Effects of electric field on particle drift orbits in a l = 2 torsatron

Particle orbits and loss regions in both real and velocity spaces are studied on the basis of the guiding center drift equations in magnetic coordinates. The boundary of loss region in pitch angle-radius (χ-ρ) plane is determined from the condition whether the drift surfaces for helically trapped and transition particles reach the outermost magnetic surface or not. The loss boundaries for the absolute particle confinement, within of which boundary no particles are lost, is evaluated. Effects of the radial electric field, Er on drift orbits and loss regions are discussed in detail. When ion motion is considered, the poloidal rotation modified by a positive Er reduces a number of trapped particles and consequently it leads the improvement of particle confinement. For a small negative Er, there is a possible particle loss caused by the helical resonance. The loss rate of ions caused by loss cone in collisionless limit is evaluated in the presence of Er. Effect of ripple modulation on the loss region is also discussed briefly. (author)