Monte Carlo computations of neoclassical transport

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Abstract
Neoclassical transport coefficients and confinement times in stellarators of general geometry and tokamaks with and without ripple are computed by Monte Carlo simulation over wide ranges of mean free paths, ratios of plasma to gyroradius, and radial electric fields. The results for monoenergetic particles can be represented by simple formulas using a transport coefficient normalized to the tokamak plateau value and a mean free path normalized to half the connection length. Transport coefficients obtained with monoenergetic particles subjected to pitch angle scattering and energy relaxation are convoluted with a Maxwellian energy distribution. The results are compared with theory and simulations using a particle distribution subjected to pitch angle as well as energy scattering. The overall agreement is good. Transport coefficients with Maxwellian energy distributions for l=2 stellarators and for various other stellarator configurations are shown. Particle transport coefficients, as well as energy transport coefficients, for these configurations are computed for ions (deuterons) as well as for electrons. Estimates of particle and energy confinement times are also obtained.