Injector for the MURA 50-MeV Electron Accelerator. IX

Abstract

An electron gun and an inflection system which satisfy the injection requirements of the MURA 50‐MeV electron accelerator are described. Electrons emitted from a tungsten ribbon filament are accelerated to 100 keV by a converging radial field of cylindrical geometry and deflected parallel to the equilibrium orbit of the accelerator by a 60° electrostatic inflector. The inflector also provides focusing of both the radial and vertical motion of the beam. The gun and inflector are located within the guide field region of the magnets and are adjustable in position as a unit. The emittances of the system are 0.5 π and 1.0 π mrad‐cm for the horizontal and vertical motions, respectively. Although the injector is capable of delivering several hundred millamperes, it is normally operated at much lower currents since fewer than 20 mA are required to reach the space‐charge limit of the accelerator when multiturn injection techniques are employed.