PLASMA KINETIC ENERGY-RF CONVERSION

A theoretical and experimental program is described aimed at studying the possibility of extracting microwave power from the kinetic energy of a plasma. The appropriate theoretical framework is established. Detailed experiments were run at X-band and at K-band. The detected microwave pulse appears before onset of opacity and attains values on the order of 50 to 250 mW for a background pressure of 20 microns Hg, discharge voltages around 20 kV, and magnetic fields around 3.5 kG. The output is studied as a function of magnetic field and of the applied electric field. At K-band two peaks become apparent and these are interpreted in terms of the fundamental and the second harmonic detected in this frequency interval. It is shown that the power output detected is too high to be explained by cyclotron radiation output from a population of temperature and density not exceeding reasonable values. The mechanism of electron acceleration by overstability processes is introduced which would seem to explain the high radiation output as the cyclotron radiation from very high speed electrons accelerated by internal processes in the plasma.