Ion cyclotron heating and optical diagnostics in Q-machine plasmas

Electrostatic ion cyclotron modes are studied with emphasis on excitation by an electron current parallel to the magnetic field. By means of this instability we observe and confirm significant ion heating in a barium plasma in a Q-machine. Ion temperatures are measured optically from the Doppler broadening of resonance radiation. The measurements show a strong coupling to the ''bulk'' of the perpendicular ion velocity distribution. The linear dispersion relations for ion cyclotron modes in the electrostatic approximation are generalized for several particle distribution functions which include a drifting Maxwellian for the electrons, anisotropic Maxwellians for the ions, and delta function distributions appropriate for beam excitation experiments. These dispersion relations are also generalized for arbitrary direction of propagation. Mode frequency, growth rates, and onset conditions are derived for excitation by a parallel electron current. For all particle distribution functions and directions of propagation, approximations which lead to various simplified forms of the dispersion relations are delineated so that the results can be applied to a broad range of experiments. Experimental results are presented in which ion temperatures are measured as a function of a broad range of Q-machine parameters. Spectroscopic techniques for obtaining optical diagnostics of Q-machine plasma density, ion and electron temperature, as well as other parameters are given