Exploratory study of PWFA-driven FEL at CLARA

本计画将发展以电子束驱动电浆韦克菲尔德加速器（PWFA）为基础之自由电子雷射（FEL）。自由电子激光是一种先进的相干光源，可以对超小结构和超快过程进行成像。这些“发现引擎”，今天完全由直线加速器产生的电子束驱动，是STFC战略的主要部分。https://stfc.ukri.org/files/fel-report-2016/由激光韦克菲尔德加速器（LWFA）中的激光脉冲驱动或由等离子体韦克菲尔德加速器（PWFA）中的电子脉冲驱动的基于等离子体的加速器是已知产生短且强的高能电子束的替代加速方法。因此，它们越来越多地被认为是未来紧凑系统中自由电子激光的驱动器。然而，等离子体加速器的一个众所周知的重大挑战是产生具有足够低发射度和能量扩散的电子束，以便在波荡器装置中实现激光发射。斯特拉斯克莱德/加州大学洛杉矶分校领导的“E210：“特洛伊木马PWFA”合作和在SLAC FACET获得的第一个实验证据表明，PWFA可以产生发射度和能量扩散以及亮度比现有技术好许多个数量级的电子束。这不仅可以使等离子体加速器电子输出满足在自由电子激光中实现激光的严格要求，而且在发射度以及5D和6D亮度方面超过最好的基于直线加速器的机器（例如LCLS或欧洲XFEL）的现有技术许多数量级。这种光束可能具有变革性的影响，因为它们可以允许实现紧凑且具有成本效益的FEL，其性能超过现有的硬X射线FEL（例如LCLS或EU XFEL），包括诸如相干阿秒尺度、高亮度、单尖峰硬X射线脉冲的新颖能力。我们的目标是开发这种技术作为下一代光子源的时间后，目前和即将到来的直线加速器驱动的自由电子激光的。

This project "Exploratory Study of PWFA-FEL at CLARA" will develop electron-beam driven plasma wakefield accelerator (PWFA) based free-electron-lasers (FEL). FEL's are advanced coherent light sources which allow imaging of ultrasmall structures and ultrafast processes. These 'engines of discovery', today driven exclusively by linac-generated electron beams, are a major part of the STFC strategy https://stfc.ukri.org/files/fel-report-2016/ . Plasma-based accelerators, either driven by laser pulses in laser wakefield accelerators (LWFA) or driven by electron pulses in plasma wakefield accelerators (PWFA), are alternative acceleration methods known to produce short and intense, high energy electron beams. They are therefore increasingly considered as drivers for FEL's in future compact systems. However, a well-known substantial challenge of plasma accelerators is the production of electron beams with sufficiently low emittance and energy spread in order to achieve lasing in an undulator setup. Recent conceptual breakthroughs by the Strathclyde/UCLA-led "E210: Trojan Horse PWFA" collaboration and first experimental evidence obtained at SLAC FACET suggests that PWFA can produce electron beams with emittance and energy spread as well as brightness many orders of magnitude better than state-of-the-art. This would not only allow plasma accelerator electron output to meet the strict requirements to achieve lasing in an FEL, but also to exceed the state-of-the art of the best linac-based machines such as LCLS or European XFEL by many orders of magnitude as regards emittance as well as 5D and 6D brightness. Such beams could have transformative impact, as they may allow the realization of compact and cost-effective FEL's with a performance exceeding those of existing hard x-ray FEL's such as LCLS or the EU XFEL, including novel capabilities such as coherent attosecond-scale, high brilliance, single-spike hard X-rays pulses. We aim to develop this technology as a next-generation photon source for the time after current and upcoming linac-driven FEL's.