Solving Inverse Transport Problems with Neutron Multiplication Measurements and Improved Differential Evolution

In the problem of inverse radiation transport, measurements of particle leakages from radioactive source/shield systems are used to infer unknown parameters within the systems. This reconstruction can be accomplished by finding the physical parameters of the unknown system that minimize the difference between calculated detector responses and measured detector responses. Recently, the differential evolution (DE) method was shown to be highly adept at solving inverse transport problems in which the measured quantities were leakages of unscattered gamma-ray lines. In this work, we present an extension of the DE method to problems in which both gamma-ray lines and neutron multiplication are measured. The neutron multiplication measurement is demonstrated to be an important addition when few gamma-ray lines are available. We also discuss the implementation of a variant of DE that significantly reduces the number of forward transport computations required to solve the inverse problem