A RADIAL SELF-ABSORPTION TECHNIQUE TO MEASURE HELIUM TRIPLET-STATE DENSITIES IN AXIALLY HETEROGENEOUS DISCHARGES

A technique of self-absorption along a plasma diameter is developed to measure triplet state densities along discharges presenting axial inhomogeneities. This technique is based on the fact that a transition line between triplet states has components of different oscillator strengths, which are thus differently self-absorbed. It has been developed to measure the 23S and 23P helium state densities of a helium surface wave discharge (at 2.45 GHz). The results are compared to ones previously obtained by the Hook method in a positive column. © 1990 IOP Publishing Ltd.