A   B   C   D   E   F   G   H   I   K   L   M   O   P   Q   R   S   T   U   V   W    

feedback

Paper Title Other Keywords Page
MOP019 Methods to Reduce the Electron Beam Energy Spread at the S-DALINAC electron, linac, recirculation, controls 73
 
  • R. Eichhorn, A. Araz, U. Bonnes, M. Brunken, M. Gopych, H.-D. Gräf, S. Paret, M. Platz, A. Richter, S. Watzlawik
    TU Darmstadt, Darmstadt
  • W. F.O. Müller, B. Steiner, T. Weiland
    TEMF, Darmstadt
  The S-DALINAC is a recirculating superconducting electron linac operating at 3 GHz. The accelerator delivers a cw beam with energies up to 130 MeV to serve electron scattering experiments where highest momentum resolutions, typ. below 1·10-4 are required. Current activities aim to reduce the energy spread of the accelerator by two methods: Long term drifts, mainly a result of temperature drifts, will be corrected by a feedback system which measures the energy variation of the extracted beam continuously using rf-monitors. By means of time-of-flight analysis in a modified beamline a correction signal can be generated as a feedback for the rf control of the accelerating cavities. This system was set-up recently and first results will be reported. Furthermore, the influence of short term fluctuations, e.g. triggered by micro-phonics, on the electron energy can significantly be reduced utilizing the inherent stability of a microtron, if the synchronous phase and longitudinal dispersion are chosen properly. The concept, particle simulations and the experimental verification will be shown as well as necessary modifications to the recirculation scheme to use it in an all-day operation.  
 
TUP001 Linac Automated Beam Phase Control System linac, controls, klystron, gun 241
 
  • S. J. Pasky, M. Borland, L. Erwin, R. M. Lill, N. Sereno
    ANL, Argonne, Illinois
  Adjustment of the rf phase in a linear accelerator is crucial for maintaining optimal performance. If phasing is incorrect, the beam will in general have an energy error and increased energy spread. While an energy error can be readily detected and corrected using position readings from beam position monitors at dispersion locations, this is not helpful for correcting energy spread in a system with many possible phase errors. Uncorrected energy spread results in poor capture efficiency in downstream accelerators, such as the Advanced Photon Source (APS’s) Particle Accumulator Ring (PAR) or Booster synchrotron. To address this issue, APS has implemented beam-to-rf phase detectors in the linac, along with software for automatic correction of phase errors. We discuss the design, implementation, and performance of these detectors and how they improved APS top-up operations. * Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.  
 
TUP016 BPM DAQ System Using Fast Digital Oscilloscope linac, controls, injection, factory 280
 
  • M. Satoh, K. Furukawa, T. Suwada
    KEK, Ibaraki
  The KEK injector linac is planned to be upgraded to perform the simultaneous injection for four rings (KEKB e-/ e+, PF and PF-AR rings). In this operation mode, each rf pulse accelerates the beam with different charge and energy by controlling the low-level rf phase. For this purpose, it is strongly required to improve the BPM DAQ system. In the current system, maximum DAQ rate is strictly limited by the oscilloscope performance, and it should be improved for the 50-Hz measurement. We made decision to replace the current DAQ system by the fast digital oscilloscope. In this presentation, the system description of the new DAQ system and the result of the performance test will be presented.  
 
TUP017 A Damper System for the Electron Cooling Beam in the Recycler electron, damping, antiproton, controls 283
 
  • P. Varghese, B. Chase, P. W. Joireman
    Fermilab, Batavia, Illinois
  The antiproton stacking rate in the Fermilab Recycler has been dramatically improved with the commissioning of the Electron Cooling system last year. Various disturbance sources such as mechanical vibrations in the Pelletron , power line fluctuations and coupling from beam ramps in the nearby Main Injector have added noise components in the electron beam position in the 0.5 to 200 Hz range. An AC coupled damping feedback loop with corrector coils for horizontal and vertical position correction at two upstream points from the BPMs was added to the existing BPM system . The system provides 10 – 20 dB damping in the frequency range above without interfering with other DC beam positioning control loops.  
 
WE2003 LLRF Systems for Modern Linacs: Design and Performance controls, linac, resonance, coupling 498
 
  • A. Brandt
    DESY, Hamburg
  Near-future linac projects put yet unreached requirements on the LLRF control hardware in both performance and manageability. Meeting their field stability targets requires a clear identification of all critical items along the LLRF control loop as well as knowledge of fundamental limitations. Large-scale systems demand for extended automation concepts. The experience gained with present systems as well as dedicated experiments deliver the basis for a design of future systems. Digital hardware has evolved quickly over the past years and FPGAs became common not only in LLRF control. A high degree of digitization in various fields, as for example beam diagnostics, suggests to aim for a convergence of the digital platform designs. Channeling of efforts of different research laboratories may be the key to an affordable solution that meets all requirements and has a broad range of applications.  
 
TH1001 The Linac Coherent Light Source (LCLS) Accelerator electron, linac, undulator, diagnostics 511
 
  • J. Wu, P. Emma
    SLAC, Menlo Park, California
  The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) based on the final kilometer of the Stanford Linear Accelerator. Such an FEL requires a high energy, high brightness electron beam to drive the FEL instability to saturation. When fed by an RF-photocathode gun, and modified to include two bunch compressor chicanes, the SLAC linac will provide such a high quality beam at 14 GeV and 1-micron normalized emittance. In this talk, we report on recent linac studies, including beam stability and tolerances, longitudinal and transverse feedback systems, conventional and time-resolved diagnostics, and beam collimation systems. Construction and installation of the injector through first bunch compressor will be complete by November 2006, and electron commissioning is scheduled to begin in December of that year.  
 
THP001 Conceptual LLRF Design for the European X-FEL controls, diagnostics, klystron, resonance 559
 
  • S. Simrock, V. Ayvazyan, A. Brandt, M. Huening, W. Koprek, F. Ludwig, K. Rehlich, E. Vogel, H. C. Weddig
    DESY, Hamburg
  • M. K. Grecki, T. Jezynski
    TUL-DMCS, Lodz
  • W. J. Jalmuzna
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw
  The LLRF System for the superconducting cavities of the European X-FEL must support an amplitude and phase stability of the accelerating fields of up to 0.01% and 0.01 deg. respectively. The stability must be achieved in pulsed operation with one klystron driving 32 cavities. This goal can only be achieved with low noise downconverters for field detection, high gain feedback loops and sophisticated feedforward techniques. State-of-the art technology including analog multipliers for downconversion, fast ADCs (>100 MHz) with high resolution (up to 16 bit), and high performance data processing with FPGAs with low latency (few hundred ns) allow to meets these goals. The large number of input channels ( >100 including probe, forward and reflected signal of each of the 32 cavities) and output channels (>34 including piezo tuners for each cavity) combined with the tremendous processing power requires a distributed architecture using Gigalink interfaces for low latency data exchange.  
 
THP002 Exception Detection and Handling for Digital RF Control Systems controls, klystron, linac, radiation 562
 
  • S. Simrock, V. Ayvazyan, M. G. Hoffmann, M. Huening, W. Koprek, K. Rehlich, E. Vogel
    DESY, Hamburg
  Exception detection and handling routines will play an important role in future large scale accelerator to ensure high availability and beam stability in presence of interlock trips, varying operational parameters, and operation close to the performance limit. For superconducting linacs typical examples for exception situations include cavity quenches, coupler and klystron gun sparcs, operation close to klystron saturation, and errors in vector-sum calibration. The goal is to identify all possible exception situations which will lead to performance degradation or downtime, detect these situations and take appropriate actions as necessary.  
 
THP003 Integrated Optical Timing and RF Reference Distribution System for Large-Scale Linear Accelerators laser, electron, linac, controls 565
 
  • A. Winter, J. Becker, F. Loehl, K. Rehlich, S. Simrock
    DESY, Hamburg
  Highly-stable timing and RF reference distribution systems are required to meet the tight specifications in large scale accelerators for next generation light sources. In this paper, we present an approach based on the distribution of an optical pulse train from a mode-locked laser via timing stabilized fiber links. The timing information is contained in the precise repetition rate of the optical pulse train (~50 MHz), so RF can be extracted at end stations with a stability on the order of 10 fs. Less timing critical signals such as ADC clocks and trigger signals can be transmitted through the same stabilized fiber using a modulated cw laser operating at a different wavelength with sub-ps stability. As multiple wavelengths can propagate without interference through the fiber, it is also possible to integrate data communication in such a fiber system. This paper will review the timing system requirements and present a conceptual layout of an optical timing and reference frequency distribution system based on work done at MIT and DESY for the XFEL.  
 
THP004 Digital Low-Level RF Control Using Non-IQ Sampling controls, SNS, linac, rfq 568
 
  • L. R. Doolittle
    LBNL, Berkeley, California
  • M. S. Champion, H. Ma
    ORNL, Oak Ridge, Tennessee
  The success of digital feedback with synchronous IQ sampling for cavity field control in recent accelerator projects make this LLRF control scheme a popular choice. This short-period synchronous sampling does not, however, average out well-known defects in modern ADC and DAC hardware. That limits the achievable control precision for digital IQ LLRF controllers, while demands for precision are increasing for future accelerators such as International Linear Collider. For this reason, a collaborative effort is developing a digital LLRF control evaluation platform to experiment using coherent sampling with much longer synchronous periods, on the order of the cavity closed-loop bandwidth. This exercise will develop and test the hardware and software needed to meet greater future RF control challenges.  
 
THP005 Digital Control of Cavity Fields in the Spallation Neutron Source Superconducting Linac controls, linac, SNS, beam-loading 571
 
  • H. Ma, M. S. Champion, M. T. Crofford, K.-U. Kasemir, M. F. Piller
    ORNL, Oak Ridge, Tennessee
  • A. Brandt
    DESY, Hamburg
  • L. R. Doolittle, A. Ratti
    LBNL, Berkeley, California
  Control of the pulsed RF cavity fields in the Spallation Neutron Source (SNS) superconducting Linac uses both the real-time feedback regulation and the pulse-to-pulse adaptive feed-forward compensation. This control combination is required to deal with the typical issues associated with superconducting cavities, such as the Lorentz force detuning, mechanical resonance modes, and cavity filling. The all-digital implementation of this system provides the capabilities and flexibility necessary for achieving the required performance, and to accommodate the needs of various control schemes. The low-latency design of the digital hardware has successfully produced a wide control bandwidth, and the developed adaptive feed forward algorithms have proved to be essential for the controlled cavity filling, the suppression of the cavity mechanical resonances, and the beam loading compensation. As of this time, all 96 LLRF systems throughout the Linac have been commissioned and are in operation.  
 
THP006 Performance of a Digital LLRF Field Control System for the J-PARC Linac controls, beam-loading, linac, klystron 574
 
  • S. Michizono, S. Anami, Z. Fang, S. Yamaguchi
    KEK, Ibaraki
  • T. Kobayashi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • H. Suzuki
    JAEA, Ibaraki-ken
  Twenty high power klystrons are installed in the J-PARC linac. The requirements for the rf field stabilities are ±1% in amplitude and ±1 deg. in phase during a 500 us flat-top. In order to satisfy these requirements, we adopt the digital feedback and feed-forward system with FPGAs and a commercial DSP board. The FPGAs (Virtex-II 2000) enable a fast PI control for a vector sum of two cavity fields. The measured stability during rf pulse was ±0.15% in amplitude and ±0.15 deg in phase. The tuner control was successively operated by a way of the DSP board by measuring the phase difference between the cavity input wave and the cavity field. Beam loading effects were emulated using a beam-loading test box. By proper feed-forward, the rf stability was less than ±0.3% and ±.15 deg.  
 
THP007 Timing Distribution in Accelerators via Stabilized Optical Fiber Links laser, controls, pick-up, linac 577
 
  • J. M. Byrd, L. R. Doolittle, A. Ratti, J. W. Staples, R. B. Wilcox
    LBNL, Berkeley, California
  We present progress on fiber-optic based systems for highly stable distribution of timing signals for accelerators. This system has application for linac-based sources of ultrafast radiation which require sub-100 fsec synchronization or for very large accelerators such as the linear collider. The system is based on optical fiber links that are stabilized with an optical interferometer with RF and timing signals distributed as modulations on the optical carrier. We present measurements of the stability of this link over distances of several hundred meters and discuss issues for testing the link over 10 km.  
 
THP009 Performance of RF Reference Distribution System for the J-PARC Linac controls, linac, klystron, injection 583
 
  • T. Kobayashi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • S. Anami, S. Michizono, S. Yamaguchi
    KEK, Ibaraki
  • E. Chishiro
    JAEA, Ibaraki-ken
  Installation of the J-PARC linac machines (Phase I) has been almost completed and the beam commissioning will be started in December this year. The error of the accelerating field must be within ±1 degree in phase and ±1% in amplitude. Thus, high phase stability is required as an RF reference. Our objective concerning the phase stability of the reference aims at less than ±0.3 degrees. Last year the installation of the RF reference distribution system was completed. The reference signal is optically distributed to all of the low-level RF control systems by using E/O, O/E, Optical Amplifier and Optical Couplers and so on. The performance of this system was evaluated. The phase stability of ±0.06 degrees was obtained.  
 
THP010 Low-level RF system for STF controls, klystron, linac, superconducting-RF 586
 
  • T. Matsumoto, S. Fukuda, H. Katagiri, S. Michizono, Y. Yano
    KEK, Ibaraki
  • Z. Geng
    IHEP Beijing, Beijing
  The Super-conducting RF Test Facility (STF) has been constructed to establish the production technique of a cavity having a high gradient and operated for the high power testing of the klystron and couplers being installed in the superconducting cavities. An accelerating electric field stability of 0.3% (rms) in amplitude and 0.3 degree (rms) in phase is also required for the RF system in STF. In order to satisfy these requirements, a digital LLRF control system using FPGA is adopted, and the components required for the digital LLRF system have been developed.  
 
THP011 High Gradient Operation with the CEBAF Upgrade RF Control System controls, resonance, linac, electron 589
 
  • C. Hovater, G. K. Davis, H. Dong, A. S. Hofler, K. King, J. Musson, T. E. Plawski
    Jefferson Lab, Newport News, Virginia
  The CEBAF Accelerator at Jefferson Lab is presently a 6 GeV five pass electron accelerator consisting of two superconducting linacs joined by independent magnetic transport arcs. It is planned to increase the energy to 12 GeV with the addition of 10 new high gradient cryomodules (17+ MV/m). The higher gradients pose significant challenges beyond what the present analog low level RF (LLRF) control systems can handle reliably; therefore, a new LLRF control system is needed. A prototype system has been developed incorporating a large FPGA and using digital down and up conversion to minimize the need for analog components. The new system is more flexible and less susceptible to drifts and component nonlinearities. Because resonance control is critical to reach high gradients quickly, the new cryomodules will include a piezoelectric tuner for each cavity, and the LLRF controls must incorporate both feedback and feed-forward methods to achieve optimal resonance control performance. This paper discusses development of the new RF system, system performance for phase and amplitude stability and resonance control under Lorentz detuning measured during recent tests on a prototype cryomodule.  
 
THP012 Adaptive Tuner Control in TRIUMF ISAC 2 Superconducting LINAC using Kalman Filter controls, linac, superconducting-RF, pick-up 592
 
  • K. Fong, M. P. Laverty, Q. Zheng
    TRIUMF, Vancouver
  The TRIUMF ISAC 2 RF control system uses phase locking self-excited control. Amplitude, phase and frequency control is achieved with I/Q voltage injection, and forward RF power is minimized with a tuner feedback loop. The phase difference between the input coupler and the output pickup drives a velocity servo system to provide tuning control. However, the presence of microphonics in the cryomodule, although under control by the Quadrature loop, still presents a noisy interference on the phase difference for the tuner. The tuner will follow this noise and generate more microphonics as a result. A first-order Kalman filter is used for an estimation of the phase difference and reduces the movement of the tuner.  
 
THP013 Adaptive Control of a SC Cavity Based on the Physical Parameters Identification controls, klystron, radio-frequency, resonance 595
 
  • T. Czarski, W. J. Jalmuzna, W. Koprek, K. T. Pozniak, R. S. Romaniuk
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw
  • S. Simrock
    DESY, Hamburg
  The paper presents preliminary results of SRF cavity control by FPGA system called "SIMCON". Algebraic model of the control system including calibration and correction procedure of the signal path was discussed. In particular, there were debated the following aspects of the automatic control procedures: compensation of the input offset, calibration of the cavity channel and correction of the klystron channel (linearization). Functional structure of FPGA based SIMCON board for LLRF Cavity Control System was explained. Alghoritm of adaptive control for cavity driven with FPGA controller supported by MATLAB system was discussed. Experimental results for 8 cavities of ACC1 module controlled by the SIMCON board were shown. The resuls lead to novel method of parameters identification of cavity system in noisy and no stationary conditions.  
 
THP016 Active Compensation of Lorentz Force Detuning of a TTF 9-Cell Cavity in CRYHOLAB simulation, klystron, controls, radiation 598
 
  • G. Devanz, P. Bosland, M. Desmons, E. Jacques, M. Luong, B. Visentin
    CEA, Gif-sur-Yvette
  • M. Fouaidy
    IPN, Orsay
  Linear colliders and free-electron lasers projects based on the superconducting RF technology require high gradient pulsed operation of superconducting elliptical multicells. The cavities are subject to Lorentz force detuning which reflects on an increased RF power consumption when trying to stabilize the accelerating field during the beam passage. This pulsed detuning can be mechanically compensated using a fast piezoelectric tuner. A new tuner with integrated piezoelectric actuators has been developed in the framework of CARE/SRF european program. The tuning system has been tested on a fully equipped 9-cell TTF cavity in the CRYHOLAB horizontal cryostat using the pulsed 1.3 GHz 1 MW RF source. In virtue of the high pulse to pulse repeatability of the detuning, the compensation of Lorentz detuning was achieved successfully using a simple feed forward scheme.  
 
THP019 Commissioning of the Digital LLRF for the CEBAF Injector/Separator controls, insertion, linac, instrumentation 607
 
  • T. E. Plawski, H. Dong, C. Hovater, K. King, G. E. Lahti, J. Musson
    Jefferson Lab, Newport News, Virginia
  The design and production of the CEBAF accelerator 499 MHz digital Low-Level RF control system has been completed. The first five systems were installed for use with the CEBAF Separator RF deflecting cavities operating at 499 MHz. The next four systems were installed in the injector on the chopping cavities (also 499 MHz deflecting cavities). The new LLRF system replaced an analog system that was over 15 years old. For initial testing an extensive acceptance plan along with a LLRF test stand was developed and incorporated to assure system performance as well as reliability. Various VHDL firmware was developed and modified to support operation of this system and included specific operational diagnostics. Once the acceptance tests were completed, the new systems were installed in the accelerator, in parallel with the existing analog LLRF, for extensive in-situ testing and comparison. After system commissioning, the new RF systems were assigned to the CEBAF accelerator and turned over to Accelerator Operations. This paper will address the VHDL firmware evolution, the automated tests and the performance measurements made through out the installation and commissioning process.  
 
THP025 R&D of the Long-Life Thyratron Tube cathode, collider, controls, pick-up 622
 
  • H. Matsumoto
    KEK, Ibaraki
  • J.-S. Oh
    PAL, Pohang, Kyungbuk
  Long lifetime over 50k hours for the thyratron is essential to provide the reasonable availability of the accelerator such as X-FEL and future e+e- linear collider. The lifetime and reliability of a solid-state device are not well confirmed yet. There are some examples that show long life of a thyratron. Many thyratrons were dead due to several common causes related to circuits and operation environment rather than intrinsic problems of a device itself. Several valuable feedback systems are easily adopted to enhance the lifetime. There are still unidentified questions to be verified in the thyratron. Close collaboration between laboratories and companies is strongly requested in order to improve the lifetime and performance of a thyratron.  
 
THP058 Proposed LLRF Improvements for Fermilab 201.25 MHz Linac linac, beam-loading, coupling, pick-up 713
 
  • T. A. Butler, E. Cullerton, V. Tupikov
    Fermilab, Batavia, Illinois
  The Fermilab Proton Plan, tasked to increase the intensity and reliability of the Proton Source for 10 or more years of operation, has identified the Low Level RF (LLRF) system as the critical component to be upgraded in the Linac. The current 201.25 MHz Drift Tube Linac was designed and built over 30 years ago and does not meet the higher beam quality demands required under the new Proton Plan. Measurement data, used to characterize the system, has been collected as input for a new computer model of the system. This model shows what improvements can be made by replacing the LLRF system to improve beam quality. The model includes RF driver amplifiers, a 5 MW 7835 triode power amplifier, the high voltage switch tube modulator, and the drift tube cavity. Complete system gain and bandwidth characterization data has been collected for the 7835 triode power amplifier, modulator and RF driver stages. This model will be a useful analysis tool for present and future Linac system upgrades.  
 
THP097 FPGA BASED DIGITAL RF CONTROL FOR FLASH controls, klystron, gun, cathode 809
 
  • W. J. Jalmuzna, P. F. Fafara, W. Koprek, P. K. Perkuszewski, K. T. Pozniak, P. Pucyk, R. S. Romaniuk
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw
  • S. Simrock
    DESY, Hamburg
  Most parts of the LLRF control system used in FLASH are based on the DSP processors. Actual computation power of the system is close to the limit, the algorithm is performed in a time longer than 1μs. The only way to extend the system with new features was to add more DSP processors. This solution requires integration of new DSP board into existing system. It may cause some additional problems and delays in the machine operations. During past years very fast progress on the FPGA market was observed. Nowadays FPGA chips have reached the computation power that can be compared with DSP processors. These chips offer variety of the embedded solutions such as PowerPC, Microblaze, Nios which can be easily used in addition to fast, parallel signal processing. Moreover large number of user pins makes it possible to integrate all the elements necessary for the control into one PCB board. Therefore, for the evaluation purposes, some parts of the system were replaced by FPGA based boards. This article summarizes the FPGA boards that are currently in use and describes algorithms executed by these boards.