Speaker
Description
To ensure advanced operation of KSTAR, KSTAR ECH power has been increased since 2017. ECH system was designed so that each ECH system has a source power of 1 MW and operates independently with its own individual power supply and transmission line and launcher [1]. To date, four 105/140 GHz dual frequency and one 170 GHz Russian gyrotrons have been installed and operated, out of a total 6 MW ECH system. The final unit, a multi-frequency gyrotron similar to Japan’s ITER gyrotron is scheduled to be installed and commissioned from the end of this year. This multi-frequency gyrotron system will be very useful in operating KSTAR over a wide operation range of Bt from 1.7 T to 3.7 T without vacuum break of EC TL even if only short pulse operation is possible at a specific frequency. High voltage power supply for cathode supplies 55kV/55A power by 120 PSM modules. This HVPS is controlled by a main control system (called ECFC) based on D-Tacq’s FPGA with sampling rates up to 2MHz for the real time control and can modulate RF power up to 5 kHz [2]. The generated ECH power is injected into KSTAR through 60~70 m long 63.5 mm corrugated waveguide and front steering launcher with theoretical loss of less than 10 %. For advanced operation KSTAR, stable and reliable operation of ECH is very important. ECH assisted start-up [3, 4] and EC wall cleaning [5] were routinely performed and ECH is an essential tool for long pulse [6], high Ip operation [7], and NTM control to KSTAR operation. The injected maximum ECH power was approximately 1.5MW by three ECH systems and typically one ECH with power of 0.5~0.7 MW was injected for the start-up and ECWC and the remaining ECHs added at the flat top. EC power can be controlled by PCS which allows pre-programming of pulses and beam angle and deposition position for optimizing operating conditions at start-up and at flat top of the discharge [8]. This presentation reports the development status of KSTAR ECH system and briefly explains the results of KSTAR’s ECH experiments and future plan of multi-frequency ECH system.
