Plasma Production and Heating with ICRF in the Gamma 10 Tandem Mirror

Three ICRF sources (RF1, RF2 and RF3) are used for the plasma production and heating in the GAMMA 10 tandem mirror. The initial plasma in a standard mode of operation is produced by using RF1 and RF2 with near fundamental ion cyclotron frequencies. Under the present experimental conditions, an eigenmode which has a fundamental radial structure is only excited and the density is clamped so as to satisfy the boundary conditions in the axial direction. When RF3 with a frequency range of high harmonic fast waves is applied, several eigenmodes with different radial structures can be excited and the density clamping is released. Two different frequencies are used in the RF3 system; one is 63 MHz which corresponds to the 10th harmonic ion cyclotron frequency near the midplane of the central cell and the other is 41.5 MHz. The density increase due to the excitation of the high harmonic fast waves are observed in both cases. It is observed the high energy ions are produced due to the higher harmonic resonance.