Study on the Unidirectional Vacuum Gauge by Detecting Excited Neutrals

Abstract

An unidirectional vacuum gauge, which detects gas molecules coming from a certain direction in chaotic space, can be realised by means of detecting excited neutrals which are generated by electron impact. To eliminate photons and ions from detection was found to be effective measure in order to improve the performance of the gauge. The advantages of sharp directivity, small size, and high signal to background ratio were confirmed. The measured value of the gauge sensitivity is in good agreement with the expected one. This type of gauge, moreover, can measure the time of flight spectrum of gas molecules, that makes it possible to evaluate not only the anisotropy of molecular density in space but also the anisotropy and the nonequilibrium of molecular velocity distribution.