PRODUCTION OF A PLASMA WITH HIGH-LEVEL PULSED MICROWAVE POWER

A method is presented for producing a dense plasma in a resonant cavity with microwave energy. The plasma is contained in a quartz tube lying along the axis of a resonant cavity that is excited near the TE111 coaxial-mode resonance with 10-microsec pulses of up to 800 kw of peak power in the 10-cm band. The plasma serves as a center conductor for the coaxial mode, shifting the mode resonance near the exciting frequency. The initial transient in the plasma electron density occurs very rapidly, and the system appears to reach a steady state in less than 10-microsec. A second microwave system excites the cavity in the TE011 coaxial mode, which is used as a low-level probe to measure the properties of the plasma. A perturbation formula is developed that can be used to calculate the perturbing effects of the dense plasma. This formula is used to develop methods of calculating the electron density and collision frequency of the plasma by measurements of the detuning of the cavity mode. Plasma electron densities of over 10 to the 14th power per cc are measured when over 80 kw of peak power are dissipated in the discharge. Studies are also presented of helium discharges and of light generated by the discharges.