Benchmark of the Monte Carlo code PENHAN for the simulation of low energy proton microdosimetric spectra using 3D-cylindrical silicon detectors

Purpose: The performance of the Monte Carlo code PENHAN is benchmarked for the simulation of the microdosimetric spectra of low-energy protons ( ≤ 14 MeV) using 3D-cylindrical silicon detectors. Methods: Simulations were validated against experimental spectra obtained from a proton beam cyclotron at the Centro Nacional de Aceleradores (CNA, Seville) and compared with results from the TOPAS (Geant4) code, using the same methodology reported in the paper that presented the reference experimental data. Results: The results showed that PENHAN reproduced the shape and position of the energy spectra, matching the maximum peak of the energy distribution to within 6% relative error in all cases. Absolute relative errors in the frequency-mean lineal energy remained below 8% across all proton energies (6-14 MeV). We also emphasize the importance of accurate modeling of the electronic stopping power, S e , for protons: variations in S e for tungsten alone led to differences of up to 14% in frequency-mean lineal energy. Conclusion: These findings underscore the potential of PENHAN as a simulation tool in proton therapy and microdosimetry, and highlight the necessity of validated stopping power data for reliable simulations.