Characteristics of DC plasma torches and the use of magnetic probes for diagnostics

This research aims to experimentally study DC plasma torches and gain an overall understanding of the process for developing new torch designs. This research also introduces a magnetic probe as a diagnostic tool for DC plasma torches.; Two anode nozzle materials, tungsten and copper, were tested for a wide range of arc currents, plasma gas flow rates, and plasma gas compositions in mixtures of argon-hydrogen and argon-nitrogen. The DC plasma torch used in these experiments offers the flexibility to work with different anode geometries and the possibility of connecting the electrical power to the anode nozzle at two different locations. Torch characteristics studied included arc voltage drop, arc voltage fluctuation, energy efficiency, and arc column motion.; The efficiency of the torch, derived from a conventional energy balance, showed a significant change as the location of the electrical connection to the anode nozzle was changed. An explanation for this behavior is given, based on an analysis of the forces acting on the anode arc column and their influence on the variation of the arc column length.; The results of magnetic probe measurements, interpreted based on a simple model, showed the expected trend for the arc column behavior when the arc current was varied. Experimental data were in good agreement with analytical predictions.