New Insights into Nuclear Structure at Extremes of Isospin usng the Stopped

RISING Array at GSI Paddy Regan for the

Stopped Beam Rising Collaboration

Dept. of Physics, University of SurreyGuildford, Surrey, GU2 7XH, UK

p.regan@surrey.ac.uk

RISING

Rare Isotopic Spectroscopic

INvestigations @ GSI =

15 x Cluster germaniums for

(the most) exotic gamma-ray

spectroscopy

Physics aims of the RISINGstopped beam campaign

82Nb,86Tc

54Ni

130Cd, N=82

204Pt, N=126

106Zr

~190W, Terra Incognita

Stopped RISING Physics Aims• Study the evolution of single-particle / shell structure (shell melting ?) as a function of N:Z ratio.

– 56Ni (N=28 ; Z=28) Emma Johannson Mon. 7.50pm– 100Sn (N=50: Z=50) – 132Sn (N=82 : Z=50) Juergen Gerl, Tues. 11.30am– 208Pb (N=126 : Z=82) Steve Steer, poster

• Spin input in fragmentation. Stephane Pietri, poster– High(est) spins in projectile fragmentation Juergen Gerl, Tues. 11.30am

• Study the structure of nuclei with the most exotic proton-to-neutron ratios:

– Proton drip-line N=Z Adam Garnsworthy, poster– (Very) neutron-rich, Jurgen Gerl, Tues. 11.30am

• 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)

Accelerator facility at GSI

The Accelerators:UNILAC (injector) E=11.4 MeV/n

SIS 18Tm corr. U 1 GeV/nBeam Currents:

238U - 108 ppssome medium mass nuclei- 109

pps (A~130)

FRS provides secondary radioactive ion beams:• fragmentation or fission of primary beams • high secondary beam energies: 100 – 700 MeV/u• fully stripped ions

Ion-by-ion identification with the FRS

TOF

E

Cocktail of secondary, exotic fragments with ~ x00 MeV/u thru. FRS.

Separate and identify event-by-event. Chemically independent.

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., in press NIM B + poster

S. Pietri et al., in pressNIM B (2007)

High granularity of RISINGreduces ‘prompt flash’ problems….~ 7/105…

DGF timing of flash, comparable to former ‘analog’timing.

(g9/2

)-2I=8

+ +g

9/2)-2

I=8+ +

(g9/2

)-2,4I=14

+

g9/2

)-2,4I=14

+

S. Pietri et al., Nucl. Inst. Meth. B.in press. (2007)

I=12+ isomer N. Marginean

et al., PRC67 (2003) 061301

Physics aims of the RISINGstopped beam campaign

82Nb,86Tc

54Ni

130Cd

204Pt

106Zr

~190W, Terra Incognita

S. Pietri et al.,RISING data 107Ag beam

T=0, 1 Competition in Deformed N=Z odd-odd Nuclei

• Use projectile fragmentation to populate exotic N=Z=41,43 nuclei 82Nb , 86Tc. • Measure gammas from isomeric decays.

• Construct (partial) decay schemes

• Look for energy competition between T=1 (I=0+) and T=0 (I=1+ ?) lowest states.

Structure of Odd-Odd N=Z NucleiEven-even core plus one valence proton and one valence neutron in equivalent orbits

Neutron-Proton Pairing

T=1 and T=0

Residual Interactions

Ground state angular momentumcan be 0+, Jmin or Jmax

New Data point

-2000

-1000

0

1000

2000

3000

4000

0 20 40 60 80 100

A

E(T

=1-T

=0)

(keV

)

T=0 Dominant

T=1 More Competitive

40Ca

16O

56Ni

86Tc

The Trend Continues?!?

?

T=1: I=0+

T=0 : I=1+or (2j)+

E (

T=

0 –

T=

1) (

keV

)

82Nb 86Tc

T1/2= 133(20) ns T1/2= 1.59(20) s

A.B. Garnsworthy,submitted to PRL

T=1 (T=0) T=1 (T=0)T=1 T=1

82Nb 86Tc82Zr 86Mo

Level structure of 82Nb and 86Tc comparedto their TZ=+1 isobars

A. Garnsworthy et al., submitted to PRL

A.B. Garnsworthy et al., submitted to PRL

128 keV M1 in 82Nb gives f=18.

First Isospin changing K isomer?

*Note, E2 conversion for 128 keV would give unphysical IR~200%.

*

Mappingisospinsymmetryacross thefpg shell.

Physics aims of the RISINGstopped beam campaign

82Nb,86Tc

54Ni

130Cd

204Pt

106Zr

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.,

190W isomer decay

from 208Pb beam

(poster by G. Farrelly).

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.

β-delayed γ-rays in 192W – Decay of 192Ta

P.D. Stevenson et al., Phys. Rev. C72 (2005) 047303

190W

188W

192W

205Au

190Ta192Ta

203Au

188Ta

194Re

198Ir 202Ir

Summary of Stopped RISING to Date• 2006 passive stopper (isomer) experiments

– N~Z isomers, isospin symmetry/pairing studies around 56Ni (Rudolph) and highly deformed A~80 N=Z (PHR).

– N~126 seniority isomers (204Pt) (Podolyak)

– Neutron-rich ~ 132Sn nuclei with 136Xe fragmentation (Jungclaus) and 238U projectile fission (Gorska,Pfutzner)

– A~110 fission fragment isomers (Bruce)

• ‘Active Stopper’ campaign I (March 2007)

– N=126, 205Au M4 (Z=82 holes) electron conversion – Beta-delayed spectroscopy, 188,190,192Ta → 188,190,192W

• ‘Active Stopper’ campaign II (July 2007)

– N=126 part II (J. Benlliure et al.,)– A~50/60 N=Z decays (Gadea, Rubio, Gelletly & Fujita)

First Results from the Stopped RISING Campaign at GSI: The Mapping of Isomeric Decays in Highly Exotic Nuclei

P.H.Regan1, A.B.Garnsworthy1,2, S.J.Steer1, S.Pietri1, Zs.Podolyák1, D.Rudolph3, M.Górska4, L.Caceres4,5, E.Werner-Malento4,6, J.Gerl4, H.J.Wollersheim4, F.Becker4, P.Bednarczyk4, P.D.Doornenbal4, H.Geissel4, H. Grawe4, J.Grębosz4,7,

R.Hoischen3, A.Kelic4, I.Kojouharov4, N.Kurz4, F.Montes4, W.Prokopowicz4, T.Saito4, H.Schaffner4, S.Tashenov4, A.Heinz2, M.Pfützner6, T.Kurtukian-Nieto8, G.Benzoni9, M.Hellström2, A.Jungclaus5, L.-L.Andersson3, L.Atanasova10,

D.L.Balabanski11, M.A.Bentley12, B.Blank13, A.Blazhev14, C.Brandau1,4, J.Brown12, A.M.Bruce15, F.Camera9, W.N.Catford1, I.J.Cullen1, Zs.Dombradi16, E.Estevez8, C.Fahlander3, W.Gelletly1, G.Ilie14, E.K.Johansson3, J.Jolie14, G.A.Jones1,

M.Kmiecik7, F.G.Kondev17, S. Lalkovski10,15, Z.Liu1, A.Maj7, S.Myalski7, S.Schwertel18, T.Shizuma1,19, A.J.Simons1, P.M.Walker1, O. Wieland9

1Dept. of Physics, University of Surrey, Guildford, GU2 7XH, UK2WNSL, Yale University, New Haven, CT 06520-8124, USA

3Department of Physics, Lund University, S-22100 Lund, Sweden4GSI, Planckstrasse 1, D-64291, Darmstadt, Germany

5Departamento de Fisica Teórica, Universidad Autonoma de Madrid, E-28049, Madrid, Spain6IEP Warsaw University, Hoźa 69, PL-00-681

7The Henryk Niewodniczański Institute of NuclearPhysics, PL-31-342, Kraków, Poland8Universidad de Santiago de Compostela, E-15706, Santiago de Compostela, Spain

9INFN, Universitá degli Studi di Milano, I-20133, Milano, Italy10Faculty of Physics, University of Sofia, BG-1164, Bulgaria & The Institute for Nuclear Research, Bulgarian Academy of

Science, BG-1784, Sofia, Bulgaria11Dipartimento di Fisica, Universit ´a di Camerino, I-62032, Italy

12Dept. of Physics, University of York, Heslington, York, Y01 5DD, UK13CENBG, le Haut Vigneau, Bordeaux, F-33175, Gradignan Cedex, France

14IKP, Universit¨at zu Köln, D-50937, Köln, Germany15School of Engineering, University of Brighton, Brighton, BN2 4GJ, UK

16Institute for Nuclear Research, Debrecen, H-4001, Hungary17Nuclear Engineering Division, Argonne National Laboratory, Argonne IL-60439, USA

18Physik Department E12, Technische Universität München, Garching, Germany19Japan Atomic Energy Agency, Kyoto, 619-0215, Japan

Workshop on RISING PhysicsMadrid 6-8 November 2006

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

See Jeff Tostevinfor related reaction theory

Steer, Podolyak et al.,to be submitted to PRL

204Pt populated via 4-proton-knockout from 208Pb

T1/2=8.41(16) s

T1/2=152(16) ns

short isomer:

long isomer:

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

205Au126 electron conversion!!

h11/2 → d3/2 M4 transition

(half-life a few seconds…..)

New single particle (hole)

information around 208Pb core.

K

L

Fragmentation reaction studies: •‘cold’ (proton removal only) fragmentation (N=126: 206Hg, 204Pt)• hot fragmentation (190Pb: =18, =0!)• high-spin states 27ħ in 148Tb, (49/2) in 147Gd

Z1

Z2

A/Q

Pos. at S4

148Tb

Tb

E. Werner-Malento, Zs. Podolyak et al.

NB: 148Tb:= (82-65)=17 =(126-83)= 33 from 208Pb beam.

Highest discrete spinobserved to date via rragmentation reaction.

Physics aims of the RISINGstopped beam campaign

82Nb,86Tc

54Ni

130Cd

204Pt

106Zr

Is there evidence for a N=82 shell quenching ?

Assumption of a N=82 shell quenching leads to a considerableimprovement in the global abundance fit in r-process calculations !

r-p

roce

ss a

bu

nd

ance

s

mass number A

exp.pronounced shell gapshell structure quenched

70 72 74 76 78 80 820

500

1000

1500

60Nd

58Ce

56Ba

54Xe

52Te

48Cd

Ene

rgy

of 2

+ sta

te

Neutron number N

Indirect evidence for a N=82 shell quenching ?

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

from ß-decay studiesat ISOLDE

Can the anomalous behaviour of 2+ energies in the Cd isotopestowards N=82 be attributed to a change in the N=82 shell gap ?

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)

A/q

pos

itio

n a

t S

4

S4 position

Identification of 130Cd in the fragmentation of 136Xe

A/q

pos

itio

n a

t S

2

S2 position

Z=48130Cd

4000 identified 130Cd ions in fragmentation (2300 in fission)

750 MeV/u

136Xe

4 g/cm2

Be

meas(130Cd)~150 pb

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 quenching !A. Jungclaus, L. Cáceres et al.,

0+

(2+)

(4+)

(6+)(8+)

0+

(2+)

(4+)(6+)(8+)

0+

(2+)

(4+)(6+)(8+)

1

0

2

Ex (

MeV

)

76Ni482898Cd5048

130Cd8248

g9/2-2 g9/2

-2 g9/2-2

992

1922

2276

2420

1395

2083

2281

2428

1325

18641992/2002

2130

Unexpected scaling of (g9/2)2 two-body interaction

2+-8+ levels arepure (g9/2)-2 states

2+-8+ energy spread

scales with A-1

not with ħ=41·A-1/3

as commonly assumed

idea of H. GraweC. Mazzocchi et al.,PLB 622 (2005) 45