Two simple diagnostic techniques for RF plasma reactors have been studied. The first one consists in injection of yttria powders into the plasma. They induce coloured emissions varying with temperature. The results is a direct
visualisation of the effect of operating conditions, like injection flow rate, injector diameter or hydrogen addition, to the temperature inside the plasma. The second one
allows the determination of the residence time of powders injected into a plasma. These techniques are calibrated by using more classic and more precise methods:
spectroscopic techniques for temperature determination and emission particle analysis (EPA) for velocity and residence time evaluation. These simple and rough techniques
can be easily implemented in an industrial environment.