Physical processes in the Pirani type low vacuum sensor

Auger electron spectroscopy and thermoresistive methods are used to study the physical processes leading gas cooling of heated molybdenum filaments in a wide temperature range 350-1300 K pressures 760-10 -3 Torr, corresponding operating Pirani-type vacuum sensor. Nitrogen was as gas. It is shown that nitrogen atoms chemisorbed on surface do not contribute cooling, which occurs only due physisorbed N 2 molecules. In intermediate region 10 -1 heater cooled equilibrium between flux incident thermally desorbed molecules, well described by Hertz--Knudsen formula first-order desorption with an activation energy ~0.55 eV. On contrary, at high close atmospheric, this thermal molecules from almost filled monolayer, reduces its relative efficiency many orders magnitude. Keywords: vacuum, adsorption, Pirani sensor, molybdenum, desorption, nitrogen.