Simulations freezes when muons enters the black hole?

Dear FLUKA experts,

I am carrying out detailed simulations of the neutron flux in the Canfranc Underground Laboratory (Canfranc, Spain). Three different neutron sources are considered: (alpha, neutron) reactions, spontaneous fission and (muon, neutron) reactions. The code works as follows:

  • For the alpha-induced neutron flux primary neutrons are created within the laboratory walls with energies selected according to an (alpha, neutron) energy spectrum which has been previously calculated using specialized codes. The neutron flux in different regions of the main hall is then computed using the USTRACK card.
  • For the spontaneous fission neutron flux an equivalent procedure is used.
  • For the muon-induced neutron flux primary muons are created within the laboratory. The (muon, neutron) reactions are therefore computed using FLUKA. Again, the neutron flux in different regions of the main hall is then computed using the USTRACK card.

For the calculations using the neutrons as primary FLUKA particles (alpha-induced reactions and spontaneous fission) the code works fine. However, there is a problem when muons are used: at some point of the simulations the calculation freezes. I have tracked each particle using the mgdraw routine and I have concluded that the freezing happens when muons enter the black hole region. I have no idea of which could be the reason for this behavior.

  • The FLUKA version is 4-3.2
  • The FLAIR version 3.2-4.4

Relevant files attached:

  • LSC_HallA_v3.inp (the input file)
  • RunTest.exe (the FLUKA executable)
  • Source_LSC.f (the source routine)
  • mgdraw_user.f (the mgdraw routine)

Dear @nil.mont,

Unfortunately, the files were not attached.

Dear amario,

You are right. I attach tem now. (200.9 KB)


Dear Nil,

it look like to me that the issue is with the source routine.

Most of the jobs stop with the error:

 Abort called from DEDX reason Exceeded upper dp/dx abscissa. Run stopped!
 STOP Exceeded upper dp/dx abscissa.

And when I looked at the sampled energy, I got a nonsensical ~ 1e17 GeV in one case.

Other jobs freeze without printing out the sampled energy, so I assume the source routine is stuck in a do while loop in these cases.

One note on the mgdraw routine: You left the close(unit=11) line uncommented. This interferes the standard FLUKA output. Please avoid using unit numbers 20 and below.


Dear David,

Thanks for your answer.