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)