Relativistic ultrafast electron diffraction at high repetition rates

TL;DR

This paper introduces the HiRES instrument, which combines relativistic electrons and high repetition rates to significantly enhance average beam current in ultrafast electron diffraction, enabling new experiments in chemistry, biology, and materials science.

Contribution

The paper presents a novel high repetition rate electron diffraction instrument that achieves orders of magnitude higher average current using relativistic electrons and a new electron source.

Findings

Demonstrated femtosecond electron pulses at MHz repetition rates

Achieved high-quality diffraction on solid and gas-phase samples

Showcased potential for advanced UED experiments

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 UED instruments. The setup utilizes a novel electron source to deliver femtosecond duration electron pulses at up to MHz repetition rates for UED experiments. We provide example cases of diffraction measurements on solid-state and gas-phase samples, including both micro- and nanodiffraction modes, which showcase the potential of the instrument for novel UED experiments.