Abstract
In fast wave current drive, fast waves accelerate resonant electrons in the direction parallel to the static magnetic field, causing parallel velocity to increase. The trajectory of a trapped resonant electron is calculated by computer code in which fast wave induced diffusion in velocity space is accounted for by a quasi-linear operator. Simulations show that the orbit of a trapped resonant electron transits from trapped to passing in some cases, reducing the effect of trapped electrons on current drive and improving current-drive efficiency. We determined the conditions under which this type of transition occurs.
