Induction plasma torches

Abstract

The design principles and construction are first presented and the important problem of plasma stability and the methods of maintaining stability, over a range of conditions and in different gases, are then considered. The power supplies and the various methods that have been used to initiate the torches are described. The various measurements that have been made of the gas heating efficiency are summarized showing that with the latest torches up to 70% of the input power can be coupled to the plasma even in the highest power units ( approximately 1 MW) developed. The measurements of the temperature distributions that have been reported are also presented showing that off-axis peak temperatures occur as a result of rf heating being confined to a certain skin depth. The theoretical attempts that have been made to describe the plasma behaviour are presented. The numerous applications of induction plasma torches are described under four headings: use a spectroscopic source the spheroidation of refractory materials, the growth of crystals and the production of chemicals