How to score the energy of primary and secondary electrons respectively

Dear FLUKA experts,

I am scoring the spatial dose (or energy deposition) distribution of one 8 MeV electron beam injected into the water by using the USRBIN card in FLUKA. Definitely the energy deposition is a total value from all the electrons including the primary and the secondary.
I am wondering, is there any method to score the energy of primary electrons (sourced electrons) and secondary electrons even tertiary (if there are) produced during the radiation respectively? I am trying to calculate the contributions of different sources of electrons to the dose distribution so that I can vary my electron beam to make that dose distribution uniform.
Your reply and advice are highly appreciated.


Dear Xi,

Fundamentally, no: electrons are indistinguishable, so in an e-/e- scattering problem there’s no way of telling which of the final-state electrons was which before the collision.

Technically, you could (e.g. in USDRAW you can intercept secondaries and examine the generation number via the LTRACK variable). Note however that this generation-number labeling for secondary electrons set in motion by primary electrons is merely an operational/conventional assignment. Your generation-number bookkeeping will furthermore vary if you vary the transport/production thresholds (if you lower the threshold you’ll get more explicitly tracked electrons), though the energy deposition will remain essentially unaltered (except in ill-posed situations where the binning/geometry is thinner than the electron range).

Thus, the exercise is questionable.



A post was split to a new topic: How to access LTRACK through Flair