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Title: Use of non evaporable getter pumps to ensure long term performances of high quantum efficiency photocathodes

High quantum efficiency photocathodes are routinely used as laser triggered emitters in the advanced high brightness electron sources based on radio frequency guns. The sensitivity of “semiconductor” type photocathodes to vacuum levels and gas composition requires special care during preparation and handling. This paper will discuss the results obtained using a novel pumping approach based on coupling a 20 l s{sup −1} sputter ion getter pump with a CapaciTorr® D100 non evaporable getter (NEG) pump. A pressure of 8⋅10{sup −8} Pa was achieved using only a sputter ion pump after a 6 day bake-out. With the addition of a NEG pump, a pressure of 2⋅10{sup −9} Pa was achieved after a 2 day bake-out. These pressure values were maintained without power due to the ability of the NEG to pump gases by chemical reaction. Long term monitoring of cathodes quantum efficiencies was also carried out at different photon wavelengths for more than two years, showing no degradation of the photoemissive film properties.
Authors:
; ;  [1] ; ;  [2]
  1. Istituto Nazionale di Fisica Nucleare Sez. Milano – LASA, Via Fratelli Cervi 201, I-20090 Segrate (Italy)
  2. SAES Getters S.p.A., Viale Italia 77, 20020 Lainate (Italy)
Publication Date:
OSTI Identifier:
22258633
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films; Journal Volume: 32; Journal Issue: 3; Other Information: (c) 2014 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BRIGHTNESS; CHEMICAL REACTIONS; ELECTRON SOURCES; FILMS; GASES; IONS; LASERS; PHOTOCATHODES; PHOTONS; QUANTUM EFFICIENCY; RADIOWAVE RADIATION; SPUTTER-ION PUMPS