Complex Particle and Light Fragment Emission in the Cascade-exciton Model of Nuclear Reactions

A brief description of our improvements and refinements that led from the CEM95 version of the CascadeExciton Model (CEM) code to CEM97 and to CEM2k is given. The increased accuracy and predictive power of the code CEM2k are shown by several examples. To describe fission and light-fragment (heavier than He) production, the CEM2k code has been merged with the GEM2 code of Furihata. We present some results on proton-induced fragmentation and fission reactions predicted by this extended version of CEM2k. We show that merging CEM2k with GEM2 allows us to describe many fission and fragmentation reactions in addition to the spallation reactions which are already relatively well described. Nevertheless, the current version of GEM2 does not provide a completely satisfactory description of complex particle spectra, heavy-fragment emission, and spallation yields. We have initiated another approach to describe fission, complex particles and fragment emission by developing further our CEM2k code addressing specifically these problems. In this effort, we have developed our own universal approximation for inverse cross sections. We have also developed new routines to calculate Coulomb barriers and widths of emitted particles and to simulate their kinetic energy using arbitrary approximations for the inverse cross sections. To describe fission-fragment production, we have incorporated into CEM2k a thermodynamical model of fission by Stepanov. This extended version of CEM2k allows us to describe much better complex particle emission and many fission fragments, but it is still incomplete and needs further work.