Photocathodes: Mapping, Controlled Porosity, Cesium, and Gold
Riddick, Blake Cutler
O'Shea, Patrick G
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Photocathodes play a critical role in a large variety of applications, from detectors in medical imaging to electron beam sources for fundamental science. Via the photoelectric effect, photocathodes emit electrons in response to light of sufficient energy. Three important characteristics of photocathodes are quantum efficiency (the fraction of incident photons that generates emitted electrons), lifetime (how long the cathodes are operational), and emission uniformity. Coating a photocathode with an atomic layer of cesium dramatically improves quantum efficiency, but the inherent fragility of this layer worsens lifetime. The design and testing of a cesium rejuvenation system which prolongs lifetime will be presented, and a controlled porosity design which could improve emission uniformity will be discussed. A new method of mapping quantum efficiency will be presented. The initial results of testing cesium auride will be discussed, as they show the cathodes have surprisingly high quantum efficiency and the potential for very long lifetime.