Rare ISotope INvestigation at GSI experimental set-up sub-shell closure (N=32 gap) for Cr nuclei...
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Transcript of Rare ISotope INvestigation at GSI experimental set-up sub-shell closure (N=32 gap) for Cr nuclei...
![Page 1: Rare ISotope INvestigation at GSI experimental set-up sub-shell closure (N=32 gap) for Cr nuclei pairing interaction in semi-magic Sn nuclei shapes and.](https://reader035.fdocuments.in/reader035/viewer/2022062309/56649f4f5503460f94c71062/html5/thumbnails/1.jpg)
Rare ISotope INvestigation at GSI experimental set-up
sub-shell closure (N=32 gap) for Cr nuclei pairing interaction in semi-magic Sn nuclei shapes and shape coexistence: 136Nd, 134Ce Pygmy dipole resonance in 68Ni T=2 mirrors 36Ca and 36S
future: PreSPEC
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Rare ISotope INvestigation at GSI
Nuclear structure of exotic nuclei studied by secondary fragmentation and relativistic Coulomb excitation
g-factor measurements
Isomeric γ- and β-decay studies
FRS → secondary radioactive ion beams:
• Fragmentation or fission of primary beams
• High secondary beam energies (100 - 400 AMeV)
• Fully stripped ions
• Reactions on a secondary target
• Implantation inside a stopper
The Accelerators:UNILAC (injector) - E<15 AMeV
SIS 18Tm 238U 1 AGeVBeam currents:
238U 109 ppsmedium mass nuclei 1010 pps
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The Accelerators:UNILAC (injector) - E<15 AMeV
SIS 18Tm 238U 1 AGeVBeam currents:
238U 109 ppsmedium mass nuclei 1010 pps
Fast beam campaign (2003-2005)
g-factor campaign (2005)
Stopped beam campaign (2006-2009)
Rare ISotope INvestigation at GSI
Rare ISotope INvestigation at GSI
• FRS: excellent in-flight A and Z selection energy resolution: ~ 1 GeV • EUROBALL: excellent γ-ray spectrometer intrinsic energy resolution: ~ 2 keV
131Sn 132Sn
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FRagment Separator
86Kr, 480 MeV/u
CATEMWPC
• 15 EUROBALL Clusters (105 Ge crystals)• ΔEγ=1.6% (1.3 MeV, d = 70 cm)
• εγ = 2.8%
Ring angular range
1 10.50-21.30
2 27.60-38.40
3 30.60-41.40
Experimental set-up
56Cr
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70cm
20cm
beam
target
γ-ray set-up with higher efficiency
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Atomic Background RadiationBremsstrahlung
Bremsstrahlung: slowing down of a moving point-charge
Radiative electron capture (REC) capture of target electrons into bound states of the projectile:
Primary Bremsstrahlung (PB)capture of target electrons into continuum states of the projectile:
Secondary Bremsstrahlung (SB)Stopping of high energy electrons in the target: 22~ tp ZZ
tp ZZ 2~
tp ZZ 2~
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EUROBALL Cluster Detectors Miniball: HPGe segmented detectors
HECTOR Large 14.5 x 17 cm BaF2 Detectors
CATE : ΔE-E telescope event by event beam identification
Coulomb Excitation at Relativistic Energy
New Shell structure at N>>Z Relativistic Coulomb excitation of nuclei near 100Sn Triaxiality in even-even core nuclei of N=75 isotones E1 Collectivity in neutron rich nuclei 68Ni
nucleus σ (mb)
56Cr 91
108Sn 314
136Nd 338 / 2180
beam
Rare ISotope INvestigation at GSI
H.J. Wollersheim NIM A537, 637(2005)
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Relativistic Coulomb Excitationof 54,56,58Cr → 197Au
Identification before the secondary target
after secondary target
γ-efficiency = 2.8% , ΔEγ = 1.6% (1.3 MeV, d=70 cm)
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Relativistic Coulomb Excitationof 54,56,58Cr → 197Au
A. Bürger et al., Phys. Lett B622, 29 (2005)
E [keV] B(E2) [Wu]
54Cr 835 14.6 (6)56Cr 1006 8.7 (3.0)58Cr 880 14.8 (4.2)
Indication for N=32 sub-shell closure
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The 100Sn / 132Sn region
d5/2
g7/2
Naïve single particle filling
s1/2 d3/2
h11/2
Z = 50
N=50g7/2
s1/2
d3/2
h11/2
00.5
1.62.22.6
MeV
d5/2
Single particle energies
N=82
Pairing interaction:Large spin-orbit splitting implies a jj-coupling scheme
mid shell
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Relativistic Coulomb Excitationof 108Sn → 197Au
Seniority: a broken-pair model
Constant 2+ energy Simple B(E2) trend as function of shell filling
22++
44++
66++
00++
minmin
ener
gy a
xis
jj
j
j
j
j
j jJJ
JJJJ
=0
=2
=2
=2
Seniority scheme:
Emerging discrepancy:Do we need to open the proton space near 100Sn or do we need to improve the effective interaction?
A. Banu, Phys Rev C72, 061305 (2005)
B(E2) ~ Nparticles* Nholes
mid shell
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Relativistic Coulomb Excitationof 136Nd → 197Au
2 1+
0+
2 2+
0+
2 2+
2 1
+
136136NdNd
energy [keV]
cou
nts
First observation of a second excited 2+ state populated in a Coulomb experiment at 100 AMeV using EUROBALL and MINIBALL Ge detectors.
collective strength shape symmetry triaxiality (in N=76) in even-even core nuclei of the odd-odd chiral isotones
T.R. Saito, Phys.Lett B669, 19 (2008)
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Pygmy Dipole ResonanceCollective oscillation of neutron skin against the core
Excess Yield
Statistical model (Cascade) calculation of -rays following statistical equilibration of excited target nuclei (197Au) and of the excited beam nuclei (68Ni) folded with RF and in the CM system
NP-Core
N-Skin
O.Wieland et al. PRL 102, 092502 (2009)
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40
80
120
(,n)
10-1
100
101
102
103 VP VP and R
[m
b]
8 10 12 14 16 18 200.1
1
GDR PDR Total
d/
dE
[mb/M
eV
]
E [MeV]
GDR
PDR
PDR5% +/-1 GDR
Folded with the detector response function
O.Wieland et al. PRL 102, 092502 (2009)without pygmy
virtual photonsvirtual photons
branching
Photonuclear Photonuclear cross sectioncross section
Pygmy Dipole Resonance
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Mirror symmetry at the proton drip-line: 36Ca – 36SDeviations from the classical shell model
34Si
32Mg
36S
40Ca36Ca
Z
N
d5/2 s1/2 d3/2
d5/2
s1/2
d3/2
34Ca32Ca
20
20 CLUSTER
MINIBALL
HECTOR
Double fragmentation reaction: Primary: 40Ca, 420 A·MeV, 3·108 ions/s, 4 mg/cm2 9Be
Secondary: 37Ca, 196·A MeV, 2·103 ions/s, 0.7 mg/cm2 9Be
E2+ (36Ca) - E2+ (36S) = -276(16) keV
too large to result from Coulomb corrections
P. Doornenbal et al., Phys. Lett. B647, 237 (2007)
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*H. Herndl et al., Phys. Rev. C 52 (1995) 1078P. Doornenbal et al., Phys. Lett. B647, 237 (2007).A. Gade et al. Phys. Rev. C 76, 024317 (2007)
Mirror energy differences for T=1,2 nuclei Deviations from the classical shell model
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Future: PreSPEC and AGATA
LYCCA
BeamDirection
Detectorat rear
10 ATC+ 5 double Cluster detectors beam pipe diameter = 12cm
chamber diameter = 46 cm
S2´-configuration:10 AGATA Triple Cluster+ 5 double Cluster detectors
γ-efficiency = 17.5% γγ-efficiency = 2.5%
resolution (FWHM)
intrinsic spatial
resolution
8.5 keV 5 mm
4 keV 2 mm
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PreSPEC fast-beam campaign great perspectives …
AGATA increases-sensitivity ≈ 10x
LYCCA-0 provides mass resolution up to A ≈ 100
SIS/FRS intensitiesincrease up to ≈ 10x
Tracking det. and EDAQ upgrade increase max. rate and throughput 10x
PreSPEC Fast Beam Campaignconvener: W. Korten
Very attractive and competitivespectroscopy themes
Unique combination of beams, set-up and people
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