General questions

Running and Runtime Errors
1

DEMO_100ms.flair (3.8 KB)
source_newgen.f (20.8 KB)

Screenshot 2025-02-18 091008
Screenshot 2025-02-18 091008657×591 51.4 KB

distribution1_100ms.txt (3.2 KB)

Dear FLUKA experts,
I’m a beginner user whose recently approached the FLUKA code to model Runaway Electrons impact on wall tiles regarding fusion reactors. My simulation seems to work correctly, but I have some questions to which I couldn’t find an answer:

  1. As you can see, I defined the electron beam by imposing the coordinates of the point where it should impinge, is it right or is it an error? Because I feel that the tracking of the beam starts on the surface of my geometry, while in my thinking it should start outside.
  2. Is there the possibility to define “half-bodies”? I try to make myself clearer: since my geometry is periodic, is it possible to build it in the flair interface from the center of one coolant channel to the center of the other one, leaving two “half cylinders”?
  3. When particles are tracked inside the material, how it is defined the computational grid-mesh on which the interactions are scored? Is it uniform or can it be refined for example where the beam impinges?

I’m sorry if these might be dumb questions, but I hope that they might help some beginner user like me too. In the attachments I also leave the simuation case with associated files (source routine and file needed for it). I wish you all a good day
Kind regards
Matteo Robaldo

2

Buongiorno Matteo,

  1. The starting point of your beam is indeed on the surface, where you put it. That’s still fine (starting on a boundary may be a problem, since it can cause issues with the region identification, but the specified direction - which is not along the surface - helps FLUKA to overcome them and move into the tungsten region). If you want the beam to start outside, just change the BEAMPOS coordinates accordingly.
  2. Sure, but for this you do not need “half-bodies”: cut the respective regions with an infinite plane (namely, YZP) at the proper (x) coordinate, e.g., [as finally appearing in the .inp file]
    YZP cut 1.4
    […]
    *Half Coolant1
    COOLANT1 5 +Water1 -cut
    [I let you figure out how to do it directly in the Flair geoviewer]
  3. I understand you refer to the USRBIN 3D mesh, where you can score energy deposition (in the form of energy density or dose) or particle fluence. The Cartesian mesh may have a different resolution for any axis, but it is uniform on each axis. Nonetheless, you can define multiple distinct meshes, namely, a refined one around the impact point and a coarse one farther away.

Questions are not dumb.

3

Dear Francesco,
Thank you very much for your time and answers! I take also the opportunity to ask if it is possible to score a total energy balance of the deposited one: I saw that in the output file, at the end, there is one, but is it possible to know the amount that is deposited in the different materials or is escaping the system?
Kind regards
Matteo

4

You can insert a USRBIN card that scores ENERGY deposition per region (but in BLCKHOLE, and obviously VACUUM).
Also, towards the end of the standard output file, you find already a region table with an ENERGY Density column, which should be actually read as GeV deposited in each region (divided by a fake 1 cm3 volume, hence the historical Density wording and header units).
In the very last table of the same file, you get GeV particles escaping the system, which is nothing else than the amount of energy deposited in the BLCKHOLE region(s).