Super Cool Energy Deposition

A while ago I did a short post about the positional energy deposition in polymeric films.  I recently ran the simulation for 25 cm thick films, and it is cool that it is possible to see a lot of fundamental physics in the simulation.

Neutron Energy Deposition. (I wish I was good enough such that you could rotate the figure)

First, you can see for very thick films pratically of the energy is deposited in the film (the neutron reaction has a q-value of 4.78 MeV). There is some backscattering lost of the front edge of the film, shown by the number of events in the first thickness bin.  This effect is decreased as one goes into the film. Secondly, you can see the exponential attenuation of neutrons through the film by th linear decrease in the frequency of counts as you go through the film at 4.78 MeV -  just taking the slice at 4.78 MeV.  This decrease is linear on a log scale, and therfore follows an exponential attenutation.  From this it would then be possible to esimate the macroscopic absoribition cross section, which determines the rate of attenuation in the medium. Pretty cool, huh?