I am planning to simulate an experiment involving the irradiation of a calcium target with a proton beam, followed by the measurement of the radiation dose resulting from the decay of individual isotopes produced in the nuclear reactions. For instance, in the reaction \text{Ca-40} + p \rightarrow \text{Ca-39} + \ldots , I aim to assess the dose emitted from the decay of specific isotopes such as Ca-39, K-35, and Ar-35, among others.
In an initial attempt, I performed a single simulation using a USRBIN estimator set to DOSE, combined with AUXSCORE cards to score contributions from individual nuclides. However, the results indicated zero dose from each nuclide, which is clearly inconsistent with expectations.
After reviewing the literature, I understand that such simulations typically require a two-step approach. The first step involves simulating the irradiation of the calcium target to determine the induced activity and the yield (per cm³) of each residual nuclide, for instance using RESNUCLE cards. In the second step, each nuclide of interest is independently placed within the target volume, and its radiation decay is simulated using the data obtained from the first step. However, in this approach, the initial spatial distribution of isotopes obtained from the first step cannot be fully preserved—isotopes are often simply placed at the center of the target, which may compromise the accuracy of the simulation results.
Is it possible to simulate this experiment in a single run, i.e., to irradiate the target and directly score the dose contribution from the radioactive decay of each individual isotope during or after irradiation? If so, I would greatly appreciate any guidance on the methodology, and if possible, an example project in FLUKA or FLAIR would be extremely helpful.
It is possible to simulate this in just one run, and indeed is one of the many benefits of FLUKA!
I have attached here the FLUKA course material and example exercises for calculations which includes details on the two step process and scoring for specific nuclides.
A brief summary is as follow:
Ensuring the correct physics cards are used. When scoring residual nuclei one should use: COALESCE and EVAPORAT to use coalescence and evaporation respectively (and run with flukadpm)
Use of the RADDECAY card, which activates the production and simulation of decay of radionuclides produced (possibly this was missing for the case detailed).
Addition of the IRRPROFI card to define the duration and intensity (irradiation profile) for the calculation. Multiple IRRPROFIs can be used.
DCYTIMES allows the setting of cooling times with respect to the end of the irradiation (a selection of times can be chosen).
For this case, to filter the dose contributions from a specific nuclide one should use AUXSCORE coupled with the USRBIN to score the quantity of interest (DOSE),
If the induced activity is of interest the ACTIVITY (Bq/cm3) or ACTOMASS (Bq/g) can be used.
To observe all the radionuclides produced RESNUCLE can be used.
DCYSCORE matches the scoring detectors with decay times chosen (matches the USRBIN to cooling time).
Thank you for your assistance. I have set up the .inp card in accordance with the instructions. However, it is still producing a zero dose result—for example, for 39Ca—which is clearly not correct. Could you please review my .inp card and advise on what I may have done incorrectly?
For the AUXSCORE if you are intending to observe the dose contribution from a specific nuclide it should be included in the filter. In the current arrangement this is not being scored. Examples of this are shown in 05_RPtopical_CERN2024_Residual.pdf Page 32 and 04_RPtopical_CERN2024_Activation.pdf Page 18.
To add to this as I do not think I was clear, this is to provide the activity per nuclide. To see all nuclides use RESNUCEI. For the dose it is more complex.
