Special Issue on Perspectives on Thermal Plasma Research for Industrial Applications: Introduction

Thermal plasmas have very useful properties that are not easily achievable using other means, in particular high power densities, high temperatures, high-velocity flows, high fluxes of active species and intense radiative emission. Moreover they are available in a wide range of configurations (direct-current transferred arcs, direct-current non-transferred arcs or plasma torches, alternating-current arcs, radio-frequency inductively-coupled plasmas, microwave plasmas and laser-produced plasmas) and powers (from hundreds of watts to a hundred megawatts). It is therefore not surprising that they find application in many industrial processes, including those for joining, melting, cutting, coating and deposition, refining, waste treatment, chemical analysis, lighting, propulsion and circuit interruption. It is these many applications that underlie all thermal plasma research; even when arcane questions such as the extent of deviations from local thermodynamic equilibrium in an arc are being investigated, the ultimate goal is to develop better thermal plasma processes for industry. This special issue brings together eight articles written by leading researchers from universities, industry and government research laboratories, presenting their perspectives on particular aspects of thermal plasma research. Each author was asked to present their views on important topics for research and development, outstanding scientific questions, and barriers to future success. The aim is not to present a comprehensive overview of the subject. Rather, the intention is that the special issue will guide researchers towards the important topics that warrant their close attention, and that are critical for future progress in the field. Three of the articles take a wider view, looking at thermal plasma sources, diagnostics and modelling respectively, across a range of applications. The first article considers plasma torches and inductively-coupled plasmas in particular, the second looks mainly at diagnostics of transferred arcs, while the third examines modelling issues that relate to