Density, Temperature, and LOW-PWXS Usage

Dear FLUKA experts,

I’m currently running a simulation to determine the neutron capture rate in liquid xenon using RESNUCLEi among other things. This liquid xenon (LXe) is around 150-160K in temperature. It isn’t pure in one isotope, but is composed of 90% Xe-136 and 10% Xe-134. With my simulation, I’m using the ENDF libraries in conjunction with the LOW-PWXS card to (hopefully) point to the neutron capture cross sections for the xenon.

I am not encountering any syntax errors, compilation errors, or others. However, using the attached input, the rate at which I’m counting residual Xe-137 atoms is far lower than anticipated— as if it’s being simulated in the gaseous phase instead of liquid.

Would someone have a look at this input card to make sure the scoring makes sense, and then to ensure that the Xenon would indeed be interpreted by FLUKA as having a density around 3.3-3.6 g/cc?

As always, I’m grateful for your insight.


nEXO_OD.inp (7.8 KB)

Dear Regan,
your problem is not the density (3.58 g/cc according to your input), rather the isotopic composition, which turns out to be the natural one, where 136Xe is one order of magnitude less abundant than in your intended composition. This is due to a classical and evergreen mistake in the MATERIAL card, where you input the isotope mass number in the wrong place (as a general rule, let WHAT(2) - atomic weight - and WHAT(4) - material index - be empty).
Additionally, you can remove all LOW-MAT cards (applying to group-wise neutron treatment), in view of the LOW-PWXS presence.
Also, I’m not sure I understand what you aim to achieve with the PHYSICS/DECAYS card (muons naturally decay in FLUKA by default).
Let us know if the anticipated yield remains unmatched.

Thank you! I will make these changes and report back.

Dear Francesco,

This appears to have solved my problem. The amount of Xe-137 being produced is within my anticipated range.

Thank you for the help.


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