Editing Ignitron (section)

==Construction and operation==
[[Image:Ignitrons.jpg|thumb|Ignitron rectifiers powering industrial process, 1945]]
An ignitron is usually a large steel container with a pool of [[mercury (element)|mercury]] in the bottom that acts as a [[cathode]] during operation. A large [[graphite]] or [[refractory metals|refractory metal]] cylinder, held above the pool by an insulated electrical connection, serves as the [[anode]]. An igniting [[electrode]] (called the ''ignitor''), made of a [[refractory]] [[semiconductor]] material such as silicon carbide,<ref> Turner pg. 7-182</ref> is briefly pulsed with a high current to create a puff of electrically conductive mercury [[plasma (physics)|plasma]]. The plasma rapidly bridges the space between the mercury pool and the anode, permitting heavy conduction between the main electrodes. At the surface of the mercury, heating by the resulting arc liberates large numbers of [[electron]]s which help to maintain the mercury [[electrical arc|arc]]. The mercury surface thus serves as the cathode, and [[Electric current|current]] is normally only in one direction. Once ignited, an ignitron will continue to pass current until either the current is externally interrupted or the voltage applied between cathode and anode is reversed.<ref> L.W. Turner,(ed), ''Electronics Engineer's Reference Book'', 4th ed. Newnes-Butterworth, London 1976 {{ISBN|0408001682}} pages 7-181 through 7-189</ref>