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Author(s):
M. Yokoyama, N. Nakajima, M. Okamoto, Y. Nakamura and M. Wakatani
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Title:
Roles of Bumpy Field on Collisionless Particle Confinement in Helical-Axis Heliotrons
Date of publication:
Feb. 1999
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Key words:
bumpy field, collisionless particle, mod-B_min contour, helical-axis heliotoron
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Abstract:
Roles of bumpy field on collisionless particle confinement in helica1-axis heliotrons are investigated with the model magnetic field and particle orbit calculations in the Boozer coordinates. The mod-B_min contours can be shifted in the major radius direction with the control of the bumpy field, where B_min is the minimum value of |B| in the toroidal direction within one field period. The area of closed mod-B_min contours is a useful measure to evaluate global collisionless particle confinement as long as the mod-B_min contours connect toroidally. Negative value of ratio between the bumpy and the helicity components contributes to obtain the largest area of closed mod-B_min contours for finite ratio between the toroidicity and the helicity components. The radial variation of the bumpy field attributes to realize a toroidally localized mod-B_min Structure, which is significantly effective to improve collisionless particle confinement.
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