FLUKA [1-3] is a general-purpose Monte Carlo code for the simulation of radiation transport used, among other applications, for the assessment of single-event-upset (SEU) production in electronic devices. FLUKA predictions for SEUs induced by protons below 10 MeV in commercial RAM modules significantly underestimate experimental values [4], due in part to the present lack of a nuclear elastic scattering model in FLUKA for protons below 10 MeV.

In order to overcome this limitation, the Coulomb and nuclear elastic scattering of protons on nuclei has been revisited within the distorted-wave Born approximation (DWBA), relying on spin-dependent optical potential models for protons of up to 200 MeV in the vicinity of nuclei [5], and accounting for the contribution of the compound elastic channel in the first few MeV above the Coulomb barrier [6]. A numerical database of differential cross sections for the elastic scattering of protons with energies from Coulomb barrier up to 200 MeV on targets ranging from Z=2 to Z=100 has been evaluated. To minimize memory requirements, an effective parametrized expression based on the black-disk limit [7] has been fitted to the numerical database, reducing it to a handful of energy-dependent coefficients, while still capturing the most relevant features in the differential cross section and providing a systematic means of disentangling Coulomb and nuclear elastic scattering. An efficient sampling scheme relying on the aforementioned parametrization has been implemented. This model supersedes the legacy model for nuclear elastic scattering of protons presently employed in the code (currently just above 10 MeV), dating back to the 1970s [8].

The model presented here substantially improves the agreement between FLUKA predictions and experimental cross sections for the production of SEUs in RAM modules under irradiation by protons below 10 MeV. Furthermore, it also gives an overall better description of large-angle nuclear elastic collisions of protons up to 200 MeV compared to the effective model presently in use in the code.

[1] https://fluka.cern
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[4] Coronetti A., PhD thesis, JYU Dissertations series, number 453, Jyväskylä, ISSN 2489-9003, ISBN 978-951-39-8915-6 (2021).
[5] Koning A., et al., Nucl. Phys. A 713 3, 231-310 (2003).
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