-08 1E-06 1E-04 1E-02 1E+00 1E+02 1E+04
without Cd
without box
whole_setup
absorption done by 238U resonance capture
Comparison of HE part of spectra
0,85
0,9
0,95
1
1,05
1,1
1,15
0,1 1 10 100 1000
Neutron energy [MeV]
Ratio
w ith Cd/all
w ith box/all
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Aluminum and iron holders, upper iron plate
Two simulations with and without Al, Fe components. The results do not differ outside the limits of statistical error - (HE 3%, LE 10%)
The upper iron plate reduces the number of neutrons for 2%.
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The wooden plate
Wooden plate under the target(1+2cm,0.5kg/l).
Without box. Detectors from top to
bottom. Asymmetry 5% =>
negligible wood influence. 0E+0
1E-5
2E-5
3E-5
4E-5
5E-5
-10 -5 0 5 10
Radial foil position [cm]
Pro
du
ctio
n r
ate
Au-198
Au-194
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Systematic error Systematic error may be done,
because we can/did not measure all the experimental conditions.
Simulations give us the estimation of the error.
In simulations we vary experimental conditions in limits of the accuracy with which we measured them.
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Beam parameters influence Beam profile is approximated with Gaussian
distribution (good only near the beam center !). We must always count with beam displacement. Experimentally determined beam profiles and
displacement (V Wagner using monitor and track detector data – for profile mainly I Zhuk data):
Experiment
(Energy) Beam
integral [1013]
Beam integral on lead target [1013]
FWHM (vertical)
[cm]
FWHM (horizontal)
[cm]
Fraction of beam outside
Pb target [%]1)
Position (vertical)
[cm]
Position (horizontal)
[cm]
700 MeV 1.47(5) 1.04(8) 5.91(21) same < 27 -0.4(9) 0.2(2) 1 GeV 3.40(15) 3.25(14) 4.1(3) 2.5(3) < 6 0.2(2) 0.0(2)
1.5 GeV 1.14(6) 1.10(5) 3.7(5) 2.4(5) < 6 0.1(2) 0.3(2) 2.0 GeV 1.25(6) 1.07(10) 5.4(3) 3.8(3) <20 0.3(2) -1.4(2)
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Beam profile
Simulations with 3mm, 3cm homogenous beams and with a beam with gaussian profile (FWMH=3cm).
Differences only for few percents.
Not important.-10
-8
-6
-4
-2
0
2
4
6
1 2 3 4 5 6 7 8 9 10
Foil and reaction number
beam
/3cm
-1 (i
n %
)
3mm/3cm-1
gauss/3cm-1
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Beam displacement
Beam displaced for 3,5,8, and 10 mm.
Differences between results up to tens of % Displacement must be measured as accurately as possible !
0
10
20
30
40
50
60
70
1 2 3 4 5 6 7 8 9 10
Foil and reaction
Dis
pla
ced
bea
m/c
ente
r b
eam
-1 (
in %
)
3 mm
5 mm
8 mm
10 mm
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The influence of protons
Activation detectors could also be activated by protons.
Cross-sections for reactions with protons are not included in MCNPX.
Estimations from Phasotron experiment and neutron/proton ratio : in gaps, near the central axis ca. 10% of activation is due to protons.
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The influence of detectors on neutron field
Metal plate on top reduces the number of neutrons only for 2%. Our detectors are much smaller.
Golden strap (2mm, 4mm) in the first gap has no influence on detectors in other gaps.
Only 0.1 mm thick golden strap is an obstacle for thermal neutrons : it can reduce the production rates of reactions with thermal neutrons inside the same gap for 20%.
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The influence of plastic foils for detectors on neutron field
The 4mm and 8mm polyethylene on which were placed the detectors for 1.5 GeV experiments had effect on LE neutrons.
Au in sandwich of 2 Bi foils => no influence.
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E-10 1E-7 1E-4 1E-1 1E+2 1E+5
nothing
4mm polyeth foil
full poly
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Intra-Nuclear Cascade models
In MCNPX are 3 models (above 150 MeV): Bertini CEM Isabel
The differences are up to 50% (standard, our detectors).
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
1 2 3 4 5 6 7 8 9 10
Foil and reaction
mo
del
/ber
tin
i-1
(in
%)
cem
isabel
-40
-30
-20
-10
0
10
20
30
40
50
60
1 6
11
16
21
26
31
36
41
46
51
56
61
Foils and reactions of the Rez group
mo
del
/BE
RT
INI-
1 (i
n %
)
CEM/BERTINI-1
ISABEL/BERTINI-1
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Neutrons per proton, criticality,..
Experimentally we cannot measure these.
For 1.5 GeV experiment, neutron production :
29 in nuc. Interactions 8 in (n,xn) 14 prompt fission.
Together 54 neutrons per 1 proton.
Without box 49 neutrons, box reflects back 10% of them.
KCODE calculations for criticality :
k=19.2% k was calculated also
by S.R. Hashemi-Nezhad - 22%.
If we add polyethylene wall at the back, k stays the same.
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Neutrons per proton with beam energy
Neutrons per 1 proton and per 1 MeV in the beam
Box adds ca. 5 neutrons
Saturation Peak at 1500 MeV
0
0,005
0,01
0,015
0,02
0,025
0,03
0,035
0,04
0 500 1000 1500 2000 2500 3000
Energy [MeV]N
eutr
ons/
prot
on/M
eV
withoutwith box
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Comparison with the experiment
The Greek group measures the ratios of neutrons inside and outside the box.
Calculated results do not agree with experiment.
Possible reason...
1E-07
1E-06
1E-05
1E-04
1E-03
1E-02
1E-01
1E+00
1E-10 1E-08 1E-06 1E-04 1E-02 1E+00 1E+02 1E+04
Energy [MeV]
Nne
utro
ns
on the target
under Cd
outside box
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Density of polyethylene ?
density 0.35kg/l
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E-10 1E-8 1E-6 1E-4 1E-2 1E+0 1E+2 1E+4
Energy [MeV]
Nn
eutr
on
s
on the target
under Cd
outside box
density 0.7 kg/l
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E-10 1E-8 1E-6 1E-4 1E-2 1E+0 1E+2 1E+4
Energy [MeV]
Nn
eutr
on
s
on the target
under Cd
outside box
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Group from Řež
4 detector types A lot of cross-section
libraries Trends in ratios
experiment/simulation are seen
3 GeV experiment would confirm these trends
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d)
0.0
0.5
1.0
1.5
2.0
2.5
0 5 10 15Radial distance from the target axis R [cm]
exp
/sim
Au196 1.0 GeV Au196 1.5 GeV Au196 0.7 GeV
c)
0.0
0.5
1.0
1.5
2.0
2.5
0 5 10 15Radial distance from the target axis R [cm]
exp
/sim
Au194 1.0 GeV Au194 1.5 GeV Au194 0.7 GeV
b)
0.0
0.5
1.0
1.5
2.0
2.5
-10 0 10 20 30 40 50Position along the target X [cm]
exp
/sim
Au196 1.0 GeV Au196 1.5 GeV Au196 0.7 GeV
a)
0.0
0.5
1.0
1.5
2.0
2.5
-10 0 10 20 30 40 50Position along the target X [cm]
exp
/sim
Au194 1.0 GeV Au194 1.5 GeV Au194 0.7 GeV
Comparison between experiment and simulations
194Au 196AuR
adia
l dis
trib
uti
onL
ongi
tudi
nal d
istr
ibu
tion
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Longitunidal direction
0
0.5
1
1.5
2
2.5
0 10 20 30 40 50 60
l [cm]
EX
P/C
EM
24Na
196Au
194Au
206Bi
58Co
6 MeV
8 MeV
11 MeV
23 MeV23 Mev
Radial direction
0
1
2
3
4
5
6
0 5 10 15
r [cm]
EX
P/C
EM
24Na
196Au
194Au
206Bi
58Co6 MeV
8 MeV
11 MeV
23 MeV 23 MeV
Experiment: Ep = 1.5 GeV
1.5 GeV -different shape of radial distribution for experiment and simulation
0.7 GeV, 1.0 GeV - the similar shape of radial distribution for experiment and simulation
Clear dependence on reaction energy threshold ↔ on the neutron energy
Longitudinal distribution – small differences, maybe done by not included protons
Radial distribution – big differences, description is worse for neutrons with higher energy
ratios normalized on first foil
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Radial distribution 0.7 GeV
0.700.800.901.001.101.201.301.401.50
0 2 4 6 8 10 12
r [cm]
EX
P/S
IM 196Au
194Au
Radial distribution 1.0 GeV
0.70
0.80
0.90
1.00
1.10
1.20
1.30
1.40
1.50
0 2 4 6 8 10 12
r [cm]
EX
P/S
IM 196Au
194Au
Radial distribution for 0.7 GeV and 1.0 GeV
1) Very small differences of shape2) Maybe increase with energy?
Conclusions:
Very important: 1) To analyze 2 GeV experiment 2) To make 3 GeV experiment
0
0.2
0.4
0.6
0.8
1
1.2
0 500 1000 1500 2000
Beam energy [GeV]
EX
P/S
IM 196Au
194Au
Necessary systematic of experiments with different beam energy
Dependence of EXP/SIM ratios for firstradial foil on beam energy