MICROWAVE ELECTRON GUN

摘要

An electron gun (10) that suppresses the non-linear space charge forces and phase-dependant focusing forces that are chiefly responsible for the high emittance of conventional electron guns. The gun comprises a resonant microwave cavity (15), a cathode (12) mounted in the cavity wall, and a momentum analyzer system (17). The resonant microwave cavity, when supplied with microwave power, supports an electromagnetic field having a high-gradient electric component directed along an acceleration axis. The cavity is formed with an exit aperture (32) at a location relative to the cathode such that emitted electrons are accelerated along the axis and pass through the exit aperture. The cavity length is chosen to allow the microwave field within the cavity volume to accelerate the electrons to an energy of about 0.5-1.0 MeV prior to the electrons' passing through the aperture. Bunching is provided by the momentum analyzer. An electron emerging from the cavity has an energy determined by the phase of the microwave field at the time of that electron's emission. Those electrons having energies corresponding to the desired inital phase value are permitted to pass through the momentum analyzer, thereby forming a prebunched electron beam for injection into a linear accelerator.