Relativistic ultrafast electron diffraction at high repetition rates

Abstract

The ability to resolve the dynamics of matter on its native temporal and spatial scales constitutes a key challenge and convergent theme across chemistry, biology, and materials science. The last couple of decades have witnessed ultrafast electron diffraction (UED) emerge as one of the forefront techniques with the sensitivity to resolve atomic motions. Increasingly sophisticated UED instruments are being developed that are aimed at increasing the beam brightness in order to observe structural signatures, but so far they have been limited to low average current beams. Here, we present the technical design and capabilities of the HiRES (High Repetition-rate Electron Scattering) instrument, which blends relativistic electrons and high repetition rates to achieve orders of magnitude improvement in average beam current compared to the existing state-of-the-art instruments. The setup utilizes a novel electron source to deliver femtosecond duration electron pulses at up to MHz repetition rates for UED experiments. Instrument response function of sub-500 fs is demonstrated with < 100 fs time resolution targeted in future. We provide example cases of diffraction measurements on solid-state and gas-phase samples, including both micro- and nanodiffraction (featuring 100 nm beam size) modes, which showcase the potential of the instrument for novel UED experiments.

A comparative review of time-resolved x-ray and electron scattering to probe structural dynamics

“…Beyond the mentioned MeV-UED facilities, various research institutions—such as Shanghai Jiao Tong University, Lawrence Berkeley National Laboratory, and Osaka University—are actively developing their own MeV-UED facilities. These endeavors go beyond the existing SLAC MeV-UED system, aiming to achieve higher temporal resolution by adopting DBA (Shanghai Jiao Tong University), 122 enhancing repetition rates with slightly reduced acceleration voltages (HiRES from Lawrence Berkeley National Laboratory), 123 or venturing into new domains like incorporating MeV-accelerated electrons into microscopy (Osaka University). 124 …”