Ultralaminar 250 kV gun for fast-wave devices

Fast-wave devices require an extremely laminar electron beam with low axial velocity spread, low beam scalloping and less than 0.005 cm beam centroid offset in confined flow focusing field. The design and fabrication of a high quality electron gun for applications in fast-wave devices will be described. This gun will be used in the NRL Ubitron amplifier development program to generate a 100 A, 250 kV, 8 mm diameter beam. Design of the confined-flow magnetic field for this device will also be discussed. Varian computer design data as well as computer-controlled beam analyzer results will be presented.