Improvements and validation of particle channeling model in GEANT4

In this work several modifications to the default GEANT4 channeling model are provided and the results are validated against experimental data. The channeling model in GEANT4 10.3 version comes with physical process wrapper classes instead of cross section biasing operations which are used in the version 11.0. Initial simulations have shown that inaccurate energy losses of channeled particles are simulated with the original GEANT4 11.0 channeling model. In order to correct this, the cross section biasing operations were changed with the wrapper classes and the energy loss of channeled particles was compared to experimental results. The energy loss of protons and deuterons was evaluated and validated along the (100), (110) and (1 1 1) directions of Si, Ge and GaAs in the energy region 1-20 MeV. The difference between the simulated and the experimental stopping powers was less than 10 % in most cases. Higher deviations (up to ~ 20 %) were observed in the low energy region, below 4 MeV. The overall good agreement with the experimental results shows that the modified model is able to accurately predict stopping powers in channeling conditions for protons and deuterons. Another modification to the model was the inclusion of the condition of critical channeling angle. The simulations have shown that the simulated critical angle is in good agreement with the theoretical one. Also, the comparison of different particle step size limitations during the simulations has shown that the channeling process is particularly sensitive to simulation conditions such as beam spread, sample rotation, lattice quality etc. The modified model is being further developed and the possibility of RBS/C spectra simulation is investigated.