Configuration of RISING for Measurements of Spin-alignment and g-factors by TDPAD

1. Configuration of RISING for Measurements of Spin-alignment and g-factors by TDPAD

2. 82 Regions of Interest 50 82 50

3. Isotope Production 129Xe 130Xe 131Xe 132Xe 133Xe 134Xe 135Xe 136Xe 137Xe 138Xe 139Xe 140Xe 141Xe 142Xe 143Xe 144Xe 141Xe prod. rates = 0-100 pps 128I 129I 130I 131I 132I 133I 134I 135I 136I 137I 138I 139I 140I 141I 90 prod. rates = 100-200 pps 127Te 128Te 129Te 130Te 131Te 132Te 133Te 134Te 135Te 136Te 137Te 138Te prod. rates = 200-300 pps 126Sb 127Sb 128Sb 129Sb 130Sb 131Sb 132Sb 133Sb 134Sb 135Sb 136Sb prod. rates = 300-400 pps 125Sn 126Sn 127Sn 128Sn 129Sn 130Sn 131Sn 132Sn 133Sn 134Sn 50 prod. rates = 400-500 pps 124In 125In 126In 127In 128In 129In 130In 131In 132In 133In 134In 123Cd 124Cd 125Cd 126Cd 127Cd 128Cd 129Cd 130Cd prod. rates = 500-600 pps 122Ag 123Ag 124Ag 125Ag 126Ag 127Ag 128Ag 82 prod. rates = 600-700 pps 80 no isomer observed isomer observed at GSI A~130 region U+Pb at 750 AMeV, 108 pps FRS, GSI

4. Spin-alignment • • Spontaneous fission - almost complete oblate alignment initially • BUT loss of alignment during de-excitation • Alignment ~ 0.28 for low-lying levels • Preservation of alignment  (i) fully-stripped fragments  (a) high primary beam energy  GSI not GANIL (b) production target not too thick (ii) Low (~ 20%) electron pick-up probability - depends on A and Z • high secondary beam energy > 150 MeV/u (iii) implant into appropriate (thick) crystal, e.g. Pb

5. TDPAD Set-up: Plan View • • Bruker B-E 25v Electromagnet • - Pole diameter 250 mm • - Total weight 1850 kg • Excellent homogeneity • < 10-4 under typical conditions

6. TDPAD Set-up: Side View

7. TDPAD Method • Observe Larmor precession of nuclear spins via • • Sensitivity depends on • Radiation parameter A2 • Total number of emitted γ-rays • Number of detectors • Intrinsic efficiency of detectors • Detector dimensions • Crystal-detector distances

8. Prompt Background • Prompt flash  (i) shield detectors against low-energy photons (ii) observe high-energy γ-rays in experiments (iii) discard spin rotation data for t < 0.5 μs  (a) lose a lot of statistics (b) isomers having t1/2 0.5 μs difficult to access

9. Summary • • 500 MeV/u 238U  150 MeV/u 135Te • 22% probability of electron pick-up in thin plastic scintillator • 22% of nuclei not aligned • reduced amplitude of oscillations in spin rotation pattern • greater statistics required • higher energies excluded because of prompt flash and crystal thickness • lower energies excluded because of increased probability of pick-up BUT existing production cross-section based on 750 MeV/u 238U • what is the production cross-section at 500 MeV/u? • • In A ~ 80 region, electron pick-up less probable • 90 MeV/u acceptable  prompt flash less severe • The region A 140 may be completely excluded

10. Outstanding Issues • • Support structure for stopped beam campaign • • Support for magnet • • Installation and testing of magnet • - starting no earlier than July 2004 • • Map of stray magnetic field • • Immunity of Cluster detectors to magnetic field • - insertion of detectors between coils of magnet possible? • • Require collaborators with experience in • conducting isomer experiments • tuning FRS • operating data acquisition system • • Other groups invited to use our set-up