| 摘要 |
<p>A plasma system has a plug-in cartridge (20) having a pair of identical opposed electrode blocks (21, 22) each comprising a series of electrodes (23) in the form of ridges on one side (facing the ionisation path), and on the outside heat sink fins (24). There is a process gas inlet manifold (25). The path between the electrodes (23) outlets into a treatment conduit (26) having openings into catalytic converters (27, 29) through which waste gas is driven to atmosphere by fans (28, 30) respectively. Process gas such as air is drawn in a flow A into the manifold (25), and passes in a flow B along the path where it is ionised. Ionised air outlets into the treatment conduit (26) in a flow C where it impinges against the sample S being treated. Waste air flows (D) through the catalytic converters (27, 29) where ozone is converted to oxygen for safe discharge E to atmosphere. Each pair of opposed electrodes (23) is an ionisation stage in which a high voltage sine wave causes breakdown of the gas in the gaps between the electrodes. The output of the first stage contains some ions and a large number of excited species including metastables. Recombination occurs to some of the species while in transit to the second stage. The species arriving at the second stage cause seeding of the next discharge at that stage and a larger amount of species is created than produced by the first stage. This is because the collision frequency increases with increase in the number of ions, thus accelerating the production of further ions under an electric field. The process continues through each successive stage, yielding a much higher density of active species than would be produced by a single pair of electrodes with an equivalent surface area.</p> |
