Preliminary Results from a Superconducting Photocathode Sample Cavity

Pure niobium has been proposed as a photocathode material to extract directly photo-currents from the surface of a RF-gun cavity [1]. However, the quantum efficiency of niobium is ∼ 3 · 10^-4, whereas electro-or vacuum deposited lead has a ∼ 10 times higher quantum efficiency. We have designed and tested a photo-injector niobium cavity, which can be used to insert photo-cathodes made of different materials in the high electric field region of the cavity. Experiments have been conducted with niobium and lead, which show that neither the Q-values of the cavity nor the obtainable surface fields are significantly lowered. This paper reports about the results from these tests.