Author: Byrd, J.M.
Paper Title Page
MOOAA02 Instrumentation and Diagnostics for High Repetition Rate Linac-driven FELs 23
  • J.M. Byrd, S. De Santis, L.R. Doolittle, D. Filippetto, G. Huang, M. Placidi, A. Ratti
    LBNL, Berkeley, California, USA
  Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
One of the concepts for the next generation of linac-driven FELs is a cw superconducting linac driving an electron beam with MHz repetition rates. The beam is then switched into an array of independently configurable FELs. The demand for high brightness beams and the high rep-rate presents a number of challenges for the instrumentation and diagnostics. The high rep-rate also presents opportunities for increased beam stability because of the ability for much higher sampling rates for beam-based feedbacks. In this paper, we present our plans for instrumentation and diagnostics for such a machine.
slides icon Slides MOOAA02 [1.710 MB]  
TUOAB01 Timing and Synchronization for the APS Short Pulse X-ray Project 1077
  • F. Lenkszus, N.D. Arnold, T.G. Berenc, G. Decker, E.M. Dufresne, R.I. Farnsworth, Y.L. Li, R.M. Lill, H. Ma
    ANL, Argonne, USA
  • J.M. Byrd, L.R. Doolittle, G. Huang, R.B. Wilcox
    LBNL, Berkeley, California, USA
  Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Short-Pulse X-ray (SPX) project, which is part of the APS upgrade, will provide intense, tunable, high-repetition-rate picosecond x-ray pulses through the use of deflecting cavities operating at the 8th harmonic of the storage-ring rf. Achieving this picosecond capability while minimizing the impact to other beamlines outside the SPX zone imposes demanding timing and synchronization requirements. For example, the mismatch between the upstream and downstream deflecting cavities' rf field phase is specified to be less than 0.077 degrees root mean squared (rms) at 2815 MHz (~77 femtoseconds). Another stringent requirement is to synchronize beamline pump-probe lasers to the SPX x-ray pulse to 400 femtoseconds rms. To achieve these requirements we have entered into a collaboration with the Beam Technology group at LBNL. They have developed and demonstrated a system for distributing stable rf signals over optical fiber capable of achieving less than 20 femtoseconds rms drift and jitter over 2.2 km over 60 hours*. This paper defines the overall timing/synchronization requirements for the SPX and describes the plan to achieve them.
* R. Wilcox et al. Opt. Let. 34(20), Oct 15, 2009
slides icon Slides TUOAB01 [2.515 MB]  
TUPPP070 Next Generation Light Source R&D and Design Studies at LBNL 1762
  • J.N. Corlett, B. Austin, K.M. Baptiste, D.L. Bowring, J.M. Byrd, S. De Santis, P. Denes, R.J. Donahue, L.R. Doolittle, P. Emma, D. Filippetto, G. Huang, T. Koettig, S. Kwiatkowski, D. Li, T.P. Lou, H. Nishimura, H.A. Padmore, C. F. Papadopoulos, G.C. Pappas, G. Penn, M. Placidi, S. Prestemon, D. Prosnitz, J. Qiang, A. Ratti, M.W. Reinsch, D. Robin, F. Sannibale, D. Schlueter, R.W. Schoenlein, J.W. Staples, C. Steier, C. Sun, T. Vecchione, M. Venturini, W. Wan, R.P. Wells, R.B. Wilcox, J.S. Wurtele
    LBNL, Berkeley, California, USA
  Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
LBNL is developing design concepts for a multi-beamline soft x-ray FEL array powered by a superconducting linear accelerator, operating with a high bunch repetition rate of approximately one MHz. The cw superconducting linear accelerator is supplied by an injector based on a high-brightness, high-repetition-rate photocathode electron gun. Electron bunches are distributed from the linac to the array of independently configurable FEL beamlines with nominal bunch rates up to 100 kHz in each FEL, and with even pulse spacing. Individual FELs may be configured for different modes of operation, and each may produce high peak and average brightness x-rays with a flexible pulse format, and with pulse durations ranging from sub-femtoseconds to hundreds of femtoseconds. In this paper we describe conceptual design studies and optimizations. We describe recent developments in the design and performance parameters, and progress in R&D activities.
WEEPPB004 Status of the APEX Project at LBNL 2173
  • F. Sannibale, B.J. Bailey, K.M. Baptiste, J.M. Byrd, C.W. Cork, J.N. Corlett, S. De Santis, L.R. Doolittle, J.A. Doyle, P. Emma, J. Feng, D. Filippetto, G. Huang, H. Huang, T.D. Kramasz, S. Kwiatkowski, W.E. Norum, H.A. Padmore, C. F. Papadopoulos, G.C. Pappas, G.J. Portmann, J. Qiang, D.G. Quintas, J.W. Staples, T. Vecchione, M. Venturini, M. Vinco, W. Wan, R.P. Wells, M.S. Zolotorev, F.A. Zucca
    LBNL, Berkeley, California, USA
  • M. J. Messerly, M.A. Prantil
    LLNL, Livermore, California, USA
  • C.M. Pogue
    NPS, Monterey, California, USA
  Funding: This work was supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231.
The Advanced Photo-injector Experiment (APEX) at the Lawrence Berkeley National Laboratory is focused on the development of a high-brightness high-repetition rate (MHz-class) electron injector for X-ray FEL applications. The injector is based on a new concept gun, utilizing a normal conducting 186 MHz RF cavity operating in cw mode in conjunction with high quantum efficiency photocathodes capable of delivering the required repetition rates with available laser technology. The APEX activities are staged in 3 main phases. In Phases 0 and I, the gun will be tested at its nominal energy of 750 keV and several different photocathodes are tested at full repetition rate. In Phase II, a pulsed linac will be added for accelerating the beam at several tens of MeV to reduce space charge effects and measure the high-brightness performance of the gun when integrated in an injector scheme. At Phase II energies, the radiation shielding configuration of APEX limits the repetition rate to a maximum of several Hz. Phase 0 is under commissioning, Phase I under installation, and initial activities for Phase II are underway. This paper presents an update on the status of these activities.
WEEPPB006 LCLS Femto-second Timing and Synchronization System Update 2176
  • G. Huang, J.M. Byrd, R.B. Wilcox
    LBNL, Berkeley, California, USA
  • A.R. Fry, B.L. Hill
    SLAC, Menlo Park, California, USA
  Femto second timing and synchronization system has been installed on LCLS operation for 2 years. The requirement of more receiver at different location of the experimental hall urge us to develop a new version of receiver chassis and sync-head. Two sets of the new receiver chassis has been installed to the SXR and CXI end station. To help end user the diagnose the system, a intermediate GUI is developed to show some diagnostic information.  
WEPPC038 Status of the Short-Pulse X-ray Project at the Advanced Photon Source 2292
  • A. Nassiri, N.D. Arnold, T.G. Berenc, M. Borland, B. Brajuskovic, D.J. Bromberek, J. Carwardine, G. Decker, L. Emery, J.D. Fuerst, A.E. Grelick, D. Horan, J. Kaluzny, F. Lenkszus, R.M. Lill, J. Liu, H. Ma, V. Sajaev, T.L. Smith, B.K. Stillwell, G.J. Waldschmidt, G. Wu, B.X. Yang, Y. Yang, A. Zholents
    ANL, Argonne, USA
  • J.M. Byrd, L.R. Doolittle, G. Huang
    LBNL, Berkeley, California, USA
  • G. Cheng, G. Ciovati, P. Dhakal, G.V. Eremeev, J.J. Feingold, R.L. Geng, J. Henry, P. Kneisel, K. Macha, J.D. Mammosser, J. Matalevich, A.D. Palczewski, R.A. Rimmer, H. Wang, K.M. Wilson, M. Wiseman
    JLAB, Newport News, Virginia, USA
  • Z. Li, L. Xiao
    SLAC, Menlo Park, California, USA
  Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source Upgrade (APS-U) Project at Argonne will include generation of short-pulse x-rays based on Zholents’* deflecting cavity scheme. We have chosen superconducting (SC) cavities in order to have a continuous train of crabbed bunches and flexibility of operating modes. In collaboration with Jefferson Laboratory, we are prototyping and testing a number of single-cell deflecting cavities and associated auxiliary systems with promising initial results. In collaboration with Lawrence Berkeley National Laboratory, we are working to develop state-of-the-art timing, synchronization, and differential rf phase stability systems that are required for SPX. Collaboration with Advanced Computations Department at Stanford Linear Accelerator Center is looking into simulations of complex, multi-cavity geometries with lower- and higher-order modes waveguide dampers using ACE3P. This contribution provides the current R&D status of the SPX project.
* A. Zholents et al., NIM A 425, 385 (1999).
WEPPP073 Dynamic Feedback Model for High Repetition Rate Linac-driven FELs 2879
  • J.M. Byrd, L.R. Doolittle, P. Emma, G. Huang, A. Ratti, C. Serrano
    LBNL, Berkeley, California, USA
  Funding: Work supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
One of the concepts for the next generation of linac-driven FELs is a cw superconducting linac driving an electron beam with MHz repetition rates. One of the challenges for next generation FELs is improve the shot-to-shot stability of the energy, charge, peak current, and timing jitter of the electron beam. The use of a cw RF system with MHz beam repetition rates presents an opportunity to use broadband feedback to stabilize the beam parameters. To understand the performance of such a feedback system, we are are developing a dynamic feedback model of the machine with a focus on the longitudinal beam properties. The model is being developed as an extension of the LITrack code and will include the dynamics of the beam-cavity interaction, RF feedback, beam-based feedback, and multibunch effects. In this paper, we will present the status of this model along with results.
THPPC028 Kinetic Modeling of RF Breakdown in High-Pressure Gas-filled Cavities 3341
  • D. Rose, C.H. Thoma
    Voss Scientific, Albuquerque, New Mexico, USA
  • J.M. Byrd, D. Li
    LBNL, Berkeley, California, USA
  • R.P. Johnson, M.L. Neubauer, R. Sah
    Muons, Inc, Batavia, USA
  • A.V. Tollestrup, K. Yonehara
    Fermilab, Batavia, USA
  Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86352
Recent studies have shown that high gradients can be achieved quickly in high-pressure gas-filled cavities without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual vacuum and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of radiofrequency and surface preparation. A series of experiments at 805 MHz using hydrogen fill pressures up to 0.01 g/cm3 of H2 have demonstrated high electric field gradients and scaling with the DC Paschen law limit, up to ~30 MV/m, depending on the choice of electrode material. For higher field stresses, the breakdown characteristics deviate from the Paschen law scaling. Fully-kinetic 0D collisional particle-in-cell (PIC) simulations give breakdown characteristics in H2 and H2/SF6 mixtures in good agreement with the 805 MHz experimental results below this field stress threshold. The impact of these results on gas-filled RF accelerating cavity design will be discussed.
THPPC088 LLRF Control Algorithm for APEX 3488
  • G. Huang, K.M. Baptiste, J.M. Byrd, L.R. Doolittle, F. Sannibale
    LBNL, Berkeley, California, USA
  Advanced photo-cathode experiment is an ongoing experiment of a high repetition rate low emittance VHF band gun experiment. A low level RF control and monitor subsystem is developed base on the 5 LLRF4 board. One of them is used for low level RF control and the other 4 are used as interlock and RF monitor at different point of the system. The laser is also controlled by the system to be synced to the RF system. This paper we summarize the control algorithm used in the system firmware.  
THPPC089 LLRF Control for SPX @ APS Demonstration Experiment 3491
  • G. Huang, J.M. Byrd, K. Campbell, L.R. Doolittle, J.B. Greer
    LBNL, Berkeley, California, USA
  • N.D. Arnold, T.G. Berenc, F. Lenkszus, H. Ma
    ANL, Argonne, USA
  The SPX experiment at APS is part of the APS upgrade project, using two deflecting cavity to chirp the electron pulse and then generate short pulse x-ray. To minimize the influence to other users on the storage ring, the phase synchronization of the two deflecting cavity are required to be better then 77 femto-second. A LLRF4 board based system is designed to demonstrate the capability of meeting this requirement. This paper discuss the hardware and firmware design of the demo experiment including the cavity emulator, frequency reference generation and LLRF control algorithm.