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Abstract

In the last years, new interest has grown in exploring the biological effects of free radicals produced by ionising radiation (IR), since this “indirect action” plays a prominent role in damage induction. From the modelling perspective, Monte Carlo (MC) codes can be helpful in this regard. However, to extend the time range of predictability, a computationally lighter approach is needed in combination with the accurate initial description of MC simulations, limited typically to water targets and to μs temporal scales. To this end, TRAX-CHEMxt has been developed. In what follows, this novel code is presented. The calculation is based on the coordinates of the chemical species produced around one particle track, and solves the set of reaction-diffusion equations numerically with a computationally light approach based on concentration distributions. Its computational structure and abilities in investigating both water and biological environments, following the radicals’ and molecules’ dynamics to longer time regimes (μs – s), are showcased. The robustness of the algorithm has been tested, by comparing its predictions with MC counterparts around the μs. Deviations less than 6% have been registered, together with an improvement in the computational speed by more than three orders of magnitude. TRAX-CHEMxt results have also been contrasted with those from other codes and experimental data, still showing good agreements. Dependencies of chemical yields on the primary particles’ radiation quality, energy, linear energy transfer (LET) and target oxygenation have been studied as well. Due to its reliability and accuracy, TRAX-CHEMxt can be applied to investigate the impact of radiation-induced radicals on biological targets at longer times, under different radiation and environmental conditions.