Demonstration of an All-Optically Driven Sub-keV THz Gun

Intense ultrashort THz and optical pulses with single-cycle pulse duration became possible after the recent advances in ultrafast technologies. Using such ultrashort pulses for electron acceleration offers advantages in terms of higher thresholds for material breakdown which opens up a promising path towards increased acceleration gradients. In addition, using optically generated THz pulses enable inherently synchronized acceleration schemes, since accelerating field and particle injecting field are excited by a single seed laser. In this contribution, we present the first experimental demonstration of laser-driven THz acceleration of electrons initially at rest. It is shown that strong-field, single-cycle THz fields accelerate electrons with peak energies of up to 0.8 keV in an ultracompact THz gun with bunch charge of 40 fC. The achieved energy spreads are as low as 5.8%