Experimental characterization of TIAGO torch discharges: surface wave discharge behavior and (post-)discharge kinetics

The Torche a Injection Axial sur Guide d'Ondes source-better-known as the TIAGO torch-is a particular type of microwave-induced plasma that has become a focus of technological and scientific interest due to its outstanding features. Moreover, the TIAGO torch device arouses interest thanks to its remarkable performance in many challenging areas, such as green energy generation and graphene production by hydrocarbon decomposition. Although it has not been experimentally demonstrated to date, discharges generated by a TIAGO torch have been theoretically predicted to be surface wave discharges (SWDs), a kind of plasma leading the development of new materials. Therefore, deeper and fundamental research on this device is needed to optimize the implementation of plasma technology in these fields. In this study, the axial distribution of gas temperature, electron density and intensity of the main atomic and molecular emissions have been studied by optical emission spectroscopy when feeding the discharge with different input power values (200, 400 and 600 W). A complete axial characterization of both the dart and the plume regions is depicted and, according to the data obtained for the main plasma parameters, different regions can be identified, with the radiation zone being reported for the first time at atmospheric pressure. The kinetics of both the dart and the plume are discussed and an experimental verification of TIAGO torch behavior as a SWD is presented for the first time.