Keyword: cavity
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MOBL01 Diagnostic Systems for the PAL-XFEL Commissioning electron, radiation, undulator, target 11
  • C. Kim, S.Y. Baek, H. J. Choi, J.H. Hong, H.-S. Kang, G. Kim, J.H. Kim, I.S. Ko, S.J. Lee, G. Mun, B.G. Oh, B.R. Park, D.C. Shin, Y.J. Suh, H. Yang
    PAL, Pohang, Kyungbuk, Republic of Korea
  In 2011, an X-ray Free-Electron-Laser project was started in the Pohang Accelerator Laboratory (PAL-XFEL). The construction of the PAL-XFEL was finished at the end of 2015, and the commissioning was started from April 2016. The electron beam energy of 10 GeV was achieved at the end of April and the bunch compression was tried in May. The undulator commissioning was started from June. During the commissioning process, various kinds of instruments were used for the beam parameter monitoring including beam position monitors, beam profile monitors, beam charge monitors, beam arrival-time monitors, and beam loss monitors. This work will introduce the PAL-XFEL diagnostic system which was used in the commissioning process.  
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DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-MOBL01  
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MOCL02 Harmonically Resonant Cavity as a Bunch Length Monitor electron, laser, real-time, vacuum 24
  • B.F. Roberts, M.H. Pablo
    Electrodynamic, Albuquerque, New Mexico, USA
  • M.M. Ali
    ODU, Norfolk, Virginia, USA
  • E. Forman, J.M. Grames, F.E. Hannon, R. Kazimi, W. Moore, M. Poelker
    JLab, Newport News, Virginia, USA
  Funding: US DOE DE-SC0009509
RF cavities have been designed and constructed that simultaneously and exclusively resonate many harmonic TMono modes. These modes are axially symmetric and have their electric field maximum along the cavities bore. A periodic beam passing through a harmonic cavities bore excites these modes whose superposition can be measured at the cavities antenna with a sampling oscilloscope. Processing the detected waveform with the harmonic cavities transfer function yields the Fourier series of the beam, and a near real-time, non-invasive measurement of the beams longitudinal bunch shape and duration. Experiments have been performed on the 130 kV injector at the Thomas Jefferson National Accelerator Facilities Continuous Electron Beam Accelerator Facility. The harmonic cavities sensitivity was near 1 mV/μA and measured beam bunches ranging in width from 45 to 150 picoseconds (FWHM). These measurements were in close agreement with measurements made using an invasive bunch measurement system as well as predictions by a particle tracking simulations.
slides icon Slides MOCL02 [11.027 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-MOCL02  
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MOPG12 A Wire-Based Methodology to Analyse the Nanometric Resolution of an RF Cavity BPM experiment, software, alignment, dipole 63
  • S. Zorzetti, K. Artoos, F.N. Morel, P. Novotny, D. Tshilumba, M. Wendt
    CERN, Geneva, Switzerland
  • L. Fanucci
    Università di Pisa, Pisa, Italy
  Funding: The PACMAN project is funded by the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 606839
Resonant Cavity Beam Position Monitors (RF-BPMs) are diagnostic instruments capable of achieving beam position resolutions down to the nanometre scale. To date, their nanometric resolution capabilities have been predicted by simulation and verified through beam-based measurements with particle beams. In the frame of the PACMAN project at CERN, an innovative methodology has been developed to directly observe signal variations corresponding to nanometric displacements of the BPM cavity with respect to a conductive stretched wire. The cavity BPM of this R&D study operates at the TM110 dipole mode frequency of 15GHz. The concepts and details of the RF stretched wire BPM test-bench to achieve the best resolution results are presented, along with the required control hardware and software.
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MOPG25 Industrialisation of Cavity BPMs electronics, FPGA, simulation, controls 98
  • E. Yamakawa, S.T. Boogert, A. Lyapin
    JAI, Egham, Surrey, United Kingdom
  • S. Syme
    FMB Oxford, Oxford, United Kingdom
  The industrialisation project of a cavity beam position monitor (CBPM) has been commissioned aiming at providing reliable and economical CBPM systems for future Free Electron Lasers (FEL) and similar linac-based facilities. The first prototype of a CBPM system was built at Versatile Electron Linear Accelerator (VELA) in Daresbury Laboratory. We report on the measurement results from the first prototype of our system at VELA and current developments of CBPMs, down-converter electronics and DAQ system.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-MOPG25  
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MOPG50 Deflecting Cavity Dynamics for Time-Resolved Machine Studies of SXFEL User Facility electron, FEL, diagnostics, simulation 169
  • M. Song, H.X. Deng, B. Liu, D. Wang
    SINAP, Shanghai, People's Republic of China
  Radio frequency deflectors are widely used for time-resolved beam energy, emittance and radiation profile measurements in modern free electron laser facilities. Here, we present the beam dynamics aspects of the deflecting cavity of SXFEL user facility. With a targeted time resolution around 10 fs, it is expected to be an important tool for time-resolved machine studies for SXFEL user facility.  
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MOPG51 Electron Beam Longitudinal Diagnostic With Sub-Femtosecond Resolution laser, undulator, electron, diagnostics 173
  • G. Andonian, M.A. Harrison, F.H. O'Shea, A.G. Ovodenko
    RadiaBeam, Santa Monica, California, USA
  • J.P. Duris, J.B. Rosenzweig, N.S. Sudar
    UCLA, Los Angeles, California, USA
  • M.G. Fedurin, K. Kusche, I. Pogorelsky, M.N. Polyanskiy, C. Swinson
    BNL, Upton, Long Island, New York, USA
  • M.K. Weikum
    DESY, Hamburg, Germany
  Ultra-short, high brightness electron beams, with applications to next generation light sources or advanced accelerators, require enhanced resolution of the longitudinal bunch properties to study effects such as the micro-bunching instability. In this paper, we describe a diagnostic that has the promise to achieve sub-femtosecond longitudinal resolution. The diagnostic employs a laser-electron beam interaction in an undulator magnet in tandem with a RF bunch deflecting cavity to impose a angular-longitudinal coordinate correlation on the bunch which is resolvable with standard optical systems. The fundamental underlying concepts of the diagnostic have been tested experimentally at the Brookhaven National Laboratory Accelerator Test Facility (BNL ATF) with the high-brightness electron beam and >100GW IR laser operating in the TEM10 mode. The results include a systematic study of the effects of this laser mode, and energy, on the beam angular projection. Initial runs from the x-band deflecting cavity will also be presented here.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-MOPG51  
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MOPG55 Streak Camera Calibration Using RF Switches impedance, synchrotron, injection, storage-ring 186
  • U. Iriso, M. Alvarez, A.A. Nosych
    ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
  • A. Molas
    UAB, Barcelona, Spain
  The streak camera has been used to measure the bunch length since the ALBA storage ring commissioning in 2011. Previously, we developed an optical calibration system based on the Michelson interferometry. Similar to the work at the DLS*, in this report we show the calibration kit based on the different electrical delays which can be used via rf switches. We compare both calibration systems and we show measurements of the longitudinal impedance obtained with the new calibration.
*L. Bobb, A. Morgan, and G. Rehm, "Streak Camera PSF optimisation and udal sweep calibration for sub-ps bunch length measurements", Proc. of IBIC2015 (Australia)
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TUAL03 Beam Loss and Abort Diagnostics during SuperKEKB Phase-I Operation hardware, injection, kicker, timing 282
  • H. Ikeda, J.W. Flanagan, H. Fukuma, T. Furuya, M. Tobiyama
    KEK, Ibaraki, Japan
  Beam commissioning of SuperKEKB Phase-I started in Feb., 2016. In order to protect the hardware components of the accelerator against unstable Ampere class beams, the controlled beam abort system was upgraded. Because of the higher beam intensity and shorter beam lifetime than at the original KEKB, a beam abort monitor system is important for machine tuning and the safety of the components. The system collected the data of all aborts of more than 1000 in this operation period, and we diagnosed not only the hardware performance but the tuning software by analyzing the relations between beam current, loss monitor signals and RF cavity voltages. This paper will give the outline of the monitoring system, and will present typical examples of signal and diagnoses.  
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DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUAL03  
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TUPG10 LCLS-1 Cavity BPM Algorithm for Unlocked Digitizer Clock detector, timing, operation, dipole 336
  • T. Straumann, S.R. Smith
    SLAC, Menlo Park, California, USA
  Funding: Work supported by U.S. Department of Energy Contract No. DE-AC02-76SF00515
Cavity BPMs commonly use the fundamental TM010 mode (excited either in the x/y cavity itself or in a separate "reference" cavity) which is insensitive to beam position as a reference signal, not only for amplitude normalization but also as a phase/time reference to facilitate synchronous detection of the signal derived from the position-sensitive TM110 mode. When taking these signals into the digital domain the reference and position signals need to be acquired by a synchronous clock. However, unless this clock is also locked to the accelerating RF, absolute timing information is lost which affects the relative phase between reference and position signals (assuming they are not carefully tuned to the same frequency). This contribution presents a method for estimating the necessary time of arrival information based on the sampled reference signal which is used to make the signal detection insensitive to the phase of the digitizer clock. Running an unlocked digitizer clock allows for considerable simplification of infrastructure (cabling, PLLs) and thus decreases cost and eases maintenance.
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TUPG12 Design for the Diamond Longitudinal Bunch-by-Bunch Feedback Cavity impedance, resonance, HOM, coupling 340
  • A.F.D. Morgan, G. Rehm
    DLS, Oxfordshire, United Kingdom
  In 2017 it is planned to install some additional normal conducting cavities into the Diamond storage ring. In order to deal with the potential higher order modes in these we are designing a longitudinal bunch-by-bunch feedback system. This paper will focus on the design of the overloaded cavity kicker, adapted to the Diamond beam pipe cross section. The design has evolved in order to reduce the strong 3rd harmonic resonance seen on the introduction of the racetrack beam pipe. Through a combination of geometry optimisation and the addition of integrated taper transitions this harmonic has been greatly reduced while also minimising sharp resonances below 15GHz. The major features will be described, as well as the expected performance parameters.  
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TUPG16 Performance of Nanometre-Level Resolution Cavity Beam Position Monitors and Their Application in an Intra-Train Beam Position Feedback System feedback, kicker, factory, electron 352
  • N. Blaskovic Kraljevic, T. Bromwich, P. Burrows, G.B. Christian, C. Perry, R.L. Ramjiawan
    JAI, Oxford, United Kingdom
  • P. Bambade
    LAL, Orsay, France
  • D.R. Bett
    CERN, Geneva, Switzerland
  • S.W. Jang
    Korea University Sejong Campus, Sejong, Republic of Korea
  • T. Tauchi, N. Terunuma
    KEK, Ibaraki, Japan
  A system of three low-Q cavity beam position monitors (BPMs), installed in the interaction point (IP) region of the Accelerator Test Facility (ATF2) at KEK, has been designed and optimised for nanometre-level beam position resolution. The BPMs have been used to provide an input to a low-latency, intra-train beam position feedback system consisting of a digital feedback board and a custom stripline kicker with power amplifier. The feedback system has been deployed in single-pass, multi-bunch mode with the aim of demonstrating intra-train beam stabilisation on electron bunches of charge ~1 nC separated in time by c. 220 ns. The BPMs have a demonstrated resolution of below 50 nm on using the raw measured vertical positions at the three BPMs, and has been used to stabilise the beam to below the 75 nm level. Further studies have shown that the BPM resolution can be improved to around 10 nm on making use of quadrature-phase signals and the results of the latest beam tests will be presented.  
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TUPG17 Design and Beam Test Results of the Reentrant Cavity BPM for the European XFEL electronics, linac, controls, cryomodule 356
  • C. Simon, M. Luong, O. Napoly
    CEA/DSM/IRFU, France
  • N. Baboi, D. Lipka, D. Nölle, G. Petrosyan
    DESY, Hamburg, Germany
  • R. Baldinger, B. Keil, G. Marinkovic, M. Roggli
    PSI, Villigen PSI, Switzerland
  • M. Baudrier
    CEA/DRF/IRFU, Gif-sur-Yvette, France
  • L. Maurice
    CEA/IRFU, Gif-sur-Yvette, France
  The European X-ray Free Electron Laser (E-XFEL) will use reentrant beam position monitors (BPMs) in about one quarter of the superconducting cryomodules. This BPM is composed of a radiofrequency (RF) reentrant cavity with 4 antennas and an RF signal processing electronics. Hybrid couplers, near the cryomodules, generate the analog sum and difference of the raw pickup signals coming from two pairs of opposite RF feedthroughs. The resulting sum (proportional to bunch charge) and difference signals (proportional to the product of position and charge) are then filtered, down-converted by an RF front-end (RFFE), digitized, and digitally processed on an FPGA board. The task of CEA/Saclay was to cover the design, fabrication and beam tests and deliver these reentrant cavity BPMs for the E-XFEL linac in collaboration with DESY and PSI. This paper gives an overview of the reentrant BPM sys-tem with focus on the last version of the RF front end electronics, signal processing, and overall system performance. Measurement results achieved with prototypes installed at the DESY FLASH2 linac and in the E-XFEL injector are presented.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUPG17  
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TUPG21 Beam-Loss Monitoring Signals of Interlocked Events at the J-PARC Linac linac, operation, proton, EPICS 368
  • N. Hayashi, Y. Kato, A. Miura
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • K. Futatsukawa, T. Miyao
    KEK, Ibaraki, Japan
  It is important to understand why the beam gets lost during normal operation. If RF cavity gets interlocked due to its failure, it is understandable. But it is still useful to study its detail mechanism and which beam loss monitor (BLM) receives higher loss or it is more sensitive in order to reduce a numbers of interlocked events and stabilize the accelerator operation in future. The J-PARC Linac BLM has a simple data recorder system consists of multi-oscilloscopes. Although its functionality is limited, it can record events when an interlock is triggered. Particular interest is the events associate with only BLM MPS (Machine-Protection-System). They may reveal hidden problems in the accelerator.  
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TUPG28 Accelerator Optimization Through Beam Diagnostics network, diagnostics, ion, beam-diagnostic 391
  • C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  Funding: This project has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289485.
A comprehensive set of beam diagnostics is key to the successful operation and optimization of essentially any accelerator. The oPAC project received 6 M€ of funding within the EU's 7th Framework Programme. This has allowed to successfully train 23 Fellows since 2011. The network joins more than 40 institutions from all around the world, including research centers, universities and private companies. One of the project's largest work packages covers research in beam diagnostics. This includes advanced instrumentation for synchrotron light sources and medical accelerators, enhanced beam loss monitoring technologies, ultra-low emittance beam size diagnostics, diagnostics for high intensity beams, as well as the development of electronics for beam position monitors. This contribution presents an overview of the research outcomes from the diagnostics work package and the demonstrated performance of each monitor. It also shows how collaborative research helps achieving beyond state-of-the-art solutions and acts as an ideal basis for researcher training. Finally, an overview of the scientific events the network has been organizing for the wider accelerator community is given.
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TUPG46 Improvements to the LHC Schottky Monitors pick-up, insertion, synchrotron, coupling 453
  • M. Wendt, M. Betz, O.R. Jones, T. Lefèvre, T.E. Levens
    CERN, Geneva, Switzerland
  The LHC Schottky monitors have the potential to measure and monitor some important beam parameters, tune, momentum spread, chromaticity and emittance, in a non-invasive way. We present recent upgrade and improvement efforts of the transverse LHC Schottky systems operating at 4.8 GHz. This includes optimization of the slotted waveguide pickups and a re-design of the RF front-end electronics to detect the weak, incoherent Schottky signals in presence of large, coherent beam harmonics.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUPG46  
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TUPG57 5 MeV Beam Diagnostics at the Mainz Energy-Recovering Superconducting Accelerator MESA diagnostics, dipole, detector, beam-diagnostic 479
  • S. Heidrich, K. Aulenbacher
    IKP, Mainz, Germany
  Within the next few years a new energy recovering superconducting electron accelerator will be built at the institute for nuclear physics in Mainz. To adjust the properties of the beam correctly to the first acceleration in the superconducting cavities, a high resolution longitudinal beam diagnosis is required at the 5 MeV injection arc. The system employs two 90-degree vertical deflection dipoles to achieve an energy resolution of 500 eV and a phase resolution of 60 micrometers. As a second challenge the transverse emittance measurements will take place at full beam current. This demands an extremely heat resistant diagnosis system, realized by a method similar to flying wire.  
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WEAL01 Longitudinal Diagnostics Methods and Limits for Hadron Linacs linac, diagnostics, space-charge, simulation 563
  • A.P. Shishlo, A.V. Aleksandrov
    ORNL, Oak Ridge, Tennessee, USA
  Funding: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy. The United States Govern-ment retains and the publisher,
A summary of the longitudinal diagnostics for linacs is presented based on the Spallation Neutron Source (SNS) linac example. It includes acceptance phase scans, Bunch Shape Monitors (BSM), and a method based on the analysis of the stripline Beam Position Monitors (BPM) signals. The last method can deliver the longitudinal Twiss parameters of the beam. The accuracy, applicability, and limitations of this method are presented and discussed.
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DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEAL01  
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WEPG03 HOM Characterization for Beam Diagnostics at the European XFEL Injector HOM, dipole, monitoring, electron 616
  • N. Baboi, T. Hellert, L. Shi, T. Wamsat
    DESY, Hamburg, Germany
  • R.M. Jones, N.Y. Joshi, L. Shi
    UMAN, Manchester, United Kingdom
  • N.Y. Joshi
    University of Manchester, Manchester, United Kingdom
  Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 31245.
Higher Order Modes (HOM) excited by bunched elec-tron beams in accelerating cavities carry information about the beam position and phase. This principle is used at the FLASH facility, at DESY, for beam position monitoring in 1.3 and 3.9 GHz cavities. Dipole modes, which depend on the beam offset, are used. Similar monitors are now under design for the European XFEL. In addition to beam position, the beam phase with respect to the accelerating RF will be monitored using monopole modes from the first higher order monopole band. The HOM signals are available from two couplers installed on each cavity. Their monitoring will allow the on-line tracking of the phase stability over time, and we anticipate that it will improve the stability of the facility. As part of the monitor designing, the HOM spectra in the cavities of the 1.3 and 3.9 GHz cryo-modules installed in the European XFEL injector have been measured. This paper will present their dependence on the beam position. The variation in the modal distribution from cavity to cavity will be discussed. Based on the results, initial phase measurements based on a fast oscilloscope have been made.
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WEPG08 Fast Orbit Feedback with Linux PREEMPT_RT feedback, controls, insertion-device, insertion 630
  • Y.E. Tan
    SLSA, Clayton, Australia
  • D.J. Peake
    The University of Melbourne, Melbourne, Victoria, Australia
  • D.O. Tavares
    LNLS, Campinas, Brazil
  The fast orbit feedback system in development at the Australian Synchrotron aims to improve the stability of the electron beam by reducing the impact of insertion devices and targeting orbit perturbations at the line frequency (50 Hz, 100 Hz and 300 Hz). The system is designed to have a unity gain at a frequency greater than 300 Hz with a simple PI controller with harmonic suppressors in parallel (as was done at Elettra). With most of the system in place (position aggregation, power supplies and corrector coils) we decided to implement a PC based feedback system to test what has been installed as well as the effectiveness of the proposed control algorithms while the firmware for the FPGA based feedback processor is being developed. This paper will report on effectiveness of a feedback system built using a Linux Operating System with the PREEMPT patch running on an Intel CPU.  
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WEPG10 Phase and Energy Stabilization System at the S-Dalinac electron, controls, linac, injection 638
  • T. Bahlo, C. Burandt, L.E. Jürgensen, T. Kürzeder, N. Pietralla, J. Wissmann
    TU Darmstadt, Darmstadt, Germany
  • F. Hug
    IKP, Mainz, Germany
  The Superconducting Darmstadt Linear Accelerator S‑DALINAC is a recirculating electron accelerator with a design energy of 130 MeV operating in cw. Before entering the 30 MeV main accelerator the low energetic electron beam passes both a normal-conducting injector beamline preparing the beam's 3 GHz time structure as well as a superconducting 10 MeV injector beamline for preacceleration. Since the superconducting injector accelerates on-crest while the main accelerator accelerates off-crest the beam phase is crucial for the efficiency of the acceleration process and the minimization of the energy spread. Due to thermal drifts of the normal-conducting injector cavities this injection phase varies by about 0.2 degree over a timescale of an hour. In order to compensate for these drifts, a high level phase controller has been implemented. Additionally a low-energy scraper system has been installed between the injector and main linac in order to lock both the phase and the energy spread at the linac entrance. We will present the hardware for the phase controller, the control algorithm and the scraper setup. A report on measurements showing the effect of both systems will be given.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG10  
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  • L.W. Lai, F.Z. Chen, Z.C. Chen, Y.B. Leng, Y.B. Yan, W.M. Zhou
    SSRF, Shanghai, People's Republic of China
  • J. Chen
    SINAP, Shanghai, People's Republic of China
  Funding: Work supported by National Natural Science Foundation (No.11305253, 11575282)
During the past several years a digital BPM (DBPM) processor has been developed at the SINAP. After continuous development and optimization, the processor has been finalized and has come to batch application on the signal processing of cavity BPMs and stripline BPMs at the Dalian Coherent Light Source (DCLS) and the Shanghai Soft X-ray FEL (SXFEL). Tests have been done to evaluate the performances, such as the noise level, the SNR and the cross talk. The system resolution of the cavity and stripline BPMs can achieve 1um and 10um respectively. The test results on the Shanghai Deep-Ultra-Violet (SDUV) and the DCLS will be introduced.
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DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG17  
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WEPG18 Cavity BPM System for DCLS FEL, electron, pick-up, undulator 661
  • J. Chen, J. Chen, L.W. Lai, Y.B. Yan, L.Y. Yu, R.X. Yuan
    SINAP, Shanghai, People's Republic of China
  • Y.B. Leng
    SSRF, Shanghai, People's Republic of China
  Dalian Coherent Light Source (DCLS) is a new FEL fa-cility under construction in China. Cavity beam position monitor (CBPM) is employed to measure the transverse position with a micron level resolution requirement in the undulator section. The design of cavity, RF front end and data acquisition (DAQ) system will be introduced in this paper. The preliminary measurement result with beam at Shanghai Deep ultraviolet (SDUV) FEL facility will be addressed as well.  
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WEPG25 Beam Diagnostics for Charge and Position Measurements in ELI-NP GBS linac, electron, diagnostics, electronics 682
  • G. Franzini, F. Cioeta, O. Coiro, D. Pellegrini, M. Serio, A. Stella, A. Variola
    INFN/LNF, Frascati (Roma), Italy
  • A. Mostacci, S. Tocci
    University of Rome La Sapienza, Rome, Italy
  The advanced source of Gamma-ray photons to be built in Bucharest (Romania), as part of the ELI-NP European Research Infrastructure, will generate photons by Compton back-scattering in the collision between a multi-bunch electron beam and a high intensity recirculated laser pulse. An S-Band photoinjector and the following C-band Linac at a maximum energy of 720MeV, under construction by an European consortium (EurogammaS) led by INFN, will operate at 100Hz repetition rate with trains of 32 electron bunches, separated by 16ns and a 250pC nominal charge. The different BPMs and current transformers used to measure transverse beam position and charge along the LINAC are described. Design criteria, production status and bench test results of the charge and position pickups are reported in the paper, together with the related data acquisition systems.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG25  
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WEPG51 A Transverse Deflecting Structure for the Plasma Wakefield Accelerator Experiment, FLASHForward plasma, emittance, optics, quadrupole 759
  • R.T.P. D'Arcy, V. Libov, J. Osterhoff
    DESY, Hamburg, Germany
  The FLASHForward project at DESY is an innovative plasma-wakefield acceleration experiment, aiming to accelerate electron beams to GeV energies over a few centimeters of ionized gas. These accelerated beams must be of sufficient quality to be used in a free-electron laser; achievable only through rigorous analysis of both the drive- and accelerated-beam's longitudinal phase space. The pulse duration of these accelerated beams is typically in the few femtosecond range, and thus difficult to resolve with traditional diagnostic methods. In order to longitudinally resolve these very short bunch-lengths, it is necessary to utilize the properties of a transverse RF deflector (operating in the hybrid electromagnetic mode, HEM11), which provides a relation between longitudinal and transverse co-ordinates. It is proposed that this type of device, commonly known as a Transverse Deflecting Structure (TDS) due to its 'streaking' in the transverse plane, will be introduced to the FLASHForward beamline in order to perform these single-shot longitudinal phase space measurements. The initial investigations into the realization of this diagnostic tool are outlined.  
poster icon Poster WEPG51 [10.726 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG51  
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WEPG54 Bunch Shape Measurements at the National Superconducting Cyclotron Laboratory ReAccelerator (ReA3) timing, background, electron, bunching 771
  • R. Shane, S.M. Lidia, Z. Liu, S. Nash, A.C.C. Villari, O. Yair
    FRIB, East Lansing, USA
  Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University.
The longitudinal bunch shape of a reaccelerated heavy-ion beam at the National Superconducting Cyclo-tron Laboratory's (NSCL) ReA3 beamline was measured using an Ostrumov-type bunch-shape monitor. The phase of the last accelerating cavity was varied to change the bunch length, while the energy was kept constant by adjusting the amplitude of the voltage on the cavity. Two peaks were observed in the longitudinal projection of the bunch shape distribution. The widths of the two peaks did not vary much when the cavity phase was changed, while the peak separation decreased to the point that the two peaks became unresolvable as the bunching was increased. The relative amplitudes of the two peaks was very sensitive to tuning parameters. This, coupled with a lack of information about the transverse profile of the bunch, complicated the analysis and made a simple width assignment difficult. Measurements were also made with an MCP timing grid for comparison. The general shape and trend of the two data sets were similar; however, the widths measured by the timing grid were about 30-50% smaller.
poster icon Poster WEPG54 [2.160 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG54  
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WEPG77 Sub-fs Resolution with the Enhanced Operation of the X-band Transverse Deflecting Cavity using an RF pulse Compression SLED Cavity klystron, electron, operation, photon 833
  • P. Krejcik, G.B. Bowden, S. Condamoor, Y. Ding, V.A. Dolgashev, J.P. Eichner, M.A. Franzi, A.A. Haase, J.R. Lewandowski, T.J. Maxwell, S.G. Tantawi, J.W. Wang, L. Xiao, C. Xu
    SLAC, Menlo Park, California, USA
  Funding: Work supported by DOE contract DE-AC03-76SF00515.
The successful operation of the x-band transverse deflecting cavity (XTCAV) installed downstream of the LCLS undulator has been further enhanced by the recent addition of an RF pulse compression "SLED" cavity that doubles the temporal resolving power of this powerful diagnostic system for measurement of the longitudinal profile of both the electron bunch and the x-ray FEL pulse. RF pulse compression has allowed us to use the existing SLAC X-band klystron with nominal output power of 50 MW and extend the RF pulse length by a factor 4 to give us 4 times the peak power after compression. A new, innovative SLED cavity was designed and built at SLAC to operate efficiently at X-band*. The elegant design uses a small spherical cavity combined with a polarizing mode coupler hybrid. We will report on the installation, commissioning and beam measurements demonstrating the sub-femtosecond resolution of the XTCAV system.
*J.W. Wang et al., "R&D of a Super-compact SLED System at SLAC", in Proc. 7th International Particle Accelerator Conference (IPAC'16), Busan, Korea, May 2016, paper MOOCA01, pp. 39-41.
poster icon Poster WEPG77 [20.909 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG77  
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THAL03 Multi-Laser-Wire Diagnostic for the Beam Profile Measurement of a Negative Hydrogen Ion Beam in the J-PARC LINAC laser, linac, electron, ion 856
  • A. Miura, K. Okabe, M. Yoshimoto
    JAEA/J-PARC, Tokai-mura, Japan
  • I. Yamane
    KEK, Ibaraki, Japan
  In the J-PARC linac, the negative hydrogen ion beam is acceralated to be 400 MeV. Repitition rate will be increased to be from 25 Hz to 50 Hz. The half of 400 MeV beams are injected to the downstream scynchlotoron (RCS) and the other half will be transported to the planned experimental laboratory of the accelerator driven transmutation facility. One of the important issues for the high-current and high-brilliance accelerators is to understand the beam dynamics. The wire scanner monitor is reliably operated in many accelerator facilities around the world. Because the heat loading on a wire is getting increaced in high-current beam tuning, we focused to use a laser wire system. Ionization potential of the negative hydrogen ion is 0.75 eV and one electron is easily detached by a laser beam whose wavelength is adjusted by the Doppler-shift to a large cross-section point. In addition, we propose to use a new multi-laser-wire system. In the new system, we use a pair of concave millors with different diameters to make multi-paths of laser beam, and the beam waists of the laser paths are aligned in principle. In the paper, we propose the multi-laser-wire system and its application.  
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DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-THAL03  
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