Exhaust Processes of Vacuum Tubes



The high operating temperature of some electrode parts in finished tubes, the impurities occurring after preliminary outgassing (welding spots, gas absorption, contamination of surfaces), as well as economy (life and cost of operation of preliminary outgassing furnaces with high temperature), generally require that parts in sealed off tubes be outgassed again during the pumping process. The limiting temperature permissible in such outgassing is determined by the dimensional stability of the electrodes, radiation heating of glass parts, and vapor pressure of electrode materials which increases considerably with temperature. If the vapor pressure is permitted to increase above a certain limit, the metal vapors will condense on cooler places (glass walls, stems, insulating supports) of the vacuum tube during the outgassing period and may cause disturbances (light absorbing coatings, leakage, poisoning of cathode surfaces, etc.). The vapor pressures of metals as a function of temperature are indicated in Fig. A/1a and A/1b (appendix). Metallic materials with lower vapor pressure permit higher outgassing temperatures without causing harmful deposits. In alloys, the component with the higher vapor pressure is the controlling one.


Welding Spot Vacuum Tube Incandescent Lamp Electron Bombardment Heating Coil 
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References on Exhaust Processes of Vacuum Tubes

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Copyright information

© Springer-Verlag OHG., Berlin Göttingen/Heidelberg 1959

Authors and Affiliations

  1. 1.Technische Hochschule MünchenGermany
  2. 2.Dept. El. EngineeringPrinceton UniversityUSA

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