Electron Cyclotron Heating and Current Drive Program for KSTAR Based on the 170-GHz Gyrotron

Electron cyclotron heating and current drive (ECH/ECCD) has become an essential tool for fusion plasma research in toroidal devices. In the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak, development of a high power and multifrequency ECH/ECCD system is in progress. The multiple frequency sources employed in KSTAR (84 GHz and 110 GHz have been used, and 170 GHz and possibly 140 GHz are planned) support the wide range of operating magnetic fields from similar to 1.5 to 3.5 T. In particular, 170-GHz power, which will be used on ITER, corresponds to the second harmonic of the cyclotron frequency for the KSTAR operating range from 2.5 to 3.5 T. This frequency will be mainly used for control of the local plasma current profile, in order to manipulate the internal magnetohydrodynamic instabilities such as the sawtooth and neoclassical tearing mode, which can be harmful to steady-state high-beta operation. This paper presents the status of the KSTAR ECH/ECCD program and the ray-tracing calculations of the 170-GHz electron cyclotron wave propagation for various plasma conditions in KSTAR. In the ray-tracing simulation, the TORAY-GA ray-tracing code is used to study the dependence of the ECH/ECCD on the plasma profiles as a function of the beam aiming angles.