Operation of high power 84-GHz gyrotron for KSTAR ECH system

Abstract

The initial objective of the KSTAR ECH system is to produce seed plasmas by irradiation of powerful millimeter waves for the main ohmic discharges. A specially designed gyrotron, manufactured by CPI, has specifications of 500 kW, 84 GHz, and 2- second pulse duration. It adopts the state-of-arts technologies of a diode gun, a depressed potential collector, an internal mode converter, and a diamond window. As a part of the final acceptance tests of the gyrotron, we constructed a test and including a test modulator to confirm its operating conditions. With short-pulses of 20 microseconds, we produced the output peak power of 500 kW at 84 GHz. The output power distribution is confirmed to be a Gaussian by IR images on targets. In this experimental study, we describe details of the gyrotron, the test stand, and experimental results.