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RUSSIAN FEDERAL
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OF EXPERIMENTAL PHYSICS
 
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WEIGHTING FACTOR AND SELECTION METHODS. SIMULATION OF COHERENT SCATTERING OF PHOTONS

D. G. Modestov
VANT. Ser.: Mat. Mod. Fiz. Proc 2010. Вып.1. С. 48-54.

Weighting methods are the important part of statistical simulation methods. The analysis of weighting factor with statistical expectation being proportional to the distribution density of the random value specified is common to all the methods. However, it is not always possible to find the density. Particularly, it happens when selection methods are used with unnormalized distribution density. The work suggests using certain conditional random value with statistical expectation being equal to the density function for the arbitrary parameter. This approach is precise (as opposed to the use of approximate value of normalization factor), but at the same time it does not require additional computational efforts and is easily implemented for the arbitrary selection algorithm. The method is implemented for the simulation of coherent scattering of photons and compared to the other methods.

Keywords: transport equation, scattering of photons, statistical simulation, upgrading method.
COMPUTATION OF NEUTRON DISTRIBUTION DENSITY AT ELASTIC SCATTERING

D. G. Modestov
VANT. Ser.: Mat. Mod. Fiz. Proc 2010. Вып.1. С. 55-58.

The distribution density is not often directly used to solve the problems using statistical simulation methods. The sample design, for which the density use is not required, is quite sufficient. However, the use of distribution density can be useful for computational efficiency improving, or for estimation of development which is impossible by other means. In particular, it is also important for neutron transfer simulation accounting for the motion of medium structure elements, for example atoms. This account is more important for elastic scattering simulation. However, distribution density of scattering angle cosine is often defined in the center-of-mass system. Given here is the computational algorithm for the distribution density in the arbitrary reference system and use case.

Keywords: transport equation, scattering of neutrons, statistical simulation, upgrading methods.







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