Numerical Evaluation of Neoclassical Transport in Stellarators at Arbitrary Collisionality

The neoclassical diffusion losses of an l = 2 stellarator and an advanced stellarator are analysed with a modified version of the Boozer-Kuo-Petravic Monte-Carlo Code. Particle loss and confinement of a monoenergetic ion distribution are determined at arbitrary collisionality under stationary conditions. Special attention is given to the long mean free path regime. Due to the drift motion of localized particles a depopulation of the distribution function around v∥ = 0 occurs. The confinement time is determined by pitch angle scattering in this case. It is analysed under which conditions the 1/v-scaling of diffusion losses arises. A comparison is made between the loss rate of an advanced stellarator and a classical l = 2-stellarator. Also a tokamak with ripple losses is considered