AVS 51st International Symposium
    Vacuum Technology Tuesday Sessions
       Session VT-TuA

Invited Paper VT-TuA5
The Science and Technology of Pumping Residual Gases in Vacuum Tubes

Tuesday, November 16, 2004, 2:40 pm, Room 303D

Session: Special Session at the 51st International AVS Symposium: "Fleming Centenary Session: The Birth and Evolution of Electronics"
Presenter: B. Ferrario, Saes Getters SpA, Italy
Correspondent: Click to Email
Since the invention of the vacuum oscillation valve by Fleming impressive developments have been made in the field of vacuum tubes and related applications. Vacuum tubes are nowadays widespread devices in spite of the introduction of the transistors as substitutes for the vacuum valves; here they are referred to as a large family of products which has been growing along many decades and include, for example, power vacuum tubes, x-ray tubes, CRTs for black&white and color television, and the more recent so called "thin CRTs", i.e. Field Emission Displays (FED).Vacuum science and technology have been playing an essential role in these developments and have evolved symbiotically with them, often generating fundamental knowledge useful for many other vacuum related applications. The evolution of the vacuum tube family has required an increasing degree of vacuum and longer lifetimes along with more and more cost effective manufacturing processes; particular attention has therefore been drawn on the phenomena which are responsible for vacuum deterioration after seal-off , among which outgassing is usually the most relevant. This has made the study of outgassing phenomena , the residual gas analysis, the selection of the appropriate materials and the optimization of the manufacturing processes increasingly important. Concurrently, important developments have been made concerning getters which, after seal-off, act as in situ pumps to countermeasure the outgassing effects; indeed they are used, in various materials and configurations, to minimize the total residual pressure and particularly the partial pressures of the so called “active” gases (H@sub 2@O, CO@sub 2@, H@sub 2@, O@sub 2@, etc.) which are usually most detrimental and account for most of the total pressure in vacuum tubes.This paper reviews the issues related to residual gases in vacuum tubes and the early as well as especially the modern getter solutions developed to ensure the desired residual gas pumping in various vacuum tube types.