T-2, Nuclear and Particle Physics, Astrophysics and Cosmology

Number of particles in fission fragments with a Monte-Carlo approach

Marc Hugo Verriere

The fission process is at the core of many applications including national security, energy production and fundamental science. Among all the observables associated with fission, a substantial amount of effort have been made to construct theoretical frameworks able to predict the pre-neutron fragments yields. The macroscopic-microscopic and the fully microscopic approaches for the description of fission have been developed for this purpose. In both approaches, a potential energy surface, consisting in a set of several thousand or million of static states is generated. Each state corresponds to a given shape configuration of the nucleus. The scission or breaking configuration is commonly calculated by approximating the average fragmentation using the relative population of each quasi-scissioned state. In this standard picture, the average fragmentation associated with a quasi-scissioned state is a non-integer value. Furthermore, 1- and 2-body correlations, relevant for the description of odd-even staggering in the charge yields, are not taken into account. We present a novel Monte Carlo technique based on the particle degrees of freedom in a decomposition of quasi-scissioned states. This furnishes the fragmentation probabilities associated with each quasi-scissioned state and further allows us to take into account 1- and 2-body correlations. We show that our method can reproduce odd-even staggering in charge-yields and is model independent. Thus, it requires no additional parameters and does not depend on the underlying approach to fission. Our powerful new technique can be used as a basis for an improved description of fission yields with wide applicability.


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