Optimization of KSTAR ICRF system and radio frequency heating experiment

ICRF system is modified to drive four antenna current straps for high power RF injection. The current phases and amplitudes of antenna system is analyzed to have optimum values after designing and installation. Coaxial transmission elbow and insulator was upgraded as a preparation of the ultimate long pulse operation of KSTAR. In addition, coolant supplying system for the vacuum feed through which is operated at high RF current is designed and installed. ICRF ion heating experiment is carried after the installation of the whole system. High energy neutral particle analyzer is used to estimate the energy distribution of heated ions through the measurement of neutral particles which escape through charge exchange. Unstable behavior of transmitter is analyzed and suggestions are made for stable high power injection