A second gas inlet is provided above the plasma tube. Through this tube may be passed a reacting species. Reactions are induced by the active species coming from the plasma tube. These may include atoms, metastables, free radicals or ions. This configuration permits the reaction to proceed in a stable environment, i.e. away from the discharge, and also keeps the reaction products from contaminating the chamber walls in the discharge region.
Gas flow through each inlet is controlled by stainless steel needle valves.
I obtained the valves from American Science and Surplus. Since I obtained several ovens of similar size and since the major components are all interchangeable I have opted to add a second transformer to keep the filament voltage constant. This added transformer also serves as the power control. I removed the high voltage secondary, a task that left a pile of fine copper wire all over the driveway. After soldering, insulating varnish was applied and allowed to dry.