MCNP6 fragmentation of light nuclei at intermediate energies

Fragmentation reactions induced on light target nuclei by protons and light nuclei of energies around 1 GeV/nucleon and below are studied with the latest Los Alamos Monte Carlo transport code MCNP6 and with its cascade-exciton model (CEM) and Los Alamos version of the quark-gluon string model (LAQGSM) event generators, version 03.03, used as stand-alone codes. Such reactions are involved in different applications, like cosmic-ray-induced single event upsets (SEUs), radiation protection, and cancer therapy with proton and ion beams, among others; therefore, it is important that MCNP6 simulates them as well as possible. CEM and LAQGSM assume that intermediate-energy fragmentation reactions on light nuclei occur generally in two stages. The first stage is the intranuclear cascade (INC), followed by the second, Fermi breakup disintegration of light excited residual nuclei produced after INC. Both CEM and LAQGSM account also for coalescence of light fragments (complex particles) up to He4 from energetic nucleons emitted during INC. We investigate the validity and performance of MCNP6, CEM, and LAQGSM in simulating fragmentation reactions at intermediate energies and discuss possible ways of further improving these codes.

Fission Fragments Produced from Proton Irradiation of Thorium Between 40 and 200 MeV

The cross sections for the formation of five residual radionuclides (72Se, 97Zr, 112Pd, 125Sb, and 147Nb) from 40- to 200-MeV proton irradiation of thorium have been measured and are reported. The atomic masses of these fragments span the expected mass distribution of radionuclides formed by fission of the target nucleus. Especially in mass regions corresponding to transitions between different relaxation mechanisms employed by available models, these data are expected to be useful to the improvement of high-energy transport codes. The predictions of the event generators incorporated into the latest release of the Monte Carlo N-Particle code (MCNP6) are compared with data measured in this work in the hope that these results may be useful to the continued process of code verification and validation in MCNP6.