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feedback

Paper Title Other Keywords Page
MOPAN009 Transverse Feedback Development at SOLEIL impedance, damping, emittance, betatron 161
 
  • R. Nagaoka
  • L. Cassinari, J.-C. Denard, J.-M. Filhol, N. Hubert, M.-P. Level, P. Marchand, C. Mariette, F. Ribeiro, R. Sreedharan
    SOLEIL, Gif-sur-Yvette
  • K. Kobayashi, T. Nakamura
    JASRI/SPring-8, Hyogo-ken
  With reduced vertical chamber aperture adopted all around the machine, the transverse impedance for the SOLEIL ring is enhanced both in its resistive-wall and broadband content. The predicted instability threshold currents being significantly low as compared to the nominal current in multibunch and in several single bunch modes, a decision was taken to install a digital bunch by bunch feedback system, with an aim to make it operational since the beginning of the storage ring operation. The system implemented comprises components developed elsewhere, particularly the FPGA processor of SPring-8, chosen among different possible solutions. Using a BPM and a stripline in the diagonal mode, a single unit of the FPGA processor board has shown to successfully suppress resistive-wall and ion induced multibunch instabilities in either one or both transverse planes. On top of the system characteristics, the paper discusses details of the obtained performance, as well as future extensions to overcome the encountered limitations.  
 
MOPAN014 DESY and ILC EDMS: Engineering Data Management for Large Scientific Projects controls, linear-collider, simulation 173
 
  • L. Hagge
  • J. Buerger, J. A. Dammann, S. Eucker, A. Herz, J. Kreutzkamp, S. Panto, D. Szepielak, P. Tumidajewicz, N. Welle
    DESY, Hamburg
  DESY is using an Engineering Data Management System (EDMS) for supporting the XFEL and PETRA III projects. The system offers a wide range of applications for managing complexity: It enables 3D CAD design collaboration, supports the manufacturing and preparation processes of s.c. cavities and provides general project documentation. The system is now also adopted by the ILC for the collaborative 3D CAD design of cryomodules in the three regions and for change management of the baseline configuration document. The DESY EDMS is based on a commercial system which has been customized to the specific needs of large scientific projects, making it a unique system. In addition to general engineering requirements, the EDMS supports ad-hoc teamwork, provides mechanisms for process industrialization and offers powerful yet easy-to-use web frontends. The paper gives an overview of the EDMS capabilities and reports experience and benefits of using the EDMS.  
 
MOPAN018 Performance of the New Coupled Bunch Feedback System at HERA-p controls, kicker, diagnostics, luminosity 185
 
  • M. G. Hoffmann
  • S. Choroba, F. Eints, U. Hurdelbrink, P. Morozov, Y. Nechaev, J. Randhahn, S. Ruzin, S. Simrock, V. Soloviev
    DESY, Hamburg
  A longitudinal broadband damper system to control coupled bunch instabilities (LMBF) has been installed in the 920~GeV proton accelereator HERA-p at the Deutsches Elektronen-Synchrotron DESY in Q4/2005. The Feedback system was fully automated, in order to relieve the operator from manual control during system operation. During comissioning in Q1/2006 it turned out that the performance goals were reached and the noise is not as much a problem as expected. The proton bunch length is significantly reduced as is the stretching of the bunches over runtime. Without additional damping the bunch length is about 1.5~ns (FWHM) at the beginning of a typical luminosity run. With the new feedback system in operation the bunch length could be decreased to 1.0 ns at best. Although the bunches get longer during the luminosity run, the integrated luminosity gain is thus up to 5%. System optimization points were found in automatic gain adjustment during acceleration ramp, oscillation level triggering and timing of kicker pulse to bunch. We describe the commissioning of the multibunch feedback system and the adjustment procedures. A performace overview after one year of operation is given.  
 
MOPAN020 Status of the Laser Master Oscillator System at FLASH laser, diagnostics, electron, controls 191
 
  • A. Winter
  • W. J. Jalmuzna
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw
  • F. Loehl, H. Schlarb, P. Schmuser
    DESY, Hamburg
  An optical synchronization system based on the timing-stabilized distribution of ultra-short optical pulses has been proposed for next generation light sources, e.g. the European XFEL. The concept will be implemented and tested at FLASH at DESY. This paper describes the status of the optical master oscillator, which consists of two mode-locked Erbium-doped fiber lasers running in parallel.  
 
MOPAN024 Commissioning of the ELETTRA Fast Orbit Feedback System electron, controls, power-supply, photon 203
 
  • M. Lonza
  • D. Bulfone, V. Forchi', G. Gaio
    ELETTRA, Basovizza, Trieste
  A fast orbit feedback system has been installed at ELETTRA. It globally corrects the closed orbit at 10 kHz rate using all the BPMs and corrector magnets of the storage ring. The Libera Electron device has been used to upgrade the original detectors in order to provide micrometric accuracy and fast data rate of the beam position measurements. The article reports the experience gained during the commissioning of the system and the first operational results.  
 
MOPAN030 Analysis of Transverse Beam Oscillation at Photon Factory betatron, injection, damping, factory 221
 
  • W. X. Cheng
  • T. Obina
    KEK, Ibaraki
  FPGA based bunch by bunch feedback system to cure the transverse instabilities has been in operation stably since Oct. 2005. Specification and performance of the system will be introduced, transient measurement has been done to analyze the instability modes, which helps to understand the instability sources. Bunch by bunch beam oscillation, together with the digital turn-by-turn beam position measurement, injection oscillation damping is recorded and analyzed, transverse beam oscillation with and without the bunch by bunch feedback system will be shown in this paper. Precise tune measurement during this period will be presented. Turn by turn phase space monitor is also available with the data, from which the nonlinear beam dynamics can be revealed.  
 
MOPAN036 Longitudinal Feedback System for the Photon Factory kicker, synchrotron, factory, impedance 233
 
  • T. Obina
  • W. X. Cheng, T. Honda, M. Tobiyama
    KEK, Ibaraki
  In the KEK-PF, longitudinal coupled-bunch instabilities are suppressed by means of the RF phase-modulation technique during the users operation. This method is very effective not only to suppress the instabilities but also to enlarge the beam lifetime. Together with the feasibility study for top-up operation, bunch-by-bunch feedback system have been developed. A two-port longitudinal kicker based on dafne-type cavity were designed and installed in the storage ring in the summer of 2006. FPGA-based signal processing part is under development based on the KEKB design. As an preliminary test of the longitudinal kicker, a simple mode-feedback system which suppress a specific coupled-bunch mode were tested successfully.  
 
MOPAN043 Beam Charge Feedback System for Thermionic Cathode RF-Gun cathode, controls, gun, electron 254
 
  • H. Ohgaki
  • T. Kii, K. Masuda, T. Yamazaki, K. Yoshikawa, H. Zen
    Kyoto IAE, Kyoto
  A beam current feedback system to stabilize the long-time operation of thermionic cathode RF-Gun has been developed in Kyoto University FEL facility where a 4.5-cell thermionic cathode RF-gun provides electron beam to drive a mid-infrared free electron laser. However, the back-bomberdment effect seriously increases the temperature of the cathode surface, and thus the stable operation was quit difficult without continuous control of the cathode temperature or the beam current. We have tried to stabilize the beam current by using a feedback system. The beam current was monitored with current transformer, which was located at the exit of the gun or at the downstream of the energy analyzer, was read by oscilloscope. The total charge was calculated in a PC and the LabView PID-unit controlled the cathode heater current. As a result, the long term stability of the beam current dramatically improved.  
 
MOPAN053 Development of Transverse Feedback System and Instabilities Suppress at HLS kicker, single-bunch, storage-ring, impedance 269
 
  • J. H. Wang
  • J. Cao, L. Ma, J. Yue
    IHEP Beijing, Beijing
  • Y. B. Chen, L. J. Huang, W. Li, L. Liu, B. Sun, L. Wang, Y. L. Yang, K. Zheng, Z. R. Zhou
    USTC/NSRL, Hefei, Anhui
  • D. K. Liu, K. R. Ye
    SINAP, Shanghai
  In order to cure and damp coupled bunch (CB) instabilities, a transverse bunch-by-bunch feedback system is under commission at Hefei Light Source (HLS). In this paper, we introduce the HLS Bunch-by-Bunch measurement system and transverse feedback system. The experiment result in HLS ring is also presented in this paper.  
 
MOPAN054 Beam Instabilities Measurement and Cures at HLS injection, electron, synchrotron, storage-ring 272
 
  • Y. L. Yang
  • Y. B. Chen, L. J. Huang, W. Li, L. Liu, B. Sun, J. H. Wang, K. Zheng, Z. R. Zhou
    USTC/NSRL, Hefei, Anhui
  In Hefei Light Source (HLS), coupled-bunch instabilities are major limiting factors in achieving higher beam intensity while maintaining good beam quality. To Measure and suppress beam instabilities, turn-by-turn (TBT) measurement and bunch-by-bunch(BxB) measurement & feedback system are under commission [1][2]. The design of the two systems and primary experiment results is presented. Measurement and detail analysing results in injection status will also be shown.  
 
MOPAN055 Bunch-by-Bunch Measurement and Feedback System of HLS controls, damping, injection, emittance 275
 
  • K. Zheng
  • Y. B. Chen, L. J. Huang, W. Li, L. Liu, B. Sun, J. H. Wang, L. Wang, Y. L. Yang, Z. R. Zhou
    USTC/NSRL, Hefei, Anhui
  Funding: Supported by National Natural Science Project (10175063); National Natural Science Key Project (10535040)

In this paper, HLS (Hefei light Source) bunch-by-bunch measurement and feedback system will be introduced. This system is integrated with longitudinal oscillation measurement system, fast vector control, fiber notch filter and bunch current detection system. The detail of the two fronts will be shown. Some experimental results by this system are also present in this paper, as phase-space tracing, mode dumping rate, and feedback experiments.

 
 
MOPAN056 Development of Digital Transverse Bunch-by-Bunch Feedback System of HLS kicker, single-bunch, pick-up, damping 278
 
  • Z. R. Zhou
  • Y. B. Chen, L. J. Huang, B. Sun, J. H. Wang, Y. L. Yang, K. Zheng
    USTC/NSRL, Hefei, Anhui
  • K. Kobayashi, T. Nakamura
    JASRI/SPring-8, Hyogo-ken
  Funding: Supported by "National 211 Project"

To promote the transverse feedback system of HLS, we develop the transverse digital feedback system. The scheme of HLS digital feedback system is presented in this paper, and the primitive digital feedback experiment we have done in HLS is also included in the paper.

 
 
MOPAN060 Compensation of BPM Chamber Motion in PLS Orbit Feedback System vacuum, photon, electron, controls 290
 
  • H.-S. Kang
  • J. Choi, K. M. Ha, E.-H. Lee, W. W. Lee, I. S. Park
    PAL, Pohang, Kyungbuk
  The false BPM reading resulting from the BPM vacuum chamber motion due to thermal load change by synchrotron radiation is compensated by the real-time monitoring of the chamber position in the PLS orbit feedback system. The BPM chamber moves up to 20 μm during the beam refill and the chamber motion has a time constant of about one and half hour, which is related to thermal equilibrium of the vacuum chamber. To monitor the BPM chamber motion, LVDTs with 0.2 μm reading accuracy were installed on all BPM chambers, and the measured data are used in the orbit feedback every 1 minute. In this paper, we will describe how serious the BPM chamber motion are and how well it is compensated.  
 
MOPAN061 Compact Output Filter for Switching Frequency Elimination at the PLC Linac New Magnet Power Supply linac, power-supply, controls, damping 293
 
  • S.-C. Kim
  • J. Choi, K. M. Ha, J. Y. Huang
    PAL, Pohang, Kyungbuk
  Funding: This work is supported by the Ministry of Science and Technology, Korea.

At 2006, PLS Linac magnet power supply (MPS) has been upgraded for the stable beam injection and 4th generation light source research. New MPS are developed new compact MPS of 16-bit resolution and 20ppm stability using four-quadrant switching scheme with 50kHz MOSFET switching device, and consists of main power board, control power board, regulator board and CPU board. Size of each board is only 100mm width and 240mm depth. Output of MPS is 10V, ±10A for the bipolar and 50V, 50A for the unipolar magnet. Main board is consisted four-quadrant FET switch, driver and output filter. Output filter must be perfectly eliminating switch frequency and compact size. In this paper, we report on development and characteristics of compact output filter of the new MPS for PAL linac.

 
 
MOPAN071 Characteristics of Burden Resistors for High-precision DC Current Transducers controls, collider 317
 
  • G. Fernqvist
  • P. Dreesen, G. Hudson
    CERN, Geneva
  • J. R. Pickering
    Metron, Norwich
  The DC current transducer (DCCT) and accompanying A/D converter determine the precision of a power converter in accelerator operation. In the LHC context this precision approaches 10-6. Inside the DCCT, a burden resistor is used to convert the current to an output voltage. The performance of this resistor is crucial for the accuracy, temperature behaviour, settling time and long-term drift of the DCCT. This paper reports on evaluations, a new parameter called "power coefficient" (PC) and test results from some different types of resistors available on the market.  
 
MOPAN074 Influence of Varying Tune Width on the Robustness of the LHC Tune PLL and its Application for Continuous Chromaticity Measurement resonance, controls, betatron, synchrotron 326
 
  • R. J. Steinhagen
  • A. Boccardi, M. Gasior, O. R. Jones, K. K. Kasinski
    CERN, Geneva
  Tune and chromaticity measurement is an integral part for safe and reliable LHC operation. Tight tolerances on the maximum transverse beam excursions allow oscillation amplitudes of less than 30 um. This leaves only a small margin for transverse beam and momentum excitations required for measuring tune and chromaticity. This contribution discusses a robust tune phase-locked-loop (PLL) operation in the presence of non-linearities and varying chromaticity. The loop design was tested at the SPS, using the LHC PLL prototype system. The system was also used to continuously measure tune width and chromaticity, using resonant transverse excitations of the tune side-slopes.  
 
MOPAN090 Logging of Operation Data at TLS injection, booster, kicker, linac 371
 
  • C.-K. Chang
  • H. C. Chen, M. J. Horng, J. A. Li, T. F. Lin, Y. K. Lin, Y.-C. Liu
    NSRRC, Hsinchu
  The Taiwan Light Source had been Top-Up operation in October 2005 and the beam current had increased to 300mA in early 2006. For normal operation, there are some important parameters of Top-up operation, such as beam stability, filling pattern and injection efficiency etc. These data have to be recorded and to be reference for the accelerator operating. Therefore, a LabVIEW-based data logging system had been developed. The system handles communication with other instruments via Ethernet and IEEE-488 interconnections. In this report, the design concept and the current status are described. The planned improvements are carried out in the future.  
 
MOPAN094 Operation Experiences of the Bunch-by-Bunch Feedback System for TLS kicker, injection, controls, damping 383
 
  • K. T. Hsu
  • J. Chen, P. C. Chiu, S. Y. Hsu, K. H. Hu, C. H. Kuo, D. Lee
    NSRRC, Hsinchu
  Severe multi-bunch instabilities are bothered the operation of Taiwan Light Source (TLS) during the operation during 2004 just after SRF system upgrade. FPGA-based bunch-by-bunch feedback system was commissioning during late 2005 and early 2006. Multi-bunch instability in both transverse plans and longitudinal are well control. Delivery up to 400 mA stored beam was demonstrated. Transverse feedback system make low chromaticity operation is possible; this is very helpful to improve injection efficiency which are essential for routine top-up operation. Operation experiences of the bunch-by-bunch feedback system will be summary in this report.  
 
MOPAN108 The FONT4 ILC Intra-train Beam-based Digital Feedback System Prototype kicker, linear-collider, electron, positron 416
 
  • P. Burrows
  • G. B. Christian, C. I. Clarke, B. Constance, A. F. Hartin, H. D. Khah, C. Perry, C. Swinson, G. R. White
    JAI, Oxford
  • A. Kalinin
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • S. Molloy
    SLAC, Menlo Park, California
  We present the design of the FONT4 intra-train beam-based digital position feedback system prototype. The system incorporates a fast analogue beam position monitor front-end signal processor, a digital feedback board, and a fast kicker-driver amplifier. The system latency goal is less than 150ns. We report preliminary results of beam tests at the Accelerator Test Facility (ATF) at KEK using electron bunches separated by c. 150ns.  
 
MOPAN112 Digital Control Interface for Bipolar Corrector Power Supplies for LCLS controls, power-supply, monitoring, diagnostics 428
 
  • S. Cohen
  • S. R. Babel
    Bira, Albuquerque, New Mexico
  We detail the development, testing and commissioning of a single-board digital interface for modular bipolar corrector magnet power supplies to installed at the Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator (SLAC). The sixteen-channel VME-form-factor board replaces the passive the control-interface board in the MCOR (Magnet Corrector) Chassis. The board is a self-contained system with both serial and Ethernet connectivity intended for use with an EPICS accelerator control system IOC, however, the ASCII protocol allows generic computer control. The interface card contains 16 independent ADC and DAC channels, each with 16 bits of resolution. Additionally, the interlock, fault, reset and digital control lines are remotely controllable via either the serial or Ethernet connections. The design has been planned so that a mini-IOC can be included on board for direct Channel Access connectivity.  
 
MOPAN113 The P0 Feedback Control System Blurs the Line between IOC and FPGA controls, photon, storage-ring, monitoring 431
 
  • N. P. Di Monte
  Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

The P0 Feedback System is a new design at the APS with the main intent to stabilize a single bunch in order to operate at a higher accumulated charge. The algorithm for this project required a high-speed DSP solution for a single channel that would make adjustments on a turn-by-turn basis. An FPGA solution was selected that not only met the requirements of the project, but far exceeded the requirements. By using a single FPGA, we were able to adjust up to 324 bunches on two separate channels with a total computational time of ~6x109 multiply-accumulate operations per second. The IOC is a Coldfire CPU tightly coupled to the FPGA, providing a dedicated control and monitoring of the system through EPICS process variables. One of the benefits of this configuration is having a four-channel scope in the FPGA that can be monitored on a continuous basis.

 
 
MOPAN116 An FPGA-Based Bunch-to-Bunch Feedback System at the Advanced Photon Source damping, kicker, storage-ring, simulation 440
 
  • C. Yao
  • N. P. Di Monte, W. E. Norum
    ANL, Argonne, Illinois
  Funding: Work supported by U. S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.

The Advanced Photon Source storage ring has several bunch fill patterns for user operation. The hybrids fill pattern consists of a single bunch with a charge of 16 mA and a bunch train of 56 bunches. Both horizontal and vertical instabilities are observed. Currently chromaticity correction is the only method available to overcome the instability. Beamlife time and injection efficiency suffer because of high sextupole currents. A bunch-to-bunch feedback system is designed to overcome beam instability and reduce the required chromaticity correction. The feedback system is based on an FPGA DSP processor. The signal filtering algorithm is based on the time-domain-least-square method developed at SPring-8. We have just completed the integration of the system. We report the system design and some test results.

 
 
MOPAS031 Hardware and Software Development and Integration in an FPGA Embedded Processor Based Control System Module for the ALS controls, instrumentation, booster, power-supply 503
 
  • J. M. Weber
  • M. J. Chin, CA. Timossi, E. C. Williams
    LBNL, Berkeley, California
  Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U. S. Department of Energy under Contract No. DE-AC02-05CH11231.

The emergence of Field Programmable Gate Arrays (FPGAs) with embedded processors and significant progress in their development tools have contributed to the realization of system-on-a-chip networked front-end systems. Embedded processors are capable of running full-fledged Real-Time Operating Systems (RTOSs) and serving channels via Ethernet while high speed hardware functions, such as digital signal processing and high performance interfaces, run simultaneously in the FPGA logic. Despite significant advantages of the system-on-a-chip implementation, engineers have shied away from designing such systems due to the perceived daunting task of integrating software to run a RTOS with custom hardware. However, advances in embedded development tools considerably reduce the effort required for software/hardware integration. This paper will describe the implementation and integration of software and hardware in an FPGA embedded processor system as illustrated by the design of a new control system module for the ALS.

 
 
MOPAS037 New Generation Digital Longitudinal Feedback System for Duke FEL and HIGS Facilities kicker, storage-ring, synchrotron, electron 518
 
  • Y. Kim
  • M. D. Busch, P. Wang, W. Wu, Y. K. Wu
    FEL/Duke University, Durham, North Carolina
  • J. Choi, I. S. Ko, I. S. Park
    PAL, Pohang, Kyungbuk
  • D. Teytelman
    Dimtel, Redwood City, California
  To increase intensity of the High Intensity Gamma-ray Source (HIGS) which is driven by the Duke storage ring FEL via Compton scattering, stored beam current should be increased. However, high-current multi-bunch operation in the Duke storage ring is limited by strong longitudinal coupled-bunch beam instabilities. To control those instabilities, we have been developing an active longitudinal feedback system which is based on the Integrated Gigasample Processor (iGP) through collaboration with Dimtel, Inc. and Pohang Accelerator Laboratory. In this paper, we report the present status of our longitudinal feedback system.  
 
MOPAS048 Quantitative Evaluation of Magnet Hysteresis Effects at LANSCE with Respect to Magnet Power Supply Specifications power-supply, controls, quadrupole, linac 542
 
  • J. T. Bradley III
  • C. J. Andrews, L. F. Fernandez, M. F. Fresquez, W. Reass, W. Roybal, J. B. Sandoval
    LANL, Los Alamos, New Mexico
  Funding: Work supported by US Department of Energy.

The proton beam in the LANSCE accelerator is guided and focused almost exclusively by electromagnets. Magnet hysteresis has had significant impacts on the tuning of the LANSCE accelerator.* Magnet hysteresis can also have an impact on Magnet Power Supply (MPS) control, regulation and repeatability requirements. To date, MPS performance requirements have been driven by the requirements on the magnetic fields as determined by the accelerator physicists. Taking hysteresis effects into account can significantly change MPS requirements, as some requirements become more stringent and some are found to be overspecified. Overspecification of MPS requirements can result in significant increases in MPS cost. Conversely, the use of appropriate MPS requirements can result in significant cost savings. The LANSCE accelerator's more than three decades of operation provide a wide variety of magnet power supply technologies and operational experience. We will survey the LANSCE magnet power supply history and determine how performance specifications can be refined to both reduce costs and improve the operators abilities to control the magnetic fields.

*R. McCrady, "Mitigation Of Magnet Hysteresis Effects at LANSCE", LINAC 2006, August, 2006.

 
 
MOPAS050 Active Damping of the e-p Instability at the LANL PSR damping, electron, linac, proton 548
 
  • R. C. McCrady
  • S. Assadi, C. Deibele, S. Henderson, M. A. Plum
    ORNL, Oak Ridge, Tennessee
  • J. M. Byrd
    LBNL, Berkeley, California
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
  • R. J. Macek, S. B. Walbridge, T. Zaugg
    LANL, Los Alamos, New Mexico
  • M. T.F. Pivi
    SLAC, Menlo Park, California
  Funding: This work was supported by the United States Department of Energy under contracts DE-AC52-06NA25396 and W-7405-ENG-36.

A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos National Laboratory Proton Storage Ring (PSR). This system was able to improve the instability threshold by approximately 30% (as measured by the change in RF buncher voltage at instability threshold). Evidence obtained from these tests suggests that further improvement in performance is limited by beam leakage into the gap at lower RF buncher voltage and the onset of instability in the horizontal plane, which had no feedback. Here we describe the present system configuration, system optimization, results of several recent experimental tests, and results from studies of factors limiting its performance.

 
 
MOPAS058 A Parallel Controls Software Approach for PEP II: AIDA & Matlab Middle Layer controls, collider, vacuum, sextupole 566
 
  • W. Wittmer
  • W. S. Colocho, G. R. White
    SLAC, Menlo Park, California
  Funding: US-DOE

The controls software in use at PEP II had originally been developed in the eighties. The functionality and maturity of the applications in that system have made it very successful in routine operation, but this same longevity and orientation toward fixed requirements, make it largely unsuitable for rapid machine development and ad-hoc online experimentation. A successful recent trend at light sources has been to use the so called MATLAB Middle Layer (MML). This package abstracts each underlying control system framework to which it is connected, such as Channel Access. We describe the middle layer implementation for PEP II and LCLS based on AIDA (described elsewhere in these proceedings), which is unusual in that it provides access to the high level functionality of the legacy control system, as well as to a very large assortment of useful data in addition to channel access read and control. The MML had to be adapted for the implementation at PEP II since colliders differ significantly from light sources by scale and symmetry of the lattice, and PEP II is the first collider at which such an implementation is being done.

 
 
MOPAS059 ILC - ATF2 DC-Magnet Power Supplies power-supply, controls, quadrupole, extraction 569
 
  • B. Lam
  • P. Bellomo, D. Macnair, A. C. de Lira
    SLAC, Menlo Park, California
  Funding: The development and commissioning of DC magnet power supplies for ATF2 is supported by KEK and SLAC.

In 2008 KEK is commissioning ATF2 - an extension to the existing ATF. ATF2 is a mockup of the final focus test beam accelerator envisioned in the ILC. SLAC is designing the power supply systems for the dc magnets in the ATF2, which will require 38 power supplies ranging from 1.5 to 6 kW, currents from 50 to 200 A, all rated at output voltages not higher than 30 V. Because of the extensive quantities of magnets required for the ILC, high availability is paramount to its successful operation, so the power supply topology chosen for the ATF2 uses N+1 redundancy, with 50-A power modules to construct each power supply. These power modules are current-mode buck regulators, which operate in parallel with each other and one redundant module. One bulk power supply provides off-the-line regulated dc input to a number of the power supplies. Current stability requirements for the magnets range from 10 to 1000 ppm. A precision current transductor and a recently developed SLAC-built 20-bit Ethernet Power Supply Controller will provide the current regulation required. In this paper we present the conceptual design, prototype results, and the status of the power supply systems for the ATF2.

 
 
MOPAS062 Analysis of the Longitudinal Low-order Mode Beam Dynamics in PEP-II Rings at High Current Beams klystron, simulation, damping, impedance 575
 
  • T. Mastorides
  • J. D. Fox, C. H. Rivetta, D. Teytelman, D. Van Winkle
    SLAC, Menlo Park, California
  Funding: Work supported by Department of Energy (USA) under contract # DE-AC02-76SF00515

PEP-II operations will increase the beam currents to 4A for LER and 2.2A for HER to achieve the final goal in luminosity. These magnitudes are challenging in part because they will push toward the limit the longitudinal low-order mode (LOM) beam stability due to beam loading. To analyze the behavior of both rings at high currents and understand the limits in the longitudinal feedback systems a simulation tool has been developed at SLAC. This tool is based on a reduced model of the longitudinal LOM dynamics of the beam interacting with the effective impedance presented by RF station. Simulations and measurements of the longitudinal beam behavior in both rings have been performed to understand the ultimate limit of the system. These studies have defined the impact of control loop parameters in the longitudinal beam dynamics, identified the poor performance of RF devices affecting the optimal performance of the RF stations and quantified the behavior of the longitudinal LOM beam dynamics. Results of sensitivity to parameter variations in the beam dynamics and limits in the maximum current that LER/HER can achieve based on the longitudinal beam stability are reported in this paper.

 
 
MOPAS067 Control and Measurements of Longitudinal Coupled-bunch Instabilities in the ATF Damping Ring damping, single-bunch, injection, extraction 584
 
  • D. Teytelman
  • W. X. Cheng, J. W. Flanagan, T. Naito, M. Tobiyama
    KEK, Ibaraki
  • A. Drago
    INFN/LNF, Frascati (Roma)
  • J. D. Fox
    SLAC, Menlo Park, California
  Funding: Work supported by U. S. Department of Energy contract DE-AC02-76SF00515 and by the US-Japan collaboration in High Energy Physics

Damping ring at the Accelerator Test Facility (ATF) is a storage ring with 714 MHz RF frequency and harmonic number of 330. The ring is used in both single and multibunch regimes. In both cases significant longitudinal dipole motion has been observed in the ring. A prototype longitudinal feedback channel using a Gproto baseband processing channel and a set of horizontal striplines has been constructed for the machine. The prototype allowed both suppression of the longitudinal motion and studies of the motion sources. In this paper we present the results of these studies including measurements of steady-state oscillation amplitudes, eigenmodal patterns, and growth and damping rates. Using measured growth rates we estimate the driving impedances. We also present the effect of the longitudinal stabilization on the energy spread of the extracted beam as documented by a screen monitor.

 
 
MOPAS071 A Precision 75kW, 25kV Power System for a Klystron Amplifier controls, klystron, power-supply, vacuum 593
 
  • L. Bees
  • L. Simpson, A. Tydeman
    Lambda, Neptune, New Jersey
  A compact water-cooled high power, high voltage power supply system is described. The system must deliver an output voltage up to 25kV, and a current up to 4A to power a Klystron Amplifier. The amplifier demands very high voltage stability, low output voltage ripple, and low stored energy. The solution presented is based around Lambda's proven 303 series DC supplies to provide the bulk high voltage power, an advanced controller for high performance operation, and a precision filter/feedback assembly for low ripple and high accuracy. The system has demonstrated ripple of less than 0.015%, stability better than 10ppm per degree C, power factor of 0.92 and efficiency of 90%, with an output stored energy of less that 8J.  
 
MOPAS072 First Measurements of RF Properties of Large Ferroelectric Rings for RF Switches and Phase Shifters resonance, controls, plasma, radiation 596
 
  • V. P. Yakovlev
  • J. L. Hirshfield
    Omega-P, Inc., New Haven, Connecticut
  • A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio
  • S. Kazakov
    KEK, Ibaraki
  • E. Nenasheva
    Ceramics Ltd., St. Petersburg
  • S. V. Shchelkunov
    Columbia University, New York
  Funding: Research supported by the Department of Energy, Division of High Energy Physics

Fast, electrically-controlled ferroelectric RF vector modulators are under development for different accelerator applications in the frequency range 0.4 - 1.3 GHz. The exact design of a vector modulator depends on the electrical parameters of particular ferroelectric material to be used, namely its dielectric constant, loss tangent and tunability. The exact values of these parameters were unknown in this frequency domain for low loss BST material that is planned to be used. A special two-disc test cavity has been designed and built that allows direct measurements of these parameters for large (100 mm in diameter) ferroelectric rings that are to be used in vector modulators. The results of measurements are presented.

 
 
MOPAS077 A Beat Frequency RF Modulator for Generation of Low Repetition Rate Electron Microbunches for the CEBAF Polarized Source laser, electron, gun, controls 608
 
  • J. Musson
  • J. M. Grames, J. Hansknecht, R. Kazimi, M. Poelker
    Jefferson Lab, Newport News, Virginia
  Funding: Authored by Jefferson Science Associates, LLC under U. S. DOE Contract No. DE-AC05-06OR23177

Recent upgrades to the CEBAF Polarized Source include a fiber-based seed laser, capable of producing pulses with frequency centered at 499 MHz. Combined with the existing three-beam Chopper, an aliasing, or beat frequency technique is used to produce long time intervals between individual electron microbunches (tens of nanoseconds) by merely varying the nominal 499 MHz drive laser frequency by <20%. This RF Laser modulator uses a divider and heterodyne scheme to maintain coherence with the accelerator Master Oscillator, while providing delay resolution in increments of 2ns. Laser repetition frequencies producing bunch repetition rates between 20 MHz and 100 MHz are demonstrated, resulting in time delays between 50 and 10 ns, respectively. Also, possible uses for such a beam are discussed as well as intended development. Authored by Jefferson Science Associates, LLC under U. S. DOE Contract No. DE-AC05-06OR23177

 
 
MOPAS078 Digital RF Control for Spallation Neutron Source Accumulator Ring controls, beam-loading, linac, simulation 611
 
  • H. Ma
  • M. S. Champion, M. T. Crofford, T. W. Hardek, K.-U. Kasemir, M. F. Piller, Y. Zhang
    ORNL, Oak Ridge, Tennessee
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.

The proposed upgrade plan for RF control of the Spallation Neutron Source (SNS) accumulator ring requires that the new digital field control module (FCM) support both the conventional narrow-band feed forward control and a new beam-based feed forward control. Both are necessary for compensating the heavy beam loading in SNS ring. The ring FCM also has the integrated control and monitoring features for the cavity bias, cavity resonance, and tetrode grid boost. A user-friendly Epics GUI for all these FCM functionalities is also a part of the requirement. The ring FCM under development is being implemented on the hardware of the proven FCM of SNS Linac. Both the controller architecture and the design code of the digital hardware for the Linac system will be largely reused in the ring system.

 
 
MOPAS080 A Digital Ring Transverse Feedback Low-Level RF Control System pick-up, damping, controls, simulation 617
 
  • A. K. Polisetti
  • S. Assadi, C. Deibele, J. C. Patterson
    ORNL, Oak Ridge, Tennessee
  • R. C. McCrady
    LANL, Los Alamos, New Mexico
  • M. J. Schulte
    UW-Madison, Madison, Wisconsin
  A digital wide-band system for damping ring instabilities in an accelerator is presented. With increased beam intensity, the losses of an accumulator ring tend to increase due to the onset of various instabilities in the beam. An analog feedback damper system has been implemented at Los Alamos National Laboratory. This analog system, while functional, has certain limitations and a lack of programmability, which can be overcome by a digital solution. A digital feedback damper system is being designed through a collaborative effort by researchers at Oakridge National Laboratory, Los Alamos National Laboratory, and the University of Wisconsin. This system, which includes analog-to-digital converters, field programmable gate arrays and digital-to-analog converters can equalize errors inherent to analog systems, such as dispersion due to amplifiers/cables, gain mismatches, and timing adjustments. The digital system features programmable gains and delays, and programmable equalizers that are implemented using digital FIR and comb filters. The flexibility of the digital system allows it to be customized to implement different configurations and extended to address other diagnostic problems.  
 
TUYAB02 Generation and Control of High Precision Beams at Lepton Accelerators coupling, electron, target, controls 780
 
  • Y.-C. Chao
  Parity violation experiments require precision manipulation of helicity-correlated beam coordinates on target at the nm/nrad-level. Achieving this unprecedented level of control requires a detailed understanding of the particle optics and careful tuning of the beam transport to keep anomalies from compromising the design adiabatic damping. Such efforts are often hindered by machine configuration and instrumentation limitations at the low energy end. A technique has been developed at CEBAF including high precision measurements, Mathematica-based analysis for obtaining corrective solutions, and control hardware/software developments for realizing such level of control at energies up to 5 GeV. Further, results on achieving rms energy stability at 10-5, rms relative energy spread below 3x10-5, and position control at micron level are presented. These results manifest the CW SRF electron linac stability capabilities and are valuable for a large range of applications, including ERLs and Electron-Ion Colliders for Nuclear and Particle Physics.  
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TUZAC01 The ILC Control System Design controls, monitoring, linac, linear-collider 868
 
  • J. Carwardine
  • N. D. Arnold, F. Lenkszus, C. W. Saunders
    ANL, Argonne, Illinois
  • B. Banerjee, B. Chase, E. G. Gottschalk, P. W. Joireman, P. A. Kasley, J. R. Lackey, P. M. McBride, J. F. Patrick, V. Pavlicek, M. Votava, S. A. Wolbers
    Fermilab, Batavia, Illinois
  • R. W. Downing, R. S. Larsen
    SLAC, Menlo Park, California
  • K. Furukawa, S. Michizono
    KEK, Ibaraki
  • K. Rehlich, S. Simrock
    DESY, Hamburg
  Funding: Work supported in the U. S. by the U. S. Department of Energy under contract Nos. DE-AC02-06CH11357, DE-AC02-76CH03000, and DE-AC02-76SF00515.

The scale and performance parameters of the ILC require new thinking in regards to control system design. This design work has begun quite early in comparison to most accelerator projects, with the goal of uniquely high overall accelerator availability. Among the design challenges are high control system availability, timing reference distribution, standardization of interfaces, operability, and maintainability. We present the current state of the design and take a prospective look at ongoing research and development projects.

 
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TUOCC02 Progress in Tune, Coupling, and Chromaticity Measurement and Feedback during RHIC Run 7 coupling, controls, injection, betatron 886
 
  • P. Cameron
  • J. Cupolo, W. C. Dawson, C. Degen, A. Della Penna, L. T. Hoff, Y. Luo, A. Marusic, R. Schroeder, C. Schultheiss, S. Tepikian
    BNL, Upton, Long Island, New York
  • M. Gasior
    CERN, Geneva
  Funding: US DOE

Tune feedback was first implemented in RHIC in 2002 as a specialist activity. The transition to full operational status was impeded by dynamic range problems, as well as by overall loop instabilities driven by large coupling. The dynamic range problem was solved by the CERN development of the Direct Diode Detection Analog Front End. Continuous measurement of all projections of the betatron Eigenmodes made possible the world's first implementation of coupling feedback during beam acceleration, resolving the problem of overall loop instabilites. Simultaneous tune and coupling feedbacks were utilized as specialist activities for ramp development during the 2006 RHIC run. At the beginning of the 2007 RHIC run there remained two obstacles to making these feedbacks fully operational in RHIC - chromaticity measurement and control, and the presence of strong harmonics of the power line frequency in the betatron spectrum. We report here on progress in tune, coupling, and chromaticity measurement and feedback, and discuss the relevance of our results to the LHC commissioning effort. The results of investigations of power line harmonics in RHIC are presented elsewhere in these proceedings.

 
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TUPMN009 Commissioning of the SOLEIL Synchroton Radiation Source injection, insertion, insertion-device, coupling 932
 
  • A. Nadji
  • J. C. Besson, F. Bouvet, P. Brunelle, A. Buteau, L. Cassinari, M.-E. Couprie, J.-C. Denard, J.-M. Filhol, C. Herbeaux, J.-F. Lamarre, V. Le Roux, P. Lebasque, M.-P. Level, A. Loulergue, P. Marchand, L. S. Nadolski, R. Nagaoka, B. Pottin, M.-A. Tordeux
    SOLEIL, Gif-sur-Yvette
  The French 3rd generation synchrotron light source, SOLEIL, was successfully commissioned in 2006. The Linac and the Booster are operational at their design performances. During the early phase of the storage ring commissioning, the essential design parameters were reached very quickly while the project incorporates some innovative techniques such as the use of a superconducting RF cavity, solid state RF amplifiers, NEG coating for all straight parts of the storage ring and new BPM electronics. Prior to the start of the commissioning, some insertion devices and most of the insertion devices low gap vacuum vessels, including 10 mm inner vertical aperture vessels for the Apple-II type, were installed on the ring. The main results of the commissioning will be reviewed here, including discussion on diagnostics performances, orbit stability and control, optics correction, Top-up and the challenges in achieving operational status. The 10 beamlines of phase 1 are now under commissioning and regular user operation will start by spring 2007.  
 
TUPMN036 Laser and RF Synchronization Measurements at SPARC laser, gun, linac, emittance 992
 
  • A. Gallo
  • M. Bellaveglia, G. Gatti, C. Vicario
    INFN/LNF, Frascati (Roma)
  Funding: Work supported by the EU Commission in the sixth framework programme, contract no. 011935 - EUROFEL.

The SPARC project consists in a 150 MeV B-band, high-brilliance linac followed by 6 undulators for FEL radiation production at 530 nm. The linac assembly has been recently completed. During year 2006 a first experimental phase aimed at characterizing the beam emittance in the first 2m drift downstream the RF gun has been carried out. The low level RF control electronics to monitor and synchronize the RF phase in the gun and the laser shot on the photocathode has been commissioned and extensively tested during the emittance measurement campaign. The laser synchronization has been monitored by measuring the phase of the free oscillation of an RF cavity impulsively excited by the signal of a fast photodiode illuminated by the laser shot. Phase stability measurements are reported, both with and without feedback correction of the slow drifts. A fast intra-pulse phase feedback system to reduce the phase noise produced by the RF power station has been also positively tested.

 
 
TUPMN050 Development of Pulsed-Laser Super-Cavity for Compact X-Ray Source Based on Laser-Compton Scattering laser, electron, photon, storage-ring 1034
 
  • K. Sakaue
  • S. Araki, M. K. Fukuda, Y. Higashi, Y. Honda, T. Taniguchi, N. Terunuma, J. Urakawa
    KEK, Ibaraki
  • N. Sasao, H. Yokoyama
    Kyoto University, Kyoto
  • M. Takano
    Tsukuba-shi, Ibaraki-ken
  • M. Washio
    RISE, Tokyo
  A compact and high quality x-ray source is required from various field, such as medical diagnosis, drug manifacturing and biological sciences. Laser-Compton based x-ray source that consist of a compact electron storage ring and a pulsed-laser super-cavity is one of the solutions of compact x-ray source. Pulsed-laser super-cavity has been developed for a compact high brightness x-ray sources at KEK-ATF. The pulsed-laser super-cavity increases the laser power and stably makes small laser beam size at the collision point with the electron beam. Recently, 357MHz mode-locked Nd:VAN laser pulses can be stacked stably in a 420mm long Fabry-Perot cavity with 1'000 enhancement in our R&D. Therefore, we have planned a compact hard x-ray sources using 50MeV multi-bunch electrons and a pulse stacking technology with 42cm Fabry-Perot cavity. (LUCX Project at KEK) The photon flux is multiplied with the number of bunches by using multi-bunch beam and super-cavity. Development of the super-cavity and present result of LUCX will be presented at the conference.  
 
TUPMN058 The Operation Status of HLS (Hefei Light Source) radiation, synchrotron, synchrotron-radiation, damping 1058
 
  • W. Li
  • G. Feng, L. Liu, B. Sun, J. H. Wang, L. Wang, H. Xu, K. Xuan
    USTC/NSRL, Hefei, Anhui
  • S. C. Zhang
    USTC, Hefei, Anhui
  National Synchrotron Radiation Lab, University of Science and Technology of China, P. R.China HLS(Hefei Light Source) is a dedicated synchrotron radiation research facility, spectrally strongest in Vacuum Ultra Violet and Soft X-ray. Designed and constructed in 1980's, accepted to regular service in 1991. From 1999 to 2004, the National Synchrotron Radiation Lab carried out its Phase II Project, in which quite a few sub-systems of HLS storage ring were upgraded and 8 new beamline were constructed. After the project, the performance of HLS is improved considerably. In this paper, the operation status and performance of storage ring in recent years were presented. With some measures, the operation beam intensity is about 300mA, beam lifetime is higher than before, orbit stability is met requirement of users, and the capability to provide synchrotron radiation exceeds the design value.  
 
TUPMN085 The Commissioning of the Diamond Storage Ring optics, storage-ring, injection, single-bunch 1109
 
  • R. Bartolini
  The Diamond Light Source opened for user operation at the end January 2007. The storage ring was successfully commissioned at 3 GeV in three months by the end of December 2006. An intensive Accelerator Physics program allowed the design emittance of 2.7 nm with 150 mA stored beam to be reached as well as the commissioning of the first seven insertion devices. We describe here the results of the measurements performed to characterise accelerator optics, to bring the insertion device in operation and a first analysis of orbit stability and collective instabilities, as well as the status and plans for fast orbit feedback, multi-bunch feedback and top-up operation.  
 
TUPMS055 SPEAR3 Accelerator Physics Update photon, optics, injection, electron 1311
 
  • J. A. Safranek
  • W. J. Corbett, S. M. Gierman, R. O. Hettel, X. Huang, J. J. Sebek, A. Terebilo
    SLAC, Menlo Park, California
  The SPEAR3 storage ring at Stanford Synchrotron Radiation Laboratory has been delivering photon beams for three years. We will give an overview of recent and ongoing accelerator physics activities, including 500 mA fills, work toward top-off injection, long-term orbit stability characterization & improvement, fast orbit feedback, new chicane optics, low alpha optics & short bunches, low emittance optics, and new insertion devices. The accelerator physics group has a strong program to characterize and improve SPEAR3 performance.  
 
TUPAN048 Beam-beam Effects With an External Noise in LHC emittance, simulation, luminosity, betatron 1496
 
  • K. Ohmi
  • R. Calaga
    BNL, Upton, Long Island, New York
  • W. Hofle, R. Tomas, F. Zimmermann
    CERN, Geneva
  Proton beam do not have any damping mechanism for an incoherent betatron motion. A noise, which kicks beam particles in the transverse plane, gives a coherent betatron amplitude. Nonlinear force due to the beam-beam interactions causes a decoherence for the betatron motion with keeping an amplitude of each beam particle, with the result that an emittance growth arises. We focus fast transverse turn by turn noises caused by a bunch by bunch feedback system and a cavity phase zitter in crab collision.  
 
TUPAN062 RF Amplitude and Phase Tuning of J-PARC SDTL linac, klystron, simulation 1529
 
  • G. B. Shen
  • H. Sako
    JAEA, Ibaraki-ken
  • S. Sato
    JAEA/LINAC, Ibaraki-ken
  In the beam commissioning of J-PARC Linac, RF phase and amplitude of SDTL (Separate-type Drift Tube Linac) cavities have been tuned with a phase-scan method based on the beam-energy measurement. The output beam energy is measured with two FCTs (Fast Current Transformer) using the TOF (Time-Of-Flight) method. The detailed results of RF tuning for SDTL cavity is presented.  
 
TUPAN091 LHC Beam-beam Compensation Using Wires and Electron Lenses optics, electron, emittance, simulation 1589
 
  • U. Dorda
  • W. Fischer
    BNL, Upton, Long Island, New York
  • V. D. Shiltsev
    Fermilab, Batavia, Illinois
  • F. Zimmermann
    CERN, Geneva
  We present weak-strong simulation results for a possible application of current-carrying wires and electron lenses to compensate the LHC long-range and head-on beam-beam interaction, respectively, for nominal and Pacman bunches. We show that these measures have the potential to considerably increase the beam-beam limit, allowing for a corresponding increase in peak luminosity  
 
WEOCKI01 Operational Experience with HERA luminosity, proton, electron, polarization 1932
 
  • J. Keil
  The electron-proton collider HERA (Hadron Electron Ring Accelerator) at DESY which collides 920 GeV protons with polarized electrons or positrons with an energy of 27.5 GeV will conclude operations in July 2007 after 16 successful years. After an upgrade of the interaction regions in the year 2001 the luminosity of HERA has been increased by a factor of 2.5 resulting in a peak value of 5.1*1031 cm-2 s-1. For a special experiment, HERA will run in the last three month of operation with a reduced proton energy of 460 GeV. An overview of the accelerator physics and operational challenges, the performance over the last years, the continuous efforts to upgrade and improve the accelerator and an assessment of reliability and availability issues of HERA will be presented.  
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WEOBAB01 Electromagnetic Background Tests for the ILC Interaction Point Feedback System background, electron, luminosity, extraction 1970
 
  • P. Burrows
  • R. Arnold, S. Molloy, S. Smith, G. R. White, M. Woods
    SLAC, Menlo Park, California
  • G. B. Christian, C. I. Clarke, B. Constance, A. F. Hartin, H. D. Khah, C. Perry, C. Swinson, G. R. White
    JAI, Oxford
  • A. Kalinin
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  We present results obtained with the T-488 experiment at SLAC Endstation A (ESA). A material model of the ILC extraction-line design was assembled and installed in ESA. The module includes materials representing the mask, beamline calorimeter, and first extraction quadrupole, encompassing a stripline interaction-point feedback system beam position monitor (BPM). The SLAC high-energy electron beam was used to irradiate the module in order to mimic the electromagnetic (EM) backgrounds expected in the ILC interaction region. The impact upon the performance of the feedback BPM was measured, and compared with detailed simulations of its expected response.  
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WEOBAB02 Studies of Emittance Bumps and Adaptive Alignment method for ILC Main Linac emittance, alignment, linac, linear-collider 1973
 
  • N. Solyak
  • V. Ivanov, C. S. Mishra, K. Ranjan
    Fermilab, Batavia, Illinois
  Funding: U. S. Department of Energy

International Linear Collider (ILC) is a proposed electron-positron accelerator requiring very small spot-size at the interaction point, and thus necessitates very tight tolerances on beamline elements. For static tuning of the machine a few methods like dispersion-free steering (DFS) or kick minimization (KM) techniques was proposed. The further suppression of emittance growth can be achieved by using close orbit emittance bumps. Stability of ILC is determined by the stability of the site, additional noises of beamline component, energy and kicker jitter and performance of the train-to-train and intra-train feedback. We discuss the performances of the Adaptive Alignment technique, which keeps accelerator dynamically aligned in presence of ground motion an technical noises. This presentation is an overview of two posters THPMN107 and THPMN108, presented at PAC07.

 
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WEXC01 Experimental Tests of a Prototype System for Active Damping of the E-P Instability at the LANL PSR proton, damping, electron, pick-up 1991
 
  • C. Deibele
  • S. Assadi, V. V. Danilov, S. Henderson, M. A. Plum, A. K. Polisetti
    ORNL, Oak Ridge, Tennessee
  • J. M. Byrd
    LBNL, Berkeley, California
  • J. D. Gilpatrick, R. C. McCrady, J. F. Power, T. Zaugg
    LANL, Los Alamos, New Mexico
  • S.-Y. Lee
    IUCF, Bloomington, Indiana
  • M. T.F. Pivi
    SLAC, Menlo Park, California
  • M. J. Schulte, Z. P. Xie
    UW-Madison, Madison, Wisconsin
  Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U. S. Department of Energy under contract DE-AC05-00OR22725.

A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos Proton Storage Ring (PSR). This talk describes the system configuration, results of several experimental tests and studies of system optimization along with studies of the factors limiting its performance.

 
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WEOBC01 Beam Instability Observations and Analysis at SOLEIL impedance, single-bunch, electron, ion 2019
 
  • R. Nagaoka
  • L. Cassinari, M.-E. Couprie, M. Labat, M.-P. Level, C. Mariette, R. Sreedharan
    SOLEIL, Gif-sur-Yvette
  Due to reduced vertical chamber aperture around the machine, the impedance was systematically evaluated and optimized 3D-wise at SOLEIL during the design stage, whose budget was then utilized to predict instability thresholds for multi and single bunches. These theoretical calculations are compared with observed instabilities. Transverse multibunch current thresholds are followed as a function of chromaticity, identifying the transition of different head-tail regimes that reflects the broadband impedance spectrum. Although low thresholds due to resistive-wall are basically confirmed, its combined effect with ion-induced instability is found to be significant, exhibiting a strong beam filling pattern dependence. To analyse the involved dynamics, a multibunch tracking code is developed in a structure that allows parallel computations with a cluster of processors. The obtained results are compared with empirical data. Analysis of single bunch instabilities is also made with an aim to identify the enhanced reactive impedance due to NEG coating.  
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WEPMN002 Tuner Control in TRIUMF ISAC 2 Superconducting RF System controls, linac, coupling, superconducting-RF 2047
 
  • K. Fong
  • M. P. Laverty, Q. Zheng
    TRIUMF, Vancouver
  The TRIUMF ISAC 2 superconducting RF system operates on self-excited, phase locking mode. A mechanical tuner is used to minimize the required RF power. The tuner derives the tuning information from the phase shift around the self-excited loop. Its accuracy is however reduced by phase drift in the amplifier due to thermal effects. Cross correlation between the In-phase and the Quadrature-phase errors is used to detect this drift. A Kalman filter is used to combine these information to control the movement of the tuner.  
 
WEPMN004 Operation of the SOLEIL RF Systems injection, controls, cryogenics, booster 2050
 
  • P. Marchand
  • P. Bosland, P. Bredy
    CEA, Gif-sur-Yvette
  • H. D. Dias, M. D. Diop, M. E. El Ajjouri, J. L. Labelle, R. L. Lopes, M. Louvet, C. M. Monnot, F. Ribeiro, T. Ruan, R. Sreedharan, K. Tavakoli, C. G. Thomas-Madec
    SOLEIL, Gif-sur-Yvette
  The 352 MHz RF accelerating systems for the SOLEIL Booster (BO) and Storage Ring (SR) have been commissioned. In the BO, a 5-cell copper cavity of the CERN-LEP type is powered with a 35 kW solid state amplifier. In the SR, the required RF accelerating voltage (up to 4.4 MV) and power (650 kW at full beam current of 500 mA) will be provided by two cryomodules, each containing a pair of superconducting cavities, specifically designed for SOLEIL. The parasitic impedances of the high order modes are strongly attenuated by means of four coaxial couplers, located on the tube connecting the two cavities. The first cryomodule is operational, while the second one, which is being constructed by ACCEL (Germany), will be implemented beginning of 2008. Both cryomodules will be cooled down with liquid helium from a single 350 W liquefier and each cavity is powered with a 190 kW solid state amplifier. With the first cryomodule and two amplifiers in operation, the first year objective of storing 300 mA was successfully achieved. The RF system commissioning and operation results are reported.  
 
WEPMN024 RF Feedback Control Systems of the J-PARC Linac controls, linac, beam-loading, proton 2101
 
  • Z. Fang
  • S. Anami, S. Michizono, S. Yamaguchi
    KEK, Ibaraki
  • T. Kobayashi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • H. Suzuki
    JAEA, Ibaraki-ken
  The commissioning of the J-PARC 181MeV proton linac was started from October of 2006. The RF sources of the linac consist of 4 solid-state amplifiers and 20 klystrons. In each RF source, the RF fields are controlled by a digital RF feedback system installed in a compact PCI (cPCI) to realize the accelerating field stability of ±1% in amplitude and ±1 degree in phase. In this paper the performance of the RF feedback control systems will be reported in detail.  
 
WEPMN028 Development of Digital Low-level RF Control System using Multi-intermediate Frequencies controls, klystron 2110
 
  • T. Matsumoto
  • S. Fukuda, H. Katagiri, S. Michizono, Y. Yano
    KEK, Ibaraki
  • Z. Geng
    IHEP Beijing, Beijing
  Digital low level rf (LLRF) control system has been developed in Superconducting RF Test Facility (STF) at KEK to carry out the accelerating electric field stability of 0.3% (rms) in amplitude and 0.3 degree (rms) in phase, respectively. In the digital LLRF system, rf probe signal from cavity is down-converted to intermediate frequency (IF) for acquisition at analog-to-digital converter (ADC) and the number of ADCs required is equal to the number of cavities. In order to decrease the number of ADCs, a new digital LLRF control system is under development. In this LLRF system, rf signals are down-converted to different IF and combined. The combined signal is detected with one ADC and I/Q components of each rf signal are calculated with digital signal processing. This paper describes a result of simulation and estimation using cavity simulator based on FPGA board about this new technique.  
 
WEPMN029 Status of the Low-Level RF System at KEK-STF controls, linac, linear-collider, klystron 2113
 
  • S. Michizono
  • S. Fukuda, H. Katagiri, T. Matsumoto, T. Miura, Y. Yano
    KEK, Ibaraki
  • Z. Geng
    IHEP Beijing, Beijing
  RF field stabilities of less than 0.3%, 0.3deg. are required at STF llrf system. In order to satisfy these requirements, digital FB system using a FPGA is adopted. The FB system consists of a FPGA (VirtexIIPro30) with ten 16-bit ADCs and two 14-bit DACs. The rf (1.3 GHz) probe signals are downconverted to the IF (10 MHz) and directly acquired at ADCs. Total 8 cavities will be installed at STF-Phase 1 in 2007 and vector sum control of 8 cavity signals will be carried out. The performance of the FB system is examined with electric cavity simulators prior to the rf operation.  
 
WEPMN039 Performance of J-PARC Linac RF System controls, klystron, linac, beam-loading 2128
 
  • T. Kobayashi
  • S. Anami, Z. Fang, Y. Fukui, M. Kawamura, S. Michizono, K. Nanmo, S. Yamaguchi
    KEK, Ibaraki
  • E. Chishiro, T. Hori, H. Suzuki, M. Yamazaki
    JAEA, Ibaraki-ken
  High power operation of all the RF systems of J-PARC linac was started for the cavity conditioning in October 2006. Twenty 324-MHz klystrons have powered the accelerating cavities successfully, and the beam commissioning was started in November 2006. The performance of the RF drive and control system will be presented.  
 
WEPMN043 The Modulator Stability System for the BEPCII Klystron klystron, target, linac, controls 2137
 
  • L. Shen
  • Y. L. Chi, Q. M. Dai, X. W. Yang
    IHEP Beijing, Beijing
  The stability of the modulator high voltage output pulse is the important target for the klystron. The stability of the BEPCII modulator is demanded less than 0.15%. To achieve this target, we use thyristor voltage regulator having feedback function to stabilize the DC high voltage of the modulator and the De-Qing circuit to stabilize the charging voltage. This paper describe the modulator stability system and the stabilization measurement .  
 
WEPMN052 FPGA - based Control System for Piezoelectric Stacks used for SC Cavity's Fast Tuner controls, resonance, simulation, radio-frequency 2155
 
  • P. M. Sekalski
  • J. W. Jalmuzna, A. Napieralski
    TUL-DMCS, Lodz
  • L. Lilje, K. P. Przygoda, S. Simrock
    DESY, Hamburg
  • R. P. Paparella
    INFN/LASA, Segrate (MI)
  Funding: We acknowledge the support of the ECRIA under the FP6 program (CARE, contract number RII3-CT-2003-506395), and Polish National Science Council Grant "138/E-370/SPB/6. PR UE/DIE 354/2004-2007"

The SC cavities need a fast tuning system, which is able to adjust the shape during the pulse operation. The first attempts were focused on the compensation of the repetitive and periodic distortion. The algorithms were implemented in Matlab and allow compensating only the Lorentz force detuning. However, the previous solution was too slow to be able to compensate the microphonics. The paper presents recent development in the field. The previously worked out algorithms are implemented in the FPGA-based control system. The SIMCON board is used, which allows to perform parallel, deeply pipelined calculation. The new approach allows integrating the algorithm dedicated for cavity shape control with the LLRF system used for vector sum control. Moreover, the new algorithm for on-line detuning calculation which base on the electromechanical model of the cavity is presented. The system is tested with Module Test Stand (MTS) at DESY with the high gradient cavities (37 MV/m). The active elements are the NOLIAC's and PI's multilayer, low voltage piezostacks. The paper will present the first results from these measurements.

 
 
WEPMN057 Development of the PEFP Low Level RF Control System controls, rfq, proton, simulation 2167
 
  • H. S. Kim
  • Y.-S. Cho, I.-S. Hong, D. I. Kim, H.-J. Kwon, K. T. Seol, Y.-G. Song
    KAERI, Daejon
  Funding: This work is supported by the 21C frontier R&D program in the Ministry of Science and Technology of the Korean government.

The RF amplitude and the phase stability requirements of the LLRF system for the PEFP(Proton Engineering Frontier Project) proton linac are within 1% and 1 degree, respectively. As a prototype of the LLRF, a simple digital PI control system based on commercial FPGA board is designed and tested. The main features are a sampling rate of 40 MHz which is four times higher than the down-converted cavity signal frequency, digital in-phase and quadrature detection, pulsed mode operation with the external trigger, and a simple proportional-integral feedback algorithm implemented in a FPGA. The developed system was tested with 3 MeV RFQ and 20 MeV DTL, and satisfied the stability requirements.

 
 
WEPMN058 Analog Components Configuration and Test results for PEFP LLRF system controls, rfq, proton, pick-up 2170
 
  • K. T. Seol
  • Y.-S. Cho, D. I. Kim, H. S. Kim, H.-J. Kwon
    KAERI, Daejon
  Funding: This work is supported by the 21C Frontier R&D program in the Ministry of Science and Technology of the Korean government.

The PEFP LLRF system for the 3MeV RFQ and 20MeV DTL has been developed. The stability of ±1% in the amplitude and ±1˚ in the phase is required. Therefore, the drift of the analog components should be low to satisfy the requirement. Analog chassis as a prototype of LLRF system is configured and tested. RF components including an IQ modulator, an RF switch, a mixer, phase comparators, RF splitters, RF filters and trip circuit for high VSWR are installed in this chassis. This performs the shift of RF amplitude and phase from IQ signal, down-conversion to 10MHz IF signal, interlock for arc and high VSWR, and RF/clock distribution. The amplitude and phase stability of each component are measured to check the effect on the whole system performance. The detailed configuration and test results are presented.

 
 
WEPMN066 Progress Towards Development of a Superconducting Traveling Wave Accelerating Structure acceleration, coupling, linac, collider 2182
 
  • P. V. Avrakhov
  • A. Kanareykin
    Euclid TechLabs, LLC, Solon, Ohio
  • S. Kazakov
    KEK, Ibaraki
  • N. Solyak
    Fermilab, Batavia, Illinois
  • V. P. Yakovlev
    Omega-P, Inc., New Haven, Connecticut
  In the ILC project the required accelerating gradient is higher than 35 MeV/m. For current technology the maximum acceleration gradient in SC structures is limited mainly by the value of the surface RF magnetic field. In order to increase the gradient, the RF magnetic field is distributed homogeneously over the cavity surface (low-loss structure), and coupling to the beam is improved by introducing aperture ?noses? (re-entrant structure). These features allow gradients in excess of 50 MeV/m to be obtained for a singe-cell cavity. Further improvement of the coupling to the beam may be achieved by using a TW SC structure with small phase advance per cell. Calculations show that an additional gradient increase by up to 40% is possible if a p/2 TW SC structure is employed. However, a TW SC structure requires a SC feedback waveguide to return the few GW of circulating RF power from the structure output back to the structure input. We describe a single-cell test TW SC structure with a feedback waveguide. The test cavity is designed to demonstrate the possibility of achieving a significantly higher gradient than existing SC structures.  
 
WEPMN092 Capture Cavity II Results at FNAL resonance, controls, linac, electron 2245
 
  • J. Branlard
  • G. I. Cancelo, R. H. Carcagno, B. Chase, H. Edwards, R. P. Fliller, B. M. Hanna, E. R. Harms, A. Hocker, T. W. Koeth, M. J. Kucera, A. Makulski, U. Mavric, M. McGee, A. H. Paytyan, Y. M. Pischalnikov, P. S. Prieto, R. Rechenmacher, J. Reid, K. R. Treptow, N. G. Wilcer, T. J. Zmuda
    Fermilab, Batavia, Illinois
  Funding: FRA

As part of the research and development towards the International Linear Collider (ILC), several test facilities have been developed at Fermilab. This paper presents the latest LLRF results obtained with Capture Cavity II at these test facilities. The main focus will be on controls and RF operations using the SIMCON based LLRF system. Details about hardware upgrades and overall system performance will be also explained. Finally, design considerations and objectives for the future test facility at the New Muon Laboratory (NML) will be presented.

 
 
WEPMN112 Multichannel Vector Field Control Module for LLRF Control of Superconducting Cavities controls, klystron, diagnostics, impedance 2298
 
  • P. Varghese
  • B. Barnes, J. Branlard, B. Chase, P. W. Joireman, D. W. Klepec, U. Mavric, V. Tupikov
    Fermilab, Batavia, Illinois
  The field control of multiple superconducting RF cavities with a single Klystron, such as the proposed RF scheme for the ILC, requires high density (number of RF channels) signal processing hardware so that vector control may be implemented with minimum group delay. The MFC (Multichannel Field Control) module is a 33-channel, FPGA based downconversion and signal processing board in a single VXI slot, with 4 channels of high speed DAC outputs. An LO input of upto 1.6 GHz can be divided down to provide 8 clock signals through a clock distribution chip. A 32-bit, 400MHz floating point DSP provides additional computational capability for calibration and implementation of more complex control algorithms. Both the FPGA and DSP have external SDRAM memory for diagnostic data and nonvolatile Flash memory for program and configuration storage. Multiple high speed serial transceivers on the front panel and the backplane bus allow a flexible architecture for inter-module real time data exchanges. An interface CPLD supports the VXI bus protocol for communication to a Slot0 CPU, with Ethernet connections for remote in system programming of the FPGA and DSP as well as for data acquisition.  
 
WEPMN114 Modular Multiple Frequency RF Amplifier controls, power-supply, klystron, ion 2304
 
  • M. A. Kempkes
  • M. P.J. Gaudreau, J. Kinross-Wright, I. Roth
    Diversified Technologies, Inc., Bedford, Massachusetts
  The construction and support of a wide range of RF amplifiers are significant cost components in the operation of the research community's accelerator facilities. This situation exists because amplifiers have been designed for a single application, often by multiple vendors, and therefore have very little commonality in their design, construction, and control interfaces for remote operation. To address these shortcomings, Diversified Technologies, Inc. (DTI) is developing a versatile and cost effective, modular RF amplifier design that can be employed across a wide range of RF amplifier requirements. Regardless of frequency or power, amplifiers built on this model feature commonality of design, controls system, and spares. A marriage of solid-state RF driver, power conditioning and control circuitry with high power Vacuum Electronic Device (VED) power amplifiers provide the ultimate in modular, cost-effective, and re-configurable RF power sources. In this paper, DTI will describe the modular RFA amplifier's topology and operating theory, and progress to date in the development of a prototype.  
 
WEPMN116 Plans for Precision RF Controls for FERMI@ELETTRA controls, linac, klystron, beam-loading 2310
 
  • L. R. Doolittle
  • J. M. Byrd, A. Ratti, J. W. Staples, R. B. Wilcox
    LBNL, Berkeley, California
  • G. D'Auria, M. Ferianis, M. M. Milloch, A. Rohlev
    ELETTRA, Basovizza, Trieste
  • M. W. Stettler
    CERN, Geneva
  FERMI@ELETTRA is a 4th generation light source under construction at Sincrotrone Trieste. It will be operated as a seeded FEL driven by a warm S-band linac presently serving as the injector for the ELETTRA storage ring. Operation as an FEL driver places much more stringent specifications on control of the amplititude and phase of the RF stations than in its present operation. This paper describes a conceptual design of an upgrade to the RF controls to achieve these specifications. The system consists of a stabilized distribution of the master oscillator signal providing a reference to local digital RF controllers . The RF reference distribution system takes advantage of recent breakthroughs in optical techniques where stabilized fiber lasers are used to provide a very accurate control of RF phases over long distances. The RF controller is based on recent improvements on modern digital systems, using a 14-bit high speed digitizer in combination with an FPGA and high speed DAC. This paper also presents experimental results of early tests performed as a feasibility study of the system.  
 
WEPMS018 Superconducting Materials Testing with a High-Q Copper RF Cavity klystron, cryogenics, superconductivity, monitoring 2370
 
  • A. Canabal
  • G. B. Bowden, V. A. Dolgashev, J. R. Lewandowski, C. D. Nantista, S. G. Tantawi
    SLAC, Menlo Park, California
  • I. E. Campisi
    ORNL, Oak Ridge, Tennessee
  • T. Tajima
    LANL, Los Alamos, New Mexico
  Magnesium diboride (MgB2) has a transition temperature (Tc) of ~40 K, i.e., about 4 times higher than niobium (Nb) that has been used for recent accelerators. The studies in the last 3 years have shown that it could have about one order of magnitude less RF surface resistance (Rs) than Nb and much less power dependence compared to high-Tc materials such as YBCO up to ~400 Oe. The tests to check the RF critical magnetic field, an important parameter to determine the feasibility for accelerator application, are underway. We are planning to test different thickness films and with different coating methods. This paper describes the results obtained so far. One of the objectives is to verify Gurevich's theory of getting higher critical field than Nb by adding a very thin layer (less than penetration depth) to Nb. In addition, some CW tests on power dependence up to higher magnetic fields are planned and some results will be shown if available at the time of conference.  
 
WEPMS022 Gain Scheduled Neural Network Tuned PI Feedback Control System for the LANSCE Accelerator controls, linac 2379
 
  • S. Kwon
  • J. Davis, M. T. Lynch, M. S. Prokop, S. Ruggles, P. A. Torrez
    LANL, Los Alamos, New Mexico
  The current LANSCE LLRF system is an analog proportional/integral (PI) feedback control system that achieves amplitude and phase errors within 1% and 1 degree. The feedback system receives the cavity amplitude and phase, and the crosstalk between the amplitude and phase is significant. In this note, we propose an In-phase (I) and Quadrature (Q) based feedback control system which easily decouples the crosstalk of I and Q channels. For LANSCE-R, the current RF amplifier chain has to be preserved, so the controller output I/Q is transferred back to amplitude/phase values which drive the RF amplifier chain. The resultant feedback system reduces transient peaks of the RF and hence reduces the degradation of the RF amplifier chain. Self-tuning is performed every clock cycle. This feature of the feedback controller can reduce the beam loading transient drastically. The proposed control system is implemented with the Altera Stratix II FPGA. The proposed control system will first be tested on the low power test-stand to determine the robustness of the algorithm and will then be tested on a LANSCE Drift Tube Linac (DTL) tank.  
 
WEPMS025 LANSCE-R Low Level RF Control System controls, resonance, beam-loading, monitoring 2388
 
  • M. S. Prokop
  • S. Kwon, S. Ruggles, P. A. Torrez
    LANL, Los Alamos, New Mexico
  The Los Alamos Neutron Science Center proton accelerator is scheduled for refurbishment. A new low level RF(LLRF) system is part of the refurbishment plan since the existing LLRF system is analog-based and requires significant setup and maintenance time. Both field and resonance control aspects of the current system do not have the flexibility to meet future performance requirements. The LANSCE accelerator provides both H+ and H- beams and due to the various user requirements there are a number of different beam pulse types varying in timing and current. In order to meet user needs, LANSCE must simultaneously transport both H+ and H- in the accelerator. These requirements have motivated the development of a new LLRF system based on software defined radio technology. The new system will include field control using feedback and adaptive feed forward techniques, an upgraded resonance controller with frequency agility to improve startup and fault recovery times and a high power amplifier pre-compensation controller for improved cavity fill times and amplifier efficiency. Among the challenges with implementing the new system are interfacing with existing subsystems of the accelerator.  
 
WEPMS026 Improved Tuning Methods for Converter-Modulators linear-collider, collider, impedance, operational-performance 2391
 
  • W. Reass
  • R. F. Gribble
    LANL, Los Alamos, New Mexico
  Funding: This work is supported by the office of Basic Energy Sciences and the Office of Science of the Department of Energy

The converter-modulator is a resonant power conditioning configuration that is optimized for a particular load impedance or parameter space. Although traction motor IGBT's are typically used for hard-switching application in the 1 kHz regime, the present use of high-power (10 - 15 MW) converter-modulators have used a 20 kHz resonant switching topology. This presents design challenges to maintain efficient and reliable switching characteristics for the IGBT's. Improved tuning methods and circuit topological changes now offer a significant reduction in IGBT switching losses as compared to those used with the Spallation Neutron Source (SNS) design (perhaps by 10). These circuit and topology changes should also permit Pulse Width Modulation (PWM) of the modulator output voltage to provide a regulated voltage without anomalous IGBT switching characteristics. This paper will review the results of this investigation based on models developed from the SNS converter-modulator operational data.

 
 
WEPMS032 Pre-conceptual Design of Automated Systems for SRF Cavity Assembly and Optical Inspection linear-collider, superconductivity, radio-frequency, vacuum 2409
 
  • T. Tajima
  • M. J. Borden, A. Canabal, T. A. Harden, P. C. Pittman
    LANL, Los Alamos, New Mexico
  The International Linear Collider (ILC) will require ~20,000 Superconducting Radio- Frequency (SRF) cavities. Improving the yield of high-gradient (>35 MV/m) cavities is currently one of the most critical issues for the ILC. The LANL has been tasked to analyze the failure and feedback the results to the industry and academia. We have started an effort to develop a pre-conceptual design of an automated system to optically inspect the inner surface that showed heating with a thermometry system. We have also started a pre-conceptual design of an automated system for assembling and sealing the flanges after high-pressure rinsing in the clean room. This could reduce the chance of particle contamination due to touch labor, leading to a field emission free cavities and higher yield of high-gradient cavities.  
 
WEPMS036 LCLS LLRF Upgrades to the SLAC Linac linac, klystron, controls, laser 2421
 
  • R. Akre
  • J. M. Byrd
    LBNL, Berkeley, California
  • D. Dowell, P. Emma, J. C. Frisch, B. Hong, K. D. Kotturi, P. Krejcik, J. Wu
    SLAC, Menlo Park, California
  Funding: DOE

The Linac Coherent Light Source at SLAC will be the brightest X-ray laser in the world when it comes on line. In order to achieve the brightness a 100fS length electron bunch is passed through an undulator. To creat the 100fS bunch, a 10pS electron bunch, created from a photo cathode in an RF gun, is run off crest on the RF to set up a position to energy correlation. The bunch is then compressed chicanes. The stability of the RF system is critical in setting up the position to energy correlation. Specifications derived from simulations require the RF system to be stable to below 100fS in several critical injector stations and the last kilometer of linac. The SLAC linac RF system is being upgraded to meet these requirements.

 
 
WEPMS047 Selecting RF Amplifiers for Impedance Controlled LLRF Systems - Nonlinear Effects and System Implications controls, impedance, klystron, simulation 2451
 
  • J. D. Fox
  • T. Mastorides, C. H. Rivetta, D. Van Winkle
    SLAC, Menlo Park, California
  Funding: Work supported by the U. S. Department of Energy under contract #DE-AC02-76SF00515

Several high-current accelerators use feedback techniques in the accelerating RF systems to control the impedances seen by the circulating beam. These Direct and Comb Loop architectures put the high power klystron and LLRF signal processing components inside feedback loops, and the ultimate behavior of the systems depends on the individual sub-component properties. Imperfections and non-idealities in the signal processing leads to reduced effectiveness in the impedance controlled loops. In the PEP-II LLRF systems non-linear effects have been shown to reduce the achievable beam currents, increase low-mode longitudinal growth rates and reduce the margins and stability of the LLRF control loops. We present measurements of the driver amplifiers used in the PEP-II systems, and present measurement techniques needed to quantify the small-signal gain, linearity, transient response and image frequency generation of these amplifiers. Results are presented from measurements of 5 different types of amplifiers, and the trade-offs in selecting between them highlighted.

 
 
WEPMS060 A Digital Self Excited Loop for Accelerating Cavity Field Control controls, resonance, linac, electron 2481
 
  • C. Hovater
  • T. L. Allison, J. R. Delayen, J. Musson, T. E. Plawski
    Jefferson Lab, Newport News, Virginia
  Funding: Notice: Authored by Jefferson Science Associates, LLC under U. S. DOE Contract No. DE-AC05-06OR23177.

We have developed a digital process that emulates an analog oscillator and ultimately a self excited loop (SEL) for field control. The SEL, in its analog form, has been used for many years for accelerating cavity field control. In essence the SEL uses the cavity as a resonant circuit – much like a resonant ?tank? circuit is used to build an oscillator. An oscillating resonant circuit can be forced to oscillate at different, but close, frequencies to resonance by applying a phase shift in the feedback path. This allows the circuit to be phased locked to a master reference, which is crucial for multiple cavity accelerators. For phase and amplitude control the SEL must be forced to the master reference frequency, and feedback provided for in both dimensions. The novelty of this design is in the way digital signal processing (DSP) is structured to emulate an analog system. While the digital signal processing elements are not new, to our knowledge this is the first time that the digital SEL concept has been designed and demonstrated. This paper reports on the progress of the design and implementation of the digital SEL for field control of superconducting accelerating cavities.

 
 
WEPMS062 Development of a Superconducting Connection for Niobium Cavities vacuum, electron, superconductivity, coupling 2484
 
  • P. Kneisel
  • G. Ciovati, J. S. Sekutowicz
    Jefferson Lab, Newport News, Virginia
  • A. Matheisen, W. Singer, X. Singer
    DESY, Hamburg
  Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U. S. DOE Contract No. DE-AC05-06OR23177.

Several, partially successful attempts have been made to develop a superconducting connection between adjacent niobium cavities with the capability to carry up to 30 mT of the magnetic flux. Such a connection would be particularly of great benefit to layouts of long accelerators like ILC because it would shorten the distances between structures and therefore the total length of an accelerator with the associated cost reductions. In addition the superconducting connection would be ideal for a super-structure, two multi-cell cavities connected through a half wavelength long beam pipe providing the coupling. Two welded prototypes of super-structure have been successfully tested with the beam at DESY. The chemical treatment and water rinsing was rather complicated for these prototypes. We have engaged in a program to develop such a connection based on the Nb55Ti material. Several options are pursued such as e.g.a two-cell cavity is being used to explore the reachable magnetic flux for the TESLA like connection with a squeezed niobium gasket between the flanges. In this contribution we will report about the progress of our investigations.

 
 
WEPMS081 Simulation and Initial Test Result of the SNS Ring RF System simulation, controls, beam-loading, beam-losses 2520
 
  • Y. Zhang
  • M. S. Champion, P. Chu, S. M. Cousineau, V. V. Danilov, T. W. Hardek, J. A. Holmes, H. Ma, M. F. Piller, M. A. Plum
    ORNL, Oak Ridge, Tennessee
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy

A simulation code has been developed for the study of the Spallation Neutron Source (SNS) ring RF control. The code uses the time-domain solvers to compute beam-cavity interactions, and FFT methods to simulate time responses of the linear RF system. The important ingredients of the system are considered in the simulation model, which include the beam loading, dynamic cavity detuning, circuit bandwidth, loop delay, proportional-integral (P-I) controller for feedback and adaptive feed forward, stochastic noise, with-in-turn RF parameter change, beam current fluctuation and beam bunch leakage, etc. The beam loss in the accumulation ring goes up as the beam power increases, and thus a precise control of bunching voltage phase and amplitude is required to limit beam loss. This simulation tool will help the development a correct RF control and to achieve the goal of minimizing the beam loss.

 
 
WEPMS082 PVC - An ILC RF Cryomodule Software Simulator controls, klystron, simulation, superconducting-RF 2523
 
  • J. K. Keung
  • N. Lockyer
    TRIUMF, Vancouver
  • S. Nagaitsev
    Fermilab, Batavia, Illinois
  • F. M. Newcomer
    University of Pennsylvania, Philadelphia, Pennsylvania
  The Penn Virtual Cavity (PVC) simulator is a object oriented RF Cavity simulator with a user friendly Linux GUI, as well as a web interface. It is a tool to help understand the effects of each component in the RF system. It can simulate an International Linear Collider (ILC) cryomodule consisting of eight 9-cell cavities, together with its associated high voltage modulator, a klystron, and RF power distribution system. The uses range from experts designing LLRF control algorithms, to beginners learning about the general RF characteristics of the SRF cavities. PVC explores effects such as Lorentz Detuning, beam loading (with bunch to bunch fluctuations), 8/9pi modes, I/Q feedback and feedforward, cavity Q-drop, amplitude and phase jitter and ripples, as well as calibration errors. The current status of the PVC and the conclusions derived from the simulations will be reported, along with comparisons to the DESY-TTF cryomodules.

http://einstein.hep.upenn.edu/~keungj/simulation.html

 
 
WEPMS085 A 17 GHz High Gradient Linac having Stainless Steel Surfaces in the High Intensity Magnetic and Electric Field Regions of the Structure linac, coupling, linear-collider, collider 2532
 
  • J. Haimson
  • B. L. Mecklenburg
    HRC, Santa Clara, California
  Funding: Work performed under the auspices of the U. S. Department of Energy SBIR Grant No. DE-FG02-05ER84362.

To avoid surface erosion damage and to assist in understanding RF breakdown limitations imposed on high gradient linac operation, a gradient hardened structure is being fabricated having high temperature brazed and machined stainless steel surfaces located in the high E-field region of the beam apertures and in the high H-field regions of the racetrack shaped coupling cavities. The microwave design parameters and physical dimensions of this 17GHz, 2pi/3 mode, 22-cavity structure were established specifically to allow comparison of its high gradient performance to that of a similar all-copper structure tested under identical conditions, using an existing 4X power amplifying, RF recirculating dual ring system. Use of the 6X thicker skin depth material, the resulting de-Q-ing effects and the minimal reduction of beam energy (2%) associated with the strategically located lossy surfaces are discussed; fabrication techniques are described; and design parameters of the gradient hardened linac and the 17GHz power amplifying system are presented.

 
 
WEPMS087 Conceptual Design of an L-Band Recirculating Superconducting Traveling Wave Accelerating Structure coupling, acceleration, collider, simulation 2538
 
  • A. Kanareykin
  • P. V. Avrakhov, Z. Liu
    Euclid TechLabs, LLC, Solon, Ohio
  • W. Gai
    ANL, Argonne, Illinois
  • S. Kazakov
    KEK, Ibaraki
  • N. Solyak
    Fermilab, Batavia, Illinois
  • V. P. Yakovlev
    Omega-P, Inc., New Haven, Connecticut
  Funding: This research is supported by the US Department of Energy

We describe a conceptual design for a superconducting traveling wave accelerator for the ILC. The RF feedback system plus phase shifter can redirect the accelerating wave that passed through the STWA section back to the input of the accelerating structure. In this paper, the STWA cell shape optimization, coupler cell design and rat race ring coupler in the feedback loop are presented. The STWA cell shape is similar to the LL cavity with a 60 mm disk diameter. A 9-cell STWA operates at the mode with group velocity as low as 0.0106 c. Both the ratio of peak electric field and magnetic field to the axial electric field are smaller than in the TESLA 9-cell cavity. The STWA structure has more cells per unit length than a TESLA structure but provides an accelerating gradient higher than a TESLA structure, consequently reducing the cost. The designed rat race directional coupler with four ports has ?3 dB direct coupling coefficients, 16.5 MHz bandwidth between ?30 dB isolations and 1.1 MHz bandwidth between ?30 dB reflection coefficients. Effects of the mechanical tolerances are also discussed.

 
 
THXC01 LHC Beam Instrumentation coupling, beam-losses, synchrotron, pick-up 2630
 
  • O. R. Jones
  The LHC will have very tight tolerances on all beam parameters. Their precise measurement is therefore very important for controlling and understanding the machine. With over two orders of magnitude higher stored beam energy than previous colliders, machine protection is also an issue, with any beam losses having to be closely monitored. This presentation will aim to give an overview of the beam instrumentation foreseen for the LHC together with the requirements for initial and nominal operation. A summary of the main systems will be followed by a discussion of areas where there have been recent advances, such as in the measurement of tune, chromaticity and coupling.  
slides icon Slides  
 
THPMN056 Comparison of ILC Fast Beam-Beam Feedback Performance in the e-e- and e+e- Modes of Operation luminosity, ground-motion, simulation, lattice 2832
 
  • M. Alabau
  • P. Bambade
    LAL, Orsay
  • A. Faus-Golfe
    IFIC, Valencia
  • A. Latina, D. Schulte
    CERN, Geneva
  Several feedback loops are required in the Beam Delivery System (BDS) of the International Linear Collider (ILC) to preserve the luminosity in the presence of dynamic imperfections. Realistic simulations have been carried out to study the performance of the beam-beam deflection based fast feedback system, for both e+e- and e-e- modes of operation. The beam-beam effects in the e-e- collisions make both the luminosity and the deflections more sensitive to offsets at the IP than in the case of the e+e- collisions. This reduces the performance of the feedback system in comparison to the standard e+e- collisions, and may require a different beam parameter optimization.  
 
THPMN059 Feedback Studies luminosity, emittance, ground-motion, linac 2841
 
  • A. Latina
  • G. Rumolo, D. Schulte, R. Tomas
    CERN, Geneva
  Funding: Supported by the European Community under the 6th Framework Programme "Structuring the European Research Area".

Dynamic imperfections in future linear colliders can lead to a significant luminosity loss. We discuss different orbit feedback strategies in the main linac that can mitigate the emittance dilution and compare their efficiency. We also address the impact of ground motion in the beam delivery system and the potential cures.

 
 
THPMN079 Simulation of ILC Feedback BPM Signals in an Intense Background Environment background, simulation, extraction, alignment 2889
 
  • A. F. Hartin
  • R. Arnold, S. Molloy, S. Smith, M. Woods
    SLAC, Menlo Park, California
  • P. Burrows, G. B. Christian, C. I. Clarke, B. Constance, H. D. Khah, C. Perry, C. Swinson, G. R. White
    JAI, Oxford
  • A. Kalinin
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  Funding: This work is supported in part by the Commission of the European Communities under the 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899.

Experiment T-488 at SLAC, End Station A recorded distorted BPM voltage signals and an accurate simulation of these signals was performed. Geant simulations provided the energy and momentum spectrum of the incident spray and secondary emissions, and a method via image charges was used to convert particle momenta and number density into BPM stripline currents. Good agreement was achieved between simulated and measured signals. Further simulation of experiment T-488 with incident beam on axis and impinging on a thin radiator predicted minimal impact due to secondary emission. By extension to worst case conditions expected at the ILC, simulations showed that background hits on BPM striplines would have a negligible impact on the accuracy of beam position measurements and hence the operation of the FONT feedback system

 
 
THPMS072 Superconducting Traveling Wave Ring with High Gradient Accelerating Section beam-loading, resonance, coupling, controls 3148
 
  • P. V. Avrakhov
  • N. Solyak
    Fermilab, Batavia, Illinois
  Considerable gain of a superconducting linac accelerating gradient provides using of a traveling wave structure instead of a standing wave accelerating section. Preservation of the superconducting structure advantages requires to put the TW accelerating section into a superconducting traveling wave ring (STWR). We discuss two variants of the STWR with one and two feeding couplers. The STWR application allows to increase the superconducting section accelerating gradient up to ~50 MV/m and essentially reduce the price of the section tuning system.  
 
THPAN037 Beam-Beam Effects Observed at KEKB luminosity, simulation, emittance, betatron 3309
 
  • Y. Funakoshi
  • K. Ohmi, K. Oide, M. Tawada
    KEK, Ibaraki
  KEKB is an e+ e- collider with a world-highest luminosity of 1.7 x 1034 /cm2/s. It has a half-crossing angle of 11 mrad. We are installing crab cavities for the purpose of eliminating effects of crossing angle in the begining of 2007. Another feature of KEKB is that its operating points are very close to the half interger in the horizontal direction. This report summarizes beam-beam effects observed at KEKB.  
 
THPAN048 Numerical Solver with CIP Method for Fokker Planck Equation of Stochastic Cooling simulation, pick-up, kicker, impedance 3336
 
  • T. Kikuchi
  • T. Katayama
    CNS, Saitama
  • S. Kawata
    Utsunomiya University, Utsunomiya
  A Fokker Planck equation for a Stochastic cooling* is solved by using the CIP method**. The Fokker Planck equation can be described in a convection-diffusion equation as a function of time and energy. The equation is a non linear form and the evolution of the distribution function should be numerically solved. The CIP method, which is an effective scheme to solve the convection term numerically, is applied to the Fokker Planck equation of the Stochastic cooling. By using the CIP method for the numerical solver, we can effectively calculate the time-dependent Fokker Planck equation in more few computational costs. The developed numerical solver can give us the energy spectrum of the particle distribution during the beam cooling. The simulation results show the good agreements compared with the experimental results.

* S. Van der Meer, CERN/PS/AA/78-22, 1978.** T. Yabe and T. Aoki, Comp. Phys. Commun. 66 (1991) 219.

 
 
FROAKI02 LHC Magnet Tests: Operational Techniques and Empowerment for Successful Completion cryogenics, dipole, quadrupole, superconducting-magnet 3742
 
  • V. Chohan
  • N. Ali, P. Awale, S. Bahuguna, V. Chauhan, M. Y. Dixit, J. A. Gore, J. John, E. Kandaswamy, A. Kasbekar, P. Kashyap, C. P. Kulkarni, A. Laddha, S. Malhotra, M. Mascarenhas, J. K. Mishra, P. Motiwala, K. Nair, R. Narayanan, S. Padmakumar, A. Pagare, D. Peruppayikkad, S. Raghunathan, S. Rao, D. Roy, S. Sethumadhavan, S. Sharma, S. Shimjith, S. Singh, S. T. Sonnis, P. Surendran, A. Tikaria
    BARC, Mumbai
  • U. Bhunia
    DAE/VECC, Calcutta
  • G. H. Hemelsoet, F. Pirotte, K. Priestnall, E. Veyrunes
    CERN, Geneva
  • A. Kasliwal
    RRCAT, Indore (M. P.)
  The LHC magnet tests operation team* developed various innovative techniques, particularly since early 2004, to complete the superconductor magnet testing by end 2006. Overall and cryogenic priority handling, rapid on-bench thermal cycling, rule-based goodness evaluation on round-the-clock basis, multiple, mashed web systems are some of these techniques applied with rigour for successful tests completion in time. This paper highlights these operation empowerment tools which had a pivotal role for success. A priority handling method was put in place to enable maximum throughput from twelve test benches, having many different constraints. For the cryogenics infrastructure, it implied judicious allocation of limited resources to the benches. Rapid On-Bench Thermal Cycle was a key strategy to accelerate magnets tests throughput, saving time and simplifying logistics. First level magnet appraisal was developed for 24 hr decision making so as to prepare a magnet further for LHC or keep it on standby. Web based systems (Tests Management and E-Traveller) were other essential ideas to track & coordinate various stages of tests handled by different teams.  
slides icon Slides  
 
FROAC04 Sub-10 Femtosecond Stabilization of a Fiber Link Using a Balanced Optical Cross Correlator laser, polarization, free-electron-laser, electron 3804
 
  • F. Loehl
  • J. Chen, F. X. Kaertner, J. Kim, F. Wong
    MIT, Cambridge, Massachusetts
  • J. M. Mueller
    TUHH, Hamburg
  • H. Schlarb
    DESY, Hamburg
  Synchronization of various components with fs stability is needed for the operation of free-electron-lasers such as FLASH or the European XFEL. One possibility to realize a high precision synchronization is to use a mode-locked Er-doped fiber laser as a master clock and to distribute ultra short laser pulses inside the machine using actively stabilized fiber links. In this paper we demonstrate the stabilization of a 300 m long fiber link with a self-aligned balanced cross-correlator using a single type II phase-matched PPKTP crystal. This approach allowed us to reduce the timing jitter added by the link to below 10 fs.  
slides icon Slides  
 
FROAC06 Survey of LLRF Development for the ILC controls, klystron, linac, linear-collider 3810
 
  • J. Branlard
  • B. Chase
    Fermilab, Batavia, Illinois
  • S. Michizono
    KEK, Ibaraki
  • S. Simrock
    DESY, Hamburg
  Funding: FRA

The key to a successful LLRF design for the International Linear Collider (ILC) relies on a combined effort from the different laboratories involved in this global project. This paper covers the ILC LLRF design progress both long term and for current test facilities around the world. Much of the focus is towards the ILC Test Area and on inter-laboratories collaborations. The SIMCON controller board, originally developed at DESY has been successfully used at FNAL to control the superconducting capture cavity I and II. A joined effort is also underway to modify its hardware to improve its noise performance and upgrading the firmware to achieve a higher intermediate frequency operation. In parallel, several simulation models (U-Penn, FNAL) have been developed in addition to the Simulink based model from DESY. The motivation is to investigate such issues as variable gradients, low beam conditions and bunch compression. Finally, an active exchange of knowledge and expertise continues to occur during collaboration meetings and through mutual participation in accelerator tests and commissioning (Dec06/Jan07 at DESY).

 
slides icon Slides  
 
FRPMN037 Ion Instability in the ILC Damping Ring ion, damping, simulation, electron 4030
 
  • E.-S. Kim
  • K. Ohmi
    KEK, Ibaraki
  Ions created by electron beam trapped in a bunch oscillate with a certain frequency, with the result that the beam oscillate with the same frequency. Recent high intensity and low emittance rings, the growth rate of this ion instability is very rapid. Super B factory and ILC damping ring, which are similar design parameter, are extremely low emittance. We discuss the ion instability for these rings.  
 
FRPMN038 Simulation of Synchro-betatron Sideband Instability caused by Electron Clouds at KEKB simulation, electron, betatron, emittance 4033
 
  • J. W. Flanagan
  • E. Benedetto
    CERN, Geneva
  • J. Hyunchang
    POSTECH, Pohang, Kyungbuk
  • K. Ohmi
    KEK, Ibaraki
  Electron cloud causes a fast head-tail instability above a threshold density. Experiments at KEKB showed synchro-betatron sideband, which indicates the head-tail instability. The sideband appears near νy+kνs, where 1<k<2, that differs from ordinary instability seen near νys. We investigate the origin of the sideband using a computer simulation.  
 
FRPMN069 Longitudinal Coupled-Bunch Instabilities in the CERN PS impedance, emittance, dipole, brightness 4180
 
  • H. Damerau
  • S. Hancock, C. Rossi, E. N. Shaposhnikova, J. Tuckmantel, J.-L. Vallet
    CERN, Geneva
  • M. Mehler
    GSI, Darmstadt
  Funding: Work supported by EU Design Study DIRACsecondary-Beams (contract 515873).

Longitudinal coupled bunch instabilities in the CERN PS represent a major limitation to the high brightness beam delivered for the LHC. To identify possible impedance sources for these instabilities, machine development studies have been carried out. The growth rates of coupled bunch modes have been measured, and modes have been identified using mountain range data. Growth rate estimations from coupled bunch mode theory are compared to these results. It is shown that the longitudinal impedance of the broad resonance curve of the main 10 MHz RF system can be identified as the most probable source. Possible methods to improve the beam stability are analyzed together with the performance of a damping system.

 
 
FRPMN076 Nominal LHC Beam Instability Observations in the CERN Proton Synchrotron electron, extraction, betatron, proton 4222
 
  • R. R. Steerenberg
  • G. Arduini, E. Benedetto, A. Blas, W. Hofle, E. Metral, M. Morvillo, C. Rossi, G. Rumolo
    CERN, Geneva
  The nominal LHC beam has been produced successfully in the CERN Proton Synchrotron since 2003. However, after having restarted the CERN PS in spring 2006, the LHC beam was set-up and observed to be unstable on the 26 GeV/c extraction flat top. An intensive measurement campaign was made to understand the instability and to trace its source. This paper presents the observations, possible explanations and the necessary measures to be taken in order to avoid this instability in the future.  
 
FRPMN081 A Preliminary Study of Beam Instabilities in Top-up Operation at Taiwan Light Source storage-ring, ion, vacuum, synchrotron 4246
 
  • P. J. Chou
  • H.-P. Chang, K. T. Hsu, K. H. Hu, C.-C. Kuo, G.-H. Luo, M.-H. Wang
    NSRRC, Hsinchu
  The storage ring of Taiwan Light Source started to operate fully in top-up mode since October 2005. The beam current has been gradually increased to 300 mA in routine user operation. Phenomena of collective effects were observed at 300 mA in top-up operation mode. Active feedback systems were implemented to stabilize the beam in top-up mode. Results of beam observation and analysis will be presented.  
 
FRPMN086 Beam Position Monitoring System Upgrade for the TLS controls, electron, diagnostics, power-supply 4276
 
  • C. H. Kuo
  • J. Chen, P. C. Chiu, K. T. Hsu, K. H. Hu
    NSRRC, Hsinchu
  Taiwan light source (TLS) equips with 59 beam position monitors (BPM). Existing Bergos's type multiplexing BPM electronics are working well during last decade. To improve the functionality of the BPM system, new type of BPM electronics (Liberal Electron) will be replace some existing multiplexing BPM electronics. Seamless integration of two kinds of electronics is via reflective memory. The high precision closed orbits were measured by multiplexing BPM via multi-channel PMC form factor 16-bits ADC modules and gigabit Ethernet fast access channel of Libera Electron. Turn-by-turn beam position measurement is also supported by new BPM electronics. Tune measurement is also possible by spectra analysis of the turn-by-turn beam position data. The preliminary version of the orbit data was sampled every millisecond. Fast orbit data were shared by reflective memory network to support fast orbit feedback application. Averaged data were updated to control database at a rate of 10 Hz. The system structure, software environment and preliminary beam test of the BPM system are summarized in this report.  
 
FRPMN090 A Prototype Energy Spectrometer for the ILC at End Station A in SLAC dipole, linac, collider, linear-collider 4285
 
  • A. Lyapin
  • C. Adolphsen, R. Arnold, C. Hast, D. J. McCormick, Z. Szalata, M. Woods
    SLAC, Menlo Park, California
  • S. T. Boogert, G. E. Boorman
    Royal Holloway, University of London, Surrey
  • M. V. Chistiakova, Yu. G. Kolomensky, E. Petigura, M. Sadre-Bazzaz
    UCB, Berkeley, California
  • V. N. Duginov, S. A. Kostromin, N. A. Morozov
    JINR, Dubna, Moscow Region
  • F. Gournaris, B. Maiheu, D. J. Miller, M. Wing
    UCL, London
  • M. Hildreth
    Notre Dame University, Notre Dame, Iowa
  • H. J. Schreiber, M. Viti
    DESY Zeuthen, Zeuthen
  • M. Slater, M. Thomson, D. R. Ward
    University of Cambridge, Cambridge
  The main physics programme of the international linear collider requires a measurement of the beam energy with a relative precision on the order of 10-4 or better. To achieve this goal a magnetic spectrometer using high resolution beam position monitors (BPM) has been proposed. A prototype spectrometer chicane using 4 dipole magnets is currently under development at the End Station A in SLAC, intending to demonstrate the required stability of this method and investigate possible systematic effects and operational issues. This contribution reports on the successful commissioning of the beam position monitor system and the resolution and stability achieved. Also, the initial results from a run with a full spectrometer chicane are presented.  
 
FRPMN108 Coupled-Bunch Instability Study of Multi-cell Deflecting Mode Cavities for the Advanced Photon Source damping, dipole, impedance, photon 4348
 
  • L. Emery
  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 short-pulse X-ray project at the Advanced Photon Source (APS) uses three room-temperature nine-cell 2.815 GHz deflecting-mode cavities in a straight section. Undamped, these cavities' higher-order and lower-order resonator modes will cause multi-bunch instabilities in longitudinal and transverse planes for any bunch pattern of a 1'000mA store. Damping of these modes must be part of the design of the cavities. We report calculations of instability growth rates and tracking simulations that were essential in specifying the rf design of the damping structures. We used various operating bunch patterns and scanned levels of damping of the cavities. Because one of the operating bunch patterns is not symmetric, we used a normal mode analysis * implemented in the APS code clinchor. Our calculation included random sampling of resonator frequencies in a reasonable range. We found that staggering of frequencies is only effective for modes that could not be heavily damped.

* K. Thompson and R. Ruth, PAC 1989

 
 
FRPMN116 Status of the RF BPM Upgrade at the Advanced Photon Source storage-ring, controls, instrumentation, power-supply 4390
 
  • A. Pietryla
  • H. Bui, G. Decker, R. Laird, R. M. Lill, W. E. Norum
    ANL, Argonne, Illinois
  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 (APS), a third-generation synchrotron light source, has been in operation for twelve years. The monopulse radio frequency (rf) beam position monitor (BPM) is one of three BPM types now employed in the storage ring at the APS. It is a broadband (10 MHz) system designed to measure single-turn and multi-turn beam positions, but it suffers from an aging data acquisition system. The replacement BPM system retains the existing monopulse receivers and replaces the data acquisition system with high-speed analog-to-digital converters (ADCs) and a field-programmable gate array (FPGA) that performs the signal processing. A first article system has been constructed and is currently being evaluated. This paper presents the results of testing of the first article system as well as the progress made in other areas of this upgrade effort.

 
 
FRPMN120 Tuning the Narrow-band Beam Position Monitor Sampling Clock to Remove the Aliasing Errors in APS Storage Ring Orbit Measurements storage-ring, photon, controls 4402
 
  • X. Sun
  • O. Singh
    ANL, Argonne, Illinois
  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 storage ring employs a real-time orbit correction system to reduce orbit motion up to 50 Hz. This system uses up to 142 narrow-band rf beam position monitors (Nbbpms) in a correction algorithm by sampling at a frequency of 1.53 kHz. Several Nbbpms exhibit aliasing errors in orbit measurements, rendering these Nbbpms unusable in real-time orbit feedback. The aliasing errors are caused by beating effects of the internal sampling clocks with various other processing clocks residing within the BPM electronics. A programmable external clock has been employed to move the aliasing errors out of the active frequency band of the real-time feedback system (RTFB) and rms beam motion calculation. This paper discusses the process of tuning and provides test results.

 
 
FRPMS039 Growth Time of Longitudinal Coupled Bunch Mode Instability in the Duke FEL Facility storage-ring, kicker, damping, electron 4036
 
  • Y. Kim
  • J. Li, Y. K. Wu
    FEL/Duke University, Durham, North Carolina
  To determine the required power of an RF amplifier for the longitudinal feedback system (LFS), the growth time of the longitudinal coupled bunch mode instability (CBMI) in the Duke storage ring should be known in advance. In 2005, we measured the longitudinal beam instability with four and eight symmetrically filled buckets in the Duke storage ring. By analyzing measured data, the growth time of the longitudinal CBMI can be estimated. At a beam energy of 274 MeV, the projected growth time is about 0.37 ms for a total stored current of 160 mA. To damp harmful longitudinal CBMI with a relative energy deviation of 0.1% (rms) within the growth time, a sufficient RF power of 135 W (rms) should be delivered to an LFS kicker at a central frequency of 758.8375 MHz. In this paper, we describe measurements of the growth time and the estimation of the RF power requirement for the LFS.  
 
FRPMS046 Optical-Fiber NOTCH Filter for Storage Ring Transverse Feedback System storage-ring, insertion, laser, betatron 4075
 
  • Y. Yin
  • X. Che
    Y. Y. Labs, Inc., Fremont, California
  • J. H. Wang, K. Zheng
    USTC/NSRL, Hefei, Anhui
  An optical-fiber two-tap FIR filter has been developed for storage ring transverse feedback system. The optical FIR filter has advantage of low loss which is not related to the size of the storage ring, and high-frequency response, compact in size. Measurements have been done with storage ring beam signal. The paper will present the principle and the experimental results.  
 
FRPMS052 H+ and H- Beam Position and Current Jitter at LANSCE isotope-production, linac, quadrupole, kicker 4105
 
  • J. D. Gilpatrick
  • B. Blind, M. S. Gulley, C. Pillai, J. F. Power
    LANL, Los Alamos, New Mexico
  Funding: *Work supported by the U. S. Department of Energy.

During the CY2005 and CY2006 Los Alamos Neutron Science Center (LANSCE) beam runs, six beam-development shifts were performed in order to acquire and analyze beam-current and beam-position jitter data for both the LANSCE H+ and H- beams. These data were acquired using three beam position monitors (BPMs) from the 100-MeV Isotope Production Facility (IPF) beam line and three BPMs from the Switchyard transport line at the end of the LANSCE 800-MeV linac. The two types of data acquired, intermacropulse and intramacropulse, were analyzed for statistical and frequency characteristics as well as various other correlations including comparing their phase-space characteristics in a coordinate system of transverse angle versus transverse position. This paper will briefly describe the measurements required to acquire these data, the analysis of these jitter data, and some interesting implications to beam operation.

 
 
FRPMS066 Commissioning the Fast Luminosity Dither for PEP-II luminosity, electron, positron, controls 4165
 
  • A. S. Fisher
  • S. Ecklund, R. C. Field, S. M. Gierman, P. Grossberg, K. E. Krauter, E. S. Miller, M. Petree, N. Spencer, M. K. Sullivan, K. K. Underwood, U. Wienands
    SLAC, Menlo Park, California
  • K. G. Sonnad
    LBNL, Berkeley, California
  Funding: Supported by US DOE under contract DE-AC03-76SF00515.

To maximize luminosity, a feedback system adjusts the relative transverse (x,y) position and vertical angle (y') of the electron and positron beams at the interaction point (IP) of PEP-II. The original system sequentially moved ("dithered") the electrons in four steps per coordinate. Communication with DC corrector magnets and field penetration through copper vacuum chambers led to a full-cycle time of 10 s. Machine tuning can move the beams at the IP and so had to be slowed to wait for the feedback. A new system installed in 2006 simultaneously applies a small sinusoidal dither to all three coordinates at 73, 87 and 103 Hz. Air-core coils around stainless-steel chambers give rapid field penetration. A lock-in amplifier at each frequency detects the magnitude and phase of the luminosity's response. Then corrections for all coordinates are determined using Newton's method, based on convergence from prior steps, and are applied by the same DC correctors used previously but with only one adjustment per cycle for an expected ten-fold increase in speed. We report on the commissioning of this system and on its performance in maintaining peak luminosity and aiding machine tuning.

 
 
FRPMS073 Picosecond Bunch Length and Energy-z Correlation Measurements at SLAC's A-Line and End Station A linac, synchrotron, simulation, electron 4201
 
  • S. Molloy
  • V. Blackmore
    OXFORDphysics, Oxford, Oxon
  • P. Emma, J. C. Frisch, R. H. Iverson, D. J. McCormick, M. Woods
    SLAC, Menlo Park, California
  • M. C. Ross
    Fermilab, Batavia, Illinois
  • S. Walston
    LLNL, Livermore, California
  Funding: US DOE Contract #DE-AC02-76FS00515

We report on measurements of picosecond bunch lengths and the energy-z correlation of the bunch with a high energy electron test beam to the A-line and End Station A (ESA) facilities at SLAC. The bunch length and the energy-z correlation of the bunch are measured at the end of the linac using a synchrotron light monitor diagnostic at a high dispersion point in the A-line and a transverse RF deflecting cavity at the end of the linac. Measurements of the bunch length in ESA were made using high frequency diodes (up to 100 GHz) and pyroelectric detectors at a ceramic gap in the beamline. Modelling of the beam's longitudinal phase space through the linac and A-line to ESA is done using the 2-dimensional tracking program LiTrack, and LiTrack simulation results are compared with data. High frequency diode and pyroelectric detectors are planned to be used as part of a bunch length feedback system for the LCLS FEL at SLAC. The LCLS also plans precise bunch length and energy-z correlation measurements using transverse RF deflecting cavities.

 
 
FRPMS074 Measurements of the Transverse Collimator Wakefields due to Varying Collimator Characteristics simulation, controls, impedance, insertion 4207
 
  • S. Molloy
  • C. D. Beard, J.-L. Fernandez-Hernando
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • A. Bungau
    UMAN, Manchester
  • S. Seletskiy, M. Woods
    SLAC, Menlo Park, California
  • J. D.A. Smith
    Cockcroft Institute, Warrington, Cheshire
  • A. Sopczak
    Lancaster University, Lancaster
  • N. K. Watson
    STFC/RAL/ASTeC, Chilton, Didcot, Oxon
  Funding: EUROtev Contract #011899RIDS US DOE Contract DEAC02-76SF00515

We report on measurements of the transverse wakefields induced by collimators of differing characteristics. An apparatus allowing the insertion of different collimator jaws into the path of a beam was installed in End Station A (ESA) in SLAC. Eight comparable collimator geometries were designed, including one that would allow easy comparison with previous results, and were installed in this apparatus. Measurements of the beam kick due to the collimator wakefields were made with a beam energy of 28.5 GeV, and beam dimensions of ~100 microns vertically and a range of 0.5 to 1.5 mm longitudinally. The trajectory of the beam upstream and downstream of the collimator test apparatus was determined from the outputs of ten BPMs (four upstream and six downstream), thus allowing a measurement of the angular kick imparted to the beam by the collimator under test. The transverse wakefield was inferred from the measured kick. The different aperture designs, data collection and analysis, and initial comparison to theoretical and analytic predictions are presented here.

* "An Apparatus for the Direct Measurement of Collimator Transverse Wakefields", P. Tenenbaum, PAC '99** "Direct Measurement of the Resistive Wakefield in Tapered Collimators", P Tenenbaum, PAC '04

 
 
FRPMS084 Detection of Instumental Drifts in the PEP II LER BPM System sextupole, controls, optics, pick-up 4261
 
  • W. Wittmer
  • A. S. Fisher, D. J. Martin, J. J. Sebek
    SLAC, Menlo Park, California
  Funding: US-DOE

During the last PEP-II run a major goal was to bring the Low-Energy Ring optics as close as possible to the design. Sudden artificial jumps of the orbit, which were regularly observed by a large number of BPMs during routine operation, were interfering with this effort. The source of the majority of these jumps had been traced to the filter-isolator boxes (FIBs) near the BPM buttons. A systematic approach to find and repair the failing units had been developed and implemented. Despite this effort, the instrumental orbit jumps never completely disappeared. To trace the source of this behavior a test setup, using a spare Bergoz MX-BPM processor (kindly provided by SPEAR III at SSRL) was connected in parallel to various PEP-II BPM processors. In the course of these measurements a slow instrumental orbit drift was found which was clearly not induced by a moving positron beam. Based on the size of the system and the limited time before the end of PEP II an accelerator improvement project was initiated to install BERGOZ BPM-MX processors close to all sextupoles.