Monochromation of pulsed electron beams with terahertz radiation at a planar mirror
Phys. Rev. Applied 25, 054056 – Published 21 May, 2026
DOI: https://doi.org/10.1103/15mt-nnfc
Abstract
Exquisite control of electron beam energy is required for many electron spectroscopy and imaging applications. For both continuous and pulsed beams, the beam energy spread is fundamentally limited by the electron source, and is typically a sizable fraction of an electron-volt. In this paper, we present a means to reduce electron beam energy spread after emission to the level of a few tens of millielectron-volts rms using femtosecond photoemission and an interaction with laser-derived single- to few-cycle terahertz (THz) radiation. We show analytically and in particle tracking simulations that this interaction can remove energy spread stored in both the transverse and longitudinal degrees of freedom. We analytically formulate the limit of energy spread that this technique can achieve, and map the nonideal effects arising at high frequencies. The interaction is mediated by the beam’s passage through a mirror which is reflective of THz radiation but allows transmission of the majority of the electron beam (e.g., a wire mesh). This method then only requires beam current losses of a few tens percent, far smaller than what is achieved in prism and slit-based electron monochromators.
