Turbulent Heating Experiment

Abstract

Results are presented of an experimental investigation of turbulent heating. A current parallel to the mirror magnetic axis, produced by discharging a capacitor, excites an interaction and, with proper conditions (plasma density, magnetic field strength for trapping), it is found that some class of turbulently heated plasma electrons can be adiabatically compressed to high temperature. In the most favorable heating conditions electrons are heated to 85 keV at 25 kG (factor of 40 in magnetic compression). This corresponds to Te ≃ 2 keV immediately after turbulent heating, which is approximately equal to the total voltage drop across the electrodes. The interaction is characterized by an anomalously high resistance, and radiation that covers a broad range up to the electron plasma frequency and including the frequency range corresponding to the electron-ion streaming instabilities. At low density (< 1012 cm−3), a sheath is generated giving rise primarily to the beam plasma interaction. In the intermediate density range 2 × 1012−1013 cm−3 the anomalous resistivity had approximately a n−1/2 dependence, characteristic of the current-convective mode. At densities over 2 × 1013, all interactions are quenched due to the voltage drop across the self-inductance of the discharge circuit including the plasma column. The results are compared with related turbulent heating experiments.