Experimental characterisation of the plasma absorbtion probe

The plasma absorption probe has been developed to provide a fast and efficient diagnostic tool for the characterisation of discharges, especially of reactive plasmas. Unlike Langmuir probes, the plasma absorption probe measures electron densities in reactive plasmas undisturbed by coatings of the probe surface. It consists of a semirigid coaxial cable with protruding inner conductor as an antenna, covered by a dielectric tube. The measurement principle is based on active resonance spectroscopy. A network analyser feeds the coaxial cable with HF of variable frequency and the power reflection spectrum is detected. At resonant frequencies, characteristic for the discharge, absorption signals are observed. In this paper, we present measurements of the plasma absorption probe for various discharge conditions and we evaluate the probes' further potential for the analysis of reactive plasmas.