Second harmonic ion cyclotron heating in a divertor-stabilized tandem mirror

Summary form only given, as follows. A magnetic divertor configuration introduced in the central cell of the HIEI tandem mirror provides magnetic nulls arid stabilizes MHD activities by shorting-out the charge separation in the azimuthal direction. The density fluctuation of m = 1 flute mode is decreased significantly by using the divertor. The stabilization effect of the divertor is stronger as the radius of the nulls, is smaller. In this configuration, the magnetic field strength varies significantly in radial direction, and ion cyclotron range of frequencies (ICRF) waves may have a large transverse gradient in amplitudes. This is suitable for the second harmonic ion cyclotron resonance heating since the waves undergo significant finite Larmor radius (FLR) effects, which are essential for the harmonic heating.