gsi-ea 21 march 2005 decay studies of exotic nuclei with rising & the gsi fragment separator...

GSI-EA 21 March 2005

Decay Studies of Exotic Nuclei with RISING & the GSI Fragment Separator

Spokesperson for the Stopped Beam RISING collaboration: P.H.ReganGSI contacts: J.Gerl & H.J.Wollersheim

Part of the ‘Stopped Beam’ RISING experimental campaign at GSI.

PARTICIPANTS CENBG Bordeaux, France: B. BlankGSI-Darmstadt, Germany: J.Gerl, H.J.Wollersheim, F.Becker, H.Grawe, M.Gorska, P.Bednarczyk, N.Saitoh, T.SaitohIKP Koeln, Germany: J. Jolie, P. Reiter, N. Warr, A. Richard, A. Scherillo, N. Warr TU Munchen: R. Krücken, T. FaestermannUniversity of Camerino, Italy: D. Balabanski, K.Gladnishki, IFJ PAN Krakow, Poland: A. Maj, J. Grebosz, M. Kmiecik, K. Mazurek Warsaw University, Poland: M. PfűtznerUniversidad Autonoma de Madrid, Spain: A. JungclausUniversidad de Santiago de Compostela, Spain: D. Cortina Gil, J. Benlliure, T. Kurtukian Nieto, E. CaserejosIFIC Valencia, Spain: B. RubioINFN-Legnaro, Italy: A. Gadea, G. deAngelis, J.J. Valiente Dobon, N. Marginean, D. Napoli, INFN-Padova, Italy: E. Farnea, D. Bazzacco, S. Lunardi, R. MargineanUniversity and INFN-Milano: A. Bracco, G. Benzoni, F. Camera, B. Million, O. Wieland, S. LeoniUniversity of Surrey, UK: Zs. Podolyàk, P.H. Regan, P.M. Walker, W. Gelletly, W.N.Catford, Z. Liu, S. WilliamsUniversity of York, UK: M.A. Bentley, R. WadsworthUniversity of Brighton, UK: A.M. BruceUniversity of Manchester, UK: D.M. Cullen, S.J. FreemanUniversity of Liverpool, UK: R.D. PageUniversity of Edinburgh, UK: P. Woods, T. DavinsonCLRC Daresbury, UK: J. Simpson, D. WarnerUppsala University, Sweden: H. MachLund University, Sweden: D. RudolphLawrence Berkeley National Lab, USA: R.M. ClarkUniversity of Notre Dame, USA: M. Wiescher, A. AprahamianYoungstown State University, Ohio, USA: J.J. CarrollDebrecen, Hungary: A. Algora


Overall Physics Aims and Technical Background

• Use of FRS and RISING gamma-ray spectrometer to study internal structure of extremely exotic nuclei.

• Relativistic projectile fragmentation to populate - Heavy, neutron-rich nuclei (cold fragmentation). - N~Z nuclei approaching the proton drip-line.

• Active, position sensitive, pixellated stopper to correlate implanted ions (mother) with -decay.

• Measure rays (internal structure) from decays of- ns-ms isomeric states in original implanted ion, and / or- excited states in -daughter nucleus.


Fragmentation at relativistic energies

abrasion ablation

fragmentation


1. N~1261. N~126

2. 2. 190190W - W - 170170DyDy

3. 3. 128,130128,130CdCd4. 4. 7171KrKr5. 5. 6262GaGa

6. 6. 5050FeFe


Fragmentation at relativistic energies

- ion-by-ion identification using FRS.

-decay out from the isomers/betas time correlated with fragments (flight time through FRS: ~300ns)

Initial population in spin/energy plane reasonably well known from isomer ratio work. Good estimates of isomer populationusing ABRABLA and (neutron-rich) production cross-section with COFRA


eg. R. Grzywacz et al. Phys. Rev. C55 (1997) p1126 -> LISE M. Pfützner et al. Phys. Lett. B444 (1998) p32 -> FRS Zs. Podolyàk et al. Phys. Lett. B491 (2000) p225 -> FRS M. Pfützner et al. Phys Rev. C65 (2002) 064604 -> FRS M. Caamano et al., Eur. Phys. J. A23 (2005) p201 -> FRS

primary beamPb @ 1GeV/u

Production target

Central focus, S2Final focus, S4

E(Z2)

cu

eB

Q

A

FTO

catcher

degrader

degrader

dipole, B

scintscint

MW=x,y

scint(veto)

In-Flight Technique Using Projectile Fragmentation

Use Fragment Separator to ID individual nuclei. Transport some in isomeric states (TOF~ x00ns).Stop and correlate decays with nuclei id.


Higher spins for greater A.

M. Pfützner et al., Phys. Rev. C65 (2002) 064604; K. Gladnishki et al., Phys. Rev. C69 (2004) 024617


208Pb beam at 1 GeV/u showed production of heavy, neutron-rich (A>170-200) high-spin (>35/2 h) isomers.

Pfützner et al. Phys Rev. C65 (2002) 064604

High spins (>35/2) populated


14.3 ns

M. Caamano et al., Eur. Phy. J A23 (2005) p201

Stripping the ions of electrons lengthens the apparent isomeric decay half-life by ‘switching off’ conversion electron decay branch


197Au+9Be

5p

4p

Cold fragmentation (protons out) to produce neutron-Cold fragmentation (protons out) to produce neutron-rich nuclei is well modelled by theoretical estimates. rich nuclei is well modelled by theoretical estimates.

Charge states in the FRS: A/Q identification

Difference between B1 and B2 with a degrader and a stripper at S2

O-1

O-2

1-OO-O

E MUSIC

E d

egra

der

Charge states in the MUSICs: Z identification

Correlated measurement with two MUSICs with a stripper in between

E Music 1 E Music 2

E M

usi

c 1

E Music 2 E


Fragmentation of 1 GeV/u 208Pb, M. Caamano et al., Eur. Phy. J A23 (2005) p201

fully-stripped H-like

184Lu, H-like fully-stripped

188Ta


Prompt ‘flash’ can be a limiting problem for fragmentation isomer spectroscopy.

Can reduce the effective Ge efficiency factors of 3-4 for close geometry….

but 105 (15 x 7) detectors in RISING will improve this.


RISING set-up with stopped beams

RISING GeCluster Array.

MUSIC MUSIC

Sci

41

MW

41 MW

42

deg

rad

er

beambeam


5 at 510, 5 at 900 and 5 at 1290 all at 209.8mm Photopeak efficiency 17.2% at 1.3MeV

8 BaF2 detectors (185-220mm)


Implantation detector

double sided silicon strip detectoractive area 50x50 mm2

thickness 1 mm16 strips in x- and y-direction

Active stopper = 3 x DSSSD Active area, 15cm x 5 cm

Implantation range

Monoenergetic degrader at S2: larger implantation surface at S4 smaller dispersion in the implantation range

Achromatic degrader Monoenergetic degrader

Implantation range

Estimated implanted isotopes for a setting centered on 192W in 1 mm thickness silicon with a monoenergetic degrader at S2

Silicium thickness (m)

ch

arg

e s

tate

s

Detector setup for half lives measurement

Implantation-decay correlations with large background (half lifes similar to the implantation rate):

implantation-decay time correlation: active catcher implantation-decay position correlation: granularity implantation of several ions: thickness and area energy of the implanted ion and the emitted

Active catcher for implantation-decay correlations

3 double-side silicon-strip detectors

- surface 5x5 cm2

- thickness 1 mm - 2 x 16 3.125 mm strips - manufactured by MICRON


Count Rate Limitations with Active Stopper• 3 x 16 x 16 = 3 x 256 = 768 total pixels.

- Assume upper limit for -half-life of ~30 seconds- Each pixel hit every 5 half-lives (150 secs)

• Max. rate of ~768/150 = 5 per sec ( = 50 per 10s spill).

• Rate increases directly with decreasing half-life

- (e.g., T1/2 = 10 seconds -> 150 per 10 s spill cycle)

• Dual gain pre-amps on DSSSD to get energies of implanted ion and -particle

• All events time stamped with MHz clock.

Implantation procedure

Setting centered on 186Lu

Produced Implanted

MUSIC 1

SC4SC42

SC43

MUSIC 2

MUSIC 3

Sc43Sc42


The GSI FRS γ-Ray Spectroscopy Campaign S210 (2001)

Proposals Nuclei of Interest

Proposers Beam time approved (days)

status

Evolution of shell structure outside doubly magic 132Sn

Around 132Sn

M. Hellstrom, M. Miveva

4

Isomer decay probe of shape coexistence Lead isotopes

N <104, Pb, Po, Rn

R. Page, R. Wadsworth

5

Shape coexistence in neutron rich Po -> Th nuclei

A~230, Po - Th

Z. Podolyak 5

Isomer spectroscopy of fission fragments close to 78Ni

Around 76Ni M. Bernas, H. Grawe

7

Effective charge near 56Ni 54Ni, Tz = -1

D. Rudolph 4

Isomer spectroscopy of the odd-odd Tz=0 nuclei

82Nb, 86Tc P. Regan, B. Blank

5

Along the N=126 closed shell: Nuclei below 208Pb S299

N~126 south of 208Pb (isomers)

Z.Podolyak 7

Shape co-existence and the possibility of X(5) behaviour in neutron-rich A~110 nuclei S300

106Zr A.M.Bruce 7


RISING: Stopped Beam Campaign

Proposals Nuclei of Interest

Proposers Beam time request (days)

status

ß-decay lifetimes, ß-decay spectroscopy studies and collective evolution "south" of 208Pb S312

N~126 south of 208Pb

J. Benlliure, P.H.Regan

7

Nuclear dynamical symmetries and shape evolution in K-isomeric nuclei from 190W to the 170Dy valence maximum S313

190W- 170Dy

P.H. Regan, J.Benlliure

8

Search for the 8+(πg9/2)-2 isomer in N=82 130Cd populated via the 6 proton knockout channel in the fragmentation of 136Xe S305

130Cd A. Jungclaus 7

Exotic ß-decays near the proton-drip line: study of the ß-ecay of 70,71Kr S314

70,71Kr A.Algora, B.Rubio, B.Gelletly

7

Proton-neutron pairing effects in the ß-decay of 62Ge S315

62Ge A.Gadea, G.deAngelis

6

Isospin symmetry of transitions probed by weak and strong interactions: the ß-decay of 54Ni, 50Fe, and 46Cr S316

54Ni, 50Fe, 46Cr

Y.Fujita, W.Gelletly, B.Rubio

7

100Sn: Gamov-Teller strength in its decay, search for its isomer, and particle stability of heavier nuclei LOI41

100Sn T.Fästermann


Proposal A:1 (S312)

-Decay Lifetimes, -Delayed Spectroscopy Studies and

Collective Evolution ‘South’ of 208Pb

J. Benlliure, P.H. Regan et al.,

Universidade de Santiago de Compostela, SpainDepartment of Physics, University of Surrey, Guildford, GU2 7XH, UK

IKP, University of Cologne, 50937 Cologne, GermanyPlanckstrasse 1, GSI, Germany

TU Muenchen, GermanyWarsaw University, Poland

Uppsala University, SwedenDept. of Physics, University of Liverpool, UK

Dept. of Physics and Astronomy, University of Manchester, UKCLRC Daresbury Laboratory, Cheshire, UK

University of Camerino, ItalyUniversidad Autonoma de Madrid, Spain

STOPPED BEAM CAMPAIGN - A


Proposal A:2 (S313)

Nuclear Dynamical Symmetries and Shape Evolution in

K-isomeric Nuclei from 190W to the 170Dy Valence Maximum.

P.H. Regan, J. Benllliure et al.,

Department of Physics, University of Surrey, Guildford, GU2 7XH, UKUniversity of Santiago de Compostela, Spain

IKP, University of Cologne, 50937 Cologne, GermanyPlanckstrasse 1, GSI, Germany

Warsaw University, PolandUppsala University, Sweden

CLRC Daresbury Laboratory, Cheshire, UK University of Camerino, ItalyUniversity of Manchester, UK

Youngstown State University, Ohio, USA IJF, PAN Krakow, Poland



Effect of Nuclear Deformation on (K) isomers

50g9/2

g7/2

d5/2

s1/2

d3/2

h11/2

(8)

(6)

(2)

(4)

(12)

h9/2 (10)

82

(10)

Spherical, harmon. oscilator H = h+al.l+bl.s, quantum numbers jmj

Nilsson scheme: Quadrupole deformed 3-D HO. where h -> hx+hy+hz

axial symmetry means x=yquantum numbers [N,nx,]

K= sum of individual values.

z

x

High- (DAL) orbit

z

x

Mid- (FAL)

z

xLow-, (RAL)

> prolate 2


82

126

50

82Expect to find K-isomers in regions where high-K orbitals are at the Fermi surface.

Also need large, axially symmetric deformation

(

Conditions fulfilled at A~170-190 rare-earth reg.

High- single particle orbitals from eg. i13/2 neutrons couple together togive energetically favoured states with high-K (=i).


Search for long (>100ms) K-isomers in neutron-rich(ish) A~180 nuclei.

low-K high-K mid-K j

K

:rule sel. -K

Walker and Dracoulis Hyp. Int. 135 83 (2001)

(Stable beam) fusion limit makes high-K in neutronrich hard to synthesiseAlaga, Alder,

Bohr and Mottelson,Mat. Fys. Medd. 29 no 9 (1955)


Podolyak et al., Phys. Lett. 491B (2000) 225;Caamano et al., EPJ A23 (2005) 201

Discontinuity (change of structure)observed for 190W following GSI isomer (K=10-) spectroscopy.


0

50

100

150

200

250

300

350

400

450

Yb (70) Hf (72) W (74) Os (76) Pt (78)

108

110

112

114

116

118

120

122

E(2E(2++) is signature of deformation. Possible shape change ) is signature of deformation. Possible shape change identified from identified from 190190W data point (N=116).W data point (N=116).

Proposal to identify Proposal to identify first 2first 2++ state in state in 192192W (N=118)W (N=118)188,190188,190Hf (N=116,118)Hf (N=116,118)186,188186,188Yb (N=116,118)Yb (N=116,118)

Decays from IDecays from I=10=10- -

isomers and/orisomers and/or -- decay of decay of 192192TaTa188,190188,190Lu andLu and186,188186,188Tm Tm

tt1/21/2 ~1-5 secs ~1-5 secs


Constrained HF calculations (Stevenson)suggest prolate-oblate shape change/competition at N=116 isotones, 188Hf, 190W, etc.

Physics interpretation consistentwith O(6) ‘critical point’ in extended ‘Casten triangle’ at phase transitionbetween prolate and oblate axially symmetric shapes.See Jolie and Linnemann, Phys. Rev. C68 (2003) 031301(R)


170Dy, double mid-shell, nature’s purest K-isomer ? P.H. Regan et al. Phys. Rev. C65 (2002) 037302

Reduced hindrance correlated with N.N…max. at 170Dy...

K=6+ isomer

K=0+ band


Apparent underlying SU(3) dynamical symmetry for N=104.(see Casten et al., Phys. Rev. C31 (1984) R1991)

Is 170Dy nature’s best SU(3) nucleus too ?168Tb->168Dy, T1/2=8 s Asai et al., Phys. Rev. C59 (1999) 3060


Primary 198Pt beam @ 1GeV/u, intensity of 109 particles per spill, 10 second spill cycle. 2.5 g/cm2 thick Be target, 5.1g/cm2 Al. degrader at S2, plus a 108mg/cm2 Niobium stripper. Cross-section estimates from the COFRA.Estimated values for transmission per eight hour

shift are: Setting 1: Centred on 191W

190W 1x107 191W 0.4x107 192W 0.4 x107

Setting 2: Centred on 187Hf 187Hf 3.7x105 188Hf 9x104 189Hf 1x104

Setting 3: Centred on 185Yb 184Yb 2x104 185Yb 6x103 186Yb 240

20% -ray efficiency for 662 keV, (~50%) prompt-flash, isom. ratio

(~5%), Yield estimates for observed photopeak rays per 8 hour shift of 190W 250,000 ; 192W 100,000 ; 188Hf 2,250 ; 184Yb 500 ; 186Yb 6 Setting 4: Centred on 170Dy

170Dy 1.4x105 170Tb 4,500 168Tb 4.9x104

Assuming -ray (0.2) and -detection (0.5) efficiency for decays of 170Tb

gives 450 photopeak rays from the decay of the first 2+ state in 170Dy per

shift. Setting 1: 3 shifts (1 day) ; Setting 2: 3 shifts (1 days)Setting 3: 6 shifts (2 days) ; Setting 4: 6 shifts (2 days)2 days (6 shifts) primary beam tuning and particle id. calibrations, 191W

setting:Total beam request of 24 shifts (8 days).


Proposal A:3 (S305)

Search for the 8+ (g9/2)

-2 isomer in N=82 130Cd populated via the 6 proton knockout channel in the

fragmentation of 136Xe

A. Jungclaus et al.,

Universidad Autónoma de Madrid, Spain Institute of Nuclear Research, Debrecen, Hungary

Universidad de Santiago de Compostela, SpainGSI Darmstadt, Germany

Uppsala University, SwedenUniversity of Surrey, UK

Universität zu Köln, Germany University Warsow, Poland

IFIC Valencia, Spain Lund University, Sweden



Search for the 8+ (g9/2)-2 isomer in N=82 130Cd populated

via the 6 proton knockout channel in the fragmentation of 136Xe

Why study 130Cd ?

astrophysical reasons:

130Cd is the most important waiting-point nucleus before the r-process breakout of the N=82 shell

relation between N=82 shell closure and the A~130 peak of the solar r-process abundance distribution

r-process path

N=82

Z=50

130Cd

132Sn


nuclear structure reasons:

unexpected behaviour of the 2+ excitation energies of even Cd isotopes towards the N=82 shell closure (change of curva- ture starts already at 124Cd)

there is a series of other nuclear structure puzzles in the 132Sn region

Is this behaviour really a “signature of a weakening of the N=82shell structure already one proton-pair below 132Sn” as suggestedby the authors of the experimental study ?

50 54 58 62 66 70 74 78 82

400

800

1200

1600 Pd Cd Sn Te

E(2

+ ) [k

eV]

neutron number N

-decay @ ISOLDEKautsch et al., EPJ A9 (2000) 201

Sn

TeCd

Pd


-0.2 -0.1 0.0 0.1 0.2

-6

-4

-2

0

2

4 130Cd

128Cd

126Cd

I=2

Ene

rgy

[MeV

]

2

-0.2 -0.1 0.0 0.1 0.2

-6

-4

-2

0

2

4

I=0

130Cd

128Cd

126Cd

Ene

rgy

[MeV

]

2

-0.2 -0.1 0.0 0.1 0.2

0

2

4

6

8

10

HFB

Ene

rgy

[MeV

]

2

Is there an alternative explanation ?

mean-field after angular momentum projection

132Sn curve much broader than that for 208Pb

fluctuations in 2 much more important in132Sn indicating that a higher degree of collec-

tivity remains in 132Sn as compared to 208Pb

after angular momentum projection, 126Cd and128Cd show deep prolate minima already at I=2ħ

constrained HFB+AMP with Gogny force, J.L. Egido

Does quadrupole collectivity persists closeto N=82 in the chain of Cd isotopes ?

208Pb

132Sn

130Cd

128Cd126Cd

(Remember: 32Mg is spherical at mean field level, but deformed after projection !)


A=128

A=126

-decay study of heavy Cd isotopes at ISOLDE

In general: Problems due to beam intensity anddominating In and Cs isobaric activities !

Kautsch et al., Eur. Phys. J. A9 (2000) 201

50 54 58 62 66 70 74 78 82

400

800

1200

1600 Pd Cd Sn Te

E

(2+ )

[keV

]

neutron number N

Sn

TeCd

Pd

Can probably not be done betterat ISOLDE at the moment !

“… has to be considered speculative …”

“… close to the present limit thatcan be achieved with RILIS andGPS-ISOLDE.”


NiZn

Ge

Gd

54 56

524846444240383634323028

Sr

Mo

Ru

Pd

Cd

100Sn Te

Xe

Ba

Ce

Nd

Sm

58 60 62

68 70

72

7476 78

8082

Z

50

50

N=Z

132Sn

98Cd 102Sn 134Sn 130Sn134Te130Cd

(g9/2)-2 (d5/2 g7/2)2 (g9/2)-2 (f7/2)2 (g7/2)2 (h11/2)-2

0+

8+

0+

6+

0+

6+

165 ns

1.6 s

80 ns

480 ns

1.0 s

0+ 0+0+

6+

4+

2+

2+

2+

4+

4+

4+6+

2+

4+6+

2+

8+10+

?

N

8+ isomer with (g9/2)-2 con-figuration expected in 130Cdin analogy to the one in 98Cd

Study of 8+ isomer decay in 130Cd (and 128Cd)

already searched for withoutsuccess at LOHENGRIN andFRS (Mineva, Hellström et al.)

Advantage compared to -decay:• possible observation of whole sequence up to the 8+ state• lifetime of the isomer itself contains valuable information


Production of 130Cd @ FRS

238U fissioncold fragmentation

of 136Xe

implantation rate at the focal plane:

I [sec-1] = [cm2] · d[g/cm2] · A-1[mol/g] · [sec-1] · Ttot · NA[mol-1]

cross section

target thickness d

primary beam current

total transmission

0.1 bcalc. !

0.154 nbmeasured !

1 g/cm2 2.5 g/cm2

109/spill (15s) 5·109/spill (5s)

3.5% 95%

1.4 (2000)0.9 (1300)implanted 130Cd/min(d)

for Be target

Mineva et al.:=2·107 sec-1

in total 700implanted 130Cd measured

easier beameasier exp.


130Cd setting 131In setting

Transmission simulations with the Lieschen code

known isomers in 127Cd and 130Inwill be observed at the same timein the setting optimized for 130Cd

130Cd

127Cd

130In

N N

ZZ132Sn

129In

this setting could be used for a quickcalibration using the known isomersin the strongly populated nuclei 132Snand 129In


Proposal A:4 (S314)

Exotic Beta decays near the proton-drip line: study of the beta decay of 70,71Kr.

A. Algora, B. Rubio, W. Gelletly et al.,

Institute of Nuclear Research, Debrecen, HungaryIFIC, CSIC, Valencia, Spain

University of Surrey, Guildford, UKUniversity Santiago de Compostela, Santiago, Spain

Osaka University, Osaka, JapanUniversidad Autonoma de Madrid, Madrid, Spain

CIEMAT, Madrid, Spain GSI, Darmstadt, Germany

LNL, Legnaro, Italy


Exotic decays near the proton-drip line: study of the beta decay of 70,71Kr

71Kr case: Motivations

• Study of mirror T=1/2 pairs

• Identification of IAS of 71Kr g.s. (not known)

• N~Z region around Z=36-38: shape effects, shape coexistence, shape transitions, isospin symmetry

• Determination of the ground deformation of 71Kr


71Kr case II

Ref. Oinonen et al PRC 52 (1997) 745


Motivation: Search for states populated in the beta decay of 70Kr, which

may indicate the existence of the proton-neutron condensate

Background: Validity of the IBM-4 classification scheme in light

nuclei (18Ne18F, P. Halse, et al. NPA 417 (1984) 301) Existence of some examples in medium-heavy and

heavy nuclei that can be explained using this scheme. Transitions with small log ft, that can not be explained because of large hindrance factors in fermion transitions but can be explained assuming boson transitions. (130Sn131Sb, Iachello et. al).

Necessity to study systems in the vicinity of the N~Z line

70Kr case I


(0+)

T=1

T=0

0+

(1+ ?)

2+

0+

(700 keV)?

4.0?

3.5?

3.5

74Sr

70Kr

62Ge

58Zr

66Se

Tz = -1

Franco Iachello, private comunication

347036 Kr

357035 Br

367034 Se

70Kr case II


(0+)

T=1

T=0(1+ ?)

0+

(700 keV)?

4.0?

3.5?

Franco Iachello, private comunication

347036 Kr

357035 Br

70Kr case II

If the 1+ condensate exists, then the GT strength can be very large because may pairs can participate


Primary beam: 109 ions/s of 92MoTarget: Be (4000 mg/cm2)

Expected Yields (LIESCHEN)70Kr: 1.1 x 103 ions/h71Kr: 6.3 x 104 ions/h

Implantation area: 5 x 5 cm2 DSSD detector with 16 x 16 stripsBeam requirements: 1 week (6 days measurement + 1 day preparation)

Measurements

Assuming a feeding of 50 % at an excitation energy of ~ 700 keV, a production of 0.3 atoms/s and a detection efficiency of 15 % for a ray of 700 keV 2000 counts/day in the - coincidence spectrum

70Kr: 2 days

71Kr: 4 daysAssuming a production of 18 atoms/s, a feeding of 1 % to the level that decays consequently with a cascade of 2 -s with energies of 200 keV and 1.0 MeV ( detection efficiency of 30 % and 10 % respectively) 500 counts/day in the - coincidence spectrum


Proposal A:5 (S315)

Proton-Neutron Pairing Effects in the Beta Decay of 62Ge

A.Gadea, G.deAngelis et al.,

INFN-Laboratori Nazionali di Legnaro, Padova, ItalyUniversity and INFN-sezione di Padova, ItalyUniversity and INFN-sezione di Milano, Italy

University of Surrey, UKGSI-Darmstadt, Germany

University of Lund, SwedenUniversity of Santiago de Compostela, Spain

IFIC Valencia, SpainInstitute of Nuclear Research, Debrecen, Hungary



Proton-neutron pairing effects in the -decay of 62Ge

• Study of the p-n condensate through -decay experiments. Low lying 1+ states in odd-odd nuclei have components corresponding to a proton-neutron T=0 condensate.

• Collective transitions of correlated pairs will lead to “superallowed” GT transitions.

• Large B(GT) to 1+ T=0 states observed in light nuclei -decay (18Ne). Single fermion GT transitions in medium mass nuclei

are highly retarded logft > 4. If p-n pairing survives small logft (large G(GT) values are expected.

Boson space of correlated Boson space of correlated nucleon pairs in IBM-4nucleon pairs in IBM-4

6262Ga Ga N=3N=3


N=ZN=Z

Sequential decay:Sequential decay:

6262Ge (129ms) Ge (129ms) → → 6262Ga (116ms) → Ga (116ms) → 6262Zn (9.1h)Zn (9.1h)

With active catcher the sequence of 129ms + 116ms decays With active catcher the sequence of 129ms + 116ms decays

(Q(QECEC>9 MeV for both >9 MeV for both ++--++) can help to identify the ) can help to identify the 6262GeGe surviving surviving

implantationimplantation

F.Iachello F.Iachello


D.Rudolph et al., Phys. Rev.C69(2004)034309D.Rudolph et al., Phys. Rev.C69(2004)034309

LNL-GASP in beam experimentLNL-GASP in beam experiment

Theory: Theory: Shell model Shell model pfpf5/25/2gg9/2 9/2

S.M.Vincent, et al., Phys. Lett. B437(1998) 264 O.Juillet, et al., Phys. Rev. C63 (2001)054312A.Juodagalvis et al., Nucl. Phys. A683(2001)207

Deformed shell modelDeformed shell modelR.Sahu,et al.,Phys. Rev. C66 (2002)024301

Cranked Nilsson-StrutinskyCranked Nilsson-StrutinskyA.Juodagalvis et al., Nucl. Phys. A683(2001)207

IBM-4IBM-4O.Juillet, et al., Phys. Rev. C63 (2001)054312

Low lying Low lying states level states level

scheme scheme 4040Ca(Ca(2424Mg,pn)Mg,pn)

Added value: spectroscopy of the low lying low spin states Added value: spectroscopy of the low lying low spin states (calculated more than 10)(calculated more than 10)

4.6ns4.6ns

Lifetime 3Lifetime 3++→→11+ + 4.6ns 4.6ns B(E2) B(E2) ≈ 14W.u.≈ 14W.u.

S.M.Vincent et al. Phys.Lett. B437(1998)264S.M.Vincent et al. Phys.Lett. B437(1998)264Calculated CNS g.s. deformation: Calculated CNS g.s. deformation:

≈0.17≈0.17


6262GeGe QQECEC≈9.7≈9.7

SSpp

O.Juillet et al., Phys.Rev.C(2001)054312O.Juillet et al., Phys.Rev.C(2001)054312

0+ T=10+ T=1

SS=1=1

IBM-4 IBM-4 6262Ga N=3 Ga N=3


Beam Time request• The 62Ge is produced by 78Kr beam (400 MeV/u) fragmentation. • EPAX ~10-7 barns - 20% transmission of the FRS - primary 78Kr beam of

~109 atoms/s - 1.6g/cm2 Be target.• 62Ge rate at the implantation site ~ 2 atoms/s, (~150 MeV/u).• The efficiency of the RISING array is 11% for E=1.33 MeV and 20% for

662 keV.• Approximately 95% of the 62Ge atoms will survive implantation and will

partially decay to the 0+ ground state in 62Ga and partially to excited states and in particular to the 1+, at 571 keV

• The precise measurement of the 571 keV transition intensity, compared with the total number of decays of 62Ge nuclei will give the logft of the GT transition to the low lying 1+, and this value will allow to extract important information on the nature of the state.

• In the same experiment we will explore the population of other 1+ states that might carry also a consistent fraction of the expected collectivity.

• The investigation of the decay level scheme will require a minimum of ~105- 106 decays and a beam time of 5 days (15 shifts) of measurement will be necessary.

• One extra day necessary for the setup of RFD and detectors.• TOTAL BEAMTIME REQUESTED 18 shifts (6 days)


Proponents• A.Gadea, G.deAngelis, N.Marginean, D.R.Napoli, J.J.Valiente-Dobón, Q.Zhong

INFN-Laboratori Nazionali di Legnaro, Padova, Italy• E.Farnea, D.Bazzacco, S.Lunardi, R.Marginean

University and INFN-sezione di Padova, Italy• A.Bracco, G.Benzoni, F.Camera, B.Million, S.Leoni, O.Wieland

University and INFN-sezione di Milano, Italy• Zs.Podolyàk, P.H.Regan,W.Gelletly, W.N.Catford, S.Williams

University of Surrey, UK• M.Gorska, J.Gerl, H.J.Wollersheim, F.Becker, H.Grawe, L.Caceres,

P.Bednarczyk, N.Saitio, T.SaitoGSI-Darmstadt, Germany

• D.Rudolph, L.L.Andersson,E.K.JohanssonUniversity of Lund, Sweden

• J. Benlliure, D. Cortina GilUniversity of Santiago de Compostela, Spain

• B.RubioIFIC Valencia, Spain

• A.AlgoraInstitute of Nuclear Research, Debrecen, Hungary


Proposal A:6 (S316)

Isospin Symmetry of Transitions Probed by Weak andStrong Interactions: the beta decay of 54Ni, 50Fe, 46Cr

Y. Fujita, B. Rubio, W. Gelletly, A. Algora et al.,

Osaka University,Osaka,JapanIFIC, CSIC, Valencia, Spain

University of Surrey,Guildford,UK Inst.for Nuc.Phys.,Debrecen,Hungary

Universidad Autonoma de Madrid,SpainCCLRC,Daresbury,UK

University of Santiago de Compostela,Santiago,SpainUniversity of Leuven,Leuven,Belgium

GSI, Darmstadt, Germany



Isospin Symmetry of Transitions Probed by Weak and Strong Interactions: the decay of 54Ni, 50Fe, 46Cr.

Osaka, Valencia, Surrey, Debrecen, Leuven, Madrid, Daresbury, Santiago and GSI.

Aim:- A test of Isospin symmetry from a comparison of beta decay and charge exchange at 00

Background:- Charge independence means that Isospin should be a good quantum no.

In the absence of isospin mixing, Gamow-Teller decays from mirror parents to common daughter states should be identical.

Here we propose to measure the beta decays of 54Ni, 50Fe and 46Cr with the RISING setup with an active stopper to determine the B(GT) values to levels in the daughter nuclei for comparison with the same quantities measured at 00 in the (3He,t) reaction at Osaka with the Grand Raiden spectrometer.

The charge exchange reactions have already been studied and are being analysed.

Spokespersons:-Y.Fujita,B.Rubio and W.Gelletly


265428 Ni 28

5426 Fe

275427Co

0+TZ=-1T=1

0+TZ = 0T=1

0+TZ=+1T=1β+/EC (p,n)

(3He,t)

0+TZ = 0T = 1

A schematic illustration of the transitions to levels in the N = Z nucleus 54Co by beta decay and charge exchange reactions.

A typical example of an isobaric triplet to be studied


Typical example of the Charge Exchange Spectra

Spectrum taken with the Grand Raiden spectrometer at Osaka Uni.The energy resolution is ~ 30 keV with a 3He beam energy of 150 MeV.This spectrum was taken at zero degrees. As a result only the L = 0,S = 0 transitions are observed.


Further Examples of the Charge Exchange Spectra

● All of the charge exchange studies of interest in the present work have already been made.

● The spectra are all of high quality and have similar resoluton.

● The spectra shown are all taken at 00 .

●Analysis of all these spectra is already underway.


MeasurementsPrimary Beam: 0.1 pnA of 58Ni ions at 600 MeV/uTarget: Be of 4000 mg.cm-2 thicknessExpected yields from LISE++ 54Ni: 280 ions per sec. 50Fe: 240 ions per sec. 46Cr: 190 ions per secActive Target: Si DSSD of 5 x 5 cm2 area with 16 x 16 stripsTotal Beam requirement: 1 week(3x2 = 6 days measurement + 1 day preparation/setup)e.g. 54Ni: 2 days We assume that we have 290 ions per sec on DSSD and 10% eff. for gammas at 1MeV. We also assume preliminary value of B(GT) from Charge exchange. Gives an estimate of 1500 counts in decay of 2010 keV level.

gsi-ea 21 march 2005 decay studies of exotic nuclei with rising & the gsi fragment separator...

Documents

implantation rate

granularity implantation

implantation proceduresetting

implanted sc43sc42gsiea

larger implantation

micron gsiea

x dsssd active area

active stopper3 x