Abstract: The invention relates to a plasma apparatus where plasma is generated utilizing microwave discharge and laser excitation is performed and plasma processing is performed. More specifically, in a plasma apparatus where a microwave from a microwave oscillator is transmitted through a microwave transmission path to a microwave circuit, and plasma is generated by a microwave discharge within the microwave circuit, a plasma generating medium for generating the plasma is filled in a space formed between a conductor wall constituting a part of the microwave circuit and a dielectric installed opposite to the conductor wall, and the microwave circuit forms microwave mode having an electric field component orthogonal to the boundary between the dielectric and the plasma.

Abstract: An automatic tracking welding machine includes a pair of rotatably mounted sensors 6a, 6b disposed in advance of a welding torch 3 and coaxial therewith for detecting magnetic leakage flux across a weld line gap 10. The sensors are driven to equalize their outputs by a reversible stepping motor 15 supplied with drive pulses whose frequency is proportional to the sensor output difference up to a fixed limit, thereby implementing slowdown as the center or zero differential point is approached. Alternatively, a greater number of fixed sensors may be peripherally spaced around the torch housing and their outputs sequentially scanned and peak detected to track the weld line gap. In another embodiment a spaced pair of sensors 116a, 116b is laterally and bidirectionally driven by a reversible d.c. motor 123 supplied with a voltage proportional to the off-center distance detected by the sensors, thus also implementing slowdown as the zero point approaches.