Experience at Fermilab with high quantum efficiency photo-cathodes for rf electron guns

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As part of the A0 Photo-injector collaboration at Fermi-lab [1, 2] and the TeSLA collaboration [3], a high bright-ness, low emittance electron source has been developed. In the process, a system was constructed for coating molybde-num cathodes with a layer of cæsium telluride (Cs2 Te), a photo-emissive material of high quantum efficiency (QE). The use of Cs2 Te was first investigated at CERN [4] and LANL [5]. The development of the systems for the TeSLA Test Facility Linac and the Fermilab Photo-injector was done in Milano [6]. The system at Fermilab incorporates manipulator arms to transfer a cathode from the ... continued below

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Fry, A.; Hahn, E.; Hartung, W.; Kuchnir, M.; Michelato, P. & Sertore, D. October 1998.

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As part of the A0 Photo-injector collaboration at Fermi-lab [1, 2] and the TeSLA collaboration [3], a high bright-ness, low emittance electron source has been developed. In the process, a system was constructed for coating molybde-num cathodes with a layer of cæsium telluride (Cs2 Te), a photo-emissive material of high quantum efficiency (QE). The use of Cs2 Te was first investigated at CERN [4] and LANL [5]. The development of the systems for the TeSLA Test Facility Linac and the Fermilab Photo-injector was done in Milano [6]. The system at Fermilab incorporates manipulator arms to transfer a cathode from the preparation chamber into a 1.3 GHz photo-electron RF gun while it re-mains in an ultra-high vacuum (UHV) environment, in or-der to avoid the deleterious effects of residual gases on the QE. A first prototype electron gun has been operated with a photo-cathode for several months [1]. This paper describes preliminary results obtained with the first 2 photo-cathodes and the first gun. Some of the desired parameters for the TeSLA Test Fa-cility beam are given in Table 1. The desired characteristics for the photo-cathodes include (i) high QE, (ii) high current density (>500 A/cm{sup 2} ), (iii) long lifetime, and (iv) low field emission. The choice of Cs2 Te is a compromise between long lifetime, rugged metal cathodes with low QE (typi-cally between 10{sup -6} and 10{sup -4} and semiconductor cathodes with high QE (>10%), which generally have a short life-time because of their sensitivity to contamination.

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116 Kilobytes

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  • XIX International Linac Conference, Chicago, Illinois, August 23-28, 1998

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  • Other: DE00002013
  • Report No.: FERMILAB-Conf-98/272
  • Grant Number: NONE
  • Office of Scientific & Technical Information Report Number: 2013
  • Archival Resource Key: ark:/67531/metadc670240

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  • October 1998

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  • June 29, 2015, 9:42 p.m.

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  • April 18, 2016, 3:16 p.m.

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Fry, A.; Hahn, E.; Hartung, W.; Kuchnir, M.; Michelato, P. & Sertore, D. Experience at Fermilab with high quantum efficiency photo-cathodes for rf electron guns, article, October 1998; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc670240/: accessed September 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.