Radiation and transmission experiments in Nagoya Bumpy Torus

Microwave transmission experiment and radiation measurements are carried out to understand the mechanism of plasma production and heating, and to obtain the information of hot electrons. NBT device, which is an electron-cyclotron-heated bumpy torus (8.5 GHz, 60 kW), has both the fundamental cyclotron resonance and second harmonic resonance zone in each sector, and is characterized by the formation of hot electron ring (<approx.= to 100 keV, <approx.= to 10 10-3) at the location of second harmonic resonance. Ordinary and extraordinary waves of frequency 8-12 GHz were launched horizontally in the midplane of mirror sector. The results show that the ordinary waves can propagate into the plasma until the cutoff density is reached. The propagation of extraordinary waves is inhibited by cyclotron cutoff which appears in the midplane even in low density case compared with the ordinary waves. (author)