R&D of drive mechanism of movable mirror for ITER EC antenna

Kobayashi, Noriyuki; Takahashi, Koji; Kasugai, Atsushi; Sakamoto, Keishi

An EC antenna of ITER uses a movable metal mirror horizontally rotatable to steer the RF beams. A rotor of the mirror is supported by bearings at its top and bottom. The mirror is rotated by moving a ceramic coated pin perpendicular to the rotar axis in a groove of a cum on the rotor. The pin is connected at the head of a drive shaft supported by linear bearings. Driving force is generated by conversion of rotation of a ultrasonic motor into linear motion by a LM actuator composed of a linear guide and a ball screw. A drive test was performed in vacuum at about 100C to confir the reliability of the drive mechanism. In order to construct a high radiation resitant driver unit, neutron irradiation test of elements of the ultrasonic motor and a capacitive encoder, which eliminates photodiodes, are going on. The result of the drive test in vacuum at high temperature and the R&D of the capacitive encoder are presented.