KSTAR ICRF antenna development on the KAERI test facility

Summary form only given, as follows. The ICRF heating system of the KSTAR tokamak couples 6 MW of RF power to the plasma with a 4-strap antenna. The antenna has been designed to operate for the pulse length up to 300 sec The current strap is grounded at the center, and has two coaxial ports, one at each end. The top and bottom ports of each strap are fed by one transmitter. The two ports are connected at a tee connector to form a resonant loop, the coaxial feed line from the transmitter is connected to the tee. A proto-type ICRF antenna has been fabricated, and with no water cooling, the RF test is performed to study the standoff capability of the antenna at the RF test stand in KAERI. In this test, the half of a current strap is connected to the matching circuit via a vacuum feedthrough and a directional coupler, and the other seven ports are shorted at the input ports. Several configurations of the test circuit are used to ascertain the voltage and current limits that the antenna system can hold off. During the RF test pulse, the line voltage, forward/reflected powers, temperature on the cavity wall, and gas pressure in the test chamber are measured. Test results show the standoff voltage and pulse length of 33.2 kV for 60 sec and 25.2 kV for 300 sec.