Understanding the Impact of PROD-CUT and Transport-Cut on Penetration Depth

Physics, Transport and Magnetic Fields
1

Dear experts,

I am seeking clarification regarding PROD-CUT and Transport-Cut, as I am unsure if I have fully understood their effects. I have attached my input file for reference.

Based on my understanding, I believed that the penetration depth should vary with different values of the Transport-Cut. To test this, I tried various combinations of Transport-Cut (with PROD-CUT = KE where transport cut = KE + 511 keV) and the FUDGEM parameter:

  • (10 keV + 511 keV = 521 keV (transport cut), 10 keV (PROD-cut), FUDGEM = 0.0 & 0.5)
  • (100 keV + 511 keV = 611 keV (transport cut), 100 keV (PROD-cut), FUDGEM = 1)
  • (1000 keV + 511 keV = 1511 keV (transport cut), 1000 keV (PROD-cut), FUDGEM = 1)

If I set the beam energy (in BEAM card) to 1 MeV and use a Transport-Cut of 1.511 MeV (3rd case of above list), my expectation is that the penetration depth of electrons in water should be ~ zero. However, despite changing the cut values, the results remain the same in terms of penetration depth (i.e. ~4 mm in water).

I have attached the input files used to check the effect for different beam energies. (I have checked for above all 3 cases with different beam energies (in BEAM card), however here I am sharing only the input file for 3rd case for the reference)

BEAM_2MeV_Case3.inp (2.0 KB)
BEAM_3MeV_Case3.inp (2.0 KB)
BEAM_1MeV_Case3.inp (2.0 KB)

Could you please help clarify whether this is the expected behavior or if I am misunderstanding how the cuts should impact the results?

3

Dear @anjali.kavar,

Thank you for your question! Indeed, your understanding of the EMF cards on PROD-CUT and transport-CUT are correct, but the implementation unfortunately not.

In your EMFCUT cards:

  • on PROD-CUT: you are assigning on the materials from AIR (last) to WATER (before-last). In FLUKA, the materials are ordered/numbered, and if you increment from the last one to the before-last one, you basically do not apply this card to any material.
  • Similarly for the transport one, where you iterate from VOID (which you define as the last REGION) to WATER (the second defined).
    So you just have to double-check the ordering of materials/regions you want to apply these cards on. If you correct this, you should get what you expect, i.e. range of virtually 0, as in the attached plot.
    Capture d’écran du 2024-10-07 10-09-25

I hope this helps.

Best,
Daniel

4

Dear experts,
It worked!
Thank you for helping.