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On the solution of a few problems of multiple scattering by Monte Carlo method; Sur la solution de quelques problemes de diffusions multiples par la methode de Monte-Carlo

Abstract

Three problems of multiple scattering arising from neutron cross sections experiments, are reported here. The common hypothesis are: - Elastic scattering is the only possible process - Angular distributions are isotropic - Losses of particle energy are negligible in successive collisions. In the three cases practical results, corresponding to actual experiments are given. Moreover the results are shown in more general way, using dimensionless variable such as the ratio of geometrical dimensions to neutron mean free path. The FORTRAN codes are given together with to the corresponding flow charts, and lexicons of symbols. First problem: Measurement of sodium capture cross-section. A sodium sample of given geometry is submitted to a neutron flux. Induced activity is then measured by means of a sodium iodide cristal. The distribution of active nuclei in the sample, and the counter efficiency are calculated by Monte-Carlo method taking multiple scattering into account. Second problem: absolute measurement of a neutron flux using a glass scintillator. The scintillator is a use of lithium 6 loaded glass, submitted to neutron flux perpendicular to its plane faces. If the glass thickness is not negligible compared with scattering mean free path {lambda}, the mean path e' of neutrons in the glass  More>>
Authors:
Bluet, J C [1] 
  1. Commissariat a l'Energie Atomique, Cadarache (France)
Publication Date:
Feb 01, 1966
Product Type:
Technical Report
Report Number:
CEA-R-2971
Resource Relation:
Other Information: PBD: Feb 1966
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ANGULAR DISTRIBUTION; COLLISIONS; ELASTIC SCATTERING; LITHIUM 6; MONTE CARLO METHOD; NAI DETECTORS; NEUTRON FLUX; NUCLEAR PHYSICS; PHOSPHORS
OSTI ID:
20621970
Research Organizations:
CEA Cadarache, 13 - Saint-Paul-lez-Durance (France)
Country of Origin:
France
Language:
French
Other Identifying Numbers:
TRN: FR05R2971065621
Availability:
Available from INIS in electronic form
Submitting Site:
FRN
Size:
55 pages
Announcement Date:

Citation Formats

Bluet, J C. On the solution of a few problems of multiple scattering by Monte Carlo method; Sur la solution de quelques problemes de diffusions multiples par la methode de Monte-Carlo. France: N. p., 1966. Web.
Bluet, J C. On the solution of a few problems of multiple scattering by Monte Carlo method; Sur la solution de quelques problemes de diffusions multiples par la methode de Monte-Carlo. France.
Bluet, J C. 1966. "On the solution of a few problems of multiple scattering by Monte Carlo method; Sur la solution de quelques problemes de diffusions multiples par la methode de Monte-Carlo." France.
@misc{etde_20621970,
title = {On the solution of a few problems of multiple scattering by Monte Carlo method; Sur la solution de quelques problemes de diffusions multiples par la methode de Monte-Carlo}
author = {Bluet, J C}
abstractNote = {Three problems of multiple scattering arising from neutron cross sections experiments, are reported here. The common hypothesis are: - Elastic scattering is the only possible process - Angular distributions are isotropic - Losses of particle energy are negligible in successive collisions. In the three cases practical results, corresponding to actual experiments are given. Moreover the results are shown in more general way, using dimensionless variable such as the ratio of geometrical dimensions to neutron mean free path. The FORTRAN codes are given together with to the corresponding flow charts, and lexicons of symbols. First problem: Measurement of sodium capture cross-section. A sodium sample of given geometry is submitted to a neutron flux. Induced activity is then measured by means of a sodium iodide cristal. The distribution of active nuclei in the sample, and the counter efficiency are calculated by Monte-Carlo method taking multiple scattering into account. Second problem: absolute measurement of a neutron flux using a glass scintillator. The scintillator is a use of lithium 6 loaded glass, submitted to neutron flux perpendicular to its plane faces. If the glass thickness is not negligible compared with scattering mean free path {lambda}, the mean path e' of neutrons in the glass is different from the thickness. Monte-Carlo calculation are made to compute this path and a relative correction to efficiency equal to (e' - e)/e. Third problem: study of a neutron collimator. A neutron detector is placed at the bottom of a cylinder surrounded with water. A neutron source is placed on the cylinder axis, in front of the water shield. The number of neutron tracks going directly and indirectly through the water from the source to the detector are counted. (author) [French] On traite dans ce rapport de trois problemes avec les hypotheses communes suivantes: 1.- Le seul processus de collision possible est la diffusion electrique. 2.- La distribution angulaire est isotrope. 3.- La particule ne perd pas d'energie au cours des collisions successives. Ces hypotheses sont justifiees par les materiaux et les gammes d'energie etudies. 1er probleme: une cible de sodium de geometrie donnee est soumise a un flux de neutrons. Certains noyaux sont actives. L'activation est ensuite mesuree par un cristal au iodure de sodium. La methode de Monte-Carlo permet de calculer la distribution des noyaux actives dans l'echantillon en tenant compte des diffusions et l'efficacite du compteur. Un disque en verre au Li{sup 6} est soumis a un flux de neutrons perpendiculaire a ses faces planes. Si l'epaisseur du verre n'est pas negligeable devant le libre parcours de diffusion {lambda}, il y aura des collisions et le parcours moyen e' d'un neutron dans le verre sera different de l'epaisseur. e' est calcule par la methode de Monte-Carlo. On en tire une correction relative d'efficacite egale a (e' - e)/ e. 3eme probleme: un detecteur de neutrons est place au fond d'un cylindre entoure d'eau. Un flux de neutrons provient d'une source placee sur l'axe, en avant de la protection; on calcule le rapport du nombre de neutrons allant directement de la source au detecteur au nombre de neutrons faisant un trajet non direct avec des collisions dans l'eau. Pour les trois problemes on donne les resultats trouves pour quelques cas concrets tels qu'ils se sont poses experimentalement, et des courbes plus generales ou on utilise des variables reduites comme le rapport libre parcours/dimension geometrique ou son inverse. On donne egalement les listes d'instructions des programmes, avec les organigrammes complets et les tableaux de correspondances entre symboles. (auteur)}
place = {France}
year = {1966}
month = {Feb}
}