Editing Geiger counter (section)

==History==
[[File:PSM V87 D120 Apparatus for counting alpha particles.png|thumb|right|Rutherford & Geiger  particle counter (1908). Alpha particles from a source in the firing tube were admitted through aperture "D" to the detecting vessel, which was a brass tube with a central co-axial wire "B" at a relative potential of 1320 volts DC. The aperture had a mica window so the detecting vessel could run at an [[absolute pressure]] of 2-5 mm of mercury. These conditions enabled creation of a [[Townsend discharge]] for every alpha particle entering the vessel. At very low count rates these registered as "kicks" on an [[electrometer]] needle.]]
[[File:Early Geiger counter, made by Hans Geiger, 1932. (9663806938).jpg|thumb|Early Geiger–Müller tube made in 1932 by Hans Geiger for laboratory use]]
In 1908 [[Hans Geiger]], under the supervision of [[Ernest Rutherford]] at the [[Victoria University of Manchester]] (now the [[University of Manchester]]), developed an experimental technique for detecting alpha particles that would later be used to develop the Geiger–Müller tube in 1928.<ref>E. Rutherford and H. Geiger (1908) [{{Google books |plainurl=yes |id=jaezAAAAIAAJ |page=141 }} "An electrical method of counting the number of α particles from radioactive substances,"] ''Proceedings of the Royal Society (London)'', Series A, vol. 81, no. 546, pages 141–161.</ref> This early counter was only capable of detecting alpha particles and was part of a larger experimental apparatus. The fundamental ionization mechanism used was discovered by [[John Sealy Townsend]] between 1897 and 1901,<ref>John S. Townsend (1901) [{{Google books |plainurl=yes |id=R64mG2pv0qAC |page=198 }} "The conductivity produced in gases by the motion of negatively charged ions,"] ''Philosophical Magazine'', series 6, '''1''' (2) :  198-227.</ref> and is known as the [[Townsend discharge]], which is the ionization of molecules by ion impact.

It was not until 1928 that Geiger and [[Walther Müller]] (a PhD student of Geiger) developed the sealed Geiger–Müller tube which used basic ionization principles previously used experimentally. Small and rugged, not only could it detect alpha and beta radiation as prior models had done, but also gamma radiation.<ref name="Korff, SNTM 2012"/><ref>See:
*  H. Geiger and W. Müller (1928), "Elektronenzählrohr zur Messung schwächster Aktivitäten" (Electron counting tube for the measurement of the weakest radioactivities), ''Die Naturwissenschaften'' (The Sciences), vol. 16, no. 31, pages 617–618.
*  Geiger, H. and Müller, W. (1928) "Das Elektronenzählrohr" (The electron counting tube), ''Physikalische Zeitschrift'', '''29''': 839-841.
*  Geiger, H. and Müller, W. (1929) "Technische Bemerkungen zum Elektronenzählrohr" (Technical notes on the electron counting tube), ''Physikalische Zeitschrift'', '''30''': 489-493.
*  Geiger, H. and Müller, W. (1929) "Demonstration des Elektronenzählrohrs" (Demonstration of the electron counting tube), ''Physikalische Zeitschrift'', '''30''': 523 ff.</ref> Now a practical radiation instrument could be produced relatively cheaply, and so the Geiger counter was born. As the tube output required little electronic processing, a distinct advantage in the [[Vacuum tube|thermionic valve]] era due to minimal valve count and low power consumption, the instrument achieved great popularity as a portable radiation detector.

Modern versions of the Geiger counter use halogen quench gases, a technique invented in 1947 by [[Sidney H. Liebson]].<ref>{{cite journal |first=S. H. |last=Liebson |year=1947 |title=The Discharge Mechanism of Self-Quenching Geiger–Mueller Counters |journal=[[Physical Review]] |volume=72 |issue=7 |pages=602–608 |doi=10.1103/PhysRev.72.602 |bibcode = 1947PhRv...72..602L |hdl=1903/17793 |url=http://drum.lib.umd.edu/bitstream/1903/17793/1/DP70461.pdf |archive-url=https://web.archive.org/web/20170921235703/http://drum.lib.umd.edu/bitstream/1903/17793/1/DP70461.pdf |archive-date=2017-09-21 |url-status=live |hdl-access=free }}</ref> Halogen compounds have superseded the organic quench gases because of their much longer life and lower operating voltages; typically 400-900 volts.<ref>{{Cite web |url=http://www.national-radiation-instrument-catalog.com/ |title=History of Portable Radiation Detection Instrumentation from the period 1920–60 |access-date=2008-07-15 |archive-date=2009-01-13 |archive-url=https://web.archive.org/web/20090113173535/http://www.national-radiation-instrument-catalog.com/ |url-status=live }}</ref>