PULSE SHAPING A HIGH-CURRENT RELATIVISTIC ELECTRON-BEAM IN VACUUM

A simple method for shaping the output current pulse of a relativistic electron beam in vacuum is presented. This method has been employed to sharpen the rise time of a high-current relativistic electron beam produced by a 2-MV, 7-kA, 20-ns pulser. The beam has a pulse shape that is approximately triangular both in voltage and current, with a negligible instantaneous energy spread. The desired pulse shape is nominally rectangular in current. The technique utilizes a magnetic lens with a magnitude of approximately 1.5 kG to focus the beam. Passing beam electrons through the magnetic lens causes them to focus at different axial locations downstream from the lens depending upon their energy. The focal point of the beam current peak (corresponding to maximum energy) is then located furthest downstream. An aperture is used near the focus to select a portion of the beam having the desired parameters.