Figure 5
a Measured and simulated cathode temperatures as a function of plasma power. The gas mixture simulated was 54:200 sccm C2H2/NH3 at 12 mbar. Cathode-to-anode temperature profiles for the cases of pure plasma heating vs plasma plus external heating. b Plasma heating of the cathode at 700°C, using 200 W of plasma power with the external heater off. The chamber was filled with a gas mixture of 54:200 sccm of C2H2/NH3 at a pressure of 12 mbar. The thermocouple is mineral insulated with a stainless steel sheath and enters through the plasma (hot gas) zone before it is embedded in a 1–2 mm deep hole in the cathode. [Adapted from Ref [20]