spectroscopy studies by decay -proton-rich nuclei n~z deformation in the mass region a~75...
TRANSCRIPT
Spectroscopy studies by decay
-Proton-rich nuclei N~ZDeformation in the mass region A~75Fundamental aspects of weak interaction, test of CVC
-Neutron-rich nuclei Z~20effective interaction in the mass region A~50
Cécile Jollet, IReS Strasbourg, TAS Workshop, Caen March 31, 2004
decay: general features
Exploration of nuclei with large Q value (nuclei far from stability) Provides the first information on new speciesFundamental aspects of weak interaction
Nuclear structureNucleosynthesis
Spectroscopy detection of , and delayed particules (neutrons or protons, and -rays)
Informations provided: Mass excessHalf-life T1/2
feedings Ift = f(Z,Q-Ex) T1/2 / Ift = Cste / |Mif|2
Matrix elements, nuclear configurations
1-Proton-rich nuclei N~Z, A~75
Theoretical and experimental works in this region shape isomerism or shape coexistence strongly deformed ground states
Good efficiency for detection on the whole QEC window construction of a new Total Absorption gamma Spectrometer (TAgS)
Installation of TAgS at ISOLDE in 2001
Study by decay: 72,73,74,75Kr and 76,77,78Sr
Detection: TAgS + Ge detectors (X, ) and plastic scintillators ()
In this region, large part of the GTGR is accessible by decay Estimate the deformation by measuring the complete B(GT)
distribution
Hamamoto, Sarriguren Shape of the GT strength distribution depends on the shape of parent nucleus ground state
I. Hamamoto et X. Z. Zhang, Z. Phys. A353 (1995) 145.
Total Absorption gamma Spectrometer (TAgS) (Madrid, Strasbourg, Surrey, Valence)
NaI monocrystal (diameter=38cm, length=38cm)
+8 PMTs 5”
Ancillary X, , detectors
TAgS properties:Energy resolution: 7.1% at 662 keV
5.4% at 1332 keV
Efficiency at 662 keV: 95(8)% total 83(7)% photopeak
Solid Angle: 97% of 4
Boron polyethylene:10cmLead:5cmCopper:2cmAluminium:2cm
Shielding
Collection point
New beam line
Tape transportsystem
1-Proton-rich nuclei N~Z, A~75
76Sr --------> 76Rb+ EC
E. Nácher et al., submitted to PRLE. Poirier et al., PRC69,034307 (2004)
74Kr --------> 74Br+ EC
Shape mixing Prolate shape
Results in good agreement with theory and with previous experiments decay studies value and sign of the deformation
validation of TAgS spectroscopy
oblate
prolateexp.
1- Proton-rich nuclei N~ZFundamental aspect of weak interaction
V-A theory, hyp: the Vector Current is conserved (CVC)vector part of weak interaction not influenced by strong interaction
To test CVC: study of superallowed Fermi transitions 0+0+ Ft = ft (1+r) (1-c) = cste (r, c are correction terms)
We need to determine the complete decay scheme, r and c
TAgS measure branching ratios and T1/2 with the required precision
Current measurement with TAgS : study of 62Ga
for A=10-54, Ft=3072.3(2.0) s with precisions: 3.10-4 for T1/2
3.10-4 for branching ratios 5.10-5 for energy
In progress, new measurements for A>54
Ft
(s)
62Ga
66As
70Br
74Rb
88Y
82Nb
86Tc
Z
Ft
(s)
3065
3070
308010C
14O
26Al
34Cl
38K
42Sc
46V
50Mn54Co
Present results
g 9/2
2-Neutron-rich nucleiA~50, Z~20
(F. Perrot thesis)
Neutron-rich nuclei large Q-Sn energy windowWe need efficient neutron and gamma detection direct knowledge of I, Pxn and Ex
Allowed GT transitions non natural parity states
d3/2
f7/2
p3/2
p1/2
f5/2
x x x x
x
52K3319
x x x
x
52Ca3220
xfp shell
sd shell
Ex>4 MeV (above Sn)
p-n interaction across sd-fp shell
forbidden GT transitions natural parity states
d3/2
f7/2
p3/2
p1/2
f5/2
x x x x
x
52K3319
x x x
x
52Ca3220
x
n-n interaction across fp shell
Non nat
51, 52, 53 K(1/2,3/2+) (2-) (3/2+)
51, 52, 53 Ca(3/2-) (0+) (3/2-)
allowed
forbiddenGT
gs
Q~14-16 MeV
Sn~3.5-4.5 MeV
delayed neutrons
nat
TONNERRE Detector(LPC Caen, IFIN Bucarest)
En= 0.2-7 MeV ~ 11% at 1 MeV
Low energy neutron detectors (x8)(IReS)
En = 0.05-3.0 MeV ~ 0.5% at 1 MeV
Ge Clusters (x2) (MINIBALL collaboration)
~ 5% at 1.3 MeV and 4 (start n-TOF)
~ 70%
2-Neutron-rich nucleiA~50, Z~20
Experimental setup at ISOLDE
In red: new transitionsIn green: new neutron emitter states and transitions
52K decay detection of both low and high energy neutrons53K decay only part of the statistics
Comparison with theory for 51,52,53Ca in progress (E. Caurier, F. Nowacki, IReS)
2-Neutron-rich nucleiA~50, Z~20 Preliminary results
52K --------> 52Ca-
53K --------> 53Ca-
Conclusions & Perspectives
High efficiencystudy of N~Z nuclei deformation A~80 CVC test 74Rb … mirror decays 71Kr, 75Sr
We have 2 experimental setup which are performing to explore the nuclear structure:
TAgS LEND-TONNERRE coupling
Efficient neutron detectionEffective interaction, shell orderNeutron-rich nuclei near the closed shell35,36Al, Cu, Zn…
Such investigations can be performed using any low energy beamsat ISOLDE, Ganil, Alto…
Nuclei A at/s
ISOLDE
Kr 71
72
73
74
75
3.5
3.103
5.105
2.106
1.8.107
Sr 75
76
77
78
5
4.103
2.105
9.2.105
Rb 74 2.103
Ga 62 400
Nuclei A at/s
ISOLDE
at/s
ALTO
K 49
50
51
52
53
5.4.105
7.4.104
9.103
1.2.103
4
Na 33
3440
2
Al 34
352.6
8
Ni 69
704.104
2.104
2.104
1.104
Cu 76
77
78
79
4.104
4.103
4.102
1
2.104
2.103
2.102
Zn 76
78
80
3.2.107
2.106
2.104
5.9.105
2.105
2.104
Sn 128-132
133
134
135
136
137
4 - 6.108
3.107
4.106
2.105
6.103
2.102
1.2.106
at/s
SPIRAL
2.102
3-6.103
1.5.104
4.105
Production yield information
ISOLDE : http://isolde.web.cern.ch/isolde/ Ulli Koster
SPIRAL: http://www.ganil.fr/operation/available_beams/radioactive_beams.htm
ALTO: Fadi Ibrahim (preliminary estimation)
Collaboration
A. Algora J.C. Angélique G. Ban P. Baumann F. Benrachi C. Borcea
M.J.G. Borge A. Buta D. Cano-Ott J.C Caspar E. Caurier S. Courtin
P. Dessagne J. Devin D. Etasse L.M. Fraile F. Perrot W. Gelletly S. Grévy G. Heitz C. Jollet A. Jungclaus F.R. Lecolley E. Liénard G. Le Scornet
F. Maréchal C.Miéhé E. Nacher F. Negoita F. Nowacki N. Orr E. Poirier
M. Ramdhane B. Rubio M.D. Salsac P. Sarriguren J.L. Tain O. Tengblad
C. Weber
The IReS workshop and the ISOLDE Collaboration
Neutrons transmission
Efficiency of neutrons detector : Tonnerre, LEND