ABSTRACT
TRAX is a Monte Carlo particle track structure code realized in the early nineties. It was one of the first event by event radiation transport codes dedicated to particle beams for the nanoscale description of the specific dose deposition pattern. The main structure and methods of TRAX as well as its chemical extension TRAX-CHEM are reviewed as an exemplary framework for treating physico-chemical processes on multiple scales, with a focus on its more recent extensions and applications. TRAX supports cross sections for electron and (positive) ion projectiles, photons are envisaged for a future extension. As surrogate, their secondary electron spectrum can be used as a source distribution. TRAX so far considers the interactions elastic scattering, ionization, electronic, subelectronic and plasmon excitation. Bremsstrahlung is neglected for the time being. Nuclear fragmentation is implemented in the forthcoming version, for the purpose discussed here it is neglected since its cross sections are about eight orders of magnitude lower than the electromagnetic cross sections.
