Effect of satellite helical harmonics on the stellarator configuration

摘要

We discuss the problem of self-consistent analytical description of stellarators with a helical field which has, besides the main harmonic, two nearest satellites with the same period in the toroidal angle. The expression for the flux function explicitly incorporating the effect of such satellites on the shape of magnetic surfaces is obtained. It is shown that they produce the shift of magnetic surfaces. The expression for this shift is derived. Two problems are considered where the behavior of B(sup 2) on a magnetic surface is important: Pfirsch-Schlueter current at the presence of satellites and possibility of fulfillment of quasisymmetry condition (B(sup 2) on a magnetic surface does not depend on one of the angular Boozer coordinates) at least at a single magnetic surface. It is shown that effect of satellite harmonics on the magnitude of Pfirsch-Schlueter current turns out to be much smaller than it was predicted earlier on the basis of simplified model where the shift related with satellites was not taken into account. It is shown that quasisymmetry condition in a configuration with two satellites can be fulfilled only in linear approximation in helical field. The analysis is performed for conventional stellarators with planar circular axis making use of stellarator expansion. (author) 54 refs. (ERA citation 20:022863)