Editing Getter (section)

{{Short description|Consumable reactive substance used to fix another one such as for oxygen removal in vacuum tubes}}
{{Other uses}}
[[File:Getter diagram.png|thumb|right|300px|{{ubli
 | ''(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 tube]]s, including [[cathode-ray tube]]s (CRTs), vacuum insulating glass (or vacuum glass)<ref>IGMA (FGIA) TB-2600; Vacuum Insulating Glass</ref> and [[vacuum insulated panel]]s, 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.<ref name="O'Hanlon">{{cite book
 | last1  = O'Hanlon
 | first1 = John F.
 | title  = A User's Guide to Vacuum Technology
 | publisher = John Wiley and Sons
 | edition = 3
 | date   = 2005
 | pages  = 247
 | url    = https://books.google.com/books?id=9aNaUW-q4ygC&q=getter+%22vacuum+pump&pg=PA247
 | isbn   = 0471467154
 }}</ref><ref name="Danielson">{{cite web
  | last = Danielson
  | first = Phil
  | title = How To Use Getters and Getter Pumps
  | work = A Journal of Practical and Useful Vacuum Technology
  | publisher = The Vacuum Lab website
  | date = 2004
  | url = http://www.vacuumlab.com/Articles/VacLab23.pdf
  | access-date = November 27, 2014
  | url-status = dead
  | archive-url = https://web.archive.org/web/20050209031512/http://www.vacuumlab.com/Articles/VacLab23.pdf
  | archive-date = 2005-02-09}}</ref><ref name="Mattox">{{cite book
 | last1  = Mattox
 | first1 = Donald M.
 | title  = Handbook of Physical Vapor Deposition (PVD) Processing
 | publisher = William Andrew
 | edition = 2
 | date   = 2010
 | pages  = 625
 | url    = https://books.google.com/books?id=aGUxoVTYjA8C&q=%22getter+pump%22&pg=PA625
 | isbn   = 978-0815520382
 }}</ref><ref name="Welch">{{cite book
 | last1  = Welch
 | first1 = Kimo M.
 | title  = Capture Pumping Technology
 | publisher = Elsevier
 | date   = 2001
 | pages  = 1
 | url    = https://books.google.com/books?id=56wANznvEA8C&q=%22getter+pump%22&pg=PA1
 | isbn   = 0444508821
 }}</ref><ref name="Bannwarth">{{cite book
 | last1  = Bannwarth
 | first1 = Helmut
 | title  = Liquid Ring Vacuum Pumps, Compressors and Systems: Conventional and Hermetic Design
 | publisher = John Wiley & Sons
 | date   = 2006
 | pages  = 120
 | url    = https://books.google.com/books?id=ScQlemNoR0UC&q=%22getter+pump%22&pg=PA120
 | isbn   = 3527604723
 }}</ref>

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