Stopping power of alpha particles (and generally) vs energy or momentum

[el16044 (Artemis Taxeidi)]

Dear fluka experts,im new in flair and i want to plot the stopping power of particles(Mev*cm^2) vs energy or momentum .how can i do this?which scoring detector i have to use?i mean a curve like the below:

im waiting forward for your answer

[adonadon (Andre Donadon Servelle)]

Dear @el16044,

Thank you for your question, and welcome to the FLUKA forum!

In order to obtain the stopping power of alpha particles (and other charged particles as per the note below) you have to use a DELTARAY card with SDUM=PRINT, indicating the range of materials you’re interested in. Note that only those materials actually assigned to some region in your geometry will be considered.

After running (1 primary particle suffices), you will obtain the stopping power tabulation in the .out file for muons, charged hadrons, and heavy ions: you should search for the block corresponding to e.g. 4-HELIUM which will appear like this:

You’ll need to extract the first and second columns, manually or with a script, which should lead to the following plot, where the FLUKA stopping power of alpha particles in Pb is compared to that of the NIST ASTAR program.

Comments:

• As you can see in the screenshot above, the dE/dx reported in the output file is given in GeV/cm as a function of the kinetic energy in GeV. Should you need the dE/dx in MeV/cm, multiply by 1e3. Furthermore, if you want the mass stopping power [MeV cm^2/g] (note that in your question you are missing the 1/g), you need to further divide by the material density in g/cm^3.

• The upper limit of the dE/dx tabulation is driven by the primary energy defined in the BEAM card. Raise it accordingly in case you fall short. You will need to put a primary particle as well (PROTON by default). In case you indicate alphas as your primary, be careful, because you will need to use the dedicated executable that includes the rQMD and DPMJET libraries (bin/flukadpm ). You can find it here in Flair:
  

  

• For electrons and positrons the story is similar, but you should use the EMFFIX card.

Cheers,

André

[el16044 (Artemis Taxeidi)]

thanks for your answer ,i did it for muon+ particle ,but the curve seems to decent very fast.i dont know if its rignt.i did it in Gev/cm(Gev)

[ceruttif (Francesco Cerutti)]

Put a logarithmic scale on the horizontal axis.