Diagnosis of Gamma Energies Due to Capture of >8.5 MeV

To help understand what may have been going on for events which contained neutron captures on Gd and a total generated gamma energy of more than 8.5 MeV, I output some properties to a terminal (macro: CaptureEnergyGammaDetails.C, file: 1MeVNeutron1000k_GdCapSpectrum.root). One event in particular, highlighted here, demonstrated the truly odd behavior of these generated gammas. Two gammas of energies 4.0 MeV and 5.1 MeV were created precisely at the location of the neutron capture, and neither interacted with anything as they exited the Gd cylinder and left the simulation. There was no second order interaction or anything; everything was localized to the location of the neutron capture on Gd. Update: This was because higher energy neutrons have interactions which can produce higher energy gammas upon capture. When 1 keV neutrons were captured, rather than 1 MeV neutrons, these effects all disappeared.

Neutron Capture -- Example Gamma Details for Energy >8.5 MeV

Event Num: 999098

Total Energy of Generated Gammas: 9.44383

Initial Neutron X: -0.1548, Y: -0.03302, Z: 0.8

Final Neutron X: -0.1548, Y: -0.03302, Z: 0.500455

Neutron Initial Energy: 1

Neutron Final Energy: 0

Neutron Total Energy Deposit: 0

Gamma num: 0