Enhancing ERL development in the UK

能量恢复直线加速器(ERL)具有支持未来高能物理实验的物理范围的潜力，它允许以仅适度的射频功率消耗产生高功率电子束。这是通过对用完的束流减速来提取它们的动能，并使用这些能量来加速新的束流来实现的，从而大大降低了加速器的总体功率消耗。多圈ERL对于以经济有效的方式将电子加速到GeV的10秒具有特别重要的意义。ERL被视为未来高强度轻子-强子对撞机(FCC-EH，LHeC，EIC)和自由电子激光设施(UK-XFEL)的一项使能技术。在未来4-5年内，预计国际ERL界将开始相关技术和测试设施的原型制作。这项建议的主要目的是保持英国在与ERL相关的加速器研发方面的国际领先地位。超导射频(SRF)技术对ERL的运行至关重要，而高输出束流功率要求发展机器保护和相关诊断。最后，光束线设计，包括机器中新旧束束在多个转弯时的拓扑和交错--称为填充模式--是一个重要的新研究领域，因为最近英国的研究表明，使用优化的束团模式有可能大幅提高性能。考克罗夫特研究所在所有这些领域都拥有世界领先的专业知识，因此将这些领域确定为高度优先事项。因此，在该项目中开展的研究将针对这些领域，以增强英国的持续领先地位。PPTAP的英国加速器研发路线图将突出ERL的潜在社会应用，这些应用可能发生在规模较小的设施中，而不是未来对撞机所需的设施。特别令人感兴趣的是那些光源，即通过逆康普顿散射驱动的单能伽马光源，以及与UK-XFEL协同的高平均功率自由电子激光。解决这些问题的中型ERL设施也可以成为及时部署未来对撞机项目所需关键技术的平台。在这份路线图中，在射频和ERL部分都提到了薄膜SRF，而ERL部分强调了进一步加速器研发和诊断的必要性，提到了研发的三个高优先级主题。此外，诊断和薄膜SRF的研究可能会应用于安全和医疗加速器，提供额外的社会影响。

Energy recovery linacs (ERLs) have the potential to underpin the physics reach of future high-energy physics experiments by allowing the generation of high power electron beams with only modest RF power consumption. This is achieved by extracting the kinetic energy of the spent bunches by decelerating them and using this energy to accelerate new bunches, thus drastically reducing the overall power consumption of the accelerator. Multi-turn ERLs are of particular importance for accelerating electrons to 10s of GeV in a cost effective manner. ERLs are seen as an enabling technology for future high-intensity lepton-hadron colliders (FCC-eh, LHeC, EIC) and FEL facilities (UK-XFEL). Over the next 4-5 years, it is expected that the international ERL community will begin prototyping of relevant technologies and test facilities. The main purpose of this proposal is to maintain the UK's international leadership in accelerator R&D related to ERLs.Superconducting RF (SRF) technology is essential to the operation of an ERL, and the high delivered beam powers demand development of machine protection and related diagnostics. Finally, the beam line designs, including the topology and interleaving of new and old bunches in the machine over multiple turns - known as the filling pattern - are an important new area of study since recent UK studies have shown the potential for major improvements in performance using optimised bunch patterns. The Cockcroft Institute has world-leading expertise in all of these areas and accordingly have identified these areas as high priority. Hence the research undertaken within this project will address these areas to enhance the UK's continued leadership.The UK Accelerator R&D Roadmap by PPTAP will highlight potential societal applications of ERLs that could occur on smaller scale facilities than those required for future colliders. Of particular interest are those in light sources, namely a monoenergetic gamma source driven via inverse Compton scattering, and high average power Free Electron Lasers with synergies to a UK-XFEL. A mid-scale ERL facility addressing these could also be a platform for timely deployment of the key technologies required for future collider projects. Within this roadmap, all three high-priority themes of R&D are mentioned with thin film SRF mentioned in both the RF and ERL sections, and the ERL section highlighting the need for further accelerator R&D as well as diagnostics. Furthermore, the studies on diagnostics and thin film SRF are likely to have applications for security and medical accelerators, providing additional societal impact.