Tübingen 2003 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 41: Physik mit schweren Ionen IV

HK 41.5: Vortrag

Donnerstag, 20. März 2003, 14:45–15:00, E

Cross-Section Measurement Of Very Light Fission Fragments Produced In Spallation Reactions Of ²³⁸U At 1 GeV — •Maria Valentina 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, and M. Pravikoff⁵ — ¹GSI, Darmstadt, Germany — ²University Santiago de Compostela, Spain — ³IPN, Orsay, France — ⁴CEA, Sacley, France — ⁵CEN, Bordeaux-Gradignan, France

Light nuclides produced in collisions of 1 A GeV ²³⁸U with hydrogen have been observed with a high-resolution forward magnetic spectrometer, the fragment separator (FRS), at GSI. Fragments were identified in A and Z and their production cross-sections measured. For each nuclide the velocity was precisely determined from the measured magnetic rigidity. This insight into the kinematics of the relativistic nuclear collisions allowed disentangling different reaction mechanisms. Thanks to the combined results on A, Z, and velocity of the produced fragments it was found out that neutron-rich isotopes of elements down to around neon were formed in a binary decay process. A quantitative analysis of the cross sections revealed that the charge distribution of these light fragments, which forms a plateau around Z=15 and increases below Z=13, is in agreement with the theoretical expectations of the statistical transition-state model.