Nuclear evaporation process with simultaneous multiparticle emission

TL;DR

This paper reformulates the nuclear evaporation process to include simultaneous multiparticle emission, revealing significant effects on particle yields and fission, especially at high excitation energies relevant for spallation reactions in ADS reactors.

Contribution

It introduces a new model incorporating simultaneous multiparticle emission in nuclear evaporation, impacting predictions of particle yields and fission probabilities at high excitation energies.

Findings

Simultaneous multiparticle emission significantly alters charged particle yields.

Fission occurrence is affected by multiparticle emission channels.

Neutron multiplicity changes qualitatively with excitation energy.

Abstract

The nuclear evaporation process is reformulated by taking into account simultaneous multiparticle emission from a hot compound nucleus appearing as an intermediate state in many nuclear reaction mechanisms. The simultaneous emission of many particles is particularly relevant for high excitation energy of the compound nucleus.These channels are effectively open in competition with the single particle emissions and fission in this energy regime. Indeed, the inclusion of these channels along the decay evaporating chain shows that the yield of charged particles and occurrence of fission are affected by these multiparticle emission processes of the compounded nucleus, when compared to the single sequential emission results. The effect also shows a qualitative change in the neutron multiplicity of different heavy compound nucleus considered. This should be an important aspect for the study of spallation reaction in Acceleration Driven System (ADS) reactors. The majority of neutrons generated in these reactions come from the evaporation stage of the reaction, the source of neutron for the system. A Monte Carlo simulation is employed to determine the effect of these channels on the particle yield and fission process. The relevance of the simultaneous particle emission with the increasing of excitation energy of the compound nucleus is explicitly shown.