NIFS-053

FULL TEXT (PDF, 637 KB)


Author(s):

M.Okamoto and N.Nakajima

Title:

Bootstrap Currents in Stellarators and Tokamaks

Date of publication:

Sep. 1990

Key words:

bootstrap current, Ohkawa current, neoclassical theory, stellarator, parallel viscosity, 1/nu regime, ripple diffusion, Large Helical Device.

Abstract:

The remarkable feature of the bootstrap current in stellarators is it's strong dependence on the magnetic field configuration. Neoclassical bootstrap currents in a large helical device of torsatron/heliotron type (L = 2, M = 10, R = 4 m, B = 4 T) is evaluated in the banana ( 1/nu ) and the plateau regime. Various vacuum magnetic field configurations are studied with a view to minimizing the bootstrap current. It is found that in the banana regime, shifting of the magnetic axis and shaping of magnetic surfaces have a remarkable influence on the bootstrap current ; a small outward shift of the magnetic axis and vertically elongated magnetic surfaces are favourable for a reduction of the bootstrap current. It is noted, however, that the ripple diffusion in the 1/nu regime has opposite tendency to the bootstrap current ; it increases with the outward shift and increases as the plasma cross section is vertically elongated. The comparison will be made between bootstrap currents in stellarators and tokamaks.

List of NIFS Report (1990)Return toContents Page Return toNIFS Homepage
footer
 National Institute for Fusion Science
Copyright: 1995-2007 National Institute for Fusion Science (NIFS)
Address: 322-6,Oroshi-cho, Toki, GIFU, 509-5292, Japan
Telephone:+81-572-58-2222