Editing Anode ray

{{Short description|Beam of positively charged ions}}
[[File:Anode Ray Tube.jpg|right|thumb|200 px|Anode ray tube showing the rays passing through the perforated cathode and causing the pink glow above it.]]
[[File:Anode Ray Tube Off.jpg|thumb|Anode ray tube, turned-off condition|291x291px]]
An '''anode ray''' (also '''positive ray''' or '''canal ray''') is a beam of positive [[ion]]s that is created by certain types of [[gas-discharge tube]]s. They were first observed in [[Crookes tube]]s during experiments by the [[Germany|German]] [[scientist]] [[Eugen Goldstein]], in 1886.<ref name="isbn0-941901-31-9">{{cite book |author=Grayson, Michael A. |title=Measuring mass: from positive rays to proteins |publisher=Chemical Heritage Press |location=Philadelphia |year=2002 |pages=[https://archive.org/details/measuringmassfro0000unse/page/4 4] |isbn=0-941901-31-9 |url=https://archive.org/details/measuringmassfro0000unse/page/4}}</ref> Later work on anode rays by [[Wilhelm Wien]] and [[J. J. Thomson]] led to the development of [[mass spectrometry]].

==Anode ray tube==
[[File:Anode ray tube 800X400.jpg|thumb|left|Simplified representation of an anode ray tube, showing the rays to the right of the perforated cathode]]
[[File:Anode ray tube Schematic.jpg|thumb|left|Anode ray tube schematics|210x210px]]

Goldstein used a [[gas-discharge tube]] which had a perforated [[cathode]]. When an electrical potential of several thousand volts is applied between the cathode and anode, faint luminous "rays" are seen extending from the holes in the back of the cathode. These rays are beams of particles moving in a direction opposite to the "[[cathode ray]]s", which are streams of [[electron]]s which move toward the anode. Goldstein called these positive rays ''Kanalstrahlen'', "channel rays", or "canal rays", because these rays passed through the holes or ''channels'' in the cathode.

The process by which anode rays are formed in a gas-discharge anode ray tube is as follows. When the high voltage is applied to the tube, its [[electric field]] accelerates the small number of [[ion]]s (electrically charged [[atom]]s) always present in the gas, created by natural processes such as [[radioactivity]]. These collide with atoms of the gas, knocking electrons off them and creating more positive ions. These ions and electrons in turn strike more atoms, creating more positive ions in a chain reaction. The positive ions are all attracted to the negative cathode, and some pass through the holes in the cathode. These are the anode rays.

By the time they reach the cathode, the ions have been accelerated to a sufficient speed such that when they collide with other atoms or molecules in the gas they excite the [[chemical species|species]] to a higher [[energy level]]. In returning to their former energy levels these atoms or molecules release the energy that they had gained. That energy gets emitted as light. This light-producing process, called [[fluorescence]], causes a glow in the region behind the cathode.

==Anode ray ion source==
An anode ray [[ion source]] typically is an anode coated with the [[halide]] salt of an [[alkali metal|alkali]] or [[alkaline earth metal]].<ref name='ROPE 1921'>{{cite book |last1=Thomson |first1=J. J. |title=Rays of positive electricity, and their application to chemical analyses (1921) |year=1921 |pages=[https://archive.org/details/raysofpositiveel00thomuoft/page/142 142] |url=https://archive.org/details/raysofpositiveel00thomuoft |access-date=2013-04-22}}</ref><ref name="BainbridgeNier1950">{{cite book |author1=Kenneth Tompkins Bainbridge |author2=Alfred Otto Nier |title=Relative Isotopic Abundances of the Elements |url=https://books.google.com/books?id=xagrAAAAYAAJ&pg=PA2 |access-date=21 April 2013 |year=1950 |publisher=[[National Academies]] |pages=2– |id=NAP:16632}}</ref> Application of a sufficiently high electrical potential creates alkali or alkaline earth ions and their emission is most brightly visible at the anode.

==See also==
*[[Emil Rupp#Canal ray experiments|Canal ray experiments]]

==References==
{{Reflist}}

==External links==
*[https://web.lemoyne.edu/~giunta/canal.html Rays Of Positive Electricity by J.J. Thomson ''Proceedings of the Royal Society'', A 89, 1-20 (1913)]
*[https://www.crtsite.com/page7-2.html The Goldstein canal ray tube] at The Cathode Ray Tube site

[[Category:German inventions]]
[[Category:Ionizing radiation]]
[[Category:Luminescence]]
[[Category:Mass spectrometry]]