High-fidelity treatment for object movement in time-dependent Monte Carlo transport simulations

We investigate the use of time-dependent surfaces in Monte Carlo transport simulation to accurately model prescribed, continuous object movements. The performance of the continuous time-dependent surface technique, relative to the typical stepping approximations and the recently proposed at-source geometry adjustment technique, is assessed by running a simple test problem involving continuous movements of an absorbing object. A figure of merit analysis, measured from the method's accuracy and total runtime, shows that the time-dependent surface is more efficient than the stepping approximations. We also demonstrate that the time-dependent surface technique offers robustness, as it produces accurate solutions even in problems where the at-source geometry technique fails. Finally, we verify the time-dependent surface technique against one of the multigroup 3D C5G7-TD benchmark problems.