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. (C) 2019 The Japan Society of Plasma Science and Nuclear Fusion Research