I have been working with the Cu-nat(p,xn)Zn-63 beam monitor nuclear reaction in the energy range of 9 to 30 MeV with 0.2 MeV intervals, using data recommended by the IAEA ( natCu(p,x)63Zn ).
The objective of my simulations is to obtain the activities of the Zn-63 radioisotope for each energy interval. The parameters of my simulations were: a target made of natural copper foil with a radius of 1 cm and a thickness of 25 micrometers, a beam current of 10 microAmps, and an irradiation time of 300 seconds. The beam has a Gaussian profile with 0.1 MeV (FWHM), 50.0 mrad of divergence, and a Gaussian spatial profile (x, y) with 1.8 cm (FWHM). The number of primaries is equal to 100,000,000.
My question concerns the results obtained, which, in principle, do not agree with the IAEA-recommended data for this nuclear reaction.
For 9 MeV, the recommended cross-section is sigma = 258.3 mb, and for 15 MeV, sigma = 222.9 mb. The activities obtained are: A(9 MeV) = 97.675 MBq and A(15 MeV) = 139.83 MBq. Since the cross-section for 9 MeV is larger than the cross-section for 15 MeV, I expected to find a higher activity value for 9 MeV than that found for 15 MeV, considering that all other parameters are the same (target geometry, irradiation time, beam current), but this is not what was observed in the results.
I performed simulations using 100% enriched copper in the mass-63 isotope, and the results were as follows:
A(9 MeV) = 141.49 MBq
A(15 MeV) = 205.40 MBq
The activity at 9 MeV remains lower than the activity at 15 MeV.
I would like to know which cross-section data for beam-monitor nuclear reactions FLUKA uses, and whether it is possible to select the IAEA-recommended data for these simulations.
Thank you very much for your attention and for any help that can clarify my doubts.
See Low energy Cu(p,x) cross section - #5 by cesc, which confirms an underestimation in the 6-13 MeV proton energy range.
Note that FLUKA does not embed specific cross section data, except for low-energy neutron interactions, rather relies on reaction modelling that consistently deals with any projectile-target combination at any energy.
Thank you for your prompt reply. I quickly understood that there are discrepancies in the results obtained by FLUKA for the beam monitor nuclear reactions Cu-nat(p,n)Zn-63 and Cu-63(p,n)Zn-63 when compared to the experimental data recommended by the IAEA. As I mentioned earlier, my goal is to obtain information on the Zn-63 activities produced by these nuclear reactions in the 7-18 MeV range. Above 12 MeV, my results are within the expected range, but below 12 MeV, the values obtained diverge significantly from expectations. As you said, FLUKA is based on nuclear reaction models that are consistent with any projectile-target combination for any energy. I would like to know if there is any way to circumvent these divergences using a card I cannot find.
Thank you very much in advance for your attention.
Dear Henrique,
no FLUKA input card is meant to tune at will the physics results.
In order to address the indicated localized discrepancy, which you can appreciate in the plot I referred to and tentatively correct accordingly by a scaling factor applied to the resulting Zn-63 activity below 12 MeV, we’ll have to improve the reaction model.
I will create a graph of Zn-63 activity vs. incident proton energy using the IAEA-recommended data and the results from the FLUKA simulations, and I will send it to you for your analysis and consideration. For the IAEA data, I will use the equation A = N.I.sigma.(1 - exp(-lambda.t)).
The simulations will take some time to complete, but I believe I will have all the data ready to send next week.
Dear Henrique,
I guess that the graph will just reflect the one I linked above, confirming the underestimation in the 6-13 MeV energy range as already shown and quantified.
Once again, I want to thank you for your invaluable help in unraveling the mysteries of this nuclear reaction that has kept me awake for months.
I am running the simulations mentioned earlier, and the preliminary results reveal that, in fact, there is something wrong with the model used by FLUKA.
When I have all the results ready, I will send them to you so that we can find a clever way to circumvent this problem.