Frequency-Shifting Method of Exciting a Plasma in a Resonant Cavity

A new method of obtaining a high-density plasma (n ∼ nc0) in a resonant cavity is described. The method is to increase the frequency of the exciting microwave power source by as much as ∼ 10% while keeping the input microwave power constant and maintaining an impedance match between the source and the cavity. Density increases of the order of seven-fold have been obtained in this way. The result is explained mainly on the basis that the power loss in the impedance-matching network decreases as the excitation frequency is increased.