Acceleration and manipulation of electron bunches underlie most electron and X-ray devices used for ultrafast imaging and spectroscopy. New terahertz-driven concepts offer orders-of-magnitude improvements in field strengths, field gradients, laser synchronization and compactness relative to conventional radio-frequency devices, enabling shorter electron bunches and higher resolution with less infrastructure while maintaining high charge capacities (pC), repetition rates (kHz) and stability. We present a segmented terahertz electron accelerator and manipulator (STEAM) capable of performing multiple high-field operations on the 6D-phase-space of ultrashort electron bunches. With this single device, powered by few-micro-Joule, single-cycle, 0.3 THz pulses, we demonstrate record THz-acceleration of >30 keV, streaking with <10 fs resolution, focusing with >2 kT/m strength, compression to ~100 fs as well as real-time switching between these modes of operation. The STEAM device demonstrates the feasibility of THz-based electron accelerators, manipulators and diagnostic tools enabling science beyond current resolution frontiers with transformative impact.

We introduce a solution for producing ultrashort (∼fs) high charge (∼pC) from ultra-compact guns utilizing single-cycle THz pulses. We show that the readily available THz pulses with energies as low as 20 µJ are sufficient to generate multi-10 keV electron bunches. Moreover, It is demonstrated that THz energies of 2 mJ are sufficient to generate relativistic electron bunches with higher than 2 MeV energy. The high acceleration gradients possible in the structures provide 30 fs electron bunches at 30 keV energy and 45 fs bunches at 2 MeV energy. These structures will underpin future devices for strong field THz physics in general and miniaturized electron guns, in which the high fields combined with the short pulse duration enable electron beams with ultrahigh brightness.

Terahertz-based electron acceleration has recently emerged as a promising candidate for driving next-generation highbrightness electron sources. Although initial demonstrations have proven the feasibility of this technology for accelerating and manipulating the phase space of electrons, further demonstrations of exquisite timing control are required to make use of terahertz acceleration for demanding applications such as light sources and ultrafast electron diffraction. In this paper, we use a two-stage segmented-terahertz-electron-accelerator-and-manipulator (STEAM) setup to demonstrate control over the electron beam energy, energy spread, and emittance. The first rebunching stage is used to tune the duration of 55 keV electron bunches from a DC electron gun that enables femtosecond phase control at the second accelerating stage. For optimized parameters, energy spread and emittance are reduced by 4× and 6×, respectively, relative to operation with the first stage off. A record energy gain of ∼70 keV was achieved at a peak accelerating field of 200 MV/m, resulting in a >100% energy boost in a terahertz-powered accelerator for the first time. These results represent a critical step forward for the practical implementation of terahertz-powered devices in ultrafast electron sources.