Monte Carlo simulation of beam quality correction factork_Qfor carbon-ion beams using FLUKA and GATE for selected...

Objective. To benchmark Monte Carlo codes FLUKA and GATE/Geant4 regarding the beam quality correction factors of ionization chambers for monoenergetic carbon-ion beams against experimental results by Holmet al(2022Phys. Med. Biol.6749401).Approach. Monte Carlo codes FLUKA and GATE/Geant4 were used to simulate the beam quality correction factorkQfor one plane-parallel (PTW 34001) and two cylindrical ionization chambers (PTW 30013 and IBA FC65-G) using two monoenergetic carbon-ion beams and an energy modulated beam in accordance with Holmet al(2022Phys. Med. Biol.6749401). Additionally, chamber-specific factorfQand perturbation factorpQwere calculated. Differences between Geant4 reference physics lists were investigated by comparing simulated depth dose distributions,fQ, andpQvalues for 429 MeV u^-1.Main results. SimulatedkQfactors were found to differ from experimentally determinedkQfactors of Holmet al(2022Phys. Med. Biol.6749401) by 2.5% for cylindrical chambers, whereas the plane-parallel chamber showed larger deviations of 3.1/2.6% (GATE/FLUKA), exceeding the simulation uncertainty of 1.7%.fQandpQfactors simulated using different Geant4 physics lists were comparable within the Type-A uncertainty of 0.2%. Nevertheless, the depth dose curves for physics lists using the INCL++ model showed an increase in dose at all depths except for the fragmentation tail. Differences infQfactors between Monte Carlo codes FLUKA and GATE of up to 1.8% have been observed.Significance. More investigations are needed to understand the cause of the observed deviations between experimental results and Monte Carlo calculations of beam quality correction factorkQ. No statistically significant differences are observed between investigated Geant4 physics lists forfQ,kQ, andpQsimulations. Notably, differences between Monte Carlo codes FLUKA and GATE are one of the main sources that limit the current simulation uncertainty.