Post on 31-Mar-2015
Paddy Regan for the Stopped Beam Rising Collaboration
Dept. of Physics, University of Surrey
p.regan@surrey.ac.uk
The (Stopped Beam) RISING Experimental Campaign at
GSI:
The Mapping of Isomeric Decays and Beta-Delayed
Spectroscopy in Highly Exotic Nuclei
RISING
Rare Isotopic Spectroscopic
INvestigations @ GSI =
15 x Cluster germaniums for
(the most) exotic gamma-ray
spectroscopy
Stopped RISING Physics Aims & Philosophy
• Study the evolution of single-particle / shell structure (shell melting ?) as a function of N:Z ratio.
– 56Ni (N=28 ; Z=28) 100Sn (N=50: Z=50)– 132Sn (N=82 : Z=50)– 208Pb (N=126 : Z=82)
• Study the structure of nuclei with the most exotic proton-to-neutron ratios:
– Proton drip-line N=Z– Neutron-rich ‘terra incognita’.
• Nuclear ‘symmetries’ and relevance of quantum numbers:– Isospin, T (N:Z ratio)
– Nuclear Deformation, 2 (p-n interactions)
– Angular Momentum Projection, K (axial symmetry)
– Critical Point Symmetries e.g., X(5)
• Reaction mechanism studies in fragmentation.
Physics aims of the RISINGstopped beam campaign
82Nb,86Tc
54Ni
130Cd
204Pt
106Zr
Terra Incognita
~190W
Stopped RISING Array @ GSI: 15 x 7 element CLUSTERsPhotopeak efficiency >10% at 1.3 MeV. XIA-DGF electronics
Best -spectrometer ever used in isomer spectroscopy !
The RISING -ray spectrometer
15 EUROBALL Cluster (105 Ge crystals)digital signal processing via 30 XIA DGF modules
Ab
solu
te e
ffic
ien
cy [
%]
-energy [keV]200 600 1000 14000
10
0
20
30
40
DGF
TDC
MSU GSI
detection efficiency
very high -ray efficiencyhigh granularity (prompt flash problem)
S. Pietri et al., Acta Phys. Pol. B38 (2007) p1255
Particle Identification
N=Z lineSum of data
from 90Rh, 86Tc and 82Nb
settings with 107Ag beam
A.B. Garnsworthy et al., Acta Phys. Pol. B38 (2007) p1265
&
L. Caceres et al., Acta Phys. Pol. B38(2007) p1271
82Nb 86Tc
T1/2= 133(20) ns T1/2= 1.59(20) s
g9/2
Search for the 8+ (g9/2)-2 seniority isomer in 130Cd
two proton holes in the g9/2 orbit
6-proton-knockout from 136Xe: A. Jungclausfission of 238U: M. Górska, M. Pfützner June/July 2006
M. Górska et al., Phys. Rev. Lett. 79 (1997)
Singles -spectrum in delayed coincidencewith implanted 130Cd ions
T1/2=220(30) ns
TIME
EN
ER
GY
coincidence spectra
128 138 539 1325
Gate: 128 keV
Gate: 138 keV
Gate: 539 keV
Gate: 1325 keV0+
(2+)
(4+)(6+)(8+)
SM130Cd8248
1346
1889
2094
2207
0+
2+
4+6+8+
1325
539
Decay of the 8+ isomer in 130Cd
T1/2=173nsT1/2=220(30)ns
New results give no evidence for a N=82 shell quenchingA. Jungclaus, L. Cáceres et al.,submitted to Nature
Shell structure south of 208PbSpokesperson: Zsolt Podolyak, Surrey
cold fragmentationof 208Pb@1 GeV/u
main aim:spectroscopy of N=126 isotones206Hg, 204Pt and 202Os
204Pt
202Os
Related reaction theory by J.Tostevin et al.,
204Pt populated via 4-proton-knockout from 208Pb
T1/2=8.41(16) s
T1/2=152(16) ns
short isomer:
long isomer:
S. Steer, Zs. Podolyak et al., Acta Phys. Pol. B38 (2007) p1283
N=126 isotones: (h11/2)-2,4 I=10+ isomers
206Hg Z=80
B. Fornal et al.PRL 87 (2001)212501
s1/2-1d3/2
-1
s1/2-1h11/2
-1
d3/2-1h11/2
-1
h11/2-2
SM
92(8) ns
2.15(21) s
204Pt Z=78
152(16) ns
8.41(16) sd3/2
-1d5/2-1
d5/2-1h11/2
-1
?
Results require modification ofSPE and/or interactions !
SM
Z. Podolyak, S. Steer et al., PRL, in preparation
Active Stopper RISING
• Isomer spectroscopy requires isomers!
• Would like to be able to do beta-delayed spectroscopy on (neutron-rich)
fragments.
• Problem….implanting ~10 GeV energy followed by ~200 keV in same pixel.
• Solution? ‘Logarithmic’ pre-amps.
5 cm x 5 cm DSSSD (16 strips by 16 strips = 256 pixels) 3 positions across focal plane, room for 2 detectors deep.
R. Kumar et al.,
205Au126 electron conversion!!
h11/2 → d3/2 M4 transition
(half-life a few seconds…..)
New single particle (hole)
information around 208Pb core.
K
L
On-line beta-delayed gated 190Ta ions…..
Transitions fed in daughter 190W nucleus
by beta decay.
207 keV2+ → 0+
N. Al-Khomashi, PhD thesis
First time we see same nucleus via both
isomer decay AND beta-decay.
190W isomer decay
from 208Pb beam
Friday, April 20
Exp.- Spokesperson Co- Title
N° Spokesperson
Regan, P. Introduction to RISING Proposals: Status report of the stopped beam RISING
campaign using passive and active stoppers
S337 Gadea, A. Structure of 132In populated in the beta-decay of 132Cd: the nf7/2 pg9/2-1 multiplet
on the doubly magic 132Sn core
S340 Sohler, D. Single particle energies in the vicinity of 78Ni
S342 Balabanski, D. Quadrupole moment measurement of the 8+ isomer in 96Pd using the RISING
stopped-beam set up
S343 Simpson, G. Lozeva, R.Isomeric states containing the neutron g9/2 orbit in the very neutron-rich mass 95
region
S344 Simpson, G. Lozeva, R. Measurements of high-spin microsecond isomers near 132Sn
S346 Bruce, A. Shape evolution near 110Mo
S347 Podolyak, Z. Along the N=126 closed shell
S348 Gerl, J. Patra, S. K.; Palit, R. Search for the superheavy isotope 162Sm
S350 Benzoni, G. Valiente Dobon, J. J. Moving along Z=82, beyond the doubly-magic 208Pb nucleus
S352 Blazhev, A. Wadsworth, R. Study of the N>=Z proton dripline nuclei 96, 97, 98Cd with astrophysical consequences
S353 Caceres, L. Regan, P.Structure of the odd-odd N=Z nuclei in the vicinity of 100Sn: high spin isomers in 90Rh
studied through GT-decay
GSI-EA (Fri. 20th April 2007) 11 New Stopped RISING ProposalsAll with UK involvement, 4 with UK (co)spokespersons)