An interdisciplinary team of researchers from DESY in Germany and MIT in the US has built a new kind of electron gun that is about the size of a matchbox. The new device uses laser-generated terahertz radiation, rather than traditional radio-frequency fields, to accelerate electrons from rest. Since terahertz radiation has a much shorter wavelength than radio waves, the new device measures just 34 × 24.5 × 16.8 mm – compared with the size of a car for traditional state-of-the-art electron guns.

This device reached an accelerating gradient of 350 MV per metre, which the team says is almost twice that of current electron guns. “We achieved an acceleration of a dense packet of 250,000 electrons from rest to 0.5 keV with minimal energy spread,” explains lead author W Ronny Huang of MIT, who carried out the work at the Center for Free-Electron Laser Science in Hamburg. The electron beams emerging from the device could already be used for low-energy electron diffraction experiments, he says, and will also have applications in ultrafast electron diffraction or for injecting electrons into linacs and X-ray light sources.