Measurement of subpicosecond electron pulses

A bunch-length measuring method has been developed to measure the subpicosecond electron pulses generated at the Stanford University Short Intense Electron Source (SUNSHINE) facility. This method utilizes a far-infrared Michelson interferometer to measure coherent transition radiation emitted at wavelengths longer than or equal to the bunch length via optical autocorrelation. To analyze the measurement, a simple and systematic way has also been developed, which considers interference effects on the interferogram caused by the beam splitter; hence the electron bunch length can be easily obtained from the measurement. This simple, low-cost, frequency-resolved autocorrelation method demonstrates subpicosecond resolving power that cannot be achieved by existing time-resolved methods.