We have constructed an electron gun that delivers highly charged femtosecond electron pulses to a target with kHz repetition rate. Electron pulses are generated by femtosecond laser pulses in a photoemission process and are accelerated up to 100 kV and compressed to sub-picosecond duration. Compression is essential to compensate for the space charge effect that increases the size of electron pulses in all directions significantly. The pulses are compressed transversely by magnetic lenses and longitudinally by the longitudinal electric field of a radio-frequency cavity. The longitudinal compression is achieved by decelerating the electrons in the leading edge of the pulse, and accelerating the electrons in the trailing edge of the pulse. This results in the pulse compressing and reaching the minimum pulse duration at a known distance from the compression cavity. The short pulse duration and high repetition rate will be essential to observe subpicosecond dynamic processes in molecules in gas phase with a good signal to noise ratio. A streak camera, consisting of a millimeter-sized parallel plate capacitor, was used to measure the pulse duration in situ.

Date Published: 26 September 2016
PDF: 10 pages
Proc. SPIE 9956, Ultrafast Nonlinear Imaging and Spectroscopy IV, 995602 (26 September 2016); doi: 10.1117/12.2237381

Published in SPIE Proceedings Vol. 9956:
Ultrafast Nonlinear Imaging and Spectroscopy IV
Zhiwen Liu, Editor(s)