The characterization of metal photo-cathode for high brightness electron beam photoinjectors
Meeting Room 126 (Accelerator Division, Bldg. 2)
Meeting Room 126
Accelerator Division, Bldg. 2
R&D activity on Cu photo-cathodes is under development at the SPARC_LAB test facility to fully characterize each stage of the photocathode ‘‘life’’ and to have a complete overview of the photoemission properties in high brightness photo-injectors. The nano (n)-machining process presented here consists in diamond milling, and blowing with dry nitrogen. This procedure reduces the roughness of the cathode surface and prevents surface contamination introduced by other techniques, such as polishing with diamond paste or the machining with oil. Both high roughness and surface contamination cause an increase of intrinsic emittance and consequently a reduction of the overall electron beam brightness. To quantify these effects, we have characterized the photocathode surface in terms of roughness measurement, and morphology and chemical composition analysis by means of Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and Atomic Force Microscopy (AFM) techniques. The effects of nmachining on the electron beam quality have been also investigated through emittance measurements before and after the surface processing technique. Finally, we present preliminary emittance studies of yttrium thin film on Cu photo-cathodes.