The analysis of residual gas in electron tubes

A method has been devised for analysis of the residual gas content of small tetrodes or pentodes. In contrast to other methods which have been reported, the gas content of the tube being studied is not changed markedly by the analysis, analyses may be made repeatedly as the tube is operated, and moderately low pressures (10^-10mm Hg) and small quantities (10^-8micronliter) may be detected. A 90° sector magnetic analyzer with a 3 cm radius of curvature and 30 mil slits (resolution 1:20) is sealed to the tube to be analyzed prior to pumping. The analyzer is made of 0120 glass with a conductive lining. The tube being tested serves as an ion source, an important feature which avoids contaminatioh. The device has been calibrated by comparison with known gases on a vacuum station, and a voltage-sensitivity curve has been derived from these data.