Electron gun for diffraction experiments off controlled molecules

TL;DR

This paper presents a newly developed dc electron gun capable of generating picosecond electron pulses for advanced diffraction experiments on controlled molecules, with detailed characterization of its coherence, focus, and resolution.

Contribution

The paper introduces a novel electron gun design with velocity-map imaging configuration, enabling precise measurement and characterization for time-resolved molecular diffraction.

Findings

Achieved electron pulses with up to 8 million electrons per pulse.

Measured coherence length and pulse duration through combined experiments and simulations.

Demonstrated diffraction quality with aluminum foil, confirming setup resolution.

Abstract

A dc electron gun, generating picosecond pulses with up to $8\times10^{6}$ electrons per pulse, was developed. Its applicability for future time-resolved-diffraction experiments on state- and conformer-selected laser-aligned or oriented gaseous samples was characterized. The focusing electrodes were arranged in a velocity-map imaging spectrometer configuration. This allowed to directly measure the spatial and velocity distributions of the electron pulses emitted from the cathode. The coherence length and pulse duration of the electron beam were characterized by these measurements combined with electron trajectory simulations. Electron diffraction data off a thin aluminum foil illustrated the coherence and resolution of the electron-gun setup.