Design, construction and performance of all niobium superconducting radio frequency electron gun

Over the past several years Advanced Energy Systems, BNL, and JLab have been collaborating on the development and testing of a fully superconducting, all-niobium RF gun driven by a laser. This paper will review the simulations, design of the gun, and present results of its performance under various operating conditions. Cavity Q of 108 at 4 K and QE of 10−5 at 248 nm, charge up to 0.3 nC/RF cycle and 5 nC in 12 ns have been obtained. Even at these large charges, no effects of cavity quenching have been observed. Measurements of the cavity quality factor at various operating temperatures and quantum efficiency of Nb at superconducting temperature at various cavity field gradients, laser wavelengths and laser powers are presented. Effects of laser cleaning of the cathode and future tests using this gun will also be discussed.