MONTE-CARLO SIMULATION OF NEOCLASSICAL TRANSPORT IN STELLARATOR VACUUM FIELDS
Neoclassical transport coefficients are computed by Monte Carlo simulation over a wide range of mean free paths in the approximation of small gyroradius, monoenergetic particle distribution, and vanishing electric field for simple axisymmetric and ripple tokamak model fields, and for many stellarator fields. Stellarator configurations are presented in which transport is reduced by a factor of 2 to 4 in all three regimes as compared with a tokamak with equal aspect ratio and effective ripple, and by a factor of up to 8 as compared with an equivalent l=2 stellarator. This improvement factor is apparently not compatible with the occurrence of a magnetic well because configurations with deep magnetic well show increased ripple transport. Although this behaviour is demonstrated for vacuum fields only, it will also be true for finite beta magnetic wells, since it relies on ripple deepening on the outside part of the torus. The formation of an island chain is demonstrated as another mechanism for increased transport. Ripple transport in actual stellarators (ATF-1, Heliotron E, W VII-AS) is moderately worse than in the equivalent l=2 stellarator.
Bibliographic Reference: 5TH INTERNATIONAL WORKSHOP ON STELLARATORS, SCHLOSS RINGBERG, BAVARIA (GERMANY), SEPT. 24-28, 1984 VOL. II, PP. 493-505, EUR 9618 EN (1985) FS, VOL. I AND VOL. II, 787 P., BFR 3500 (BOTH VOLUMES), EUROFFICE, LUXEMBOURG, POB 1003
Record Number: 1989124120200 / Last updated on: 1987-01-01
Available languages: en