Whistler instability in an electron-cyclotron-resonance-heated, mirror-confined plasma

The warm-electron-driven (2 keV) whistler electron microinstability [Phys. Rev. Lett. 59, 1821 (1987)] of the Constance B electron-cyclotron-resonance-heated (ECRH), quadrupole mirror-confined plasma experiment has been studied. Experiments show (i) that the instability comes in fairly regular bursts on axis and continuously in time off axis due to the minimum-B geometry, (ii) a frequency spectrum that is insensitive to changes in the plasma parameters, and (iii) instability-induced power losses which are not greater than 10% of the ECRH power input for the regimes studied. A linear perturbation analysis of the relativistic Vlasov equation together with Maxwell's equations has been made. Using the ECRH distribution function, a new distribution function well suited for describing ECRH, mirror-confined plasmas, the analysis shows the instability frequency spectrum to be insensitive to changes in cyclotron frequency, temperature, and density, in agreement with experimental results, and only sensitive to changes in ECRH frequency