Feasibility experiments for electron ripple injection on current drive experiment-upgrade

Abstract

In search of a method to generate a radial electric field in tokamak plasmas, an experimental study has been performed to investigate the possibility of inducing radial electrical current. An external coil array has been used to create a local magnetic ripple well and the electron cyclotron resonance heating (ECH) has been used to trap some electrons that will then be subject to rapid vertical drifts into the plasma. Using a simplified experimental arrangement with only a toroidal magnetic field, an ECH-driven radial electrical current has been observed. The ECH-driven elecron temperature anisotropy, which is necessary for ripple trapping and electron drifts, has been determined by several different methods. The perpendicular temperature can be shown to be as large as 11 times the parallel temperature, which should yield a significant amount of ripple trapping and radial current. (C) 1998 American Institute of Physics.