USRBDX for FLUENCE scoring

From: Chin-Cheng, CHEN (
Date: Wed Feb 26 2003 - 09:31:10 CET

Dear FLUKA users

     We encounter a problem when using the USRBDX for FLUENCE scoring.
     The input file is simple:
     1. A point source is located at the center of a void sphere.
     2. Mono-energetic neutrons are emitted isotropically.
     I would like to estimate the FLUENCE acrossing the sphere.
     The result was expected to be exactly 1.0 and with zero variance
     (assuming the area of the sphere is1.0 cm2).
     The USRTRACK indeed gives the right answer
     but the USRBDX gives the answer 0.8045805 +/- 0.1547585%.
     Does anybody know what happens?
     The input and output files are attached.
     Thank you very much.

Sincerely yours,
C. C. Chen and R. J. Sheu
National Tsing-Hua University, Taiwan, R.O.C.

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