Helium Diffusion Through Glass

Using the mass spectrometer as an 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 –80° to 600°C. The 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 (SiO 2 , B 2 O 3 , P 2 O 5 ) 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.