NIFS-345

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Author(s):

W.X. Wang, M. Okamoto, N. Nakajima and S. Murakami

Title:

An Accurate Nonlinear Monte Carlo Collision Operator

Date of publication:

Mar. 1995

Key words:

Coluomb binary collision, Fokker-Planck collision operator, Monte Carlo collision operator, vector calculation

Abstract:

A three dimensional nonlinear Monte Carlo collision model is developed based on Coulomb binary collisions with the emphasis both on the accuracy and implementation efficiency. The operator of simple form fulfills particle number, momentum and energy conservation laws, and is equivalent to exact Fokker-Planck operator by correctly reproducing the friction coefficient and diffusion tensor, in addition, can effectively assure small-angle collisions with a binary scattering angle distributed in a limited range near zero. Two highly vectorizable algorithms are designed for its fast implementation. Various test simulations regarding relaxation processes, electrical conductivity, etc. are carried out in velocity space. The test results, which is in good agreement with theory, and timing results on vector computers show that it is practically applicable. The operator may be used for accurately simulating collisional transport problems in magnetized and unmagnetized plasmas.

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