Generation of energetic electrons by electron cyclotron heating in a magnetic mirror field

Electron cyclotron heating that generates hot-electron plasma in a magnetic mirror trap by microwaves is studied experimentally. The evolution of the energy distribution functions for the high-energy electrons is observed in steps of milliseconds during 200 ms of the heating period from the initial stage at the microwave power input until the stationary final state. According to the proposed statistical model for the cyclotron heating, heating rates are estimated to be 10 MeV/s typically, in the three characteristic cases of mirror field configuration with heating microwave power as a parameter. Some problems associated with stochastic cyclotron heating are discussed in the light of the experiments.