Neoclassical transport in a multiple-helicity torsatron in the low-collisionality (1/ν) regime

For a sufficiently high number of toroidal field periods (m/ι>l), the magnetic field of a multiple-helicity torsatron can be reduced to a simple form such that the second adiabatic invariant J can be calculated. It is found that the particle and the heat fluxes for a multiple-helicity torsatron in the low-collisionality (1/ν) regime have the same geometric dependences. An optimization of both quantities is carried out for a given equilibrium constraint. It is shown that the transport fluxes can be smaller than those of the conventional stellarator by an order of magnitude. The effect of finite plasma beta on the neoclassical fluxes is also studied.