Development of a nonlinear collision operator for GNET code

A nonlinear collision operator is formulated in the polar coordinate (v,cosθ) in order to study the effect of collisions among high-energy particles on their confinements in toroidal plasmas. The Monte Carlo collision operator is derived to be easily implemented to the orbit following code. The nonlinear collision model is benchmarked with the Boozer collision model for the Maxwellian plasma. This collision model enables the effect of self collisions of α-particles and energetic particles to be investigated on plasma heating, e.g. NBI and ICRF heating. (author)