Detailed studies of photocathodes based on Y thin films grown by PLD technique

The effects of laser fluence on the morphology of Y films in the regime characteristic of multiple-pulse laser deposition were investigated. Y thin films were deposited on Silicon and Copper substrates. The samples deposited on Silicon substrate were used to deduce the morphology and the thickness of the deposited films. On the contrary, the samples deposited on Copper substrate were tested as photocathodes in a DC photodiode cell. The interest to produce Y-based photocathodes is due to the low work function of this metal with the possibility to drive such photocathodes with a visible radiation in the radio-frequency photo-injector. In this way it is possible to reduce the thermal emittance of the photoelectron beam and to increase the photocurrent intensity by utilizing the second harmonic of Ti:Sa driver laser. The quantum efficiency was measured for the first time by using a visible CW laser diode emitting at 406 nm.