E. Chevalley, S. Hutchins, P. Legros, G. Suberlucq, H. Trautner (CERN)
For short, high-intensity electron bunches, alkali-tellurides have proved to be a reliable photo-cathode material. Measurements of the lifetime in an RF gun of the CLIC Test Facility II at field strengths larger than 100 MV/m are presented. Before and after using them in this gun, the spectral response of the Cs-Te and Rb-Te cathodes were determined with the help of an optical parametric oscillator. The behaviour of both materials could be described by Spicer's 3-step model. Whereas the threshold for photo-emission in Cs-Te was shifted to higher photon energies, that of Rb-Te did not change. Our latest investigations on the stoichiometric ratio of the components are shown. The preparation of the photo-cathodes was monitored with 320 nm wavelength light, with the aim of improving the measurement sensitivity. The latest results on the protection of Cs-Te cathode surfaces with CsBr against pollution are summarised. New investigations on high mean current production are presented.
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