Design, fabrication, and tuning of a THz-driven electron gun

We present the design, fabrication, and cold testing of a THz-driven field emission electron gun. The gun is designed as a two-cell standing-wave structure with a copper tip inserted halfway into the first cell that serves as the field emission source. It is powered by a 110 GHz gyrotron and is expected to produce 51 fC, 360 keV electron bunches with an input power of 500 kW. Several gun structures were fabricated using a high precision diamond turned mandrel and copper electroforming. The frequencies of the cavity resonances were mechanically tuned using azimuthal compression.