Abstract
Numerical analysis and measurement of longitudinal bunch length of subpico- and picosecond electron beams by the fluctuation method has been carried out at the S-band twin linear accelerators at Nuclear Engineering Research Laboratory (NERL), University of Tokyo. The diagnostics method utilizes a statistical analysis of shot-noise-driven fluctuations in incoherent radiation. Measurements were performed on Cherenkov radiation emitted by∼ 1.0 ps (FWHM), 20 MeV electron bunch. As a result, the fluctuation method indicated 5 times longer than that by the streak camera. The discrepancy was caused by neglecting the influence of the transverse emittance. Then, the influence of the transverse profile upon the measurement was analyzed and discussed.