Fragmentation of very neutronrich

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

• Production of medium-mass neutron-rich isotopes

Fission cold fragmentation
n,p 238U ? 132Sn Be ? X
GSI Feb.06
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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
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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
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Motivation

• Fragmentation of neutron-rich projectiles

Cold fragmentation is not well understood for
neutron-rich projectiles
GSI Feb.06
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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
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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 energiestemperature

• Some of these parameters can be determined from
  specific
• reaction channels

GSI Feb.06
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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

Nn ? D ? Np p- Np ? D ? Nn p
208Pbp,d ? 208Bip-
R. J. Lombard et al., Europhys. Lett. 6 (1988)
323 A. Kelic et al., PRC 70 (2004) 064608
v(cm/ns)
GSI Feb.06
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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?pp- 0.1
mb 124-132Sn Be ? 125-133Sn
neutron pickup sD?np 5 mb
GSI Feb.06
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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
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Experimental details
238U(1 A GeV)d ? 1XXSn
5 different settings centered on 124Sn, 126Sn,
128Sn, 130Sn, 132Sn
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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. lt 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
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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