ECCD performance analysis of future KSTAR ECH systems for extended applications

The ability of the KSTAR 170 GHz electron cyclotron (EC) wave launcher to drive a localized current is analyzed by means of the TORAY-GA ray-tracing code looking at extended physics application of the EC current drive (CD) in the KSTAR. Computation reveals that the EC-driven CD performance (JCD), as compared to the plasma’s boot-strap current (JBS), i.e., the ratio JCD/JBS, for the normalized minor radius, ρ > 0.5, is not good for the current design of the 1-MW 170-GHz launcher. Calculations at a lower frequency of 105 GHz have shown improved values for the JCD. Depending upon the launcher port’s availability, computations are carried out to find the pivot position for future proposed launchers by optimizing the figures of merit at respective locations. These computations show that Z = +30 cm gives the maximum figure of merit. Computations also show a possible synergy between the two launchers, one pivoted at Z = +30 cm and the other at Z = −25.2 cm. The main aim of this study is to provide guidance for the design of both launchers in order to optimize their performance according to the physics application.