Most thermal plasmas, used in materials processing, are generated by dc or ac electrical discharges or by high frequency induction discharges. The arc
discharge provides a high density and high
temperature region between two electrodes and,
in the presence of a sufficiently high gas flow, the
plasma can extend beyond one of the electrodes in
the form of a plasma jet. The plasma arc
generators can be divided into (i) non-transferred
are plasma torch (Fig. 1a), (ii) transferred arc
plasma torch (Fig. 1b). In the non-transferred arc
torch the two electrodes do not participate in the
process and have the sole function of plasma
generation.