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Fragmentation of very neutron-rich projectiles around 132 Sn GSI experiment S294

Fragmentation of very neutron-rich projectiles around 132 Sn GSI experiment S294. Universidad de Santiago de Compostela, Spain Centre d’Etudes Nucleaires Bordeaux-Gradignan, France Warsow University, Poland GSI Darmstadt, Germany VINCA-Institute Belgrade, Serbia

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Fragmentation of very neutron-rich projectiles around 132 Sn GSI experiment S294

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  1. Fragmentation of very neutron-rich projectiles around 132Sn GSI experiment S294 Universidad de Santiago de Compostela, Spain Centre d’Etudes Nucleaires Bordeaux-Gradignan, France Warsow University, Poland GSI Darmstadt, Germany VINCA-Institute Belgrade, Serbia Institute of Physics, Bratislava, Slovakia GSI Feb.‘06

  2. Motivation • Production of extremely neutron-rich isotopes (EURISOL DS task 11.2) (two-step schemes: fission + cold fragmentation) n,p + 238U  132Sn + Be  X • Ground state properties of extremely neutron-rich isotopes • Total interaction cross sections: rms matter distributions • Proton knock-out: rms charge distributions, binding energies • Proton and neutron pickup: charge versus mass distribution GSI Feb.‘06

  3. Motivation • Production of medium-mass neutron-rich isotopes Fission + cold fragmentation n,p + 238U  132Sn + Be  X GSI Feb.‘06

  4. 238U(1 A GeV) + Pb Motivation • Residue production in fission reactions • 238U(950 A MeV)+Pb (T. Enqvist et al., NPA 658 (1999) 47) • 238U(1000 A MeV)+p (M. Bernas et al., NPA 725 (2003) 213) • 238U(1000 A MeV)+d (J. Pereira et al., PhD, USC (2004)) GSI Feb.‘06

  5. Peripheral heavy-ion reactions • at relativistic energies: • large fluctuations in N/Z and excitation energy Motivation • Residue production in cold-fragmentation reactions • Proton-removal channel: • only protons are abraded and the induced excitation energy remains bellow the particle emission threshold • 197Au(950 A MeV)+Be (J. Benlliure et al., NPA 660 (1999) 87) GSI Feb.‘06

  6. EPAX ABRABLA COFRA Motivation • Fragmentation of neutron-rich projectiles Cold fragmentation is not well understood for neutron-rich projectiles GSI Feb.‘06

  7. Motivation • Production cross sections of neutron-rich residues in the fragmentation of 132Sn • 1-4 proton removal cross sections  neutron separation enegies (W.A. Friedman et al., PRC 67 (2003) 051601R) GSI Feb.‘06

  8. Motivation • Description of the residue production in fragmentation reactions (Abrasion-ablation model) 1 Abrasion phase (excited prefragment): 2 Ablation (evaporation) phase • Mass loss: impact parameter +matter/charge distribution • N/Z: hypergeometrical distribution • Excitation energy: isotopic distributions • Binding energies+temperature • Some of these parameters can be determined from specific reaction channels GSI Feb.‘06

  9. Motivation • Mass and charge rms radii from specific reaction channels • Total interaction cross sections: rms matter distributions GSI Feb.‘06

  10. Motivation • Mass and charge rms radii from specific reaction channels • Total interaction cross sections: rms matter distributions • Proton knock-out: rms charge distribution GSI Feb.‘06

  11. Motivation • Mass and charge rms radii from specific reaction channels • Total interaction cross sections: rms matter distributions • Proton knock-out: rms charge distribution • Proton and neutron pickup: charge versus mass distribution N+n  D  N+p + p- N+p  D  N+n + p+ 208Pb+p,d  208Bi+p- R. J. Lombard et al., Europhys. Lett. 6 (1988) 323 A. Kelic et al., PRC 70 (2004) 064608 v(cm/ns) GSI Feb.‘06

  12. Proposed experiment • Production of neutron-rich fission residues 238U(950 A MeV)+Pb  124-132Sn • Fragmentation of neutron-rich fission residues 132Sn + Be  131In,130Cd,129Ag,128Pd 1-4 proton removal: s1p,2p,3p,4p~ 20-1 10-4 mb 124-132Sn + Be  X total interaction: sint ~ 2 b 124-132Sn + Be  123-131In 1 proton removal: s1p ~ 20 mb 124-132Sn + Be  124-132In charge pickup: sDp+p- ~ 0.1 mb 124-132Sn + Be  125-133Sn neutron pickup: sDn+p+ ~ 5 mb GSI Feb.‘06

  13. Experimental details S0-S2:238U(950 A MeV)+Pb  124-132Sn DZ/Z ~ 5 10-3 DBr/r ~ 3 10-4 DToF ~ 150 ps L ~ 18 m DA/A ~ 4.5 10-3 S2-S4:124-132Sn + Be  X DZ/Z ~ 7 10-3 DBr/r ~ 3 10-4 DToF ~ 150 ps L ~ 36 m DA/A ~ 2.4 10-3 GSI Feb.‘06

  14. Experimental details 238U(1 A GeV)+d  1XXSn 5 different settings centered on: 124Sn, 126Sn, 128Sn, 130Sn, 132Sn GSI Feb.‘06

  15. Beam time request • Production yields and acquisition time S0-S2:238U(950 A MeV)+Pb  124-132Sn 238U beam intensity:108 ions s-1 208Pb target: 1500 mg/cm2 • total rate at S2: ~26000 ion s-1 • 132Sn rate at S2: ~ 1000 ions s-1 Limiting factor DAQ unless S1 degrader!!! S2-S4:124-132Sn + Be  X Reaction probability and acquisition time with a 2.6 g/cm2 Be target: • total interaction: ~ 2 b  5 min. < 1% statistical accuracy • 1p: ~ 25 mb  15 min. ~ 1% “ • 2p: ~0.3 mb  5 hours~ 1% “ • 3p: ~ 5 mb  3 days~ 7% “ • 4p: ~ 0.1 mb  1-2 per day • proton pickup: ~ 0.1 mb  4 hours ~ 6% “ GSI Feb.‘06

  16. Beam time request Total requested time: main beam time (238U)  7 days (21 shifts) 6 days accepted parasitic beam (136Xe)  5 days accepted GSI Feb.‘06

  17. Open issues Energy of secondary beam • Lower energy (~ 500 A MeV): closer to EURISOL conditions and higher cross sections for neutron and proton pickup • Lower energy: lower transmission Removable fragmentation target at S2 Detailed calculations of FRS magnetic settings GSI Feb.‘06

  18. Two-step process: 1 Prefragment formation (statistical equilibrium) • Mass loss: impact parameter geometry • N/Z: hypergeometrical distribution • Excitation energy: particle hole excitation+final interactions 2 Neutron evaporation • Binding energies+temperature Isospin thermometer Sensitivity of the isotopic distributions to the excitation energy induced per abraded Nucleon: 27 MeV J. Benlliure et al., NPA 660 (1999) 87 Production of heavy neutron-rich isotopes Analytical description of cold-fragmentation reactions GSI-PAC Sep‘04

  19. Motivation • Isotopic scaling in nuclear reactions • Reactions governed by the statistical model M.B. Tsang et al., PRL 86 (2001) 5023 GSI-PAC Sep‘04

  20. Medium-mass neutron-rich isotopes Two-step schemes: fission + cold fragmentation Primary beam: 1 mA Production target: 100 g/cm2 UCx Fragmentation target: 20% of range Only for extremely neutron-rich Residues the production rates by direct fission is bellow the two-step scenario Sanibel´02

  21. Medium-mass neutron-rich isotopes Two-step schemes: fission + cold fragmentation Sanibel´02

  22. Medium-mass neutron-rich isotopes Two-step schemes: fission + cold fragmentation Sanibel´02

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