Waveguide-based single and multiple nozzle plasma torches: the TIAGO concept

Various microwave-sustained, atmospheric-pressure plasma torches have been developed, investigated and applied over the last few decades. To avoid some of their shortcomings, we have designed a novel torch termed TIAGO (Torche a Injection Axiale sur Guide d'Ondes, in French). Its main advantages are simplicity, smooth impedance matching (low sensitivity to changes in operating conditions) and a short gas channel to prevent vapour condensation. Furthermore, it is possible to arrange TIAGOs in arrays to form a compact torch system which can be supplied, with equal distribution of power between plasma flames, from a single waveguide. This unique feature makes the new device particularly suitable when high gas throughputs or sequential processing are required. We describe the design, electrodynamic characteristics and experimental investigation of various torch arrangements based on the TIAGO principle, operated at 2.45 GHz with powers of a few hundred watts up to 2-3 kW per nozzle.