Engineering topics
Publications and source records attributed to Beitel, G. A..
Triode gauge with electron source, electron collector, and positive ion collector made from either graphite or carbon material extends low-pressure ranges of existing gauges by changing only materials used in construction. Advantages of graphite gauge stem from physical properties of graphite (or carbon).
Mass spectral analyses were made of gases desorbed from carbon samples at increasing temperatures up to 2200 K. Samples were initially outgassed above 2000 K, exposed to air for several hours at room temperature, and then tested in ultrahigh vacuum following a 24-hr bake at 300 C. Four forms of carbon tested were pyrolytic carbon, Grafoil, vitreous carbon, and pyrolyzed-phenolic fibers. The equivalent of several monolayers of gas (mostly H2 and CO) are evolved from all of the carbons except vitreous carbon. Less than a monolayer of gas is evolved from vitreous carbon during outgassing to 2000 K.
A prototype all carbon triode ultrahigh vacuum gage was fabricated and tested. The gage exhibited a sensitivity of 3.7 per torr for nitrogen and an X-ray background approximately 0.1 as large as would be expected of a metal gage of the same design. The gage made from these materials, showed good sensitivity and durability. A practical technique was developed for bonding carbon components together without metal fasteners. The bond is made with a cross-linked phenolic resin which is converted to vitreous carbon by a careful pyrolysis procedure. The resulting bonds are strong, electrically conductive, and can withstand repeated excursions to 2500 K in vacuum. Measurements of adsorption and outgassing characteristics of four refractory carbons have confirmed that such materials are suitable for use in ultrahigh vacuum and that some are superior refractory metals in man respects.
Adsorption of carbon monoxide and hydrogen was investigated on three graphites: a high-density pyrolytic graphite, a small-grain extruded graphite, and a processed pyrolytic graphite tape. The sticking probability of CO was found to decrease rapidly as the average surface coverage approached 0.01 monolayer. Lower sticking probabilities were observed on the highly oriented pyrolytic graphite which indicated that adsorption occurs principally on the edge atoms. There is negligible adsorption of molecular hydrogen on graphite that has been heated to 2400 K in vacuo.
Graphite properties in high and ultrahigh vacuum, suggesting use as electrode material in vacuum gages and residual gas analyzers
Literature survey and experimental evaluation of graphite properties in high vacuum environment
Modified buried collector gauge performance over He pressure range, determining sensitivity dependence on filament geometry
Collector gauge and orbitron gauge for ultrahigh vacuum measurements
Orbitron ion gauge experimental designs for low pressure applications