Infinite surface

Dear FLUKA experts,

In my simulation I created a very simple geometry. It is only a homogeneous cube (RPP) in the middle of void. With this I would like to create an infinite surface with a given depth, filled with a selected material using symmetry boundary conditions if possible. There could be 2 solutions with equivalent results:

• Mirror symmetry: make the particles reflect from those sides of the cube that are pointing to X and Y directions. So that particles could only leave the cube in +/- Z direction.
• Translational symmetry: particle that would escape from the cube on one side would return to the cube on the other side in X and Y directions.

I am not sure if I can achieve this with LATTICE card or with lattic.f user routine. Is it possible? Do you have an example or any other suggestion to solve this issue?

Szabolcs

Kedves Szabolcs!

A lattice can be used to duplicate geometry (copying the cube), but the location of the copies, and the translation (rotation, etc.) has to be defined by hand.
So duplicating with lattice is mostly used for complex geometries. To have multiple homogeneous cubes is it just simpler to use RPPs.

May I ask, what do you want to simulate? Maybe there are some better ways to construct your geometry.

Üdv.:
Dávid

Kedves Dávid!

Köszönöm a gyors választ!

I would like to simulate radiation environment on a planetary surface caused by cosmic rays, so it would be important to have a very large (ideally infinite) surface.

Üdv,
Szabolcs

Kedves Szabolcs,

FLUKA is capable to simulate cosmic rays in the Earth atmosphere (https://flukafiles.web.cern.ch/flukafiles/manual/16.html), but I assume you are looking for other planetary bodies.

To create (close to) infinite surfaces you can use infinite bodies, like XYP, XZP, YZP and PLA.

Üdv.:
Dávid

Kedves Dávid,

Thank you for suggesting infinite bodies, I have checked them in the docs, courses. It seems like a viable option. Still, I have one concern.

Do infinite bodies use symmetry conditions in their implementation? I am afraid that using these bodies would increase the length of my simulation by orders of magnitude.

Üdv,
Szabolcs

Kedves Szabolcs,

the infinite bodies, are truly infinite. There is no option in FLUKA to set up symmetry boundary conditions.

The length of the simulation of course depends on the geometry, but I’m still unsure, why would you need the infinite surface for your simulation.

Üdv.:
Dávid

Kedves Dávid,

My goal is to simulate the secondary particle spectrum. I have a USRBIN detector over the surface and secondary particles (generated by primary cosmic rays) should come from every point of the surface.

Given a finite surface, the USRBIN detector would not be hit by particles from every angle. In this case, the simulated flux is underestimated.

Üdv,
Szabolcs

Kedves Szabolcs,

I think I understand your problem.

I can only suggest to try to limit your geometry, by determining the range of secondaries created by one primary cosmic ray. This way you don’t need to simulate cosmic rays far away from your point of interest.

Üdv.:
Dávid

Kedves Dávid,

Thank you for all your help!

Köszönöm,
Szabolcs