RD of steady state and high voltage ICRF transmission line and ceramic feedthrough for LHD

摘要

The steady state and high voltage test was carried out successfully on ICRF coaxial transmission line and ceramic feedthrough for LHD ICRF heating. The transmission line has 240 mm diameter and water cooling channel inside. The Teflon insulator with small recess is used. The coaxial line can stand for the high RF voltage of over 10 kV for 30 minutes and of 60 kV for 10 seconds. Three kinds of insulation gas vias tested at 43 MHz. SF/sub 6/ and N/sub 2/ gas are usable for high voltage and steady state operation but CO/sub 2/ gas can not stand for over 30 kV for several minutes. Various types of ceramic feedthrough were tested for steady state and high RF voltage in the test stand. The cone type alumina ceramic feedthrough having gas cooling system and cylinder type silicon nitride composite ceramic feedthrough worked very well. Ceramic temperature of the cone type was measured by IR thermometer. By using the enough gas flow rate, truly steady state operation was achieved.