Beam Modulator for an Electron Linac

A system has been developed for modulating the beam of the Cornell Electron Storage Ring injection linac. It employs a sub-modulated, high frequency Lissajous raster of the electron beam on a collimator, followed by a subharmonic prebunching. In conjunction with a two amp electron gun, a variable pattern of single, one nanocoulomb, S-band bunches is produced. The Lissajous raster is generated by two orthogonal pairs of deflection plates attached to high frequency resonant coaxial lines. Submodulation of the raster is accomplished by a single pair of upstream of deflection plates driven by a broad band miniature tetrode. Details of the design calculations, hardware, and performance are given.