Finite pressure equilibrium effects on helical ripple transport in torsatrons

A three-dimensional equilibrium code (NEAR) is used to study plasma equilibrium in torsatron configurations having various winding laws. The harmonic spectra describing the variation of |B-vector| along magnetic field lines are calculated at finite plasma pressure and then used to calculate the geometric factors that determine the magnitudes of the neoclassical transport coefficients in the helical ripple trapping regime, where the particle and heat fluxes are inversely proportional to the collision frequency. The results show that an appropriate choice of winding law can reduce helical ripple transport by a factor of about 2 in the vacuum field and at high plasma pressure. (author). 14 refs, 6 figs