High current electron source for linear inductive injector

The structure of a sizable cathode unit with 180 mm outer diameter and 190 mm radius of the emitter\´s spherical concave surface for a linear inductive injector accelerator has been developed. The cathode unit provides long-term work with an emission current of not less than 2500 A in microsecond pulse mode. The cathode unit is sketched. The emitter is a dispenser. Its tungsten porous matrix is built on a molybdenum base with the aid of the plasma deposition method. The matrix is impregnated by emission material. Final processing of the emitter is ion bombardment etching and vacuum osmium deposition. The cathode heater is performed as two parallel spirals with variable winding density which depends on the radial coordinate of the emitter. This solution provides homogeneous heating of the emission surface. The cathode heat saving is achieved by means of a system of holders (similar to a "squirrel circle") and reflectors. The heater power does not exceed 3 kW at the required cathode temperature range of 1000-1100degC.