Nanometer scale description of electron transport and damage in condensed media using the TRAX Monte Carlo Code

The single interaction Monte Carlo code TRAX has been extended to describe low-energy electron creation and transport in solids. Electrons with energies below 1 keV have ranges in solids on the nanometerscale. Complete sets of electron interaction cross sections for energies below 1 keV down to 1 eV have been compiled and assessed for various target materials. The applicability of the cross sections has been validated by comparisons with experimental data as far as available. The code has further been extended to handle the production of Auger electrons and cascades. Furthermore, the capability to handle non-uniform targets has been added. With the extended TRAX code, experimental data from GSI’s Toroid electron spectrometer have been reproduced using thin solid state foils of carbon, nickel, silver and gold as targets. Furthermore, the radial dose distribution around ion tracks has been investigated on the nanometer scale. The explicit consideration of Auger electron cascades has been used to evaluate whether metallic nanoparticles can locally enhance the dose in combination with proton or electron irradiation

Nanolesions induced by heavy ions in human tissues: experimental and theoretical studies

The biological effects of energetic heavy ions are attracting increasing interest for their applications in cancer therapy and protection against space radiation. The cascade of events leading to cell death or late effects starts from stochastic energy deposition on the nanometer scale and the corresponding lesions in biological molecules, primarily DNA. We have developed experimental techniques to visualize DNA nanolesions induced by heavy ions. Nanolesions appear in cells as “streaks” which can be visualized by using different DNA repair markers. We have studied the kinetics of repair of these “streaks” also with respect to the chromatin conformation. Initial steps in the modeling of the energy deposition patterns at the micrometer and nanometer scale were made with MCHIT and TRAX models, respectively