Low power microwave plasma torches are of particular interest to analytical chemists. The torch design investigated herein, called TPS, is based on the known surfatron structure to which a coaxial section is added consisting of an impedance transformer followed by the metallic nozzle at the tip of which the discharge occurs A senes of experiments illustrate the main electromagnetic features and performance of this novel coaxial microwave plasma torch operating at 2 45 GHz and with input power in therange 10-180 W A specially devised slotted coaxial line with a movable probe arrangement can be inserted into the torch in place of the tiansformer section to provide in situ measurements of the plasma impedance Analyzing these results, we show that theshape of the torch tuning characteristics can be controlled to improve the power transfer to the plasma and stability of operation with respect to changes in discharge conditions; under these conditions, the design of the device can be simplified. The procedures presented have a general character and can be applied to various torch configurations.
展开▼
