Engineering design and R&D of Impurity Influx Monitor (divertor) for ITER

The harsh environment in the ITER device presents many diagnostic challenges. A proposed design engineered at the Japan Atomic Energy Agency (JAEA) is of an optical alignment system installed on mirrors behind double vacuum windows. Due to the harsh environment, a piezo-motor is used as an actuator and a sliding bearing is used as a pivot. The required torque of the actuator is estimated. Trial results indicate that the actuator as described fulfills requirements. A prototype of a key optical component, the micro-retro-reflector array, is produced through the electro-forming method. Measured reflectivity yields a sufficient signal for in situ calibration. A Cassegrain telescope prototype is designed and produced using simple spherical mirrors and achromatic lenses made of silica and CaF 2 . The measured focal length concurs with design objectives. Irradiation tests are necessary to verify the capabilities of these optical devices.