Editing Photocathode (section)

{{Short description|Surface which converts light into electrons via the photoelectric effect}}
[[File:Cs-K-Sb photocathode picture.png|thumb|Cs-K-Sb photocathode centered on a Molybdenum plug  (a) after growth in the preparation chamber and (b) after transfer into the photoinjector]]

A '''photocathode''' is a surface engineered to convert light ([[Photon|photons]]) into electrons using the [[photoelectric effect]].  Photocathodes are important in [[accelerator physics]] where they are utilised in a [[photoinjector]] to generate high [[Beam emittance|brightness]] electron beams.  Electron beams generated with photocathodes are commonly used for [[Free-electron laser|free electron lasers]] and for [[ultrafast electron diffraction]]. Photocathodes are also commonly used as the negatively charged [[electrode]] in a light detection device such as a [[photomultiplier]], [[phototube]] and [[image intensifier]].