A planar electrode (17) having a plurality of concentric channels (34-34) therein through which coolant fluid passes to cool the electrode during a plasma etching process. The coolant is directed through at least two of the adjacent channels in opposite directions with the inputs (31) and outputs (32)...http://www.google.se/patents/US4361749?utm_source=gb-gplus-sharePatent US4361749 - Uniformly cooled plasma etching electrode
