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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 - PowerPoint PPT Presentation
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Fragmentation of very neutron-richprojectiles around 132Sn
GSI experiment S294
Universidad de Santiago de Compostela, SpainCentre d’Etudes Nucleaires Bordeaux-Gradignan, FranceWarsow University, PolandGSI Darmstadt, GermanyVINCA-Institute Belgrade, SerbiaInstitute of Physics, Bratislava, Slovakia
GSI Oct.‘06
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 Oct.‘06
Motivation
Fission + cold fragmentation
Production of medium-mass neutron-rich isotopes
n,p + 238U 132Sn + Be X
GSI Oct.‘06
Motivation
Production cross sections of neutron-rich residues in the fragmentation of 132Sn
132Sb
132Sn
131In 132In
130Cd
129Ag
128Pd
1-4 proton removal cross sections
mb 122Pd 123Pd 124Pd 125Pd 126Pd 127Pd 128Pd
EPAX 0.285 0.182 0.109 5.93 10-2 2.90 10-2 1.25 10-2 4.74 10-3
COFRA 0.106 0.045 0.024 7.23 10-3 2.88 10-3 3.61 10-4 6.77 10-5
neutron separation enegies (W.A. Friedman et al., PRC 67 (2003) 051601R)
GSI Oct.‘06
Motivation
Mass and charge rms radii from specific reaction channels
Total interaction cross sections: rms matter distributions
GSI Oct.‘06
Motivation
Mass and charge rms radii from specific reaction channels
132Sb
132Sn
131In 132In
130Cd
129Ag
128Pd
Total interaction cross sections: rms matter distributions
Proton knock-out: rms charge distribution
GSI Oct.‘06
Motivation
Mass and charge rms radii from specific reaction channels
132Sb
132Sn
131In 132In
130Cd
129Ag
128Pd
Total interaction cross sections: rms matter distributions
Proton knock-out: rms charge distribution
Proton and neutron pickup: charge versus mass distribution
N+n N+p + -
N+p N+n + +
v(cm/ns)
R. J. Lombard et al., Europhys. Lett. 6 (1988) 323A. Kelic et al., PRC 70 (2004) 064608
208Pb+p,d 208Bi+-
GSI Oct.‘06
Proposed experiment
132Sn + Be 131In,130Cd,129Ag,128Pd 1-4 proton removal: p,2p,3p,4p~ 20-1 10-
4 mb
124-132Sn + Be X total interaction: int ~ 2 b124-132Sn + Be 123-131In 1 proton removal: 1p ~ 20 mb124-132Sn + Be 124-132In charge pickup: p+- ~ 0.5 mb124-132Sn + Be 125-133Sn neutron pickup: n++ ~ 5 b
238U(950 A MeV)+Pb 124-132Sn
Production of neutron-rich fission residues
Fragmentation of neutron-rich fission residues
GSI Oct.‘06
Experimental details
S2-S4: 124-132Sn + Be X
S0-S2: 238U(950 A MeV)+Pb 124-132Sn
Z/Z ~ 5 10-3
B/~ 3 10-4 ToF ~ 150 psL ~ 18 m
A/A ~ 2.4 10-3
Z/Z ~ 7 10-3
B/~ 3 10-4 ToF ~ 150 psL ~ 36 m
A/A ~ 4.5 10-3
GSI Oct.‘06
Experimental details
238U(1 A GeV)+d 1XXSn
5 different settings centered on: 124Sn, 126Sn, 128Sn, 130Sn, 132Sn
GSI Oct.‘06
Beam time request
S2-S4: 124-132Sn + Be X
S0-S2: 238U(950 A MeV)+Pb 124-132Sn238U 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
total rate at S4: >> 1000 ions s-1
Reaction probability and acquisition time with a 2.6 g/cm2 Be target: total interaction: ~ 2 b 15 min. < 1% statistical accuracy 1p: ~ 25 mb 1 hour ~ 1% “ 2p: ~0.3 mb 15 hours ~ 1% “ 3p: ~ 5 b 3 days ~ 7% “ 4p: ~ 0.1 b 1-2 per day proton pickup: ~ 0.5 mb 10 hours ~ 6% “
Production yields and acquisition time
Limiting factor DAQ unless S1 degrader!!!
GSI Oct.‘06
Beam time request
Projectile 1st FRS section 2nd FRS section Beam time238U(950 MeV) FRS Calibrations 1 day238U(950 MeV) 124Sn 124Sn (int. + 1p)
123Sn (pickup)
3 hours
7 hours238U(950 MeV) 126Sn 126Sn (int. + 1p)
125Sn (pickup)
3 hours
7 hours238U(950 MeV) 128Sn 128Sn (int. + 1p)
127Sn (pickup)
3 hours
7 hours238U(950 MeV) 130Sn 130Sn (int. + 1p)
129Sn (pickup)
3 hours
7 hours238U(950 MeV) 132Sn 132Sn (int. + 1p)
131Sn (pickup)134Sn (2p,3p,4p)
3 hours
7 hours
4 days
Total requested time: main beam time (238U) 7 days (21 shifts) 6 days accepted parasitic beam (136Xe) 5 days accepted
GSI Oct.‘06
Final detector setup ??
S1:
GSI Oct.‘06
Sc1 degrader
S2:MW21 MUSIC1TPC1 TPC2 Slits target TPC3 TPC4 Sc2
S4:MW41 MUSIC2TPC5 TPC6 Sc4
Open issues
Energy of primary beam
Lower energy (~ 500 A MeV): closer to EURISOL conditions and higher cross sections for neutron and proton pickup Lower energy: lower transmission
Detailed calculations of FRS magnetic settings
Larger acceptance for fission fragments (new target position) Beam intensity
GSI Oct.‘06
Setup
Degrader at S1 Optimum detector positions at S2
Participants
GSI Oct.‘06
November December
FRS Detector tests 136Xe 238U
Participant 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 2829
30 1 2 3 4 5 6 7 8
H. Alvarez USC
J.Benlliure USC
E.Casarej USC
Dragosavac
M.Gascón USC
A.Heinz
K. Helariutta
A. Kelic GSI
S. Lukic GSI
F. Montes GSI
D. Perez USC
K.-H Schmidt
M. Stanoiu GSI
K. Summerer
J. Taieb CEA
Tasks and responsibilities
GSI Oct.‘06
MUSICs S. Lukic
MWs K. Summerer E. Casarejos
Scintillators E. Casarejos
TPCs Bratislava
targets A. Kelic
DAQ C. Nocciforo D. Perez
On-line H. Alvarez D. Perez
FRS optics
FRS settings J. Benlliure D. Perez
J. Benlliure et al., NPA 660 (1999) 87
Production of heavy neutron-rich isotopes
Analytical description of cold-fragmentation reactions
Mass loss: impact parameter geometry N/Z: hypergeometrical distribution Excitation energy: particle hole excitation+final interactions
1 Prefragment formation (statistical equilibrium)
Two-step process:
2 Neutron evaporation Binding energies+temperature
Sensitivity of the isotopicdistributions to the excitationenergy induced per abraded Nucleon: 27 MeV
Isospin thermometer
GSI-PAC Sep‘04
Motivation
Isotopic scaling in nuclear reactions
GSI-PAC Sep‘04
Reactions governed by the statistical model
ZNCeZNY
ZNYZNR
),(
),(),(
1
212
ZeZNRNS ),()( 12
M.B. Tsang et al., PRL 86 (2001) 5023
Medium-mass neutron-rich isotopes
Sanibel´02
Two-step schemes: fission + cold fragmentation
Only for extremely neutron-rich Residues the production rates by direct fission is bellow the two-step scenario
Primary beam: 1 mAProduction target: 100 g/cm2 UCxFragmentation target: 20% of range
Medium-mass neutron-rich isotopes
Sanibel´02
Two-step schemes: fission + cold fragmentation
Medium-mass neutron-rich isotopes
Sanibel´02
Two-step schemes: fission + cold fragmentation
Motivation
238U(1 A GeV) + Pb
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
Motivation
Residue production in cold-fragmentation reactions
Peripheral heavy-ion reactionsat relativistic energies: large fluctuations in N/Z and excitation energyProton-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
Motivation
Cold fragmentation is not well understood for neutron-rich projectiles
Fragmentation of neutron-rich projectiles
EPAX
ABRABLA
COFRA
GSI Feb.‘06
Mass loss: impact parameter +matter/charge distribution N/Z: hypergeometrical
distribution Excitation energy: isotopic distributions
1 Abrasion phase (excited prefragment):
(Abrasion-ablation model)
Motivation
Description of the residue production in fragmentation reactions
2 Ablation (evaporation) phase
Binding energies+temperature
Some of these parameters can be determined from specific reaction channels
GSI Feb.‘06