Editing Tellurium (section)

=== Photocathodes ===
Tellurium shows up in a number of [[photocathode]]s used in solar blind [[photomultiplier tube]]s<ref>{{Cite journal|last1=Taft|first1=E.|last2=Apker|first2=L.|date=1953-02-01|title=Photoemission from Cesium and Rubidium Tellurides|url=https://www.osapublishing.org/josa/abstract.cfm?uri=josa-43-2-81|journal=JOSA|language=EN|volume=43|issue=2|pages=81–83|doi=10.1364/JOSA.43.000081|bibcode=1953JOSA...43...81T}}</ref> and for high brightness [[photoinjector]]s driving modern particle accelerators. The photocathode Cs-Te, which is predominantly Cs<sub>2</sub>Te, has a photoemission threshold of 3.5 eV and exhibits the uncommon combination of high quantum efficiency (>10%) and high durability in poor vacuum environments (lasting for months under use in RF electron guns).<ref>[[Triveni Rao|Rao, T.]], & Dowell, D. H. (2013). ''An engineering guide to photoinjectors''. CreateSpace Independent Publishing.</ref>  This has made it the go to choice for photoemission electron guns used in driving [[Free-electron laser|free electron lasers]].<ref>LCLS-II Project Team. (2015). [https://portal.slac.stanford.edu/sites/ard_public/people/tora/Temp/150921%20LCLS-II%20FDR.pdf ''LCLS-II Final Design Report'']. (LCLSII-1.1-DR-0251-R0). SLAC.</ref>  In this application, it is usually driven at the wavelength 267&nbsp;nm which is the third harmonic of commonly used [[Ti-sapphire laser]]s. More Te containing photocathodes have been grown using other alkali metals such as rubidium, Potassium, and Sodium, but they have not found the same popularity that Cs-Te has enjoyed.<ref>{{Cite patent|title=Bi-alkali telluride photocathode|gdate=1978-07-20|country=US|number=4196257|pubdate=1980-04-01|assign=[[RCA Corporation]]|inventor1-last=Engstrom |inventor1-first=Ralph W. |inventor2-last=McDonie |inventor2-first=Arthur F.}}</ref><ref>Trautner, H. (2000). ''Spectral Response of Cesium Telluride and Rubidium Telluride Photocathodes for the Production of Highly Charged Electron Bunches''. CERN.</ref>