Deconvoluting Fission Mass Distributions

Measurements of fission mass distributions provide valuable insights into the properties of fissioning systems and the dynamics of the fission process. Pre-neutron emission distributions, essential for codes like the Los Alamos -developed CGMF, are extracted from measured mass distributions since they cannot be directly observed after neutron emission, as the time scale of the fission reaction is too short for direct measurement before the emission. However, obtaining accurate pre-neutron emission distribution requires methods that eliminate the effects of mass resolution and detector inefficiency, which can impact those measurements. We propose a deblurring technique based on the Richardson-Lucy (RL) algorithm, commonly used in optics for image restoration. The RL algorithm uses the measured mass distributions and a transfer matrix to perform iterative deconvolution. The advantage of this method over others is that it does not assume any predefined shape such as a sum of Gaussians, as in CGMF for the mass distributions.

In this work, we apply the algorithm to the fission fragment mass distributions measured in both spontaneous and neutron-induced fission experiments to extract pre-neutron emission mass distribution. The results from deblurring are then used as inputs to CGMF, and we compare the CGMF results obtained using deblurring inputs with the default CGMF results. We observe good agreement between both sets of results.