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Recent research on photocathodes for photoinjectors has focused on the understanding of the photoemission process at low energy (i.e. at photon energy close to the material's work function) as well as on the study of ordered and innovative photocathode materials, with the aim of minimizing the emittance at the cathode. We here present a preliminary study on low energy photoemission from (100) oriented Ba1−xLaxSnO3 thin films, characterizing their quantum efficiency and the mean transverse energy of the photoelectrons. The aim of the study is to pave the way for future experiments on innovative photocathodes based on perovkite oxides. [ABSTRACT FROM AUTHOR]

The requirement of a short response time of a cathode with respect to the laser beam for the generation of the photoelectrons limits, in the case of SPARC photoinjectors, the choice of the cathode materials to metals that usually present response time on the order of a few tens of femtoseconds. While copper and magnesium have been extensively studied, new research activities were devoted to study the photoemission properties of yttrium and to explore the feasibility of a photocathode based on this metal. Nevertheless, to date little data has been reported in literature. We present, in this work, the results of our investigation of Y films as suitable materials for the production of bright electron beams. Bulk and thin films of Y, prepared by pulsed laser deposition on Si substrates, have been tested as photocathodes in an ultra-high vacuum photodiode chamber at 10-7 Pa. Systematic laser cleaning treatments improved the film quantum efficiency (QE) from 10-6 to 4.5×10-4 at 266 nm, comparable to those of the corresponding bulk. Preliminary QE measurements carried out in the visible range at 406 nm will be illustrated. [ABSTRACT FROM AUTHOR]

Abstract: The influence of the adsorbed gases on the photoelectron performance of Mg thin film-based photocathodes was investigated. Mg thin films were deposited on Silicon and Copper substrates by pulsed laser ablation technique. The samples deposited on Silicon substrate were used to deduce the morphology, the structure and the thickness by using different diagnostic techniques. On the contrary, the samples deposited on Copper substrate were tested as photocathodes in a DC photodiode cell. The quantum efficiency of the Mg photocathodes was systematically improved by laser cleaning treatments, which appears to be necessary before any use of a metallic photocathode. The role of the hydrogen and oxygen absorption process on the emission properties is presented and discussed. [Copyright &y& Elsevier]