Photoemission Characteristics of PLD Grown Mg Films under UV Laser Irradiation

In this paper we report a detailed description of the laser cleaning procedure and emission performance measurement on a pulsed laser deposited Mg film. During the tests performed after the end of each cleaning operation we have observed an increase in quantum efficiency (QE) in time. Then the QE apparently stabilizes at a remarkably higher value. The study of this phenomenon and its relation to chemical composition of the residual gases of vacuum environment is important because it determines both the achievable QE value and the lifetime of the Mg film based cathode. Moreover, the stability of the QE at remarkably high values has been revealed for a time scale of several days after each laser cleaning process, in our vacuum conditions. The adsorption of reactive chemical species leading to the lowering of the Mg work function is discussed