Design study of an ECRF antenna for JT-60SA

Design study of an ECRF antenna for JT-60SA is being carried out. In JT-60SA, pulse duration of 100 s and wide range of poloidal injection angle are required. Reliabilities of a cooling structure and a steering mechanism of mirrors in the JT-60SA vacuum vessel are essential in an environment of high neutron flux. Conceptual design has been performed based on an idea in which poloidal beam injection angle can be altered widely only by a linear motion of a mirror in front of a waveguide. This concept has advantages of decreasing the risk of cooling-water leakage and eliminating a link mechanism in the primary vacuum of JT-60SA. Beam width at various positions in plasma was evaluated by a numerical code. Then dependence of beam width on mirror curvature was investigated, and ranges of the poloidal injection angle and beam width were shown. Moreover, an effect of a modification of the linearly driven mirror from flat mirror to curved mirror was clarified quantitatively.