Ultrafast Electron Guns for the Efficient Acceleration using Single-Cycle THz Pulses

Over the past decades, advances in ultrafast technologies led to the production of intense ultrashort THz to optical pulses reaching single-cycle pulse duration. Using such pulses for electron acceleration offers advantages in terms of higher thresholds for materials breakdown, thus introducing a promising path towards increasing acceleration gradients. Conventional accelerator technology is based on either continuous wave or long pulse operation, where resonant or guiding structures are usually employed. We introduce novel structures for electron acceleration which operate with single-cycle pulses named as single-cycle ultrafast guns. The operating frequencies considered here are at THz wavelengths inspired by the recent progress in the optical generation of intense single-cycle THz pulses. We begin with designing guns for low energy pulses and proceed with structures designed for high energy pulses. More importantly, it is shown that the already achieved THz pulse energies of 20 uJ are enough to realize relativistic fields for electron acceleration. These structures will underpin future devices for fabricating miniaturized electron guns and linear accelerators