A local method for sampling and regulation of Monte Carlo particles in the TROLL code for radiative transfer equations (RTE)

This report presents the new local method for the sampling and the regulation of Monte Carlo particles and compares it to the baseline method used in the code FCI2 [5]. The body of this document deals with Monte Carlo methods for RTE, focusing on the sampling and the regulation of particles, and details the compared methods. For that, the first section reminds briefly the context of Monte Carlo methods for RTE, the challenges of sampling and regulating particles, and presents the benefits and drawbacks of the baseline method. Then, the second section describes the general algorithm of the local method, as well as its properties and specificities. Finally, the numerical comparison is performed on a test, simple but representative of a physical regime that occurs in Inertial Confinement Fusion experiments: a Marshak radiation wave, for which we compare means and variances of the two methods. An appendix dedicated to unfamiliar reader reminds the definitions and the main results allowing to use Monte Carlo methods in a general context. An application on a transport equation, simplified for educational purposes, is also proposed (see [12] for an exhaustive presentation of the subject). (author)