Measurement of <20fs bunch length using coherent transition radiation

Abstract

By monitoring coherent transition radiation (CTR) with a Michelson interferometer, bunch length measurement was investigated. Less-than-20-fs electron bunches were generated by a photocathode-based linear accelerator (linac) and a magnetic bunch compressor. From the femtosecond electron bunch of 2.1 pC and 32 MeV, CTR was measured using a Michelson interferometer that had two detectors with different spectral ranges, which enhanced the detection spectral range of CTR (ranging from 3 to 50 THz) and enabled us to determine the bunch length of the electron bunch. A model based on the interferometer's frequency sensitivity was proposed and introduced to analyze the measured interferograms. The measured interferograms and the frequency spectra were explained using the model. © 2014 Published by the American Physical Society.