Nuclear de-excitation gamma-ray line spectrum

Dear FLUKA experts,

I am running a simulation to obtain the nuclear de-excitation gamma-ray line spectrum produced by primary 3He ions (with a power-law energy distribution in the range from 1 MeV to 200 MeV) injected into an 16O target. The spectrum shows contributions from de-excitation of nuclei produced by several reaction channels. Is it possible to obtain a spectrum showing only the contributions from 18F* and 18Ne* produced, respectively, in the reactions 16O(3He, p)18F* and 16O(3He, n)18Ne* (e.g., by discarding the other nuclei or suppressing their contributions)?

Cheers,

Sérgio Szpigel
Centro de Rádio Astronomia e Astrofísica Mackenzie
Universidade Presbiteriana Mackenzie

Hi Sergio @szpigel, it is possible, but it requires some coding in dedicated user routines.
To this purpose, I’d advertise the use of mdstck.f, to be compiled and linked into your own executable after implementing a suitable logic. This should discard irrelevant gammas (and other secondary particles) by setting their weight WEI (IP) to ZERZER (i.e. zero), where IP runs from 1 to NP (the relevant variables are available through the included genstk.inc file). Such a weight zeroing should be done unless JTRACK (available through trackr.inc) is equal to -5 (i.e. the projectile is 3He) and IBRES = 18 and IZRES = 9 or 10 (IBRES and IZRES are the mass and atomic numbers of the residue and are available through resnuc.inc, which has to be INCLUDEd in mdstck.f as the other include files are). Also, if the target material is not monoisotopic (16O), you should check whether IBTAR = 16 and ICHTAR = 8. You may want to add some printout, into a file unit of your choice (larger than 20 and not used in any scoring card of your input), to make sure that the logic makes sense (in particular, the secondary particle identity is given by KPART (IP)). I did not have the time to run a relevant test myself, so you are especially welcome to keep us posted in case of issues.

Dear Francesco,

Thank you for the help. I tried to use the routine mdstck.f as you suggested, but it didn’t work properly. It seems that IBRES and IZRES are not being filled, so WEI(IP) is zeroed for all photons.

Cheers,

Sergiomdstck.f (1.7 KB) source-3He.f (15.5 KB) test.flair (2.9 KB) test.inp (2.9 KB)

You are right, my fault. At the mdstck.f stage, the residue is found directly among the NP secondaries in genstk.inc (no need to include resnuc.inc then), with a peculiar KPART (IP) identity below -6 to be properly decoded. I upload my mdstck.f with a logic revised accordingly, for your further testing.
Also, your SOLAR definition is somewhat weird: there is no need for a COMPOUND card in case of a single component and the respective MATERIAL card (with the Z and A fields filled) is not consistent with a compound definition. Remove the COMPOUND card, as well as the pointless MAT-PROP card, and add a LOW-MAT card to link your SOLAR single element monoisotopic (16O) material to the low energy neutron cross sections of the (8 16 296 OXYGEN) entry in the FLUKA library.

Dear Francesco,

Thank you very much for the mdstck.f routine. It works perfectly and gives the expected photon spectrum. Thanks also for the advise on the SOLAR definition. I was sloppy when modifying an input used for targets with a typical solar atmosphere composition in order to run the simulations for the single component Oxygen target. I made the changes to the input as you suggested.

Cheers,

Sergio