Fluka Physics Card Use

Hi, a relatively new user of Fluka. I was calculating the angular fluence distribution of neutrons after 300 MeV/u Ca hits a Cu target and fully stopped. I wanted to know what is the ideal PHYSICS card to use to make sure that RQMD computation modes are activated after 125 MeV? I do not think my code is doing that by default. I am seeing a higher peak in case of PHITS where I have turned on the JQMD-2.0 mode.

Dear Rajarshi,

Thanks for your question. You should include the physics cards to activate the treatment of heavy ion evaporation and coalescence. See an example here below and plese refer also to the FLUKA Manual.

Additionally, keep in mind that when you use heavy ions as your primary particles you should link the DPMJET and RQMD event generators. This is done by linking with ldpmqmd and not with lfluka. Alternatively you can use flukadpm in Flair’s run tab.

Since you are interested in neutrons, you might also want to set the particle transport thresholds (in the transport card). See an example below where ions are trasported down to an energy of 100 keV and neutrons down to 0.01 meV.

If you need further assistance, please also upload your current FLUKA input file.


Thanks Marco, I will try these ones

Dear Rajarshi,

Let me correct the second part of my previous answer. If you want to set a threshold on all ions you should specify in the card Part: 4-HELIUM (and not PROTON as in my previous message). Once the threshold is set on alpha particles, all other ions will take as transport threshold the same energy per nucleon as applied to alphas (in the example, the threshold energy per nucleon for alphas would be 25 keV). Additionally, the default transport threshold when no PART-THRES cards are specified is 25 keV/n (provided that PRECISIO is specified in the DEFAULT card).

I hope I was clear,
My apologies for the mistake,

Thanks Marco, I used yesterday the QMDThreshold with the flukadpm in Flair and now the neutron peak at higher than 125 MeV matches that with PHITS. But these are valuable info regarding the low-energy part of the neutron spectrum

Are you referring to the PHYSICS card? By default, the RQMD event generator, if linked via ldpmqmd, takes gradually over from the BME event generator in the range from 100 to 150 MeV/n (projectile energy), with no need at all for the aforementioned card, unless you wish to modify the transition between the two models. On the other hand, without the use of ldpmqmd, no ion interaction is performed above 150 MeV/n.

Yes, I realize that now. I was using Flair to run them and I changed the executable and now the results make sense.

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