Measurement of the lower hybrid wave using RF magnetic probes on the TST-2 spherical tokamak

Polarization-resolved spatial distribution of waves in the lower hybrid frequency range was measured using radio frequency magnetic probes (RFMPs) in the TST-2 spherical tokamak. Thirteen RFMPs were installed inside of the vacuum vessel, eight on the inboard-side, three on the outboard-side and two on the bottom-side. In TST-2, the lower hybrid wave (LHW) is excited by the outboard-launch antenna and the top-launch antenna. Higher plasma currents can be achieved using the top-launch antenna. Bottom-launch can be simulated by reversing the direction of the toroidal magnetic field. Propagation and absorption of the LHW were investigated numerically for outboard-, top-, and simulated bottom-launch at low and high plasma currents. Results of the wave measurement revealed different propagation characteristics for different launching, which agree partially with the results of numerical calculation. (author)