Ultrafast electron diffraction apparatus at kiloelectron-volt energies

Electron diffraction microscopy is used to study the atomic structure of crystals. When combined with modern laser technology, ultrafast electron diffraction makes it possible to visualize atomic motion on femtosecond to picosecond timescales.

However, state-of-the-art ultrafast electron diffraction setups require very high electron energies and correspondingly large equipment; or can only supply a handful of electrons per pulse, limiting the quality of the resulting images; or only produce large electron beam sizes, necessitating correspondingly large samples.

Li et al. developed an electron diffraction apparatus that avoids these problems, supplying many electrons per pulse at kiloelectron-volt energies while maintaining small beam sizes.

“Our new apparatus occupies an unfilled niche in the field,” said author William Li. “Most other ultrafast electron diffraction machines use much higher energies, much smaller charges, or larger beam sizes, leaving this middle space relatively empty.”

The team was able to build such an apparatus thanks to their homegrown photocathodes, which they used to produce the electrons. Building the electron diffraction apparatus solved a real problem and provided a useful test of their photocathodes’ capabilities.

The team hopes their template can be used by other research groups looking to build their own electron diffraction setups. They are improving their initial design by adding a direct electron detector and including a spectrometer to learn even more about the samples they study.

“Our group is really enthusiastic about collaboration, whether it be on developing techniques, transferring technology to other groups, or on new materials systems to study,” said author Jared Maxson. “We want our work to be useful to the time-resolved community, broadly defined.”

Source: “A kiloelectron-volt ultrafast electron micro-diffraction apparatus using low emittance semiconductor photocathodes,” by W. H. Li, C. J. R. Duncan, M. B. Andorf, A. C. Bartnik, E. Bianco, L. Cultrera, A. Galdi, M. Gordon, M. Kaemingk, C. A. Pennington, L. F. Kourkoutis, I. V. Bazarov, and J. Maxson, Structural Dynamics (2022). The article can be accessed at https://doi.org/10.1063/4.0000138 .