Erlangen 2001 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 23: Kernphysik/Spektroskopie III - Reaktionen

HK 23.3: Gruppenbericht

Dienstag, 20. März 2001, 17:15–17:45, D

Decay of Excited Nuclei in Proton Induced Spallation Reactions — •C.-M. Herbach¹, A. Böhm², M. Enke¹, D. Filges³, J. Galin², F. Goldenbaum³, D. Hilscher¹, U. Jahnke¹, A. Letourneau², B. Lott², R.-D. Neef³, K. Nünighoff³, N. Paul³, A. Péghaire², L. Pienkowski⁴, H. Schaal³, W.U. Schröder⁵, G. Sterzenbach³, V. Tishchenko^1,6, and I. Töke⁵ — ¹HMI Berlin — ²GANIL, France — ³FZ Jülich — ⁴Warsaw University, Poland — ⁵University of Rochester, USA — ⁶JINR, Dubna, Russia

The series of experiments at the Cooler Synchrotron COSY (Jülich) has been continued for a large number of spallation reactions p+X with protons of 0.8-2.5 GeV kinetic energy irradiating various thin targets (< 10 mg/cm²) from Al up to U. The exclusive data for neutrons and charged particles are measured event-wise with the 4π multi-detector array NESSI, which was supplemented by 6 telescopes consisting of two 80 µm and 1000 µm thick Si diodes backed by a 7 cm thick CsI crystal. Neutron multiplicity distributions as well as kinetic energy and angular distributions of light charged particles (LCPs) have been investigated as a function of thermal excitation energy E^* of the composite systems.

Drastic discrepancies for LCP production are observed between experiment and some of the computer codes widely-used to simulate the spallation process.They are associated with too high E^* calculated after the INC as well as different approaches for the Coulomb barriers and/or their dependence on E^* in the employed evaporation codes. The pre-equilibrium emission studied up to 200 MeV for p, d, t and ^3,4,6He is found to be an important source of composite particles.