Edge measurements have been conducted on the PLT Tokamak under a variety of operating conditions in order to ascertain the relevant processes at work in coupling r.f. power to plasmas. The edge density is found to increase significantly with the application of ICRF, and electron heating occurs in the vicinity of the Faraday shield surrounding with antenna. Spectroscopic measurements indicate that the energized antenna is significant particle source. The relative increase of metallic impurities was found to be approximately 2.7 times larger than the corresponding increase in deuterium. In addition, the relative increase of deuterium and impurities was approximately 3-4 times greater at the energized antenna than at other locations around the torus. Model calculations show that for deuterium released from the Faraday shield, the Dalphaemission is localized radially to a region within 4 cm of the antenna. A correlation was found between the edge density and the Dalphaintensity that justifies its use as a measure of the particle source rate.
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