Symmetries-imposed configurational limit and configurational limit-induced change of symmetry in an inductively driven, dissipative tokamak plasma

摘要

Hastie showed that, in a force-free tokamak configuration that encloses the magnetic axis, there exists a critical on-axis safety factor, q(0), above which the q profile monotonically increases with radius and below which decreases with radius [J. Hastie, Nucl. Fusion 29, 96 (1989)]. This critical q(0), when interpreted under the requirement of maximum poloidal magnetic field energy for an inductively driven, dissipative tokamak plasma, which does not allow dq/dr <0 for the toroidally symmetric configuration, becomes the onset condition of helical symmetry during current peaking in a sawtooth cycle. The value is a result of the opposing demands placed on the sign of the on-axis curvature of the safety factor, q(')(0), by the two rotational symmetries (m=0 and n=0) of the configuration. (C) 2001 American Institute of Physics. [References: 15]