Generation of short THz bunch trains in a RF photoinjector

A radiofrequency electron gun joined to a compressor can generate trains of THz sub-picosecond electron pulses by illuminating the photocathode with trains of laser pulses. Assuming a prompt electron emission, each laser pulse generates an electron disk at the cathode. The disk train evolves toward a slightly modulated slug having a peculiar sawtooth energy modulation. This kind of energy modulation is transformed into a density modulation within a velocity-bunching compressor recovering at a good extent the initial multi-disk profile. The electron beam evolution is analyzed through simulations looking at its features as function of pulse and frequency characteristics of the laser and of the accelerator parameters. (c) 2007 Elsevier B.V. All rights reserved.