Focusing Waveguide Structure for High-Gradient Electron Acceleration by Picosecond Terahertz Pulses

We propose an ultra-wideband metal–dielectric structure for high-gradient acceleration of electrons by the field of an ultrashort terahertz pulse. The structure effectively focuses the terahertz beam into the electron channel and accelerates particles under synchronism with the terahertz field. The simulations show that when using terahertz pulses obtained by conversion of laser radiation in a nonlinear crystal and having an energy of 2 μJ and a duration of about 0.5 ps of a positive electric-field polarity, the electron energy can be increased from 50 to 55.7 keV in the structure with a length of 1 mm. A scheme for a demonstration experiment is proposed, assuming that electrons are accelerated to an initial energy of 50 keV by a needle photocathode irradiated by the same laser that produces accelerating terahertz pulses.