Re: [fluka-discuss]: How to choose the types of interaction in FLUKA

From: <me_at_marychin.org>
Date: Sun, 2 Mar 2014 20:25:38 -0800 (PST)

Dear Ngoc Duy,

Do you wish to simulate case #1 or case #2:

Case #1: individual process(es) only, eg:
  input: photon energy, material
  process: generate random number, lookup cross section, plug into equations
  output: electron (maybe also photon, if Compton) energy and angle;

Case #2: radiation field (or 'radiation shower'), eg:
  input: source particle, material(s) of certain shape(s) and size(s) arranged
in certain way(s)
  process: [generate random number, lookup cross section, plug into equations]
                 loop over the square bracket many, many times -- once for each
progeny
  output: too many possibilities, depending on which we want.

FLUKA and the other major radiation transport codes are meant for case #2. You
may of course choose to output only the processes (photoelectric and Compton)
you are interested in -- within a radiation shower. By filtering, you may make
the output in case #2 *similar* to the output in case #1. 'Similar' but quite
different, because the two cases are completely different. In a radiation
shower, the photons available for undergoing photoelectric or Compton are
affected by what happened before (i. e. interactions upstream):

Example #1: After a photoelectric absorption, there will be no more photon
available for a Compton scatter after that (i.e. interactions downstream).

Example #2: After bremsstrahlung, we get a new supply of photon available for
subsequent photoelectric or Compton...

Therefore, suppressing certain types of interactions (per your request) would
skew the radiation shower and I don't know what meaning would remain. (Indeed,
sometimes some codes do omit certain interaction types but these are either
negligible, or they are compensated in some ways.)

As for case #1, packages like COMSOL might look more like it, but then by the
time we plugin the equations, I don't know what advantage we gain compared to
the simulator you already built.

:) mary


> On 28 February 2014 at 21:26 Duy Trinh Ngoc <trinhngocduy.k55_at_hus.edu.vn>
> wrote:
>
> Dear Sir, Madam,
>
> This year i do my graduation dissertation with a topic of "Simulation
> Monte-Carlo of interactions of photons gammas". I build a physics model and a
> code for simulate only the photoelectric absorption and Compton scattering,
> but not the other interaction process. I would like to compare my simulation
> results to results obtained by using FLUKA, but in FLUKA, the code simulate
> all of the interaction process possible with a particle, so could you tell me
> how to choose just some types of interaction for a simulation.
>
> Thank you in advance.
>
> Best Regards.
>
> --
> TRINH Ngoc Duy
> École supérieure des Sciences - Université Nationale du Vietnam à Hanoï
>
Received on Mon Mar 03 2014 - 06:25:54 CET