Analysis of fragmentation excitation functions of lead by carbon ions up to 400 MeV/u

Abstract

Fragmentation reaction cross-sections of lead bombarded by carbon ions below 400MeV/u are measured and compared with those simulated with Monte-Carlo radiation transport code PHITS to pinpoint the problems of simulation based on the quantum molecular dynamics model and the statistical decay model. Cross-sections for 32 fragments from A=24 to 85 and those from A=121 to 175 are measured within a reasonable uncertainty. Contribution of secondary particles to production of measured fragments are generally less than 20%. Comparison shows production cross-sections for fragments from A=20 to 60 and those from A=110 to 130 are underestimated by one order of magnitude. Further simulation shows production of each group of fragments in simulation are attributed to evaporation of fission fragments and to evaporation of highly excited prefragments, respectively. The lower the energy is, the more this trend is pronounced. Observed underestimation indicates presence of nuclear reaction mechanisms not considered in the current simulation such as multi-fragmentation.