Photoemission studies on niobium for superconducting photoinjectors

This work presents an investigation of the photoemission properties of niobium. The quantum efficiency (QE) of niobium cathodes was measured for a variety of surface preparations relevant to the operation of a superconducting injector. The dependence of the QE on wavelength, applied field, and laser cleaning energy was determined. The three-step model of photoemission was adapted to fit the observed emission behavior. QE values of 6.5×10−5 for 266 nm, 1.0×10−4 for 248 nm, and 2.8×10−4 for 193 nm were observed with a bias field of 1MV∕m.