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
p 1GeV
238U
238U 1GeV/u H2
direct kinematics inverse kinematics
~ 10 KeV/u
~ 1 GeV/u
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
Z=26
H2 + Ti
Z=26
counts Ti
longitudinal velocity

5. VELOCITY OF ALL RESDIUES
hydrogen+titanium 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 238U+p

7. experimental cross sections: light fission residues of 1 AGeV 238U+p

8. fragmentation fission
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 RESIDUESZ
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. LIGHT NUCLIDES FROM 1 AGeV 238U + p
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