DPA underestimation

Dear experts,

I am a new user and want to use fluka to calculate dpa. I am trying to reproduce results from several literatures for exercise. But the results of dpa calculated by me are all 1/2 lower than that in the literatures.

The first dpa calculations that I tried to reproduce is the blue line of Fig. 2(d) in paper
2014 Simulation of beam induced lattice defects of diamond detectors using FLUKA.pdf (688.0 KB)
. This case is the proton irradiating silicon of size 1x1x0.04 cm^3. My input file is
Si_Guthoff2014.inp (1.4 KB)
. The results of my calculation are as follows.
momentum_dpa_Guthoff2014
The dpa of every momentum seems to be 1/2 lower than that in the literature.

The second dpa calculations that I tried to reproduce is the middle red line of Fig. 1 in paper
2016 Comparative Study of Radiation damage in Si, Ge and Diamond used as Detector.pdf (572.7 KB). This case is the proton irradiating silicon of size 1x1x0.03 cm^3. My inputfile is
Si_Kumar2016.inp (1.3 KB). The results of my calculation is as follows.
energy_dpa_FP_Kumar2016
The dpa of every energy seems also to be 1/2 lower than that in the literature.

The third dpa that I tried to reproduce is the peak dpa (0.4) of Fig. 1 in paper
2013 On thermal and radiation damage to silicon crystals in the LHC proton beam.pdf (1.3 MB). This case is the proton with momentum 450 GeV/c irradiating silicon of size 0.1x1x5 cm^3. My inputfile is
Si_Smirnov2013.inp (1.3 KB). The peak dpa calculated by me is 0.22.

I wonder if there is some common mistake in my inputfile. Could someone help to have a look at my inputfile?

Best wishes!
Jiangyan Li

Hello and welcome to the Forum,

Your input seems to be correct but for the following modifications on MAT-PROP and USRBIN cards. On the first one you have to specify the material: “SILICON”. On the second, the maximum number of characters allowed for the “Name” is 8, please reduce the length of your choice.

MAT-PROP        25.0                       SILICON                    DPA-ENER  
*
USRBIN           12.   DPA-SCO      -51.    TARGET                    DPA-reg
USRBIN        TARGET                                                   &

The factor you found between your results and the one in the papers may come from the resolution of your scoring. The second USRBIN has only a single bin. Therefore, the DPA value is an average over the whole thickness of the target material. Nevertheless, the DPA changes with the material depth, i.e., along the direction of the incident particle beam. Therefore, if you increase the number of bins in Z you will see that the maximum value of the DPA increases and, also, you can check how it evolves along that direction. Do not forget to increase the statistics of the simulations accordingly (by increasing the number of primaries/cycles/spawns).

I hope this helps.

Kind regards,
Marta