Bayard-Alpert Gauge Filaments: Tungsten or Thoria? Introduction
نویسنده
چکیده
The optimum choice of filament material is very application dependent, and interactions of the gas with the cathode material must be carefully considered. Filaments, in both wire and ribbon shapes, are required to (1) supply a stable electron emission current with reasonable energy input and filament temperature, (2) have reduced chemical reactivity with the rarefied environment being measured, (3) have a reduced evaporation rate at the operating temperature (i.e. long life), (4) have a vapor pressure at least one tenth of the lowest pressure that has to be measured and (5) have low levels of ionic and neutral molecule outgassing compatible with the lowest pressure measurements.
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