Simulations of the temporal and spatial resolution for a compact time-resolved electron diffractometer

• Published in: Journal of physics. B, Atomic, molecular, and optical physics Atomic, molecular, and optical physics, 2016-02, Vol.49 (3), p.34003-34011
• Main Authors: Robinson, Matthew S, Lane, Paul D, Wann, Derek A
• Format: Article
• Language: English
• Subjects: Electron beams; Electron diffraction; Femtosecond; Photocathodes; Simulation; Solenoids; Spatial resolution; Temporal resolution; time-resolved electron diffraction
• ISSN: 0953-4075; 1361-6455
• DOI: 10.1088/0953-4075/49/3/034003

A novel compact electron gun for use in time-resolved gas electron diffraction experiments has recently been designed and commissioned. In this paper we present and discuss the extensive simulations that were performed to underpin the design in terms of the spatial and temporal qualities of the pulsed electron beam created by the ionisation of a gold photocathode using a femtosecond laser. The response of the electron pulses to a solenoid lens used to focus the electron beam has also been studied. The simulated results show that focussing the electron beam affects the overall spatial and temporal resolution of the experiment in a variety of ways, and that factors that improve the resolution of one parameter can often have a negative effect on the other. A balance must, therefore, be achieved between spatial and temporal resolution. The optimal experimental time resolution for the apparatus is predicted to be 416 fs for studies of gas-phase species, while the predicted spatial resolution of better than 2 nm−1 compares well with traditional time-averaged electron diffraction set-ups.