Fig. 1. (a) Radiation field of a single bunch; (b) superposition of radiation fields from the whole electron beam (eight bunches). (c) Total radiation field from the eight bunches. The horizontal axis is the longitudinal position normalized to the radiation wavelength (bunch head to the left) and the vertical axis is the amplitude of the radiation field normalized to that of a single bunch.

Fig. 2. (a) Frequency-chirped radiation from a single bunch; (b) superposition of radiation fields from the whole electron beam (eight bunches). (c) Total radiation field from the eight bunches.

Fig. 3. (a) Frequency-chirped radiation from a single bunch; (b) superposition of radiation fields from the whole electron beam (chirped bunches). (c) Total radiation field from the chirped bunches when the bunch chirp matches the undulator tapering.

Fig. 4. (a) Difference in time-of-flight for electrons launching at various rf phases in a photocathode rf gun; (b) compression ratio of the electron bunch launching at various rf phases.

Fig. 5. (a) Measured frequency-chirped electron bunch train (bunch head to the left); (b) separation of the bunch train.