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Title: An update to the computation of the Goudsmit-Saunderson distribution in MCNP® version 6.2

To demonstrate how the number of terms used to compute the Goudsmit- Saunderson distribution impacts results, we study a thin foil problem where the outgoing angular distribution is observed for 20-MeV electrons. The foil thickness is roughly 1.5 times the default substep size for a 20-MeV electron in gold ( 2.8e-3 cm). Therefore, for the default substep size, electrons are guaranteed to undergo at least one collision before encountering a boundary (at which point an approximation is applied). In theory, one can improve the accuracy of the MCNP6.2 electron transport method by reducing the substep size. However, one must assume that the underlying data are valid. We show that when a user reduces the substep size, the angular distribution observed is different than expected, the primary reason being that the underlying data were not computed using a sufficient number of terms. We also show that the distribution is recovered when the number of terms is increased from hundreds to thousands. Here, we showed that stabilizing the underlying angular deflection distributions used in transport improves simulation results, particularly when default parameters are adjusted such that the substep size is reduced. Stabilization is achieved by adding more terms when computing the Goudsmit-Sandersonmore » distribution.« less
Authors:
 [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
OSTI Identifier:
1330070
Report Number(s):
LA-UR--16-27959
TRN: US1700425
DOE Contract Number:
AC52-06NA25396
Resource Type:
Technical Report
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 97 MATHEMATICS AND COMPUTING; M CODES; ANGULAR DISTRIBUTION; ELECTRONS; MEV RANGE 10-100; GOLD; APPROXIMATIONS; FOILS; THICKNESS; CHARGED-PARTICLE TRANSPORT; ACCURACY; COMPUTERIZED SIMULATION; STABILIZATION; SERIES EXPANSION electron transport Goudsmit-Saunderson