Hybrid model for drift waves in fully three-dimensional plasmas: Theory and applications.

A novel fluid/gyro-kinetic hybrid model to study drift waves in low-pressure stellarator plasmas is presented. The ion population is modeled with the collisionless gyro-kinetic equation and the electron population is described using fluid equations. The model equations are written in straight-field-line coordinates and are valid for any magnetic configuration with closed, nested magnetic surfaces. The geometrical effects which enter the final eigenmode equations are derived and discussed in some detail. The numerical method used to solve the coupled, time-dependent, along-the-field-line equations is described. The geometrical effects are discussed in some detail. Numerical calculations are carried out for a three-field period toroidal heliac with small global magnetic shear.