Ceramic Membranes for the Separation of Plasma Enhancement Gases

Low and medium Z impurity seeding gases, or plasma enhancement gases (PEGs) will be injected into the plasma of a Tokamak to convert the plasma thermal energy to ultraviolet and soft X-ray radiation. Possible PEGs are nitrogen, neon, argon, xenon and other inert gases. for the exhaust processing system of the demonstration fusion reactor (DEMO), the use of inorganic membranes was recently taken into consideration. Two commercial ceramic membranes (produced by Atech Innovations GmbH, Germany) were tested at a permeation apparatus built at ENEA Casaccia laboratories. Single gas permeances for H₂, He, Ar and N₂ were measured with a pressure drop across the membranes between 10 Pa up to 130 kPa at room temperature. For both membranes the permeance order follows the Knudsen regime. The Knudsen permeance measured for the two membranes are on the order of 10⁻⁷–10⁻⁸. The selectivities found are low (similar to ideal Knudsen).