• 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

• L. Hagge
  
• J. Buerger, J. A. Dammann, S. Eucker, A. Herz, J. Kreutzkamp, S. Panto, D. Szepielak, P. Tumidajewicz, N. Welle
  DESY, Hamburg

• M. G. Hoffmann
  
• S. Choroba, F. Eints, U. Hurdelbrink, P. Morozov, Y. Nechaev, J. Randhahn, S. Ruzin, S. Simrock, V. Soloviev
  DESY, Hamburg

• A. Winter
  
• W. J. Jalmuzna
  Warsaw University of Technology, Institute of Electronic Systems, Warsaw
• F. Loehl, H. Schlarb, P. Schmuser
  DESY, Hamburg

• M. Lonza
  
• D. Bulfone, V. Forchi', G. Gaio
  ELETTRA, Basovizza, Trieste

• W. X. Cheng
  
• T. Obina
  KEK, Ibaraki

• T. Obina
  
• W. X. Cheng, T. Honda, M. Tobiyama
  KEK, Ibaraki

• H. Ohgaki
  
• T. Kii, K. Masuda, T. Yamazaki, K. Yoshikawa, H. Zen
  Kyoto IAE, Kyoto

• 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

• 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

• 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

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.

• 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

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.

• H.-S. Kang
  
• J. Choi, K. M. Ha, E.-H. Lee, W. W. Lee, I. S. Park
  PAL, Pohang, Kyungbuk

• S.-C. Kim
  
• J. Choi, K. M. Ha, J. Y. Huang
  PAL, Pohang, Kyungbuk

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.

• G. Fernqvist
  
• P. Dreesen, G. Hudson
  CERN, Geneva
• J. R. Pickering
  Metron, Norwich

• R. J. Steinhagen
  
• A. Boccardi, M. Gasior, O. R. Jones, K. K. Kasinski
  CERN, Geneva

• C.-K. Chang
  
• H. C. Chen, M. J. Horng, J. A. Li, T. F. Lin, Y. K. Lin, Y.-C. Liu
  NSRRC, Hsinchu

• K. T. Hsu
  
• J. Chen, P. C. Chiu, S. Y. Hsu, K. H. Hu, C. H. Kuo, D. Lee
  NSRRC, Hsinchu

• 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

• S. Cohen
  
• S. R. Babel
  Bira, Albuquerque, New Mexico

• N. P. Di Monte
  

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.

• C. Yao
  
• N. P. Di Monte, W. E. Norum
  ANL, Argonne, Illinois

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.

• J. M. Weber
  
• M. J. Chin, CA. Timossi, E. C. Williams
  LBNL, Berkeley, California

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.

• 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

• 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

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.

• 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

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.

• W. Wittmer
  
• W. S. Colocho, G. R. White
  SLAC, Menlo Park, California

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.

• B. Lam
  
• P. Bellomo, D. Macnair, A. C. de Lira
  SLAC, Menlo Park, California

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.

• T. Mastorides
  
• J. D. Fox, C. H. Rivetta, D. Teytelman, D. Van Winkle
  SLAC, Menlo Park, California

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.

• 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

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.

• L. Bees
  
• L. Simpson, A. Tydeman
  Lambda, Neptune, New Jersey

• 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

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.

• J. Musson
  
• J. M. Grames, J. Hansknecht, R. Kazimi, M. Poelker
  Jefferson Lab, Newport News, Virginia

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

• H. Ma
  
• M. S. Champion, M. T. Crofford, T. W. Hardek, K.-U. Kasemir, M. F. Piller, Y. Zhang
  ORNL, Oak Ridge, Tennessee

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.

• 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

• Y.-C. Chao
  

• 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

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.

• 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

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.

• 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

• A. Gallo
  
• M. Bellaveglia, G. Gatti, C. Vicario
  INFN/LNF, Frascati (Roma)

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.

• 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

• 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

• R. Bartolini
  

• J. A. Safranek
  
• W. J. Corbett, S. M. Gierman, R. O. Hettel, X. Huang, J. J. Sebek, A. Terebilo
  SLAC, Menlo Park, California

• K. Ohmi
  
• R. Calaga
  BNL, Upton, Long Island, New York
• W. Hofle, R. Tomas, F. Zimmermann
  CERN, Geneva

• G. B. Shen
  
• H. Sako
  JAEA, Ibaraki-ken
• S. Sato
  JAEA/LINAC, Ibaraki-ken

• U. Dorda
  
• W. Fischer
  BNL, Upton, Long Island, New York
• V. D. Shiltsev
  Fermilab, Batavia, Illinois
• F. Zimmermann
  CERN, Geneva

• J. Keil
  

• 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

• N. Solyak
  
• V. Ivanov, C. S. Mishra, K. Ranjan
  Fermilab, Batavia, Illinois

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.

• 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

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.

• R. Nagaoka
  
• L. Cassinari, M.-E. Couprie, M. Labat, M.-P. Level, C. Mariette, R. Sreedharan
  SOLEIL, Gif-sur-Yvette

• K. Fong
  
• M. P. Laverty, Q. Zheng
  TRIUMF, Vancouver

• 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

• 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

• T. Matsumoto
  
• S. Fukuda, H. Katagiri, S. Michizono, Y. Yano
  KEK, Ibaraki
• Z. Geng
  IHEP Beijing, Beijing

• S. Michizono
  
• S. Fukuda, H. Katagiri, T. Matsumoto, T. Miura, Y. Yano
  KEK, Ibaraki
• Z. Geng
  IHEP Beijing, Beijing

• 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

• L. Shen
  
• Y. L. Chi, Q. M. Dai, X. W. Yang
  IHEP Beijing, Beijing

• 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)

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.

• H. S. Kim
  
• Y.-S. Cho, I.-S. Hong, D. I. Kim, H.-J. Kwon, K. T. Seol, Y.-G. Song
  KAERI, Daejon

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.

• K. T. Seol
  
• Y.-S. Cho, D. I. Kim, H. S. Kim, H.-J. Kwon
  KAERI, Daejon

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.

• 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

• 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

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.

• P. Varghese
  
• B. Barnes, J. Branlard, B. Chase, P. W. Joireman, D. W. Klepec, U. Mavric, V. Tupikov
  Fermilab, Batavia, Illinois

• M. A. Kempkes
  
• M. P.J. Gaudreau, J. Kinross-Wright, I. Roth
  Diversified Technologies, Inc., Bedford, Massachusetts

• 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

• 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

• S. Kwon
  
• J. Davis, M. T. Lynch, M. S. Prokop, S. Ruggles, P. A. Torrez
  LANL, Los Alamos, New Mexico

• M. S. Prokop
  
• S. Kwon, S. Ruggles, P. A. Torrez
  LANL, Los Alamos, New Mexico

• W. Reass
  
• R. F. Gribble
  LANL, Los Alamos, New Mexico

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.

• T. Tajima
  
• M. J. Borden, A. Canabal, T. A. Harden, P. C. Pittman
  LANL, Los Alamos, New Mexico

• 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

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.

• J. D. Fox
  
• T. Mastorides, C. H. Rivetta, D. Van Winkle
  SLAC, Menlo Park, California

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.

• C. Hovater
  
• T. L. Allison, J. R. Delayen, J. Musson, T. E. Plawski
  Jefferson Lab, Newport News, Virginia

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.

• P. Kneisel
  
• G. Ciovati, J. S. Sekutowicz
  Jefferson Lab, Newport News, Virginia
• A. Matheisen, W. Singer, X. Singer
  DESY, Hamburg

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.

• 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

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.

• J. K. Keung
  
• N. Lockyer
  TRIUMF, Vancouver
• S. Nagaitsev
  Fermilab, Batavia, Illinois
• F. M. Newcomer
  University of Pennsylvania, Philadelphia, Pennsylvania

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

• J. Haimson
  
• B. L. Mecklenburg
  HRC, Santa Clara, California

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.

• 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

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.

• O. R. Jones
  

• M. Alabau
  
• P. Bambade
  LAL, Orsay
• A. Faus-Golfe
  IFIC, Valencia
• A. Latina, D. Schulte
  CERN, Geneva

• A. Latina
  
• G. Rumolo, D. Schulte, R. Tomas
  CERN, Geneva

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.

• 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

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

• P. V. Avrakhov
  
• N. Solyak
  Fermilab, Batavia, Illinois

• Y. Funakoshi
  
• K. Ohmi, K. Oide, M. Tawada
  KEK, Ibaraki

• T. Kikuchi
  
• T. Katayama
  CNS, Saitama
• S. Kawata
  Utsunomiya University, Utsunomiya

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

• 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.)

• F. Loehl
  
• J. Chen, F. X. Kaertner, J. Kim, F. Wong
  MIT, Cambridge, Massachusetts
• J. M. Mueller
  TUHH, Hamburg
• H. Schlarb
  DESY, Hamburg

• J. Branlard
  
• B. Chase
  Fermilab, Batavia, Illinois
• S. Michizono
  KEK, Ibaraki
• S. Simrock
  DESY, Hamburg

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).

• E.-S. Kim
  
• K. Ohmi
  KEK, Ibaraki

• J. W. Flanagan
  
• E. Benedetto
  CERN, Geneva
• J. Hyunchang
  POSTECH, Pohang, Kyungbuk
• K. Ohmi
  KEK, Ibaraki

• H. Damerau
  
• S. Hancock, C. Rossi, E. N. Shaposhnikova, J. Tuckmantel, J.-L. Vallet
  CERN, Geneva
• M. Mehler
  GSI, Darmstadt

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.

• R. R. Steerenberg
  
• G. Arduini, E. Benedetto, A. Blas, W. Hofle, E. Metral, M. Morvillo, C. Rossi, G. Rumolo
  CERN, Geneva

• P. J. Chou
  
• H.-P. Chang, K. T. Hsu, K. H. Hu, C.-C. Kuo, G.-H. Luo, M.-H. Wang
  NSRRC, Hsinchu

• C. H. Kuo
  
• J. Chen, P. C. Chiu, K. T. Hsu, K. H. Hu
  NSRRC, Hsinchu

• 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

• L. Emery
  

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

• A. Pietryla
  
• H. Bui, G. Decker, R. Laird, R. M. Lill, W. E. Norum
  ANL, Argonne, Illinois

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.

• X. Sun
  
• O. Singh
  ANL, Argonne, Illinois

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.

• Y. Kim
  
• J. Li, Y. K. Wu
  FEL/Duke University, Durham, North Carolina

• Y. Yin
  
• X. Che
  Y. Y. Labs, Inc., Fremont, California
• J. H. Wang, K. Zheng
  USTC/NSRL, Hefei, Anhui

• J. D. Gilpatrick
  
• B. Blind, M. S. Gulley, C. Pillai, J. F. Power
  LANL, Los Alamos, New Mexico

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.

• 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

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.

• 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

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.

• 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

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

• W. Wittmer
  
• A. S. Fisher, D. J. Martin, J. J. Sebek
  SLAC, Menlo Park, California

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.