Conceptual study of high-field LHCD in KSTAR

An innovative lower-hybrid (LH) current drive scheme in KSTAR tokamak is being studied in order to achieve high performance advanced tokamak operation. Taking advantage of less plasma wall interaction and good LH wave accessibility at the high toroidal magnetic field, the inside LH wave launch would provide good opportunity to study reactor-relevant operation scenario using LHCD. We investigated the LH wave launch parameters and plasma operation conditions to provide efficient current drive by inside high-field LH wave launch using the ray tracing code (GENRAY) and Fokker-Planck code (CQL3D). The conventional launcher structure is very unlikely to be used due to the limited space in the inboard side and complicated path of the waveguide through divertor section. The new concept of LH launcher structure is therefore suggested and discussed in this paper. (author)