Working at Jefferson Laboratory in Newport News, Va., researchers from that facility, from Brookhaven National Laboratory in Upton, N.Y., and from Lawrence Berkeley National Laboratory in Berkeley, Calif., have produced 20 W of broadband terahertz radiation from a particle accelerator. The development promises to open applications in the imaging of biological samples and semiconductors.In the Nov. 14 issue of Nature, the researchers report how they coaxed terahertz output from 500-fs bunches of photoelectrons in the lab's energy-recovered linear accelerator. They produced the electrons by illuminating a GaAs target with 530-nm light from a frequency-doubled Nd:YLF laser. The average power of the terahertz radiation in the experiments was approximately five orders of magnitude greater than that available from laser-driven tabletop sources.