Generation and Measurement of 50-fs (rms) Electron Pulses

An electron source has been developed at the Stanford SUNSHINE facility which can produce electron bunches as short as 50 fs (rms) with $(2\ensuremath{-}4.6)\ifmmode\times\else\texttimes\fi{}{10}^{8}{e}^{\ensuremath{-}}$ per microbunch. This source consists of a 2.6 MeV rf gun with a thermionic cathode and an alpha magnet for bunch compression. Coherent transition radiation emitted at wavelengths equal to the bunch length and longer is used in a Michelson interferometer to determine the bunch length by optical autocorrelation. The experimental setup and results of bunch length measurements are described.