Getter

For other uses, see Getter (disambiguation).
  • (center) A vacuum tube with a flashed getter coating on the inner surface of the top of the tube.
  • (left) The inside of a similar tube, showing the reservoir that holds the material that is evaporated to create the getter coating. During manufacture, after the tube is evacuated and sealed, an induction heater evaporates the material, which condenses on the glass.

A getter is a deposit of reactive material that is placed inside a vacuum system to complete and maintain the vacuum. When gas molecules strike the getter material, they combine with it chemically or by adsorption. Thus the getter removes small amounts of gas from the evacuated space. The getter is usually a coating applied to a surface within the evacuated chamber.

A vacuum is initially created by connecting a container to a vacuum pump. After achieving a sufficient vacuum, the container can be sealed, or the vacuum pump can be left running. Getters are especially important in sealed systems, such as vacuum tubes, including cathode-ray tubes (CRTs), vacuum insulating glass (or vacuum glass)[1] and vacuum insulated panels, which must maintain a vacuum for a long time. This is because the inner surfaces of the container release adsorbed gases for a long time after the vacuum is established. The getter continually removes residues of a reactive gas, such as oxygen, as long as it is desorbed from a surface, or continuously penetrating in the system (tiny leaks or diffusion through a permeable material). Even in systems which are continually evacuated by a vacuum pump, getters are also used to remove residual gas, often to achieve a higher vacuum than the pump could achieve alone. Although it is often present in minute amounts and has no moving parts, a getter behaves in itself as a vacuum pump. It is an ultimate chemical sink for reactive gases.[2][3][4][5][6]

Getters cannot react with inert gases, though some getters will adsorb them in a reversible way. Also, hydrogen is usually handled by adsorption rather than by reaction.

  1. ^ IGMA (FGIA) TB-2600; Vacuum Insulating Glass
  2. ^ O'Hanlon, John F. (2005). A User's Guide to Vacuum Technology (3 ed.). John Wiley and Sons. p. 247. ISBN 0471467154.
  3. ^ Danielson, Phil (2004). "How To Use Getters and Getter Pumps" (PDF). A Journal of Practical and Useful Vacuum Technology. The Vacuum Lab website. Archived from the original (PDF) on 2005-02-09. Retrieved November 27, 2014.
  4. ^ Mattox, Donald M. (2010). Handbook of Physical Vapor Deposition (PVD) Processing (2 ed.). William Andrew. p. 625. ISBN 978-0815520382.
  5. ^ Welch, Kimo M. (2001). Capture Pumping Technology. Elsevier. p. 1. ISBN 0444508821.
  6. ^ Bannwarth, Helmut (2006). Liquid Ring Vacuum Pumps, Compressors and Systems: Conventional and Hermetic Design. John Wiley & Sons. p. 120. ISBN 3527604723.