DPA scoring vs cooling time

Dear FLUKA experts,

I am using a 10MeV-electron beam to irradiate a disc of metal sample and investigating the DPA for a residual radiation. The electron beam is supposed to impinge on the sample for 8 hours at ~1mA. I scored the DPA after different cooling times, however the DPA immediately and after 1 hour hold the same and turned to be 0 after 1 week in the usrbin unit 28. After referring the other discussion How to calculate material damage (DPA) in this forum, I thought DPA should hold the same or be zero if it represents the DPA only by residual radiation since the electron beam energy is very low. The DPA scored in grids by meshing the disc region in USRBIN unit 22 showed that the DPA after 1 hour is zero. Could you possibly help check my files?
tiwindow.flair (13.9 KB)
tiwindow.inp (13.5 KB)

Any comments or suggestions will be much appreciated. Thank you.


Hi Xi,

As a preamble to my answer, let me point out that DPA is overwhelmingly due to prompt radiation. The contribution from residual nuclei should be very low which you can prove in your simulation (then likely never bother again).

The part resulting from the residual radiation can evidently only be seen if you activate your Aluminium target. However, with an electron beam, you are NOT going to activate your medium by default. You need to activate photo-nuclear and electro-nuclear interactions (PHOTONUC), otherwise you are only going to see the start of the development of the EM shower, nothing else. Here let’s insist on the electro-nuclear part, because your target is much thinner than the radiation length, and so electrons do not produce lots of bremstrahlung photons before exiting. Thus the electro-nuclear part is critical. As usual with electro/photo-nuclear, I would advise you to make use of biasing to have better statistics (LAM-BIAS).

Once the electro/photo nuclear interactions are activated, you can check the activation of your medium by adding a RESNUCLE card and check what nuclides are produced.

So this explains why you were seeing a non-zero prompt DPA and 0 for all residual DPA scorings.

Finally, there is a typo in the following DCYSCORE card

DCYSCORE          1.                        dpad1h    dpad1h          USRBIN
USRBIN           12.   DPA-SCO      -28.    Alsamp                    dpa1h
USRBIN       BLKBODY                                                   &

your DCYSCORE scoring name does not match the USRBIN, that explains why you were obtaining a non-zero value for the 1h scoring.

Hope this helps

1 Like

Dear Philippe @pschoofs,

Thank you very much for your reply. This is really helpful and clear to me and I appreciate it.
I corrected the typo in for the DPA after 1h cooling time, now it makes sense to me.

As for the produced nuclides, I set the Photonuc cards according with LAM-BIAS cards for both photo-nuclear and electro-nuclear interactions. However I am not very confident with the photo-nuclear setting since photon is not the primary particle in my simulation. Could you possibly help check my card settings?

The other thing is the score of RESNUCLE in the unit 29, I tried different methods and different beam sources, while it always shows an error for processing this file as the following shows


Could you possibly please help check my input files? Here they are,
tiwindow.flair (15.1 KB)
tiwindow.inp (13.7 KB)

Thank you very much for your time and help.

Best regards,

A PHOTONUC card with SDUM ELECTNUC will activate both photo- and electro-nuclear. Then you can define your biasing for both electrons and photons with two LAM-BIAS cards, as illustrated below (this reasoning could be extended to positrons depending on your beam and geometry).

For the RESNUCLE failing to process, I think you are trying to process it with the wrong tool. Please make sure that resnucle is selected in the Type field of the Run/Data tab.

Hi @pschoofs Philippe,

Thank you very much. This is really helpful for my simulation.


Hi @pschoofs Philippe,

I am a little confused. The PHOTONUC card shows that SDUM ELECTNUC is only the switch for the electronuclear reactions, why did you say it activate both photo- and electro- nuclear? Thank you.


Read the manual, Note 2

Ah, I see. I missed this. Thank you @ceruttif :grinning: