IMPURITY INFLUX DIAGNOSTICS ON RFX

The systems installed on the RFX reversed field pinch to study the impurity influxes are described. They comprise of telescope lenses, coupled through optical fibers and interference filters or spectrographs to photomultipliers for time-resolved analysis, and charge coupled device (CCD) cameras. The solutions adopted aim at giving an insight into the impurity production mechanisms in a situation characterized by largely asymmetric plasma-wall interactions. Main gas and various impurity influxes from the same area of the first wall are compared by means of very simple light splitters interposed between telescope lenses and narrow band filters. Four high-resolution CCD cameras also equipped with interference filters cover more than half of the first wall allowing detailed spatial studies of the impurity influx distributions. © 1995 American Institute of Physics.