Using the mass spectrometer as a n analytical tool and as a means of rate measurement, the rates of helium diffusion through nine types of glass were measured. The temperature range covered was from -No to 600OC. T h e highest rates were for fused silica and Vycor brand glass; the lowest were for the lead glasses. The rate at 100°C. decreased by a factor of one million as the percentage of glassformers (SiOz, B2O3, P205) decreased in the glass composition. A few measurements are also given for hydrogen, deuterium, and neon rates through fused silica and estimates are made of the upper limit for argon, oxygen, and nitrogen at 700" c.
The permeation process consists of the steps: adsorption, solution, diffusion, and desorption. These are discussed for glasses, polymers, and metals. There are two generalizations: (1) All gases go through all polymers. (2) No rare gas permeates any metal. Criteria are given for measurements of the permeation process.
In glasses the permeation rate depends on atomic size and glass composition. Some special processes which may simulate permeation in vacuum devices are discussed: oxide dissociation, electrolysis in ceramic materials, nuclear reactions, and ionic impact.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.