Inconsistency between simulations for indium activation

Hi everyone,

I am actually trying to reproduce an activation experiment but I’m facing some issue.

We tried to link the number of activated atoms in indium disk and its incidental flux.

The experimental geometry was similar to the picture linked. On some irradiation, we added aluminum disk of different thickness and width in front of the indium.


After each irradiation, we measured the number of activated atom in the indium disk and we divided it with the number of neutron which goes through it (monitored by a BF3 detector).

I’m able to reproduce the experiment with the indium disk only but when I try to add aluminum plate I obtain a systematic error about 15%, without regard of the width or thickness of the aluminum plate or the distance of the indium disk.

Like my aluminum plates have different shapes, i tried to make them with different methods G4Tubs, G4Polycones and even by importing them in stl and ply format thanks to CADMesh but the error is still present.

I’m using G4 11.0 and QGSP_BIC_HP as physic list (I tried with G4NDL 4.6 and ENDF-VIII.0 with same results)

Thanks in advance,


You may try QGSP_BIC_AllHP, it uses ENDF-VII.0 proton database

I tried but without results , I keep an error when I add the aluminum plate …

By using QGSP_BIC_AllHP, I realized that I only considered the neutron flux and not the particles generated by the aluminum plate (gamma, e- and proton). But I don’t know and didn’t found the cross section for theses particles so I can’t figure their contribution in activation …