Dataset for 'High gradient Terahertz-driven ultrafast photogun'

Terahertz (THz)-based electron acceleration has the potential as a technology for next-generation cost-efficient compact electron sources. Although proof-of-principle demonstrations have proven 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 millimeter scale 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 a multifunction cavity for exquisite beam control. The short driving wavelength enables a peak acceleration gradient as high as ~3 GV/m. Using microjoule-level single-cycle THz pulses, we demonstrate electron beams with up to ~14 keV electron energy, 1% energy spread and ~0.02 mm mrad transverse emittance. With a highly integrated rebunching cavity the bunch is further compressed by about 10 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 spatiotemporal 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 for the first-time real applications in electron projection microscopy and diffraction. It 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.