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By means of a mass spectrometer integral with the tube being studied, the gases in electron tubes have been investigated as a function of tube processing schedules.
The processing schedules studied were all adapted to trolley pumping of small electron tubes, and included (1) bakeout followed by radiofrequency heating and cathode breakdown, (2) cathode breakdown during bakeout followed by radiofrequency heating, and (3) cathode breakdown during bakeout followed by radiofrequency heating and operation on the pump. The results showed that the initial gas content, particularly carbon monoxide, was considerably reduced by breakdown during bakeout, from 3 x 10-6 Torr carbon monoxide to about 5 x 10-8 Torr carbon monoxide, with even lower pressure obtained by operation on the pump.
In the tubes with cathodes broken down during bakeout, the gas pressure level approached 10-9 Torr on life and remained there without getters. Other ubes without getters processed by breaking down the cathodes after bakeout frequently show pressures of hydrogen and carbon monoxide between 10-8 and 10-7 Torr on life.
Frost, H. B.
Bell Telephone Laboratories. Inc., Murray Hill, N. J.