|Message: Help with biasing thin heavy self shielding material||Not Logged In (login)|
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I am modeling a Uranium (high self shielding) spherical source. For now I am trying to test geometrical importance sampling on a 1mm radius sphere. The large majority of the gamma emissions occur around 200kev or under which has a 1/e length of about 0.2mm in the material. I do not have any scoring system set up inside the source volume. There is a detector 2m away.
I have set up a parallel geometry for biasing that consists of 0.2 mm thick hemispherical shells. For this shell thickness, importance sampling seems to work fine but if I go smaller than this (0.05 to 0.1mm), the number of counts that hit the detector decreases dramatically.
I was wondering if anyone has any suggestions as to why this is. I've thought it could be the cut value I set for gamma rays, but upon reducing this number to 0.01mm I observed no change in the output
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