Analysis of Desorbed Gases from an Insulator Excited by Electron Impact

Abstract

Gas desorption from an insulator excited by electron impact is regarded as one of major causes of surface flashover in vacuum. To enable analysis of gases only from an electron emission site on insulator surface a liquid nitrogen cooled shroud was used to prevent gases from a vacuum chamber entering into a quadrupole mass spectrometer (QMS). We observed gases released from the alumina sample and found that their mass numbers were m/e=2 (main), 18 and 28(very few). It was found that they were same components as residual gas species of a vacuum chamber. Furthermore, we investigated the effect of heat treatment on the desorbed gases from alumina.