Development status of KSTAR ECH system.

KSTAR has decided to develop six ECH systems for the advance TOKAMAK operation. To install six ECH systems in the limited space, ECH equipment room was completely newly constructed by steel beam-type deck. The existing two ECH system was totally disassembled and rearranged and cooling system were re-designed and newly developed, so two 105/140GHz ECH systems including the new gyrotron were commissioned and operated in 2018 KSTAR campaign. Other two 105/140GHz gyrotrons will be delivered in 2019 and one more ECH system will be operated in incoming 2019 campaign with newly designed power supply and control system. The remaining two gyrotron sources were also decided to GYCOM ITER 170GHz gyrotrons, but the order was postponed due to budget issues. The transmission line system has been using 63.5mm circular corrugated waveguides and there is no window in TL and antenna also, so it is kept in a tokamak vacuum by the main window of the gyrotron. The final positions of the antenna were decided considering the current drive and heating efficiency. However, due to the poloidal limiters installed inside vacuum vessel, in 2018 ECH couldn't operate in Ctr-CD. To solve this problem, the pivot position of all ECH launchers will approach 350 mm to the plasma in the radial direction. A 2-channel antenna for 3rd and 4th ECH system is in design which will be identical to the mechanism of the existing launcher. In this paper, the development status and the design parameters of ECH system will be presented and discussed and the operation results of ECH system in 2018 will be presented. [ABSTRACT FROM AUTHOR]