Recent development in optimization of superconducting thin film lead photocathodes at NCBJ in Świerk

We report the efforts undertaken at NCBJ and some of its collaborating laboratories dedicated to prepare pure and flat lead film coated onto niobium to operate as superconducting photocathodes. Three approaches to lead cathodic arc deposition have been implemented and tested: active plasma flux filtering, passive filtering and unfiltered flux. None of them allowed us to find a proper balance between thickness and surface roughness of a cathode. At that point efforts were taken to establish post-deposition heat treatment of lead film.