Coincidence and Anti-coincidence Scoring

Dear FLUKA experts,

I’m building a simulation in which a spherical proportional counter is enclosed by a scintillator box while the whole thing is being bombarded by neutrons from all directions. What I’m trying to achieve is to score the number of events that deposited energy into the scintillator only, the number of events that deposited energy into the counter only and the number of events that deposited energy into both.

My questions are:

  1. Am I right about using FLOOD setting in the BEAMPOS on a spherical shell that encloses the whole system to simulate neutrons coming from all directions enters the detector box?
  2. Did I use the right option in the DETECT card to correctly use the coincidence/anti-coincidence settings to achieve what I want?
  3. From what I’ve learned regarding DETECT, the results would be normalized to the primary particles only if there’s no trigger region. How could I compare the results that were normalized to 2 different trigger region?

Thanks in advance for the help.


Input file:
1.inp (3.7 KB)
Neutron source spectra:
1.txt (1.5 KB)

Dear @KillMartin,

Let me try to tackle your questions:

  1. Yes. However, it looks like you have a source routine that you did not provide in your post. Therefore I cannot tell if some of the beam characteristics are being changed inside it. You can always check if the beam is as intended using an USRBIN scoring. For instance, I would temporarily fill all your regions with void and create an USRBIN covering all your geometry in order to score neutron fluence. When using the SDUM = FLOOD, the fluence inside the sphere should converge towards that one specified in the BEAMPOSit entry of the manual: 1/(\pi R^2) {cm^{-2}}.

  2. Your settings are correct as far as I can tell. Most probably you are doing what you intended but just in case I would like to point out that you are not exactly looking at “events that deposited energy into the scintillator only” or “events that deposited energy into the counter only”. Note that your geometry is composed by other regions apart from your counter and your scintillator. Your (anti)coincidence setup is only considering these two and strictly speaking your are scoring those events that deposited energy into the scintillator but not into the counter and vice-versa. In both cases you may be scoring events that deposited energy also in your Acryllic region for instance.

  3. We are taking a closer look to this and will come back to you ASAP.

Hope this helps.

Kind regards,

1 Like

Dear @fogallar ,

Thank you for your time and detailed reply, it helps lift my confusion.