new insights into nuclear structure at extremes of isospin usng the stopped rising array at gsi
DESCRIPTION
Paddy Regan for the Stopped Beam Rising Collaboration Dept. of Physics, University of Surrey Guildford, Surrey, GU2 7XH, UK [email protected]. New Insights into Nuclear Structure at Extremes of Isospin usng the Stopped RISING Array at GSI. RISING R are I sotopic S pectroscopic - PowerPoint PPT PresentationTRANSCRIPT
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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
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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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Physics aims of the RISINGstopped beam campaign
82Nb,86Tc
54Ni
130Cd, N=82
204Pt, N=126
106Zr
~190W, Terra Incognita
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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)
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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
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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.
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Stopped RISING Array @ GSI: 15 x 7 element CLUSTERsPhotopeak efficiency >10% at 1.3 MeV. XIA-DGF electronics
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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
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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.
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(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
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Physics aims of the RISINGstopped beam campaign
82Nb,86Tc
54Ni
130Cd
204Pt
106Zr
~190W, Terra Incognita
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S. Pietri et al.,RISING data 107Ag beam
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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.
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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
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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
)
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82Nb 86Tc
T1/2= 133(20) ns T1/2= 1.59(20) s
A.B. Garnsworthy,submitted to PRL
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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
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A.B. Garnsworthy et al., submitted to PRL
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128 keV M1 in 82Nb gives f=18.
First Isospin changing K isomer?
*Note, E2 conversion for 128 keV would give unphysical IR~200%.
*
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Mappingisospinsymmetryacross thefpg shell.
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Physics aims of the RISINGstopped beam campaign
82Nb,86Tc
54Ni
130Cd
204Pt
106Zr
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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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R. Kumar et al.,
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190W isomer decay
from 208Pb beam
(poster by G. Farrelly).
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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.
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β-delayed γ-rays in 192W – Decay of 192Ta
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P.D. Stevenson et al., Phys. Rev. C72 (2005) 047303
190W
188W
192W
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205Au
190Ta192Ta
203Au
188Ta
194Re
198Ir 202Ir
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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)
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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
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Workshop on RISING PhysicsMadrid 6-8 November 2006
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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
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Steer, Podolyak et al.,to be submitted to PRL
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204Pt populated via 4-proton-knockout from 208Pb
T1/2=8.41(16) s
T1/2=152(16) ns
short isomer:
long isomer:
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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
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205Au126 electron conversion!!
h11/2 → d3/2 M4 transition
(half-life a few seconds…..)
New single particle (hole)
information around 208Pb core.
K
L
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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.
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Physics aims of the RISINGstopped beam campaign
82Nb,86Tc
54Ni
130Cd
204Pt
106Zr
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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
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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 ?
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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)
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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
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Singles -spectrum in delayed coincidencewith implanted 130Cd ions
T1/2=220(30) ns
TIME
EN
ER
GY
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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.,
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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