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AKBP: Arbeitskreis Beschleunigerphysik
AKBP 2: Electron Sources and Cathodes
AKBP 2.7: Talk
Monday, March 18, 2024, 13:15–13:30, E 020
Development of a metal photocathode for the DESY SRF gun — •Chirag Banjare1, Dmitry Bazyl1, Klaus Floettmann1, and Wolfgang Hillert2 — 1Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany — 2Universität Hamburg, Hamburg, Germany
DESY and its collaborators are working on future continuous wave (CW) operations of a superconducting radio-frequency (SRF) photoinjector for the European X-ray-free electron laser (EuXFEL). CW-mode operation in a photoinjector requires a sufficiently high quantum efficiency (QE) photocathode. Currently, semiconductor photocathodes are operated in pulsed mode for the Eu-XFEL. However, installing a semiconductor photocathode in the SRF gun cavity can increase the risk of contamination of the SRF cavity. Therefore, metal photocathodes such as copper, gold, or niobium, which are durable, air-stable, and have a lesser risk of contamination in the cavity, are preferable to semiconductor photocathodes. However, metallic photocathodes have a lower QE (10^{-5}) than semiconductor photocathodes. Thus, the engineering of metallic photocathode design from the backside and front side illumination for light absorption is studied. A subwavelength-sized rectangular nanohole array on the gold surface is modeled to excite surface plasmons. Using CST Studio and FDTD software, the attenuated total reflection (ATR) phenomenon in a thin metal prism and several other techniques are simulated to perfectly absorb the light in the ultraviolet to green spectrums. This phenomenon contributes to obtaining the high QE of metal photocathodes.
Keywords: Nanostructured Photocathode; Surface Plasmons; SRF