Speaker
Description
Electron cyclotron heating (ECH) is used as one of the most important auxiliary heating method for plasma heating in modern fusion research. In addition to plasma heating, EC system is used for plasma current drive and control of plasma instabilities such as NTM (Neoclassical Tearing Modes). ECH (Electron Cyclotron Heating) system for KSTAR (Korea Superconducting Tokamak Advanced Research) is composed of two dual-frequency gyrotrons, each generating 950kW of RF power at 140 GHz and 800kW of RF power at 105 GHz. In KSTAR, Gyrotron upgrade is planned up to 6MW RF power for steady-state operation. Gyrotron is the most sensitive and expensive equipment in the ECH system. In addition, high voltage power supplies (HVPS) are as important as gyrotron. HVPS must protected the gyrotron in emergency situation. In addition, the performance of the HVPS should be verified because It affects the quality of the RF beam. Generally, gyrotron requires two high-voltage power supplies (HVPS), referred to as the cathode power supply (CPS) and body power supply (BPS). EC systems of the KSTAR use the HVPS of PSM (Pulse Step Modulation) technology and the chopper type, respectively. The storing energy of the PSM type power supply is much lower than other power supply. It is very important factor to gyrotron protection. The protection time and energy are less than 5us and 10J. Output voltage stability and ripple are less than 1% (<1%). The output voltage is adjustable in 0.5kV increments. PSM type HVPSs are under development for four gyrotron system to be added from 2019. In addition, a control system for gyrotron and all power supply is under development. This control system is designed for power control in real time. In this paper, we will describe the EC system currently installed in KSTAR and explain its future plans.
