Velocity bunching dynamics of attosecond electron beam in a DC-gun based high repetition-rate beamline.

We investigate the possibility of generating attosecond electron beams with sub-fC charges and a beam energy of a few MeV from a DC-gun and two super-conducting linac based high repetition-rate photoinjector, a promising candidate for next-generation high-flux ultrafast electron diffraction (UED). Using two super-conducting linac photoinjectors, a cascade velocity bunching scheme is adopted to compress the picosecond long e-beam generated by the DC-gun. Thorough dynamic simulations showed that an electron bunch with 2 × 10 3 electrons could be compressed to a few hundreds of attoseconds. In such an ultra-low charge domain, space charge induced slice energy spread is identified to be the main obstacle for further compression, and the final bunch length will become shorter with the reduction of the bunch charge in the power function. Combining merits of the ultra-short bunch duration and the high repetition-rate, such extraordinary electron beams should have great potential to further improve the temporal resolving power of UED facilities. [ABSTRACT FROM AUTHOR]