Verification and Preliminary Results of the Generalized Boltzmann Fokker-Planck Method for Charged Particle Radiation Transport

The short mean free paths and zero/low energy transfers associated with charged particle interactions create a computationally intensive problem to model. This paper suggests an accurate and efficient momentpreserving alternative to traditional Monte Carlo transport methods. The Generalized Boltzmann Fokker- Planck Method is an approximation of the scattering cross sections used in the linear transport equation which exactly preserves a finite number of scattering moments using a discrete angle representation. Unlike condensed history, this method preserves exponentially distributed interaction sites, simplifies pre-computation and ultimately leads to simplified boundary crossing algorithms. While this method was developed using the screened Rutherford differential cross section, it has recently been updated with improved interaction physics. Transmission/reflection spectra and dose-depth profiles generated using this method has been benchmarked against both analog and condensed history calculations, and have shown an increase in computational efficiency. Moreover, this method may prove broadly applicable to any Monte Carlo simulation involving sufficiently forward-peaked probability distributions. Future work will integrate these methods into the Integrated TIGER Series (ITS) suite to analyze accuracy and performance enhancement in fully coupled photon-electron transport in realistic three dimensional (3-D) geometries.