From: Susana Cebrián (scebrian@unizar.es)
Date: Wed Feb 04 2004 - 12:10:27 CET
Hello,
I am interesting in using the USRYIELD estimator to study the energy spectrum of neutrons traversing a surface at different polar angles. I want to use one USRYIELD estimator for each interval of the polar angle.
I have a doubt on the normalization of the results when the boundary surface is vertical, parallel to the z axis.
To obtain the total number of particles (per primary beam particle) going through the surface, one has to multiply the result of USRYIELD by the width of the energy bins and by the solid angle covered. I have prepared a simple test to check this (the output files are attached) sending particles perpendicular to the vertical surface and I expect that all of them go through the boundary without changing significantly their direction. But I dont´t understand a couple of things:
1) It seems that the reference direction for the angular distribution is the vertical, and not the beam direction (as I have supposed after reading the manual).
2) In the case of a vertical surface, the solid angle covered for each interval of the polar angle (thetai,thetaf) with respect to the vertical is PI(cos(thetai)-cos(thetaf)), being PI the result of integrating the covered azimuthal angle. But using this solid angle, the calculated total number of particle going through the surface is only a half of the real number (that I have checked using USRBDX).
I am afraid that I have misunderstood the USRYIELD estimator, so any help will be wecome.
Many thanks in advance,
Susana
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