Title: The film Pb photocathodes prepared with the cathodic arc
Author: Robert Nietubyc
Institution: The Andrzej Soltan Institute for Nuclear Studies
Abstract: Superconducting thin film lead photocathodes became recently a prospective approach in constructing an electron source dedicated for long pulse and high repetition rate operating accelerators.
We report our recent works and achievements in construction and tests of such a source. In the branch of lead deposition, the efforts have been put into increase the transmission of the cathodic arc system which provides a satisfactorily macro-droplet removal from the plasma transit channel. A number of trial processes have been performed where polycrystalline and single-crystalline niobium plugs were coated. Next the surface characterization followed by cleaning procedure and quantum efficiency measurements using UV wavelength range of initiating laser were applied for deposited layers. Those experiments revealed an optimal procedure for an arc operation as well as for a laser cleaning of the Pb surface. In such conditions the value of QE equal to 0.0033 was found.
Following the preparation phase, a 100 nm lead layer was deposited onto the back wall of 1.6-cell Tesla-like accelerating structure of electron injector. Cold rf tests were performed for the cavities with and without lead. In both cases the resonant quality higher than 1010 was observed for an accelerating gradient of 46 MVm-1