On "Efficiency versus Instability in plasma accelerators"

TL;DR

This paper challenges previous claims that a fundamental efficiency-instability limit exists in plasma wakefield accelerators, suggesting instead that the relation only provides a lower bound and can be modified by recent findings on wakefields.

Contribution

The authors demonstrate that the efficiency-instability relation is not a fundamental limit but a lower bound, based on recent insights into short-range wakefields.

Findings

The efficiency-instability relation is not a fundamental limit.

Recent short-range wakefield results modify the efficiency-instability relation.

The relation provides only a lower bound for efficiency.

Abstract

Recently in a paper by Lebedev et al it was demonstrated that the efficiency of the energy transfer from the drive bunch to the witness bunch in the plasma wakefield accelerator has a limit due to the BBU instability of the witness bunch. It was stated that the efficiency-instability relation is universal and thus should be considered as a fundamental limit. In this note, we show that recent results on the short-range wakefields indicate that this relation should be modified and conclusions of the paper by Lebedev et al should be reconsidered. In particular, we argue that the efficiency-instability relation produces only the lower bound for efficiency and thus does not produce a fundamental limit.