Measurement of transverse wakefields induced by a misaligned positron bunch in a hollow channel plasma accelerator

TL;DR

This paper reports the first quantitative measurements of transverse wakefields caused by a misaligned positron bunch in a hollow plasma channel, which are crucial for designing effective beam alignment and mitigation strategies in plasma accelerators.

Contribution

It provides the first experimental measurements of transverse wakefields in a hollow plasma channel induced by off-axis positron beams, confirming theoretical predictions.

Findings

Measurements are consistent with theory.

Transverse wakefields are significant for beam alignment.

Results inform mitigation strategies for plasma accelerators.

Abstract

Hollow channel plasma wakefield acceleration is a proposed method to provide high acceleration gradients for electrons and positrons alike: a key to future lepton colliders. However, beams which are misaligned from the channel axis induce strong transverse wakefields, deflecting beams and reducing the collider luminosity. This undesirable consequence sets a tight constraint on the alignment accuracy of the beam propagating through the channel. Direct measurements of beam misalignment-induced transverse wakefields are therefore essential for designing mitigation strategies. We present the first quantitative measurements of transverse wakefields in a hollow plasma channel, induced by an off-axis 20 GeV positron bunch, and measured with another 20 GeV lower charge trailing positron probe bunch. The measurements are largely consistent with theory.