The second adiabatic invariant and neoclassical transport in stellarators

The second adiabatic invariant J(parallel to) for locally trapped particles is used for calculating neoclassical transport in stellarators. A numerica l method for calculating the variation of J(parallel to) on a magnetic surf ace is developed, which allows one to make the calculations in an arbitrary stellarator magnetic field given in real-space coordinates without transfo rming the field to magnetic coordinates. Equations for neoclassical particl e and energy fluxes for the 1/nu transport regime are derived, which are ex pressed through the variation of J(parallel to). By making use of these met hod and equations, an evaluation of neoclassical transport properties is ma de for a real-space realization of quasihelical symmetry, which has been ex amined recently in magnetic coordinates. (C) 1999 American Institute of Phy sics. [S1070-664X(99)00601-1].