Diamond Coated Insulators for Energetic Plasma Environments

Many plasma systems require electrical insulators that are exposed to energetic particles, ultraviolet radiation, x-rays, high rf and dc electric fields, and heating; the insulator surface and structure can be damaged by the plasma environment, causing degradation of system life-time and performance. Heavy elements from insulator erosion can produce serious radiation losses from high temperature plasmas. An adherent coating which is resistant to energetic particles, photons, and heat, and which has low atomic number and sputtering yield, would improve insulator performance and minimize radiation losses. Diamond and diamond-like films, applied by chemical vapor deposition (CVD) processes, appear to have considerable potential for coating insulators in plasma devices. Spire proposes to investigate the properties of very fine-graned polycrystalline diamond and diamond- like films on polymer and ceramic insulators. Samples will be coated and exposed to a simulated plasma environment in a modified flashover testing facility. The coatings will be evaluated from real-time diagnostic data and post-test analysis of adhesion, microscopic damage, weight loss, and composition of erosion products. Phase I research should lead to Phase II, in which insulator structures from plasma devices, such as Phillips Laboratory's Working Fluid Experiment or MARAUDER compact toroid experiment, are coated with diamond and/or diamond-like carbon and evaluated under actual operating conditions.