Gamma-ray spectra outside the shield

I am designing a shield for the gamma-ray sources. Among other things, I wish to get the spectrum outside the shield. I ran a test simulation with Cs-137 and Co-60, and used both USRBDX and DETECT card. With DETECT cards, I get errors while I get some results from which I expect to see the spectral features. I am not able to interpret these results apart from thinking that the full energy peaks are attributed to a very large detector case.

Please help. Here I attach my input filetest.flair (3.4 KB)

Dear Mahannyapane,

there are a couple issues with your input:

  1. The DETECT estimator scores energy deposition. Since your “VOID” region has VACUUM assigned as material, the energy deposition in this region will be always zero.
  2. You selected the Coincidence trigger option. This requires energy deposition in two (or more) regions (one marked with the negative sign) during the same event. If you are interested in only one region, leave the trigger option empty.