Longitudinal bunch profile diagnostics in the 50fs range using coherent Smith-Purcell radiation

TL;DR

This paper explores using coherent Smith-Purcell radiation for single-shot, high-resolution measurement of 50 femtosecond electron bunch profiles, demonstrating feasibility and potential for shorter bunches.

Contribution

It introduces a novel application of Smith-Purcell radiation for longitudinal bunch diagnostics at femtosecond scales, with practical implementation details.

Findings

Detectable radiation in 10-1000 micrometre wavelength range.

Feasibility of reconstructing bunch shape using Kramers-Kronig technique.

Suitable for bunch charges of 10^9 electrons or more.

Abstract

We have considered the possibility of using coherent Smith-Purcell radiation for the single-shot determination of the longitudinal profile of 50 fs (FWHM) long electron bunches. This length is typical for the bunches currently produced by Laser Wakefield Acceleration and is at the limit of what is achievable by alternative techniques, such as Electro-Optic sampling. It is concluded that there are no obstacles, either theoretical or experimental, in the implementation of this technique. A set of three gratings, with periods of 15, 85 and 500 micrometres, will produce detectable energy in the wavelength region 10-1000 micrometres, which should be adequate for the reconstruction of the bunch shape by the Kramers-Kronig technique. For bunch charges of 109 electrons, or more, the radiated energy can be detected by room temperature pyroelectric detectors. The limits of possible extension of the technique to even shorter lengths are also considered.