Enhanced Velocity Diffusion along Electron-Cyclotron-Resonance Heating Characteristics Observed in Hot-Electron Energy Spectra in the Plasma Loss Cone

A silicon surface-barrier detector was used to measure energy spectra of hot electrons coming out of an end cell of the GAMMA 10 tandem mirror. A hump was observed in an energy spectrum and it was attributed to enhanced velocity diffusion along heating characteristics of the third-harmonic resonance of the incident waves. Hot electrons were produced by second-harmonic electron-cyclotron-resonance heating and scattered into the loss cone. Good agreement was obtained among the observation, Fokker-Planck simulation, and the prediction from the relativistic resonance condition.