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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

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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


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RISING

Rare Isotopic Spectroscopic

INvestigations @ GSI =

15 x Cluster germaniums for

(the most) exotic gamma-ray

spectroscopy


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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,b2 (p-n interactions)

    • Angular Momentum Projection, K (axial symmetry)

    • Critical Point Symmetries e.g., X(5)

  • Reaction mechanism studies in fragmentation.


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Physics aims of the RISING

stopped beam campaign

204Pt

~190W

Terra Incognita

82Nb,86Tc

130Cd

54Ni

106Zr


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Stopped RISING Array @ GSI: 15 x 7 element CLUSTERs

Photopeak efficiency >10% at 1.3 MeV. XIA-DGF electronics


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40

 detection efficiency

30

DGF

TDC

20

Absolute efficiency [%]

10

MSU

GSI

0

0

200

600

1000

1400

-energy [keV]

The RISING -ray spectrometer

15 EUROBALL Cluster (105 Ge crystals)

digital signal processing via 30 XIA DGF modules

S. Pietri et al., Acta Phys. Pol.B38 (2007)p1255

very high -ray efficiency

high granularity (prompt flash problem)

Best-spectrometer ever used in isomer spectroscopy !


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N=Z line

Particle Identification

Sum 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


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82Nb

86Tc

T1/2= 133(20) ns

T1/2= 1.59(20) s


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Search for the 8+ (g9/2)-2 seniority isomer in 130Cd

6-proton-knockout from 136Xe: A. Jungclaus

fission of 238U: M. Górska, M. Pfützner

June/July 2006

two proton holes in the g9/2 orbit

g9/2

M. Górska et al., Phys. Rev. Lett. 79 (1997)


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Singles -spectrum in delayed coincidence

with implanted 130Cd ions

T1/2=220(30) ns

ENERGY

TIME


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 coincidence spectra

539

138

1325

128

2207

8+

(8+)

6+

(6+)

2094

4+

(4+)

Gate: 128 keV

1889

539

2+

(2+)

Gate: 138 keV

1346

Gate: 539 keV

1325

Gate: 1325 keV

0+

0+

130Cd82

SM

48

Decay of the 8+ isomer in 130Cd

T1/2=220(30)ns

T1/2=173ns

New results give no evidence for a N=82 shell quenching

A. Jungclaus, L. Cáceres et al.,submitted to Nature


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Shell structure south of 208Pb

Spokesperson: Zsolt Podolyak, Surrey

cold fragmentation

of 208Pb@1 GeV/u

204Pt

Related reaction

theory by J.Tostevin

et al.,

202Os

main aim:

spectroscopy of N=126 isotones

206Hg, 204Pt and 202Os


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

long isomer:

T1/2=8.41(16) s

short isomer:

T1/2=152(16) ns

S. Steer, Zs. Podolyak et al., Acta Phys. Pol. B38 (2007) p1283


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204Pt Z=78

Z. Podolyak, S. Steer et al., PRL, in preparation

h11/2-2

152(16) ns

d5/2-1h11/2-1

d3/2-1h11/2-1

?

s1/2-1h11/2-1

8.41(16) s

d3/2-1d5/2-1

s1/2-1d3/2-1

SM

B. Fornal et al.

PRL 87 (2001)212501

Results require modification of

SPE and/or interactions !

N=126 isotones: (h11/2)-2,4 I=10+ isomers

206Hg Z=80

92(8) ns

2.15(21) s

SM


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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.


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5 cm x 5 cm DSSSD (16 strips by 16 strips = 256 pixels)

3 positions across focal plane, room for 2 detectors deep.



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205Au126 electron conversion!!

h11/2 → d3/2M4 transition

(half-life a few seconds…..)

New single particle (hole)

information around 208Pb core.

K

L


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207 keV

2+ → 0+

On-line beta-delayed gated 190Ta ions…..

Transitions fed in daughter 190W nucleus

by beta decay.

First time we see same nucleus via both

isomer decay AND beta-decay.

N. Al-Khomashi, PhD thesis


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190W isomer decay

from 208Pb beam


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GSI-EA (Fri. 20th April 2007)

11 New Stopped RISING Proposals

All with UK involvement, 4 with UK (co)spokespersons)