An Analytical Study of MC Source Term Estimators in Plasma Edge Simulations of Fusion Reactors

The statistical error and computational eciency of Monte Carlo reaction rate estimation depends crucially on which Monte Carlo procedures are used. We present a systematic comparison of the variance and computational cost of the most common estimation procedures and several others, and we show a non-trivial dependence of the choice of the optimal estimator on the problem parameters. The comparison is based on an invariant imbedding procedure, in which systems of ordinary dierential equations (ODEs) are derived that quantify the statistical error and computational cost of each estimator. We analyze in detail a scenario with forward-backward scattering in a one-dimensional slab. For this test case, we perform a parametric study of the expected statistical error and computational cost by numerically solving the ODEs.status: accepte