TUCO —  Longitudinal Diagnostics and Synchronization   (10-Sep-19   14:30—16:00)
Chair: R.K. Li, TUB, Beijing, People’s Republic of China
Paper Title Page
Terahertz-Based Sub-femtosecond Metrology of Relativistic Electron Beams  
  • R.K. Li
    TUB, Beijing, People’s Republic of China
  High brightness, ultrashort electron beams are driving various advanced scientific instruments. As we push the limits of electron beams in the time domain, the challenges include not only generating the shortest possible pulse durations, but also precisely controlling or characterizing the timing of electron beams relative to optical pulses. The optical pulses can be for example the pump laser in ultrafast electron diffraction, or the drive laser in external-injection laser plasma accelerators, etc. It is not feasible to characterize the timing between electron and laser pulses to fs level using an rf-based approach, due to the phase jitter of rf sources relative to lasers. With a laser-generated THz streaking field, the timing of electron beams can be determined at sub-fs level and the pulse duration at single fs level on a shot-by-shot basis. Showing that THz compression can significantly reduce the pulse duration and intrinsically stabilize the timing jitter of electron beams. We believe that time-domain manipulation of relativistic electron beams using laser-generated THz can significantly boost the performance of electron beam-based instruments for ultrafast science.  
slides icon Slides TUCO01 [19.114 MB]  
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TUCO02 Experimental Observation of Submillimeter Coherent Cherenkov Radiation at CLARA Facility 256
  • K.V. Fedorov, P. Karataev, A.N. Oleinik
    JAI, Egham, Surrey, United Kingdom
  • K.V. Fedorov, A. Potylitsyn, A. Potylitsyn
    TPU, Tomsk, Russia
  • P. Karataev
    Royal Holloway, University of London, Surrey, United Kingdom
  • A.N. Oleinik
    BelSU, Belgorod, Russia
  • T.H. Pacey, Y.M. Saveliev
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • T.H. Pacey
    UMAN, Manchester, United Kingdom
  • Y.M. Saveliev
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  Nowadays, the method of longitudinal beam profile diagnostic based on transition radiation (TR) spectrum is well studied [1] and is constantly being applied, while using of coherent Cherenkov radiation (CCR) is a modern task that opens up new possibilities in this area [2]. In current work we conducted experiments on CCR generation, observation and it further spectral analysis at 0.1-30 THz spectral range. All experimental work was at CLARA (beam area 1) facility (~50 MeV beam energy at up to 10 Hz pulse repetition rate with sub-ps bunch length). Inside of vacuum chamber we developed movable platform where both VCR and TR target were placed, which is allows us to observe both effects during one accelerator run. For spectral analysis we used Martin-Pupplet interferometer as it provides higher signal to noise ratio and allows us to perform instabilities normalisation. As a result we will demonstrate a selection of interferograms and spectrums (as well as reconstructed longitudinal beam profiles) for different machine setups and distances between charged particle beam and Cherenkov target. By using mathematical analysis it has been shown that CLARA bunch length was about 1.2 ps.  
slides icon Slides TUCO02 [22.952 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-TUCO02  
About • paper received ※ 03 September 2019       paper accepted ※ 10 September 2019       issue date ※ 10 November 2019  
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Upgraded Bunch Arrival-Time Monitors for the European XFEL Reaching Below 3fs Time Resolution  
  • M.K. Czwalinna, C. Gerth, H. Schlarb, B. Steffen
    DESY, Hamburg, Germany
  Free electron laser facilities, such as the European XFEL and FLASH, have increasingly high demands on the temporal stability of the electron bunches, as pump-probe experiments meanwhile aim for timing stabilities of few femtoseconds residual jitter only. For a beam-based feedback control of the linear accelerator, bunch arrival-time monitors are required that are capable of reaching measurement resolutions better than the stated timing stability goals. We report on our electro-optical bunch arrival-time monitors now achieving a time resolution better than 3 fs. This new level of precision is a first step towards the ultimate goal of reaching sub-femtosecond timing stability. The system has also been upgraded to allow for multi-beam line operation with large variations of the bunch arrival times for the different pulse trains. The characteristics of the bunch arrival-time monitor system and limitations of the state-of-the-art design will be discussed.  
slides icon Slides TUCO03 [2.481 MB]  
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TUCO04 Longitudinal Phase Space Reconstruction for the Heavy Ion Accelerator HELIAC 261
  • S. Lauber, K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, V. Gettmann, T. Kürzeder, J. List, M. Miski-Oglu
    HIM, Mainz, Germany
  • K. Aulenbacher, W.A. Barth, C. Burandt, F.D. Dziuba, P. Forck, V. Gettmann, M. Heilmann, T. Kürzeder, S. Lauber, J. List, M. Miski-Oglu, A. Rubin, T. Sieber, S. Yaramyshev
    GSI, Darmstadt, Germany
  • K. Aulenbacher
    KPH, Mainz, Germany
  • F.D. Dziuba, S. Lauber, J. List
    IKP, Mainz, Germany
  • H. Podlech, M. Schwarz
    IAP, Frankfurt am Main, Germany
  At the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany, a prototype cryomodule (Advanced Demonstrator) for the superconducting (SC) continuous wave (CW) Helmholtz Linear Accelerator (HELIAC) is under construction. A transport line, comprising quadrupole lenses, rebuncher cavities, beam correctors and sufficient beam instrumentation has been built to deliver the beam from the GSI 1.4 MeV/u High Charge Injector (HLI) to the Advanced Demonstrator, which offers a test environment for SC CW multigap cavities. In order to achieve proper phase space matching, the beam from the HLI must be characterized in detail. In a dedicated machine experiment the bunch shape has been measured with a non destructive bunch shape monitor (BSM). The BSM offers a sufficient spatial resolution to use it for reconstruction of the energy spread. Therefore, different bunch projections were obtained by altering the voltage of two rebunchers. These measurements were combined with dedicated beam dynamics simulations using the particle tracking code Dynamion. The longitudinal bunch shape and density distribution at the beginning of the matching line could be fully characterized.  
slides icon Slides TUCO04 [1.810 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-TUCO04  
About • paper received ※ 30 August 2019       paper accepted ※ 08 September 2019       issue date ※ 10 November 2019  
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