Controllability of driven current profile in ECCD on ITER

The controllability of current profile driven by the fundamental resonance of the O-mode wave is examined for the parameters of the Intermediate Aspect ratio Machine option of the International Thermonuclear Experimental Reactor (ITER). The driven current is numerically evaluated by using the full relativistic adjoint method which we have extended from the non-relativistic one. By changing both the toroidal and poloidal injection angles, the optimum direction to drive a current with maximum current density at the aimed position is obtained. The position of wave launching affects the optimum injection angles and the driven current profile. The dependence of driven current profile on beam divergence is also examined. When the beam is injected from the equatorial plane, the maximum current density is reduced and the width of current profile becomes wide in the outer region of r greater than or similar to 0.5a. The localized current profile is kept well within the region of r greater than or similar to 0.4a by injection from a location away from the equatorial plane. (C) 2001 Elsevier Science B.V. All rights reserved.