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

Conference · Thu Oct 01 04:00:00 EDT 1998

OSTI ID:2013

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.

• Research Organization: Fermi National Accelerator Laboratory, Batavia, IL; Fermi National Accelerator Laboratory (FNAL), Batavia, IL
• Sponsoring Organization: USDOE Office of Energy Research (ER)
• OSTI ID: 2013
• Report Number(s): FERMILAB-Conf-98/272; ON: DE00002013
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
66 PHYSICS
Electron Guns
Photocathodes
Quantum Efficiency