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Cross-Section Measurement of Very Light Fission Fragments Produced in Spallation Reactions of 238U at 1 A GeV

This study focuses on the measurement of cross-sections and momenta of very light fission fragments produced in spallation reactions of 238U at 1 A GeV. The experiment was conducted at GSI in Germany using the FRS apparatus. The results provide important data for the design of ADS and RIB systems.

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Cross-Section Measurement of Very Light Fission Fragments Produced in Spallation Reactions of 238U at 1 A GeV

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  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) • Disentanglementof fission and fragmentation products • Results: production cross sections and momenta of residual nuclides • How to interpret the results • Conclusions

  2. direct kinematics inverse kinematics p 1GeV 238U 1GeV/u ~ 10 KeV/u ~ 1 GeV/u H2 238U 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 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. 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

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