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Author(s):
Y. Sato, M. Yokoyama, M. Wakatani and V. D. Pusovitov
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Title:
Complete Suppression of Pfirsch-Schluter Current in a Toroidal l=3 Stellarator
Date of publication:
Oct. 1999
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Key words:
Pfirsch-Schluter current, external vertical field, toroidal curvature, collisionless particle confinement
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Abstract:
Pfirsch-Schluter (P-S) current is an inherent, property of a finite pressure toroidal, equilibrium of tokamak and stellarator. However, it was pointed out recently (V.D. Pustovitov. Nuclear Fusion 36 (1996)583) that the P-S current would be suppressed completely if the external vertical field could be adjusted to satisfy the condition Omega = <Omega> in an l=3 stellarator. Here Omega = < tilde{B}^2 > /B_0^2 - 2 epsilon cos theta, l is a pole number, |tilde B| the vacuum helical magnetic field, B_0 the toroidal field, epsilon the inverse aspect ratio, theta the poloidal angle and <...> denotes the average over the toroidal angle. An example of such a stellarator equilibrium is presented in this paper. For this stellarator equilibrium, behavior of rotational transform and Boozer magnetic spectrum is clarified when the pressure is increased. Both formation of helical magnetic axis and reduction of toroidal curvature are important ingredients to reduce the P-S current. However, the collisionless particle confinement is not improved in this example.
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