Electron Gun Design Study for the IUCF Beam Cooling System

The design of a low temperature electron beam cooling system for the Indiana University electron-cooled storage ring is in progress. The storage ring, which will accept the light ion beams from the existing k-200, multi-stage cyclotron facility, requires an electron beam variable in energy from about 7 to 275 keV. The electron beam system consists of a high perveance electron gun with Pierce geometry and a flat cathode. The gun and a 28 element accelerating column are immersed in a uniform longitudinal magnetic guide field. A computer modeling study of the system was conducted to determine electron beam density and transverse temperature variations as a function of anode region and accelerator column design parameters. Transverse electron beam temperatures (Et = mc2ß2¿(¿H+¿v)) of less than a few tenths of an electron volt at a maximum current density of 0.4 A/cm2 are desired over the full energy range. This was achieved in the calculations without the use of resonant focusing for a 2 Amp, 275 keV electron beam. Some systematics of the electron beam temperature variations with system design parameters are presented. A short discussion of the mechanical design of the proposed electron beam system is also given.