Development of multilayer piezoelectric actuator valve for JT-60

Miyo, Yasuhiko; Hiratsuka, Hajime ; Masui, Hiroshi*; Hosogane, Nobuyuki; Miya, Naoyuki

In order to improve the gas injection valve used for the operation of JT-60, a new type of valve (multilayer piezoelectric actuator valve) was developed .The conventional valve (bimorph piezoelectric actuator valve) has been used for 15 years from the beginning of experimental operation in April, 1985. Consequently, it came to be hard to keep the performance of the valve as a gas injector because its driving source, piezoelectric element, has deteriorated by long time use.In the design, it is required:(1) to be hard structure for sheet leak,(2) to allow a repair work at atmosphere side without an air vent of the vacuumvessel,(3) to be more smaller and lighter compaired with the conventional one,(4) to have a high maintenance efficiency. The new valve developed was examined with various tests such as gas flow characteristic test, high magnetic field proof test, high temperature proof test and gas flow rate test for aged deterioration. As a result, the valve with desired performance for JT-60 could be obtained.