Polydiagnostics performed on high-tech plasmas

The large effluxes generated by high-tech plasmas force plasmas to non-equilibrium conditions. This implies that plasma features are decoupled from each other and that therefore different methods have to be used quasi-simultaneously to characterize the plasma. Even more insight in plasmas and methods is obtained if polydiagnostics is applied to a series of plasma conditions that gradually differ in equilibrium departure. After discussing methods of passive and active spectroscopy, we apply polydiagnostics on an argon plasma operated in open air. By introducing H2 and reducing the power we approach conditions of cool atmospheric plasmas (CAPs). It is seen that especially the passive methods for the electron temperature determination are very sensitive to the degree of equilibrium departure suggesting that active spectroscopy is preferable. However, one should realize that lasers can easily heat cool plasmas.This is due to the fact that the ionization degree of (semi-) CAPs is small.