Time profile monitor for femtosecond-long electron bunches

自由电子激光(下一代光源)和高梯度粒子加速器领域的快速发展决定了对能够精确测量飞秒单束和调制电子束的纵向轮廓和特性的纵向束团轮廓、单激发探测器的需求。时间分布是加速器和自由电子激光性能监测和理解所必需的，它决定了加速器产生相干X射线的能力以及对粒子对撞机和医疗用途的适用性。这对于基于尾迹场相互作用的新型加速器尤其重要，在这种加速器中，对初始条件和环境对电子束参数(包括其形状和长度)的影响的了解仍处于初级阶段。因此，飞秒电子束剖析的能力对于这些新技术的发展至关重要。这项提议将通过提供基于史密斯-珀塞尔辐射的单次发射监测器的概念设计，巩固英国在高梯度粒子加速器领域的科技领先地位。这将使钻石、欧洲核子研究中心和DESY的未来研究受益于设计和建造能够监测飞秒电子束纵向轮廓的探测器的能力。这项工作将基于之前由牛津团队为SLAC方面开发的多激发(电子束平均形状)探测器的非常令人鼓舞的结果。该项目旨在逐步从技术开发阶段进入技术示范阶段。拟议的项目得到了已经开展的大量基础研究的支持(根据LC-ABD项目，部分得到了STFC的支持)，以及仍在美国SLAC的Facet进行的E203实验(部分得到了STFC UK(JAI Grant)和能源部(USA)的支持(合同DE-AC02-76SF00515))。目前安装在小平面(SLAC)的E203监视器是多镜头设备。在其操作期间，栅格和毛坯被顺序地插入，即一个接一个地插入，因此，频谱不能在一次发射中被覆盖。监控器的设计(即光栅改变机械装置、信号采集光学)是这样的，项目的目标不能通过表面的修改来实现，需要进一步的研究和开发才能设想单次发射装置的设计。所提议的项目的最终目标是产生一种单击式监控器的概念设计，使其能够从技术开发阶段过渡到技术论证阶段。概念设计将适用于满足任何能够产生飞秒(Fs)和亚飞秒电子束的加速器的需求，从而允许测量带电粒子长束(微聚束)的精细f结构，尤其是我们对支持实验感兴趣：SLAC的刻面、CERN的WAKE和FlashForward(DESY)。我们要解决的关键问题是：1.改进CSPR和背景信号分辨能力的新型光栅设计。监控器单独部件的设计3.单次CSPR监控器的概念设计这些部件还将定义项目的工作包。数据采集(DAQ)将不是该项目的一部分，因为已经为SLAC(美国)的E203实验开发了DAQ。鉴于这一项目的成功完成，长期战略是与商业伙伴合作，为今后的实验建造监测仪。

The need for a longitudinal bunch profile, single shot, detector capable of measuring accurately the longitudinal profile and features of femtosecond single and modulated electron beam is dictated by the rapid developments in the fields of Free Electron Lasers (next generation light sources) and high-gradient particle accelerators. The temporal profiling is needed for an accelerator and FEL performance monitoring and understanding, which determine its ability of coherent x-ray generation and applicability for particle colliders and medical purpose. It is especially important for novel accelerators based on wake-field interactions where understanding of the effect of the initial conditions and environment on electron beam parameters including its shape and length are still in its infancy. Therefore the capability of a femtosecond electron beam profiling is crucial for development of these novel techniques. This proposal will underpin UK science and technology leadership in the area of high gradient particle accelerators by delivering conceptual design of a single shot monitor based on Smith-Purcell radiation. This will enable future research at DIAMOND, CERN and DESY benefit from ability to design and construct the detector capable to monitor the longitudinal profile of femtosecond electron bunches. This work will be based on the previous very encouraging results of multi-shot (electron bunch average shape) detector development by Oxford team for FACET, SLAC. The project aims to gradually move from technology development phase to technology demonstration. The proposed project is underpinned by a considerable amount of basic research already carried out (partially supported by STFC under the LC-ABD project) and still on-going E203 experiment at FACET, SLAC, USA (partially supported by STFC UK (JAI grant) and Department of Energy (USA) under (contract DE-AC02-76SF00515)). The E203 monitor, which is currently installed at FACET (SLAC), is multi-shot device. During its operation the gratings and blank are inserted sequentially i.e. one after another and, hence, the frequency spectrum cannot be covered in a single shot. The design of the monitor (i.e. gratings change mechanics, signal collection optics) is such that project's goal cannot be achieved via superficial modifications and further R&D is necessary before the design of a single-shot device can be envisioned.The ultimate goal of the project proposed is to produce a conceptual design of a single-shot monitor enabling the transition from the "technology development" stage to "technology demonstration". The conceptual design will be adaptable to meet the demands of any accelerator capable generating femtosecond (fs) and sub-fs electron bunches allowing to measure fine fs-structures of long bunches (micro-bunching) of charged particles and in particular we are interested in supporting experiments: FACET at SLAC, AWAKE at CERN and FlashForward (DESY). The key issues which we will address are:1. Novel grating design to improve cSPr and background signals discrimination2. Design of monitor's individual components 3. Conceptual design of the single-shot cSPr monitorThese will also define the work packages of the project. The data acquisition (DAQ) will not be a part of this project as the DAQ has been already developed for E203 experiment at SLAC (USA). Given a successful completion of this project it is the long term strategy to engage with commercial partners in the construction of the monitors for future experiments.