Gas Composition During Pumping and in Sealed-off Power Tubes
SourceGas residues in electron tubes may originate from the tube materials, from gas permeation, and also from vapor picked up from pump environment. A bakeable radiofrequency-type mass spectrometer tube of an ion-gage size was used for measuring the gas composition during the pumping of electron tubes, and also in sealed-off power tubes during their processing and life. It was found that the gas composition in a sealed-off cold tube is extremely different from gas compositions measured during operation of the same tube. These changes are usually reversible. Irreversible changes in the gas environment of the tube may take place during its processing, operation, and also in life. Sudden changes in the gas environment may occur due to changes in operating conditions with respect to filament temperature or electron current of the tube.