A1262106907OBJsm

1
Cross-Section Measurement of Very Light Fission
Fragments Produced in Spallation Reactions of
238U at 1 A GeV
M. V. Ricciardi1, K. -H. Schmidt1, F. Rejmund1,
T. Enqvist1, P. Armbruster1, J. Benlliure2, M.
Bernas3, B. Mustapha3, L. Tassan-Got3, C.
Stephan4, A. Boudard4, S. Leray4, C. Volant4, S.
Czajkowski5, M. Pravikoff5 1 GSI, Darmstadt
Germany 2 Univ. Santiago de Compostella Spain
3 IPN Orsay France 4 CEA Saclay France
5 CEN Bordeaux-Gradignan France 

• MOTIVATION
• Need of systematic knowledge on cross section for
  ADS and RIB designs (scarce and fragmentary data
  up to now)
• OUTLINE
• Experiment 1 A?GeV 238U ? hydrogen at the FRS
  (GSI)
• Disentanglement of fission and fragmentation
  products
• Results production cross sections and momenta of
  residual nuclides
• How to interpret the results
• Conclusions

2
THE EXPERIMENT 1 A?GeV 238U ? liquid hydrogen
Advantages of the inverse kinematics ? complete
identification ? knowledge of the kinematics
Disadvantage ? I need a H2 target
3
THE FRS AT GSI AND THE EXPERIMENTAL SET-UP for
LIGHT RESIDUES
Z from IC
A/Z from time and position
Once mass and charge are identified (A, Z are
integer numbers) the velocity is calculated from
B? very precise evaluation!
4
DETERMINATION OF FISSION EVENTS
Z26
H2 Ti
Z26
counts
Ti
longitudinal velocity
5
VELOCITY OF ALL RESDIUES
hydrogentitanium
titanium alone
we can interpret the counts in the two wings as
very asymmetric fission products in
proton-induced reactions on 238U
6
experimental cross sections light fission
residues of 1 A?GeV 238Up
7
experimental cross sections light fission
residues of 1 A?GeV 238Up
8
CROSS SECTIONS OF RESIDUES MEASURED AT FRS (ALL
DATA ANALYSED UP TO NOW)
Not yet analysed
fragmentation
J. Taïeb
fission
M. Bernas M. V. Ricciardi
9
CHARGE DISTRIBUTION of the LIGHT RESIDUES
Z

• fission residues (experimental data)

--- line to guide the eye
10
TRANSITION FROM FISSION TO EVAPORATION
Z distribution the statistical transition-state
model
11
TRANSITION FROM FISSION TO EVAPORATION
Velocity from scission-point model towards
asymmetric decay from undeformed nucleus
? Mean velocities in the frame of the fissioning
nucleus
238U, 185Au compound nuclei
scission-point model (deformed nuclei)
Nucleus-nucleus fusion approach (undeformed
nuclei)
12
CONCLUSIONS

• LIGHT NUCLIDES FROM 1 A?GeV 238U p
• The apparatus
• FRS allows full (A, Z) identification and very
  precise determination of the velocity of produced
  residues
• The experimental data
• Formation cross section for every isotope, with
  its velocity distribution
• Essential for technical applications (ADS, RIB)
• The physics
• Yields and velocities of light nuclides from 1
  A?GeV 238U p indicate a transition from fission
  to evaporation