Abstract
Terahertz (THz)-based electron acceleration has potential as a technology for next-generation cost-efficient compact electron sources. Although proof-of-principle demonstrations have proved the feasibility of many THz-driven accelerator components, THz-driven photoguns with sufficient brightness, energy and control for use in demanding ultrafast applications have yet to be achieved. Here we present a novel millimetre-scale multicell waveguide-based THz-driven photogun that exploits field enhancement to boost the electron energy, a movable cathode to achieve precise control over the accelerating phase as well as multiple cells for exquisite beam control. The short driving wavelength enables a peak acceleration gradient as high as ~3 GV m−1. Using microjoule-level single-cycle THz pulses, we demonstrate electron beams with up to ~14 keV electron energy, 1% energy spread and ~0.015 mm mrad transverse emittance. With a highly integrated rebunching cell, the bunch is further compressed by about ten times to 167 fs with ~10 fC charge. High-quality diffraction patterns of single-crystal silicon and projection microscopy images of the copper mesh are achieved. We are able to reveal the transient radial electric field developed from the charged particles on a copper mesh after photoexcitation with high spatio-temporal resolution, providing a potential scheme for plasma-based beam manipulation. Overall, these results represent a new record in energy, field gradient, beam quality and control for a THz-driven electron gun, enabling real applications in electron projection microscopy and diffraction. This is therefore a critical step and milestone in the development of all-optical THz-driven electron devices, validating the maturity of the technology and its use in precision applications.
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Data availability
The data that support the plots within this paper are available via figshare at https://doi.org/10.6084/m9.figshare.25391488 (ref. 50). All other data used in this study are available from the corresponding authors upon reasonable request. Source data are provided with this paper.
Code availability
The code used in this paper is available from the corresponding author upon reasonable request.
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Acknowledgements
The authors thank L. Qian for support with the laser system and helpful discussions regarding this work. D.Z. acknowledges support from the National Natural Science Foundation of China (grant no.12174255), the Science and Technology Commission of Shanghai Municipality (grant no. 22JC1401900), the Fundamental Research Funds for the Central Universities. F.X.K. acknowledges support from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) through the Synergy Grant AXSIS (609920), the Cluster of Excellence ‘Advanced Imaging of Matter’ of the Deutsche Forschungsgemeinschaft – EXC 2056 – project ID 390715994 and Project 655350 of the Deutsche Forschungsgemeinschaft and the accelerator on a chip programme funded by the Gordon and Betty Moore Foundation (GBMF4744). D.Z. also thanks the Yangyang Development Fund for sponsorship.
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F.X.K., D.Z. and N.H.M. conceived and coordinated the project. J.Y., X.H., D.S., L.Z. and D.Z. designed the experimental setup and carried out the experiments with the help of J.M. and P.Y. on the laser systems. T.K., T.R., M.F. and G.H.K. contributed with helpful discussion on the THz photogun design and experiments. All authors contributed to writing the article and reading and approving the final manuscript.
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Ying, J., He, X., Su, D. et al. High gradient terahertz-driven ultrafast photogun. Nat. Photon. (2024). https://doi.org/10.1038/s41566-024-01441-y
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DOI: https://doi.org/10.1038/s41566-024-01441-y
