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