Reduced Variance for Material Sources in Implicit Monte Carlo

Conference · Mon Jun 25 04:00:00 EDT 2012

OSTI ID:1044838

Urbatsch, Todd J ^[1]

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1. Los Alamos National Laboratory

Implicit Monte Carlo (IMC), a time-implicit method due to Fleck and Cummings, is used for simulating supernovae and inertial confinement fusion (ICF) systems where x-rays tightly and nonlinearly interact with hot material. The IMC algorithm represents absorption and emission within a timestep as an effective scatter. Similarly, the IMC time-implicitness splits off a portion of a material source directly into the radiation field. We have found that some of our variance reduction and particle management schemes will allow large variances in the presence of small, but important, material sources, as in the case of ICF hot electron preheat sources. We propose a modification of our implementation of the IMC method in the Jayenne IMC Project. Instead of battling the sampling issues associated with a small source, we bypass the IMC implicitness altogether and simply deterministically update the material state with the material source if the temperature of the spatial cell is below a user-specified cutoff. We describe the modified method and present results on a test problem that show the elimination of variance for small sources.

• Research Organization: Los Alamos National Laboratory (LANL)
• Sponsoring Organization: DOE/LANL
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1044838
• Report Number(s): LA-UR-12-22463
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
97 MATHEMATICS AND COMPUTING
ABSORPTION
ALGORITHMS
ELECTRONS
IMPLEMENTATION
INERTIAL CONFINEMENT
MANAGEMENT
MODIFICATIONS
RADIATIONS
SAMPLING
SUPERNOVAE