Terahertz-driven wakefield electron acceleration

A relativistic electron source is proposed, driven by the wakefield of an intense terahertz (THz) pulse in low-density gas plasma. In contrast to the optical and near-infrared regimes, the low (3.5 THz) frequency and the long (λT = 85.6 m) wavelength of the THz pulse offers distinct advantages, such as the λ T 2 -scaling of the electron ponderomotive energy. Two-dimension-in-space and three-dimension-in-velocity particle-in-cell simulation results show that relativistic electrons of ∼1 MeV energy and high charge can be generated by an intense THz pulse at kilohertz repetition rate from a gas plasma target. These results may lead to a new regime of applications, such as ultrafast electron diffraction or high-repetition-rate gamma ray sources for materials characterization or medical radiography, which would benefit from lower energy (1-10 MeV) but higher repetition rate (∼1 kHz) sources of relativistic electrons.