Outgassing Caused by Electron Bombardment of Glass

Abstract

A flow system used for continuous measurement of the gases evolved from aluminized glass during bombardment with 20 kev electrons is described. The system is also suitable for gettering measurements. A cathode‐ray tube containing the samples is sealed directly to the source of a mass spectrometer. Calibration of the first flow system built revealed the gettering of oxygen by the graphite‐silicate conductive coating and the hot metal parts of the electron gun of the cathode‐ray tube. This gettering was minimized in a second flow system. It was found that oxygen constitutes at least 95% of the gas evolved from each of five types of glasses investigated. Also, a graphite‐silicate coating can play a dual role in a cathode‐ray tube; when not bombarded by electrons it is an active getter for oxygen, but when bombarded it is a source of oxygen, carbon monoxide, and carbon dioxide.