Optical Plasma Diagnostics

Low temperature plasmas, in particular radio-frequency (rf) discharges, are widely used for technological applications. Fundamental mechanisms are, however, not yet fully understood. Plasma diagnostic techniques are required for detailed investigations and monitoring technologically used plasmas. Optical measurements are a powerful diagnostic tool offering high spatial and temporal resolution. Optical emission spectroscopy (OES) provides a non intrusive access, to the physics of the plasma, with comparatively simple experimental requirements. Phase resolved OES (PROES), within the rf cycle, of rf plasmas is a rather new diagnostic technique providing information on various plasma parameters and characteristics. The basic principles of PROES will be discussed. A PROES diagnostic system will be set up and aligned. A typical experiment on a current research plasma will be carried out. A relatively simple analysis of the measured data, applying a collisional radiative model, yields information on the various power coupling mechanisms within the plasma.