Quasi-stable injection channels in a wakefield accelerator

TL;DR

This paper reveals complex quasi-stable injection channels in plasma wakefield accelerators, where electrons injected in specific narrow regions can remain stable and gain significantly higher energy, impacting experimental planning.

Contribution

It uncovers the existence of quasi-stable injection channels through test-particle simulations, a previously unobserved structure affecting electron acceleration in plasma wakefields.

Findings

Quasi-stable injection channels exist away from the wake centre.

Electrons in these channels can remain in the wake longer and gain more energy.

The structure influences the optimization of external injection experiments.

Abstract

The influence of initial position on the acceleration of externally-injected electrons in a plasma wakefield is investigated. Test-particle simulations show previously unobserved complex structure in the parameter space, with quasi-stable injection channels forming for particles injected in narrow regions away from the wake centre. Particles injected into these channels remain in the wake for a considerable time after dephasing, and as a result achieve significantly higher energy than their neighbours. The result is relevant to both the planning and optimisation of experiments making use of external injection.