Magnetic systems of the stellarator type in the presence of a solenoid with a helical magnetic axis

Abstract

An investigation is made of a magnetic configuration formed by a combination of fields from a solenoid with a helical magnetic axis and a plane-geometry axis and stellarator helical conductors. The paper contains analytical expressions for the determination of the characteristics of the magnetic configuration, examples of magnetic surfaces of the system in a rectilinear approximation and the results of a numerical calculation of a toroidal variant of the configuration.

An investigation of Pfirsch-Schlüter currents in an ℓ = 2 torsatron

“…Two typical winding laws were considered which correspond to the following values of the coefficient a: oc = -1 and a = 1. At a = -1, relatively low magnetic surface distortions [6,7] produce a substantial theoretical confinement volume. Such a winding law is close to the optimum obtained in Ref.…”

“…Some common features of the L-H transition are the existence of a threshold heating power and a sharp drop of the edge magnetic and density fluctuations and of the H a /D a signals after the transition. On the basis of previous theoretical studies, Ohyabu et al [7] suggested that the L-H transition corresponds to a stabilization of microtearing modes with poloidal mode number m 5: 8 when the edge temperature exceeds a certain threshold. His stabilization criterion is probably oversimplified, since the edge plasma profiles change rapidly in the radial direction; furthermore, the parameter ranges in previous studies of microtearing modes are not applicable to the edge of tokamaks such as DIII-D.…”