Abstract
The wave guiding feature of the optical fibre optical fibres is specifically exploited to construct a novel type of electron gun to realize single-shot low-energy electron diffraction experiments with the sub-picosecond resolution for studying irreversible samples.
Highlights
In contrast to the conventional stroboscopic pump-probe scheme using hundreds of short bunches, the ultrafast streak diffraction technique exploits, ideally, a single long electron bunch in which time-varying structure information is encoded after photo-excitation of diffraction samples being probed by electron diffraction [1,2]
The long electron bunch acts as an observable time-window of the dynamics from which different temporal components are separated in space under a transient electric field generated inside the streak camera
We find a new robust mean to actively control the electron bunch length by exploiting dispersion effects of the optical fiber used for the photocathode substrate, and opening the possibility to optimize the time-window for time-resolved streak electron diffraction by tailoring geometrical parameters of the fibre and its coupling to the laser beam
Summary
In contrast to the conventional stroboscopic pump-probe scheme using hundreds of short bunches, the ultrafast streak diffraction technique exploits, ideally, a single long (typically few picoseconds) electron bunch in which time-varying structure information is encoded after photo-excitation of diffraction samples being probed by electron diffraction [1,2]. We present an optical fiber-based ultrafast lowenergy electron gun developed for time-resolved streak electron diffraction. We find a new robust mean to actively control the electron bunch length by exploiting dispersion effects of the optical fiber used for the photocathode substrate, and opening the possibility to optimize the time-window for time-resolved streak electron diffraction by tailoring geometrical parameters of the fibre and its coupling to the laser beam. Compared to conventional methods (for example, RF field induced bunch broadening or pulse stretching by using grating pairs) to deliver the picosecond long photoinjection pulses stretched from femtosecond laser pulses, our electron gun concept is relatively simple and combines all these features in a fiber optic based device
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