Numerical studies on neoclassical transport of impurity plasmas using improved multi-species collision operator

Matsuoka, Seikichi* ; Sugama, Hideo*; Idomura, Yasuhiro   

The choice of collision operator is important to precisely evaluate the collisional transport of impurity ions in fusion plasmas. In collisional transport analysis, linearized Fokker-Planck (FP) collision operators are often used to reduce computational cost, and the Sugama collision operator is widely used. Recently, however, it has been found that the friction coefficient obtained using the Sugama collision operator is a few times different from the precise FP collision operator, resulting in errors in the evaluation of transport coefficients such as the thermal diffusivity. In this study, the multi-particle collision operator in the global full-f gyrokinetic code GT5D is extended to the recently proposed improved Sugama collision operator, and its accuracy is verified regarding collisional transport.