Single-Shot Smith-Purcell Longitudinal Bunch Profile Monitor for CLARA with fs resolution

在线性对撞机、尾流场加速器和下一代光源（包括x射线FELs、太赫兹光源和康普顿激光器）的背景下，准确了解电子束的纵向（时间）分布是很重要的。随着粒子束变得更短（fs尺度）或更复杂（微调制束），剖面变得越来越难以测量。因此，它是必不可少的，能够确定的时间剖面与fs分辨率，非破坏性和在一个单一的镜头。如果没有这种能力，将很难满足下一代光源的标准（产生光谱稳定，高强度和亮度的x射线脉冲），并进一步提高尾流场加速器的性能。该项目的目标是：1/设计和制造基于相干Smith-Purcell辐射的单弹纵向束剖面监测仪的第一个原型；2/将其安装在CLARA设施（STFC的Daresbury实验室）并投入使用；3/以fs分辨率测量光束轮廓，并与CLARA其他诊断设备的结果进行比较。撰写研究论文，完成并提交博士论文。这项工作将与牛津FMB和CLARA团队密切合作。这是达到目标和项目成功的必要条件。设计将以最近的研究结果和先前开发的概念设计为基础。研究及概念设计均获科技发展基金资助。监视器的开发是JAI研究计划的一部分。概念设计的操作原理已经在FACET， SLAC（美国）和LUCX， KEK（日本）进行了测试。结果表明，相干史密斯珀塞尔辐射（cSPr）是高度极化的，而背景辐射则不是。这一特性将在监视器的设计中加以利用，以尽量减少其尺寸和复杂性。为了减少时间和成本，第一个原型的构建将使用一些为FACET研究的原始多镜头监视器构建的硬件。原型将有一个单一光栅，22个光学通道（每个偏振11个通道）和安装在真空室前后的光束定位监视器。在0.2THz到1THz的频率范围内对cSPr信号进行11个频率的采样和分析，将获得10fs的分辨率。工业合作伙伴的参与对项目的成功至关重要。FMB牛津大学将带来其在粒子加速器诊断设计方面的专业知识，以及设计和测试监测器所需的专业技术知识。该学生将在FMB设施工作，开发监视器的技术设计并测试其组件。FMB将在竞争激烈的商业环境中监督，指导和提供培训，拓宽学生的经验，超出通常的学术框架。

Accurate knowledge of the longitudinal (time) profile of an electron bunch is important in the context of linear colliders, wake-field accelerators and next-generation light sources including X-ray FELs, THz sources and Compton lasers. The profile becomes progressively more difficult to measure as the particle bunches become shorter (fs-scale) or more complex (micro-modulated bunches). Therefore, it is essential to be able to determine the temporal profile with fs resolution, non-destructively and in a single shot. Without this capability it will be very difficult to satisfy the criteria for the next generation light sources (generation of spectrally stable, high intensity and luminosity X-ray pulses) and improve further the performance of wake-field accelerators. The objectives of this project are: 1/ to design and build the first prototype of a single-shot longitudinal bunch-profile monitor based on coherent Smith-Purcell radiation;2/ to install it at CLARA facility (Daresbury Laboratory, STFC) and to commission it;3/ to measure beam profiles with fs resolution and to compare the results with those from other diagnostic devices at CLARA. 4/ to write the research papers, complete and submit the PhD thesis. The work will be carried out in close collaboration with FMB Oxford and CLARA team. This is essential for reaching objectives and the project success. The design will be based on the results of recent studies and on a conceptual design previously developed. The studies and the conceptual design were supported by STFC (PRD grant and studentship). The monitor development is a part of the JAI research plan.The operational principles of the conceptual design have been tested at FACET, SLAC (USA) and LUCX, KEK (Japan). It was shown that coherent Smith Purcell radiation (cSPr) is highly polarised while the background radiation is not. This property will be exploited in the design of the monitor, in order to minimise its size and complexity. To reduce time and cost, the construction of the first prototype will use some of the hardware built for the original multi-shot monitor studied at FACET. The prototype will have a single grating, 22 optical channels (11 channels per each polarisation) and beam positioning monitors installed before and after the vacuum chamber. Sampling and analysis of the cSPr signal at 11 frequencies in the frequency range 0.2THz to 1THz will achieve 10fs resolution. The industrial partner's involvement in the project is crucial to its success. FMB Oxford will bring its expertise in design of diagnostics for particle accelerators and knowledge of specialist techniques which will be required to design and test the monitor. The student will work at FMB facilities, developing the monitor's technical design and testing its components. FMB will supervise, mentor and provide training within the competitive business environment, broadening the student's experience beyond the usual academic framework.