Analytical Scaling Laws for Radiofrequency Based Pulse Compression in Ultrafast Electron Diffraction Beamlines

TL;DR

This paper derives analytical scaling laws for RF-based pulse compression in ultrafast electron diffraction, highlighting the dependencies on beam energy and charge, and proposing methods to achieve sub-femtosecond pulses.

Contribution

It introduces analytical formulas for pulse length limits in RF bunch compression and suggests using higher frequency RF cavities for improved ultrashort beam generation.

Findings

Relativistic energies are crucial for achieving single-digit fs pulses.

Non-linear RF curvature effects limit compression ratios.

Higher frequency RF cavities can linearize compression for sub-femtosecond pulses.

Abstract

In this paper, we use an envelope equation-based approach to obtain analytical scaling laws for the shortest pulse length achievable using radiofrequency (RF) based bunch compression. The derived formulas elucidate the dependencies on the electron beam energy and beam charge and reveal how to obtain bunches containing 1 million electrons with single-digit fs pulse lengths; relativistic energies are strongly desirable. The effect of the non-linearities associated with the RF curvature and the beam propagation in a drift is shown to strongly limit the attainability of extreme compression ratios. Using an additional higher frequency RF cavity is proposed as a method to linearize the bunch compression and enable the generation of ultrashort beams in the sub-femtosecond regime.