Measurement of Ion Cyclotron Emissions by Using High-Frequency Magnetic Probes in the LHD

Two pairs of high-frequency magnetic probes were installed in the Large Helical Device (LHD). During the injection of a perpendicular neutral beam, ion cyclotron emissions (ICEs) with the fundamental frequency corresponding to the ion cyclotron frequency at the plasma edge were detected, which are the same type of ICE as measured with the former spare ion cyclotron range of frequencies (ICRF) heating antennas. This type of ICE was further investigated with regard to the phase and intensity of signals. Another type of ICE was found in the LHD, and these ICEs were synchronized with bursts of toroidicity induced Alfv¶en eigenmodes (TAE) and the rise of intensity of lost ion °ux. Therefore the source of these ICEs was thought to be the particles transferred from the core to the outer region of plasma by the TAE bursts. The frequency of ICEs induced by the TAE bursts increases linearly with the magnetic ¯eld strength, since the ion cyclotron frequency increases with the magnetic ¯eld strength.