Preliminary result of bunch length measurement using a modified Michelson interferometer

Based on the femtosecond accelerator device which was built at the Shanghai Institute of Applied Physics (SINAP), recently a modified far infrared Michelson interferometer has been developed to measure the length of electron bunches via the optical autocorrelation method.Compared with our former normal Michelson interferometer, we use a hollow retroreflector instead of a flat mirror as the reflective mirror.The experimental setup and results of the bunch length measurement will be described in this paper.