Shielding plate in beam and detector DOSE

Dear FLUKA experts! Help me to resolve my issue.
The protons (Ep=200 MeV) that fall on tungsten (600 sec, 1e13 p/sec) create a neutron flux and a zoo of radioactive elements. I know their activity in Bq (RESNUCLEi) and how it falls over time. My task is to calculate the dose to the detector that is generated by these radioactive elements after a cooling period (4 cases after irradiation: 0 sec, 600 sec, 1800 sec, 3600 sec). In the absence of a protective aluminum plate, this is not a problem. In the presence of a protective aluminum plate, the dose is increased because the plate is activated together with the tungsten. But in reality, this protective plate appears after the flux of protons and neutrons disappears, and only decaying radioactive elements in tungsten remain. How to write an input file so that tungsten contains a zoo of decaying radioactive elements, and a protective aluminum plate was not activated by source protons and neutrons?

Kind regards,
Konstantin

You can! The ASSIGNMAt card allows you to assign to your Al plate region AIR or VACUUM as material for the prompt phase, in order to mimic its absence during proton irradiation, and Aluminium as material for the decay phase, in order to take it into account as the electromagnetic radiation from the radionuclide decay is transported towards the detector. Let us know if you observe any anomaly.

It’s work perfectly!

But several questions arise:

  1. The dose unit in my task is GeV/gr/pr. “Pr” is a proton of a source or a particle that was generated as a result of radioactive decay?

  2. Does the detector gain dose from neutrons and protons during the prompt phase (during irradiation of tungsten with protons) or is it necessary to assign a vacuum to the detector material during the prompt phase?

  3. Can I start a new task and select the isotope activity calculation result from this task as a source?

2. It’s not necessary, since prompt and decay scoring are distinct. As you may have already realized for the activity scoring with RESNUCLEi, decay results after a given cooling time are obtained by linking the scoring card to the latter through DCYSCORE. The same applies to the dose to the detector: you may choose USRBIN to score it (either per region, remembering then to divide by the region volume, or with a superimposed regular grid) and DCYSCORE to obtain - rather than the prompt dose - the absorbed dose at a given cooling time.
1. Based on the above, pr is for you a beam proton in case of prompt scoring, while for decay scoring of absorbed dose - associated to a cooling time and an irradiation profile - the resulting unit is (GeV/g)/s.
3. You could, but it’s not automatic nor so trivial. You have to properly load the obtained radioactivity distribution by coding the source user routine.