Ripple transport in helical-axis advanced stellarators : A comparison with classical stellarator/torsatrons
The neoclassical transport rates due to particles trapped in the helical ripples of a stellarator's magnetic field are calculated, based on solutions of the bounce-averaged kinetic equation. These calculations employ a model for the magnetic field strength, B, which is an accurate approximation to the actual B for a wide variety of stellarator-type devices. Comparisons show that the Helias concept leads to significant reductions in neoclassical transport rates throughout the entire long mean free path regime, with the reduction being particularly dramatic in the nu(-1) regime. These findings are confirmed by numerical simulations. Further, it is shown that the behaviour of deeply trapped particles in Helias can be fundamentally different from that in the classical stellarator/torsatrons; as a consequence, the beneficial effects of a radial electric field on the transport make themselves felt at lower collision frequency than is usual.
Bibliographic Reference: Report: IPP 2/307 EN (1993) 51 pp.
Availability: Available from Max-Planck-Institut für Plasmaphysik, 8046 Garching bei München (DE)
Record Number: 199311390 / Last updated on: 1994-11-28
Original language: en
Available languages: en