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added Thorium Iridium Hairpin
== Thoriated Tungsten ==
== Thoriated Tungsten ==
A method used in the manufacture of thermionic valves is the use of thoriated tungsten to depricate the work function and overall extend the service life of the cathode. This is accomplished by allowing up to 4% thorium into the tungsten wire. This cathode type was only experimentally uesd in the electron microscope, where it showed no aperciable advantage over the pure tungsten hairpin. Its use was thus religated to thermionic valves.
=== Thoriated Tungsten Wire ===
A method used in the manufacture of thermionic valves is the use of thoriated tungsten to deprecate the work function and overall extend the service life of the cathode. This is accomplished by allowing up to 4% thorium into the tungsten wire. This cathode type was only experimentally used in the electron microscope, where it showed no appreciable advantage over the pure tungsten hairpin. Its use was thus relegated to thermionic valves.
=== Thorium Iridium Hairpin ===
Thorium Oxide coated Iridium Hairpin Cathodes are used in [[LEED]] machines for the electron gun. They consist of a Hairpin shaped Iridium Wire, coated with Thorium Oxide.
== Oxide Cathode ==
== Oxide Cathode ==