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A Geant4 Implementation of the Generalized Boltzmann Fokker-Plank Method

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D Dixon

D Dixon*, A Prinja, University of New Mexico, Albuquerque, NM

SU-E-T-490 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: A geant4 implementation of the Generalized Boltzmann Fokker-Plank (GBFP) method, an advanced, computationally efficient Monte Carlo method for charged particle transport, is studied.

Methods: The GBFP method is a systematic approach for extending the mean free path (MFP) of particles while exactly preserving moments of the true differential cross section (DCS) to some order, $N$, and approximating higher order moments by the exact moments of the approximate DCS. The approximate DCS preserves important physical quantities like mean scattering cosine, stopping power, and energy straggling. The GBFP method is a single event method, so transport mechanics are restored and step size and boundary crossing limitations inherent to condensed history methods are a non-issue. A geant4 application with GBFP physics was developed for testing speed and accuracy of the GBFP method dose calculations.

Results: Initial testing revealed that speed-ups for the discrete GBFP model are consistent with previous work on the GBFP method. Computed dose profiles using the discrete GBFP method are in agreement with benchmarks within statistical uncertainty (in most cases $< 1$\%) for sufficiently sampled regions. This indicates that the geant4 implementation was successful. A framework for further testing is now established.

Conclusion: The GBFP method provides systematic control of calculation speed and accuracy for electron transport calculations. The GBFP method is single event Monte Carlo so pre-existing production code transport algorithms are all that are needed for the implementation. Therefore, no major changes are necessary for incorporation of the GBFP method into production code systems.

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