Numerical study of electron acceleration by microwave-driven plasma wakefields in rectangular waveguides

TL;DR

This study uses 3D particle-in-cell simulations to analyze electron acceleration in microwave-driven plasma wakefields within rectangular waveguides, highlighting optimal injection conditions and energy gains around 100 keV over meter-scale distances.

Contribution

It provides a detailed numerical analysis of electron acceleration mechanisms and conditions in microwave-driven plasma wakefields in rectangular waveguides, which was previously not well characterized.

Findings

Electron acceleration depends strongly on injection phase and initial velocity.

Optimal acceleration occurs when electrons are pre-accelerated near the microwave pulse group velocity.

Energy gains of approximately 100 keV are achieved over meter-scale interaction lengths.

Abstract

Plasma-based acceleration schemes have attracted sustained interest as a pathway toward compact particle accelerators, owing to the large electric fields supported by plasmas. Although recent studies have demonstrated the excitation of plasma wakefields using high-power microwave pulses in plasma-filled waveguides, the conditions required for efficient electron acceleration in such configurations remain insufficiently characterized. In this work, we investigate the acceleration of externally injected electrons by microwave-driven plasma wakefields in rectangular waveguides filled with low-density plasma. Three-dimensional particle-in-cell simulations are employed to analyze the dynamics of electron injection and energy gain under both reduced and fully self-consistent numerical models. The results show that electron acceleration is strongly dependent on the injection phase and initial velocity. Optimal acceleration is achieved when electrons are pre-accelerated to velocities close to the group velocity of the driving microwave pulse. For the parameters considered, energy gains of the order of $10^2 \mathrm{keV}$ are obtained over interaction lengths of the order of meters, while maintaining a quasi-monoenergetic energy distribution under suitable injection conditions. The influence of transverse dynamics and space-charge effects is also examined, revealing additional constraints on acceleration efficiency associated with the transverse electromagnetic field of the driving microwave pulse. These results provide a quantitative assessment of the acceleration stage in microwave-driven plasma wakefield schemes and support their evaluation as a viable platform for compact plasma-based accelerators.