I am trying to calculate the Compton scattered electron yield from a thin converter material, following irradiation by ~MeV photons. I am using the USRYIELD card to score the electrons emerging from this converter in the forward facing hemisphere (polar angle = Pi/2). In reviewing the _sum.lis file, I cannot rectify the double differential (#/Sr/GeV/primary) and cumulative yields (#/GeV/ primary).

I understand that I should multiply the double differential value by the solid angle subtended by the polar angles which define the bin, calculated using the equation 2Pi(cos(Theta1)-cos(Theta2)). When I do this, my calculated cumulative yield is >30% less than the FLUKA given cumulative yield. I have reviewed related topics on the FLUKA forum, and cannot find an answer for this disagreement. Any assistance with understanding this would be greatly appreciated.

The method of calculation seems correct, when I did my check I got FLUKA’s result exactly. I would suggest that you look into the .tab version of output, where the bin boundaries and results are clearly matched.

I cannot find agreement between the given FLUKA cumulative yield and my calculated one. I have verified that I am using the proper bins. I have attached my tab and sum files for reference. Note that my input file has changed since previously shared, but the issue remains.

For the first bin in polar angle, the differential yield is given as 2.581E-2 and the cumulative yield as 6.850E-3. However, I cannot unify these values with the factor 2Pi*(cos(0)-cos(7.854E-2)), which is the solution provided in a previous FLUKA forum post. I have done this calculation with separate tools, such to confirm no issues with the handling of radians vs degrees, just in case. When I multiply the differential yield by this solid angle, I get 5.00E-4, which strongly disagrees with the FLUKA given value. This disagreement continues through the other bins, with varying factors of deviation from the FLUKA value. Any assistance in finding a solution to this issue would be greatly appreciated.

The cumulative yields in the .sum file means an integrated value not just for the specific bin, but a sum of integrated values from the highest bin to the specific bin.

You can see that the last value of the cumulative yields table is equal to the total response printed at the beginning of the file.