MC6: Beam Instrumentation, Controls, Feedback and Operational Aspects
T03 Beam Diagnostics and Instrumentation
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Terahertz Oscilloscope for Ultrashort Electron Beams Diagnostics  
  • L.R. Zhao
    LLP, Shanghai, People’s Republic of China
  I base this proposal on paper PHYSICAL REVIEW LETTERS 122, 144801 (2019). The speaker should describe the design and demonstration of a terahertz (THz) oscilloscope for recording time information of an ultrashort electron beam. With such THz oscilloscope, nearly 50-fold longitudinal compression of a relativistic electron beam to about 15 fs (rms) is directly visualized with its arrival time determined with 3 fs accuracy. This technique bridges the gap between streaking of photoelectrons with optical lasers and deflection of relativistic electron beams with radio-frequency deflectors, and should have wide applications in many ultrashort electron-beam-based facilities. The speaker shall report on this work and review the world-wide efforts and progress in this domain.  
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Review of Source Size Measurement Techniques for Low-Emittance Synchrotron Sources  
  • N. Samadi
    University of Saskatchewan, Saskatoon, Canada
  • L.D. Chapman, L.O. Dallin
    CLS, Saskatoon, Saskatchewan, Canada
  • N. Samadi
    PSI, Villigen PSI, Switzerland
  • X. Shi
    ANL, Lemont, Illinois, USA
  Three radiation-based techniques - pinhole imaging, double-slit interferometry, and a K-edge filter-based beam position and size monitor (ps-BPM) system - are studied in detail for measuring small electron source sizes at low-emittance light sources. Each method has its advantages and limitations and provides complementary information. Pinhole imaging is the most commonly used technique which has the simplest setup but with limited resolution. Double-slit interferometry gives the highest sensitivity among the three methods. The ps-BPM system has a reasonable resolution in measuring source size and divergence, and at the same time, provides real-time information on source position and angle. A combination of multiple techniques is recommended for the full characterization of the source  
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Development of Digital Beam Position Monitor for HEPS  
  • Y.Y. Du, J.S. Cao, Y.F. Ma, Y.F. Sui, S.J. Wei, J. Yang, Q. Ye, J.H. Yue, X.E. Zhang
    IHEP, Beijing, People’s Republic of China
  High Energy Photon Source (HEPS) is a proposed the new generation light source with beam energy of 6GeV, high brightness and ultra-low beam emittance. A Digital BPM has been designed in IHEP as a R&D program to meet all requirements of both injection system and storage ring. The RF BPM architecture consists of an Analog Front-End (AFE) board and a Digital Front-End board (DFE) based on a custom platform. In this paper, we present the overall architecture of the RF BPM electronics system and performance evaluation of its first prototype, comprehending beam current, filling pattern and position measurement resolution as a function of the beam current.  
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A New Scheme for Recording Electron Bunch Shapes with High Resolution and Record Recording Length: Principle and Tests at European XFEL  
  • S. Bielawski
    PhLAM/CERCLA, Villeneuve d’Ascq Cedex, France
  • C. Evain, E. Roussel, C. Szwaj
    PhLAM/CERLA, Villeneuve d’Ascq, France
  • C. Gerth, B. Steffen
    DESY, Hamburg, Germany
  Funding: CEMPI Labex, CPER photonics for society, METEOR CNRS/MOMENTUM grant.
Non-destructive, single-shot recording of longitudinal bunch profiles is a prerequisite for accelerator commissioning and operation. A common strategy for the measurement of ultra-short electron bunches is to sample the Coulomb field with femtosecond laser pulses. In recent years, such electro-optic detection schemes evolved to compact and reliable techniques. However, serious limitations on time resolution have been encountered, when long recording lengths are required. This has been recognised as a fundamental bottleneck and coined the term "Fourier limit". We present here a novel electro-optic sampling strategy that is theoretically capable to overcome this limit and achieve femtosecond resolution for any recording length. This new approach is based on the mathematical concept of information diversity. We present first results obtained both with table-top experiments as well as at the European XFEL. This technique opens the way to ultrafast electric field shape characterization with femtosecond resolution in new situations, including longitudinal bunch profile monitoring, studies of microbunching instabilities, and THz pulses generated at free-electron lasers.
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The PolariX TDS: Experimental Verification of a Next-Generation of Transverse Deflection Structure Working in the X-Band Frequency Regime  
  • B. Marchetti, R.W. Aßmann, B. Beutner, F. Christie, B. Conrad, M.K. Czwalinna, R.T.P. D’Arcy, P. Gonzalez-Caminal, M. Hoffmann, M. Hüning, R. Jonas, K. Klose, O. Krebs, S. Lederer, D. Marx, J. Osterhoff, M. Reukauff, J. Rönsch-Schulenburg, H. Schlarb, S. Schreiber, G. Tews, M. Vogt, A. Wagner, S. Wesch, J. Zemella
    DESY, Hamburg, Germany
  • M. Bopp, H.-H. Braun, A. Citterio, P. Craievich, R. Ganter, T. Kleeb, F. Marcellini, M. Pedrozzi, E. Prat, S. Reiche
    PSI, Villigen PSI, Switzerland
  • N. Catalán Lasheras, A. Grudiev, G. McMonagle, W. Wuensch
    CERN, Meyrin, Switzerland
  The PolariX TDS (Polarizable X-Band Transverse Deflection Structure) is an innovative TDS-design operating in the X-band frequency-range invented at CERN*. The design gives full control of the streaking plane, which can be tuned in order to characterize the projections of the beam distribution in arbitrary transverse axes. This novel feature opens new opportunities for complete characterization of the electron beam including also the 3D reconstruction of the charge-density distribution of the bunch**. A collaboration of three research institutes (DESY, CERN and PSI) was formed to realize the prototype structure in view of future in-series production***. This new RF-cavity design requires very high manufacturing precision. The prototype was assembled using the high-precision-tuning-free assembly procedure developed at PSI****. Late 2019 the first PolariX TDS was installed in the FLASHForward beamline at DESY, where the expected performance of the structure has been validated during the first commissioning with electron beam. The experimental results open the path for novel and more extended beam characterization in the direction of multi-dimensional-beam-phase-space reconstruction.
*Grudiev A.,CLIC-Note-1067(2016).
**Marx D. et al.,J.Phys.:Conf. Ser.874 012077(2017).
***Marchetti al.,IPAC 2017, MOPAB044(2017).
****Craievich P. et al.,FEL 2019, WEP036(2019).
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WEVIR16 A Novel Nondestructive Diagnostic Method for MeV Ultrafast Electron Diffraction 67
  • X. Yang, M.G. Fedurin, J.J. Li, T.V. Shaftan, V.V. Smaluk, L. Wu, L. Yu, Y. Zhu
    BNL, Upton, New York, USA
  • W. Wan
    ShanghaiTech University, Shanghai, People’s Republic of China
  Funding: BNL LDRD
A real-time, nondestructive, Bragg-diffracted electron beam energy, energy-spread and spatial-pointing jitter monitor is experimentally verified by encoding the electron beam energy and spatial-pointing jitter information into the mega-electron-volt ultrafast electron diffraction pattern. The shot-to-shot fluctuation of the diffraction pattern is then decomposed to two basic modes, i.e., the distance between the Bragg peaks as well as its variation (radial mode) and the overall lateral shift of the whole pattern (drift mode). Since these two modes are completely decoupled, the Bragg-diffraction method can simultaneously measure the shot-to-shot energy fluctuation from the radial mode with 2,10-4 precision and spatial-pointing jitter from the drift mode having wide measurement span covering energy jitter range from 10-4 to 10-1. The key advantage of this method is that it allows us to extract the electron beam energy spread concurrently with the ongoing experiment and enables online optimization of the electron beam especially for future high charge single-shot ultrafast electron diffraction (UED) and ultrafast electron microscopy (UEM) experiments.
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DOI • reference for this paper ※  
About • paper received ※ 08 June 2020       paper accepted ※ 14 June 2020       issue date ※ 07 September 2020  
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