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Coulomb Excitation of Neutron-rich Isotopes around A~140 (IS 411). Thomas Behrens Physik-Department E12 TU München. Physical motivation: Evolution of B(E2) values around N=82. Experimental setup and realisation at REX-ISOLDE with MINIBALL. Preliminary results for 144 Xe & 124,126 Cd. - PowerPoint PPT Presentation
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Coulomb Excitation of Neutron-rich Isotopes
around A~140(IS 411)
Thomas Behrens
Physik-Department E12
TU München
Physical motivation:Evolution of B(E2) values around N=82
Experimental setup and realisationat REX-ISOLDE with MINIBALL
Preliminary resultsfor 144Xe & 124,126Cd
Conclusion & Outlook
Isospin dependent modification of Grodzins’ rule
Modified Grodzins’ rule
)(088.0288.157.2
]b)[20;2(]keV)[2(3/22
2211
NNAZ
eEBE gs
3/2
3/2
064.00.1
0128.00.1
2 A
AAN
Minimum mass for fixed A (from Weizsäcker’s mass formula)
Grodzins’ rule (version by Raman)3/2222
11 57.2]b)[20;2(]keV)[2( AZeEBE gsMotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
[S.Raman et.al., Atomic Data and Nucl. Data Tables 78,1 (2001)]
[D.Habs, R.Krücken, INTC-P-156 (2002)]
B(E2) values before IS411
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
136Te
122Cd
140Xe ?
B(E2) values after 2004
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
122,124Cd
140Xe
preliminary results:
122Cd: 0.37(11) e2b2
124Cd: 0.32(10) e2b2
136Te
B(E2) values after 2005
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
138,140,142Xe
preliminary results:
138Xe: 0.38(2) e2b2
140Xe: 0.52(2) e2b2
142Xe: 0.69(2) e2b2
136Te
Coulomb Excitation
b
Target Z
Projectile • Beam energy below Coulomb barrier “Safe Coulex”
• proj ~ 0.06 c (Doppler correction)
CE i
f
2)2(
12
1)2( if
i
JEMJJ
EB
)(
)(
)(
)(
)(
)(
)(
)(64
126
126
64
126
64
64
126
ZnN
CdN
CdW
ZnW
Cd
Zn
Zn
Cd
CE
CE
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
REX-ISOLDE & MINIBALL
MINIBALL
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
REX-ISOLDE
MINIBALL
124,126Cd(Laser Ionization)
144Xe
Experimental Setup
Gamma-spectroscopy
MINIBALL
Particles• Angles• Energies
DSSSD
Univ. of Edinburgh
Beammonitor
PPAC
TU Darmstadt
Target
Beam
Beampurity
Beam DumpDetector
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
Statistics for Cd isotopes
• Protons on converter target (didn’t hit the converter!)• new quartz transfer line improved purity!!• Laser ionization (RILIS)• varying beam intensities and purities (increasing In) problems with the ISOLDE target• tried different settings for line heating and target heating
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
Isotop Target[mg/cm2]
Laser ON [h]
Laser ON/OFF [h]
E from REX[MeV/A]
beam intensity [104 pps]
beam purity [%]
124Cd 64Zn[1.8]
15 6.5 2.85 0.9 - 1.5 40 - 85
126Cd 64Zn[1.8]
26 7 2.85 1.4 75
Statistics for Xe isotopes
• shielding to slow down ejectiles at low lab
changed due to low energy from REX • changed target to check for scattered particles beam was not focused, might have hit collimator• changes of IH phase, line & target heating improved intensity• 2h on stopper foil looking for decay lines of 144Cs
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
Isotop Target[mg/cm2]
Shield [mg/cm2]
Running time [h]
E from REX[MeV/A]
beam intensity [104 pps]
beam purity [%]
144Xe 96Mo [1.7]
Al foil[4.1]
2.5 2.55 ~5.4 ~90
144Xe 197Au [1.0]
Al foil[1.5]
1 2.55 ~5.4 ~90
144Xe 96Mo [1.7]
My foil[1.6]
19 2.7 ~5.4 ~90
CD energy vs angle
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
64Zn
124Cd
Ep
art
[a.
u .]
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
124Cd: E(21+) peaks
124CdFWHM ~12 keV
64ZnFWHM ~14 keV
runnig time: ~15 h (Laser ON)
Doppler correction incl. particle reconstruction
Contaminants: 124In, 124Cs
126Cd: E(21+) peaks
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
126CdFWHM ~15 keV
64ZnFWHM ~15 keV
runnig time: ~26 h (Laser ON)
Doppler correction incl. particle reconstruction
Contaminants: 126In, 126Cs
144Xe: E(21+) peaks
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
144XeFWHM ~6 keV
96Mo~25 counts
runnig time: ~19 h (2.7 MeV/A)
Reconstruction of Recoils for Doppler correction
elastic scattered Xe to be used for normalization
B(E2) values after 2006
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
Preliminary Results:
Isotope B(E2)[e2b2]
124Cd 0.35(6)
126Cd 0.22(3)
144Xe 0.73(18)
144Xe126Cd
136Te
Conclusion & Outlook
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
successful measurement of 144Xe & 124,126Cd no derivation from systematic
open tasks:• beam contamination• CD efficiency• angular distribution of ’s• 144Xe: normalize to Rutherford
proposed:• development of BaF+ beams for Ba isotopes• 128Cd is feasible
Future Experiments
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook
Mass Number
Ba isotopes
140Ba 148Ba
dashed line: theoretical calculation[N.Shimizu et.al., Phys.Rev.Lett. 86,1171 (2001)]
solid line: modified Grodzins` rule [S.Raman et.al., Atomic Data and Nucl. Data Tables 78,1 (2001)]
150Ba ?
Helping hands and heads...
T. Behrens1, V. Bildstein1, R. Gernhäuser1, Th. Kröll1,R. Krücken1, M. Mahgoub1, P. Maierbeck1, W. Weinzierl1,
D. Habs2, R. Lutter2, T. Morgan2, P. Thirolf2, F. Finke3, M. Seidlitz3, N. Warr3, D. Weisshaar3,
S. Franchoo4, J. Diriken5, P. van Duppen5, O. Ivanov5, I. Stefanescu5,
J. van de Walle5,6, J. Cederkall6, L. Fraile6, U. Köster6, T. Sieber6, D. Voulot6, F. Wenander6,
A. Ekström7, T. Davinson8,and the REX-MINIBALL collaboration
1TU München, 2LMU München, 3Universität zu Köln, 4IPN Orsay, 5KU Leuven, 6CERN,
7Lund University, 8University of Edinburgh,
Thank you for your attention!
IS411 – Intensity on CD
MotivationMotivation
SetupSetup
ResultsResults
OutlookOutlook 96Mo(144Xe,144Xe)96Mo:
Beam shift: ~2 mm
Hits on CD in polar coordinates
x [mm]
y [m
m]
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