Time profile monitor for femtosecond-long electron bunches

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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.