Neutron Capture on Gd simulation

Dear @John_McFee and dear All,

I was following this post on “Question in neutron Capture” Question in neutron capture (Gd155(n, gamma)Gd156) reaction and i want to do something similar.

I have a spectrum of neutron energy and i want to insert it to the Gd target in water but I have trouble implementing it in Geant4, as i am new to Geant4. Is there any example macro in Geant4 that i could try or could you send me your macro as an example please. I shall be really thankful to you.

Thank you!

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Dear @CHAO , May be you could help me out here.

You need more than a macro. You need the program that will run the macro. I have modified the B4a example program to get (n,gamma) spectra for a simple source-target-embedding medium geometry. It includes a macro to generate a neutron beam and one to generate neutrons from a point source. I cannot upload the file because the forum does not accept archive files, so I will email it to you.

Thank you very much for your help. I really appreciate it. My email address is

@John_McFee could you also send me the above-mentioned file at
I would be very thankful as I am struck on it for days.

@John_McFee Thank you for the files. I noticed that you have not used fScoringVolume to get the energy deposited in the detector of our choice. Could this be done in an easy way?

It should be easy to do. Just follow the way the B1 example accumulates deposited energy in its SteppingAction module. I did not do it my software because I only cared about the parameters of the gamma rays incident on the detector volume (which was a vacuum), rather than their interaction with it.