CERN, Geneva
The LHC hardware and beam commissioning and initial operation will be reviewed both in terms of beam and hardware performance. The implemented machine protection measures and their impact on LHC operation will be presented.
UCLA, Los Angeles, California
High brightness ultrashort electron beams have been produced at the UCLA Pegasus photoinjector lab for use in time-resolved electron diffraction applications. Beams have been generated with high enough brightness to obtain single shot diffraction patterns of thin solid targets. These beams contain a few pC at 3.5 MeV in a 200 fs pulse. Pump-probe experiments on thin metal foils have already shown promising results on picosecond time scales*. Current research focuses on materials with processes that are observable on the sub-100 fs scale. To overcome rf jitter and synchronization problems, electro-optic sampling is used as a single shot time-of-arrival diagnostic** to help reconstruct the melting "movie."
*P. Musumeci, et al., Rev. Sci. Instrum. 80, 013302 (2009)
**C. Scoby, et al., PR-ST Beams and Accel. 13 (2010)
CERN, Geneva
After the incident on the 19th September 2008 and more than one year without beam the commissioning of the LHC started again on November 20, 2009. Progress was rapid and collisions under stable beam conditions were established at 1.2 TeV within 3 weeks. In 2010 after qualification of the new quench protection system the way to 3.5 TeV was open and collisions were delivered at this energy after a month of additional commissioning. This paper describes the experiences and issues encountered during these first periods of commissioning with beam.
BNL, Upton, Long Island, New York
Since the last successful RHIC Au+Au run in 2007 (Run7), the RHIC experiments have made numerous detector improvements and upgrades. In order to benefit from the enhanced detector capabilities and to increase the yield of rare events in the acquired heavy ion data a significant increase in luminosity is essential. In Run7 RHIC achieved an average store luminosity of <L>=12x1026 cm-2 s-1 by operating with 103 bunches (out of 110 possible), and by squeezing to β*=0.8 m. Our goal for this year's run, Run10, was to achieve an average of <L>=27x1026 cm-2 s-1. The measures taken were decreasing β* to 0.6 m, and reducing longitudinal and transverse emittances by means of bunched-beam stochastic cooling. In addition we introduced a lattice to suppress intra-beam scattering (IBS) in both RHIC rings, upgraded the RF system, and separated transition crossings in both rings while ramping. We present an overview of the changes and the results in terms of Run10 increased instantaneous luminosity, luminosity lifetime, and integrated luminosity.
BNL, Upton, Long Island, New York
We report on recent developments for mitigating vibrations of the quadrupole magnets near the interaction regions of the Relativistic Heavy Ion Collider (RHIC). High precision accelerometers, geophones, and a laser vibrometer were installed around one of the two interaction points to characterize the frequencies of the mechanical motion. In addition actuators were mounted directly on the quadrupole cryostats. Using as input the locally measured motion, dynamic damping of the mechanical vibrations has been demonstrated. In this report we present these measurements and measurements of the beam response. Future options for compensating the vibrations are discussed.
BNL, Upton, Long Island, New York
For improved reproducibility of good operating conditions and ramp commissioning efficiency, new dual-plane slow orbit feedback during the energy ramp was implemented during run-10 in the Relativistic Heavy Ion Collider (RHIC). The orbit feedback is based on steering the measured orbit, after subtraction of the dispersive component, to either a design orbit or to a previously saved reference orbit. Using multiple correctors and beam position monitors, an SVD-based algorithm is used for determination of the applied corrections. The online model is used as a basis for matrix computations. In this report we describe the feedback design, review the changes made to realize its implementation, and assess system performance.
BNL, Upton, Long Island, New York
Precision measurement and control of the betatron tunes and betatron coupling in the Relativistic Heavy Ion Collider (RHIC) are required for establishing and maintaining both good operating conditions and, particularly during the ramp to high beam energies, high proton beam polarization. While the proof-of-principle for simultaneous tune and coupling feedback was successfully demonstrated earlier, routine application of these systems has only become possible recently. Following numerous modifications for improved measurement resolution and feedback control, the time required to establish full-energy beams with the betatron tunes and coupling regulated by feedback was reduced from several weeks to a few hours. A summary of these improvements, select measurements benefitting from the improved resolution and a review of system performance are the subject of this report.
BNL, Upton, Long Island, New York
Chromaticity feedback during the ramp to high beam energies has been demonstrated in the Relativistic Heavy Ion Collider (RHIC). In this report we review the feedback design and measurement technique. Commissioning experiences including interaction with existing tune and coupling feedback are presented together with supporting experimental data.
KEK, Ibaraki
STFC/RAL/ISIS, Chilton, Didcot, Oxon
ANL, Argonne
Tsukuba University, Ibaraki
A low-output-impedance RF system for the second harmonic cavity in the ISIS synchrotron has been developed by collaboration between Argonne National Laboratory (US), KEK (Japan) and Rutherford Appleton Laboratory (UK). The system has less than 30 Ω of output impedance over wide frequency range of 2.7-6.2 MHz. However, distortions of voltage waveform in the driver stage have been a long-standing issue. It was found such distortions were generated depending upon the higher-order-modes of the anode-choke impedance. In this report, method to realize the smooth sinusoidal waveform in the wideband system is presented.
Imperial College of Science and Technology, Department of Physics, London
STFC/RAL/ISIS, Chilton, Didcot, Oxon
The Front End Test Stand (FETS) is an experiment based at the Rutherford Appleton Laboratory (RAL) in the UK. The test stand is being constructed in collaboration between STFC, Imperial College London, ASTeC, the University of Warwick and the Universidad del Pais Vasco. This experiment will design, build and test the first stages necessary to produce a very high quality, chopped H- ion beam as required for the next generation of high power proton accelerators (HPPAs). HPPAs with beam powers in the megawatt range have many possible applications including drivers for spallation neutron sources, neutrino factories, accelerator driven sub-critical systems, waste transmuters and tritium production facilities. An automatic tuning system has been developed for the main 324MHz 4-vane RFQ accelerator and has been tested to fine tune the changes in the resonant frequency of a 324MHz 4-vane cold model RFQ, which been designed as part of the development of the test stand. This paper will present the electronics design of the automated tuning system along with the mechanical tuner structure. The design concepts will be discussed. Furthermore, results of the RF tuning would be presented.
U. Erlangen-Nurnberg LHFT, Erlangen
Siemens Med, Erlangen
The usability of conventional BPM topologies in compact linear accelerators used for medical and industrial applications is very limited due to tight space restrictions in such systems. To overcome these limitations, a different approach is introduced which is based on integrating the pickups into low-field regions of the accelerating structure and evaluating higher beam harmonics. Applications based on this approach will require RF frontends in frequency ranges beyond those covered by BPM dedicated hardware which is currently commercially available. Therefore, a demonstrator setup is presented which is capable of investigating suitable RF frontends for the proposed method. The demonstrator uses capacitive pickups of the button type for displacement sensing and allows for control of the beam position with the help of feedback steering coils which are typically used for compact linacs. Representative sensitivity measurement results based on the evaluation of the 2nd S-Band beam harmonic are also presented in this paper.
DESY, Hamburg
The problem of errors, arising due to finite BPM resolution in the reconstructed orbit parameters, is one of the standard problems of the accelerator physics. Even so for the case of uncoupled motion the covariance matrix of reconstruction errors can be calculated "by hand", the usage of the obtained solution, as a tool for designing of a "good measurement system", is not straightforward. A better understanding of this problem is still desirable. We make a step in this direction by introducing dynamics into this problem, which seems to be static. We consider a virtual beam obtained as a result of the application of a reconstruction procedure to ‘‘all possible values'' of BPM reading errors. This beam propagates along the beam line according to the same rules as any real beam and has all beam dynamical characteristics, such as emittances, dispersions, betatron functions, and all these values describe the properties of the BPM measurement system. As an application we formulate requirements for the BPM measurement system of high-energy intra-bunch-train feedback system of the European XFEL Facility in terms of the introduced concepts of error emittance and error Twiss parameters.
USTC/NSRL, Hefei, Anhui
A new beam current monitor (BCM) has been implemented on Hefei Light Source (HLS) recently. It has been used for bunch-by-bunch beam current measurement, which is useful for filling control and longitudinal feedback, etc. The BCM consists of three parts: the front-end circuit, a high sampling rate oscilloscope for beam current signal acquisition and the data processing system. The signals from the beam position monitor of the storage ring are manipulated by the front-end circuit first, then sampled by the Agilent MSO7104 oscilloscope and transported into the control computer for data processing. The sampling rate of the oscilloscope is up to 4GHz and the trigger rate is 4.533 MHz. The data processing program is supported by the LabVIEW. The measurement of beam current in multi-bunch operation mode is described. Some important results are summarized.
USTC/NSRL, Hefei, Anhui
In HLS we employ the TED FPGA based processor for digital feedback system. To make feedback system work better and more easily, we developed the control and analysis system based on matlab chiefly. The system do jobs as following: sampling data online and finishing its analysis; calculating fir filter parameters and generating .csv(format for FPGA) file to get the best gain and phase flexibly according to different beam working point; simulating the beam changes in different feedback gain and other stations to check whether the system work properly.
Kyungpook National University, Daegu
Royal Holloway, University of London, Surrey
KEK, Ibaraki
SLAC, Menlo Park, California
Nanometer resolution Beam Position Monitors have been developed to measure and control beam position stability at the interaction point region of ATF2. The position of the beam focused has to be measured within a few nanometer resolution at the interaction point. In order to achieve this performance, electronics for this BPM was developed. Every component of the electronics have been simulated and checked by local test and using beam signal. We will explain each component and define their working range. Then, we will show the performance of the electronics measured with beam signal.
CERN, Geneva
CERN's Large Hadron Collider (LHC) is equipped with three distinct types of intensity measurement systems: total intensity measurement using DC transformers (DCCTs) with a bandwidth up to a few kHz; total intensity measurements on a turn-by-turn basis for lifetime measurements using AC-coupled fast transformers (fast BCTs); bunch-by-bunch intensity measurements with a bandwidth up to a few hundred MHz also using the fast BCTs. In addition to providing intensity information these devices are part of the machine protection system, indicating whether or not there is beam circulating, transmitting intensity for evaluation of safe beam conditions and capable of triggering a beam dump if fast losses are detected. This paper reports on the commissioning of all these systems and their initial performance.
CERN, Geneva
The beta function has a fundamental impact on the LHC performance and on the functioning of its machine protection and collimation systems. A new beta-beat diagnostic system, prototyped at the SPS, has been used to verify the time-dependent variations of the LHC lattice with unprecedented 1% beta-beta resolution and at a measurement bandwidth of about 1 Hz.
NSRRC, Hsinchu
To keep and achieve desired performance of a modern synchrotron light source, it requires continuous efforts including good design of the accelerator, good performed subsystems and sophisticated feedback system. While some wonders happen unexpectedly and could deteriorate performance of the light source. For examples, some strong source occasionally occurred especially after long shut down or malfunction of some corrector power supply and it would result in increased noise level. Non ideal injection element will cause large perturbation as well. This report presents algorithms to spatially locate source and summarize some of our practical experience to identify the source.
JAI, Oxford
We present the design of a stripline beam position monitor (BPM) signal processor with low latency (c. 10ns) and micron-level spatial resolution in single-pass mode. Such a BPM processor has applications in single-pass beamlines such as those at linear colliders and FELs. The processor was deployed and tested at the Accelerator Test Facility (ATF2) extraction line at KEK, Japan. We report the beam test results and processor performance, including response, linearity, spatial resolution and latency.
Fermilab, Batavia
In fast ramping synchrotrons, like the Fermilab Booster, the usual methods for evaluating the betatron tunes from the spectrum of turn-by-turn data may fail due to fast decoherence of particle motion or rapid tune changes, in addition to the BPM noise. We propose a technique based on phasing of the signals from different BPMs. Although the number of the Fermilab Booster BPMs is limited to 48 per plane, this method allows to detect the beam tunes in conditions where the other algorithms were unsuccessful. In this paper we describe the method and its implementation in the Fermilab Booster control system. Results of measurements are also presented.
CLASSE, Ithaca, New York
CalPoly, San Luis Obispo, CA
During the last several years CESR has been studying the effects of electron clouds on stored beams in order to understand their impact on future linear-collider damping ring designs. One of the important issues is the way that the electron cloud alters the dynamics of bunches within the train. Techniques for observing the dynamical effects of beams interacting with the electron clouds have been developed. These methods will be discussed and examples of measurements will be presented.
University of Notre Dame, Notre Dame
Royal Holloway, University of London, Surrey
JAI, Egham, Surrey
KEK, Ibaraki
SLAC, Menlo Park, California
The demonstration of the stability of the position of the focused beam is a primary goal of the ATF2 project. We have installed a laser interferometer system that will eventually correct the measurement of high-precision Beam Position Monitors used in the ATF2 Final Focus Steering Feedback for mechanical motion or vibrations. Here, we describe the installed system and present preliminary data on the short- and long-term mechanical stability of the BPM system.
SLAC, Menlo Park, California
The talk will provide an overview of required feedback systems to guarantee stable and successful SASE operation as well as successful experiments. Recent developments and examples of various systems (including feedbacks for long bunch trains) will be discussed.
KEK, Ibaraki
Beam injections to KEKB and Photon Factory are performed with pulse-to-pulse modulation at 50Hz. Three very different beams are switched every 20ms in order to inject those beams into KEKB HER, LER and Photon Factory (PF) simultaneously. Human operators work on one of those three virtual accelerators, which correspond to three-fold accelerator parameters. Beam charges for PF injection and the primary electron for positron generation are 50-times different, and beam energies for PF and HER injection are 3-times different. Thus, the beam stabilities are sensitive to operational parameters, and if any instability in accelerator equipment occurred, beam parameter adjustments for those virtual accelerators have to be performed. In order to cure such a situation, beam energy and orbit feedback systems are installed that can respond to each of virtual accelerators independently.
DESY, Hamburg
PETRA III is a new hard x-ray synchrotron radiation source at DESY in Hamburg operating at 6 GeV with an extremely low horizontal emittance of 1 nmrad. The new light source is the result of a conversion of the former storage ring PETRA II. The conversion was carried out from middle of 2007 till March 2009. One eighth of the 2304 m long storage ring was completely rebuild and houses now 14 undulator beam lines as well as the optical and experimental hutches. The remaining seven eighths have been modernized and refurbished and in addition twenty 4 m long damping wigglers have been installed. These are required to achieve the small design emittance. Commissioning of the new light source started at the end of March 2009. In this paper we present the results that have been achieved during commissioning and the experience gained during the first user runs.
SINAP, Shanghai
Currently, the real-time data transfer system is widely implemented in the accelerator control system. If timing system and real-time data transfer system could be combined into one uniform system, it would be convenient to build distributed feedback system, fast interlock system and so on. So, a new timing system, the real-time synchronized data bus is developed to realize this idea. The architecture of the system and the hardware prototype design are introduced in the paper. The data exchange mechanism and system specification, including timing trigger synchronization accuracy, timing jitter relative to RF clock, data transfer rate and latency are described in detail. Redundant topology structure and fiber length compensation are specially considered. In the end, the results of testing in lab are presented.
DESY, Hamburg
The Free Electron Laser in Hamburg (FLASH) is a user facility providing high brilliant laser light for experiments. It is also a unique facility for testing the superconducting accelerator technologies. FLASH cavities are operating at pulsed mode. There is a filling stage to build the RF voltage in the cavities and then follow a flattop for beam operation. By the limitation of the klystron pulse length the filling time of the cavities is limited to several hundred microseconds. In order to fill the cavities to the dedicated voltage usually large RF power is required for the filling stage. For European XFEL during RF operation the klystrons will be working quite near the saturation point for better efficiency. So lowering the unnecessary klystron peak power under closed loop operation is very important for close-limitation operation. The paper will present the method which allows decreasing the required klystron peak power as well as the reflected power by filling the cavity in resonance. Simulation results will be presented as well as experimental demonstrations at FLASH.
DESY, Hamburg
For future FELs (Free-Electron-Lasers) a 3rd harmonic system was proposed to increase the SASE intensity by linearization of the beam phase space after the first bunch compression section. At DESYs FLASH facility, a 3rd harmonic cavity system, consisting of four single cavities operating at 3.9GHz has been successfully tested at the module test stand. In this paper we present field regulation measurements using a step wised down converted field detector system and a model based designed LLRF field controller. First measurements showed a promising in loop vectorsum amplitude stability of about 2·10-5 for pulse-to-pulse operation.
IPM, Tehran
CERN, Geneva
The pulse compressor is located after the klystron to increase the power peak by storing the energy at the beginning and releasing it near the end of klystron output pulse. In the CTF3 [1] pulse compressors a doubling of the peak power is achieved according to our needs and the machine parameters. The magnitude of peak power, pulse length and flatness can be controlled by using a phase modulator for the input signal of klystrons. A C++ code is written to simulate the pulse compressor behaviour according to the klystron output pulse power. By manually changing the related parameters in the code for the best match, the quality factor and the filling time of pulse compressor cavities can be determined. This code also calculates and sends the suitable phase to the phase modulator according to the klystron output pulse power and the desired pulse length and peak power.
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
JAEA, Ibaraki-ken
The output energy of the J-PARC LINAC will be upgraded from 181 to 400 MeV in the next two years by adding high-beta acceleration sections. The upgrade of the FPGA-based digital LLRF controller for the 400 MeV LINAC will be presented in this paper. The new LLRF control system works for both the 324 MHz low-beta and 972 MHz high-beta sections. Many functions are added into the LLRF controller, such as 1) working for different RF frequencies, 2) gradually increasing the feedback gains in the feedback loop instead of fixed ones, 3) automatic chopped-beam compensation, 4) automatically switching the beam loading compensation in accordance with the different beam operation mode, 5) input rf-frequency tuning carried out by a FPGA to match the rf cavities during the rf start-up, 6) auto-tuning of the rf cavity tuner by detecting the phase curve of the rf cavity during the field decay instead of the phase difference between the cavity input and output signals.
KEK, Ibaraki
S1 global will be operated at STF in KEK, where total 8 cavities will be installed. The digital llrf system to control the vector sum of the field gradients to be flat has been developed. All the digital llrf system including rf monitoring, piezo-control system will be shown. The new llrf system suitable for the DRFS scheme, which is also studied during S1 grobal, is also under development.
KEK, Ibaraki
The compact ERL(cERL) is the energy recovery linac(ERL) test facility that is under construction at KEK. The stability of accelerating electric field of 0.1% rms in amplitude and 0.1deg. in phase is required for LLRF system. The status of LLRF system for cERL will be reported.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK/JAEA, Ibaraki-Ken
KEK, Ibaraki
The wide-band RF cavities in the J-PARC RCS are operated in the dual-harmonic operation, in which each single cavity is driven by a superposition of the fundamental and the second harmonic RF signals. By the dual-harmonic operation large amplitude second harmonic signals for the bunch shape manipulation are generated without extra cavities. The phase control of the second harmonic RF is a key for the bunch shape manipulation. The fundamental RF signal is controlled by the phase feedback loop to damp the dipole oscillation. The second harmonic is locked to the phase of the vector-sum phase of the fundamental RF signals. We present the system detail and the performance in the beam operation of the RCS.
SLAC, Menlo Park, California
ANL, Argonne
DESY, Hamburg
The FLASH L-band (1.3 GHz) superconducting accelerator facility at DESY has a Low Level RF (LLRF) system that is similar to that envisioned for ILC. This system has extensive monitoring capability and was used to gather performance data relevant to ILC. Recently, waveform data were recorded with both beam on and off for three, 8-cavity cryomodules to evaluate the input RF and cavity gradient stability and study the RF overhead required to achieve constant gradient during the 800μs pulses. In this paper, we present the recent experimental results and discuss the pulse-to-pulse input RF and cavity gradient stability for both beams on and off cases. In addition, a model of the gradient variation observed in the beam off case will be described.
SLAC, Menlo Park, California
The Linac Coherent Light Source (LCLS) at SLAC is in full user operation and has met the stability goals for stable lasing. The 250pC bunch can be compressed to below 100fS before passing through an undulator. In a new mode of operation a 20pC bunch is compressed to what is believed to be about 10fS. Experimenters are regularly using this shorter X-ray pulse and getting pristine data. The 10fS bunch has timing jitter on the order of 100fS. Physicists are requesting that the RF system achieve better stability to reduce timing jitter. Drifts in the RF system require longitudinal feedbacks to work over large ranges and errors result in reduced performance of the LCLS. This paper describes the new RF system being designed to help diagnose and reduce jitter and drift in the SLAC linac.
SLAC, Menlo Park, California
CERN, Geneva
The LHC Low Level RF system (LLRF) is a complex multi-loop system used to regulate the superconductive cavity gap voltage as well as to reduce the impedance presented by RF stations to the beam. The RF system can have a profound impact on the stability of the beam; a mis-configured RF system has the potential of causing longitudinal instabilities, beam diffusion and beam loss. To configure the RF station for operation, a set of parameters in the LLRF multi-loop system have to be defined. Initial system commissioning as well as ongoing operation requires a consistent method of computer based remote measurement and model-based design of each RF station feedback system. This paper describes the suite of Matlab tools used for configuring the LHC RF system during the start up in Nov2009-Feb2010. We present a brief overview of the tool, examples of commissioning results, and basics of the model-based design algorithms. This work complements our previous presentation [1], where the algorithms and methodology followed in the tools were described.
[1] D. Van Winkle et. al. 'Feedback Configuration Tools for LHC Low Level RF System,' PAC'09, Vancouver, Canada, May 2009, THZCH03, p. 249 (2009); http://www. JACoW.org.
IN2P3-LAPP, Annecy-le-Vieux
INFN/LNF, Frascati (Roma)
Following previous measurements, more detailed preliminary ground motion measurements have been performed at the LNF site for the Super B project site characterization. First, results of vertical ground motion measurements done during 18 hours are shown in order to get an idea of the evolution of the ground motion amplitude with time. Secondly, measurements of ground motion (in the 3 directions of space) were performed at different locations on surface in order to evaluate and to compare the influence of various vibration sources. Then, results of ground motion coherence measured for different distances at two locations close to each other but with soft and rigid floor are compared. These measurements are also compared to the ones done in the ATF2 beam line where a special floor was built for stability. By this way, the results reveal that the LNF is a good site to use ground motion coherence properties for stability like it has been done for ATF2.
RIKEN/SPring-8, Hyogo
JASRI/SPring-8, Hyogo-ken
This paper describes the present status of a precise temperature-regulation system for the C-band accelerator at XFEL (X-ray Free Electron Laser)/SPring-8. It is essential to maintain a constant temperature of an rf cavity for stable lasing. We therefore installed a heater-assembly unit into a cooling water circuit of each rf cavity. By controlling the heater power, the temperature of the cavity can be stabilized. We constructed a prototype of this system at the SCSS (SPring-8 Compact SASE Source) test accelerator to check its feasibility for the XFEL. The prototype significantly contributes to a stable supply of SASE to users. For the XFEL, we simplified this system in consideration of cost and controllability. For example, to make one regulation system simultaneously controlling two C-band accelerating structures was tried. Keeping a temperature variation as tight as ±0.02 K at any operational mode could be achieved by this system. The preliminary test results of the system are also reported in this paper.
INFN/LNF, Frascati (Roma)
CERN, Geneva
BINP SB RAS, Novosibirsk
Recently the peak luminosity achieved on the DAΦNE collider has been improved by almost a factor 3 by implementing a novel collision scheme based on large Piwinski angle and Crab-Waist. This encouraging result opened new perspectives for physics research and a new run with the KLOE-2 detector has been scheduled to start by spring 2010. The KLOE-2 installation is a complex operation requiring a careful design effort and a several months long shutdown. The high luminosity interaction region has been deeply revised in order to take into account the effect on the beam caused by the solenoidal field of the experimental detector and to ensure background rejection. The shutdown has been also used to implement several other modifications aimed at improving beam dynamics: the wiggler poles have been displaced from the magnet axis in order to cancel high order terms in the field, the feedback systems have been equipped with stronger power supplies and more efficient kickers and electrodes have been inserted inside the wiggler and the dipole vacuum chambers, in the positron ring, to avoid the e-cloud formation. A low level RF feedback has been added to the cavity control in both rings.
BNL, Upton, Long Island, New York
Beam-beam effects in eRHIC have a number of unique features, which distinguish them from both hadron and lepton colliders. Due to beam-beam interaction, both electron and hadron beams would suffer quality degradation or beam loss from without proper treatments. Those features need novel study and dedicate countermeasures. We study the beam dynamics and resulting luminosity of the characteristics, including mismatch, disruption and pinch effects on electron beam, in additional to their consequences on the opposing beam as a wake field and other incoherent effects of hadron beam. We also carry out countermeasures to prevent beam quality degrade and coherent instability.
KEK, Ibaraki
Electron cloud instabilities are a great concern for the KEKB, an electron/positron collider. In order to study wakefield effects of electron cloud, a test bunch was injected behind a bunch train with the solenoid fields off, where cloud density rapidly decayed. A current-dependent tune shift and the tune spread of a test bunch were measured as a function of the bunch current while varying the bucket position of a test bunch. The vertical tune shift indicated a strong defocusing force together with widened tune spread in a region of relatively low cloud density and low bunch current. However, the vertical tune shift changed to a focusing force at high cloud density and high bunch current. On the other hand, the horizontal and vertical tune spreads tended to approach a constant value as increasing the bunch current. The turning current is approximately equal to the threshold current of the vertical size blow-up.
SOLEIL, Gif-sur-Yvette
Ever since the commissioning times, transverse instabilities, which now have been identified as the so called Fast Beam-Ion Instability (FBII), have existed in the SOLEIL storage ring. Though along with the improvement of the vacuum level with increasing beam dose its relative importance has decreased to a large extent as compared to the classical instabilities due to the coupling impedance, the FBII still exists persistently at high current, making it difficult to attain a stable beam at the final goal of 500 mA. In particular, sudden beam losses are frequently encountered after keeping the beam stable over a certain time with transverse feedback at the final current, which raised a question as to whether the observed phenomena are compatible with the saturating effect of the FBII. Experimental analysis using the bunch by bunch feedback diagnostics as well as theoretical and numerical analysis using multibunch tracking have been carried out to understand the instability quantitatively and to elucidate the mechanism of the beam losses.
SLAC, Menlo Park, California
The Linac Coherent Light Source (LCLS) at SLAC is an x-ray Free Electron Laser with wavelengths of 0.15 nm to 1.5 nm. The electron beam stability is important for good lasing. While the transverse jitter of the beam is about 10-20% of the rms beam sizes, the jitter in the longitudinal phase space is a multiple of the energy spread and bunch length. At the lower energy of 4.3 GeV (corresponding to the longest wavelength of 1.5 nm) the relative energy jitter can be 0.125%, while the rms energy spread is with 0.025% five times smaller. An even bigger ratio exists for the arrival time jitter of 50 fs and the bunch duration of about 5 fs (rms) in the low charge (20 pC) operating mode. Although the impact to the experiments is reduced by providing pulse-by-pulse data of the measured energy and arrival time, it would be nice to understand and mitigate the root causes of this jitter. The thyratron of the high power supply of the RF klystrons is one of the main contributors. Another suspect is the multi-pacting in the RF loads. Phase measurements down to 0.01 degree (equals 10 fs) along the RF pulse were achieved, giving hints to the impact of the different sources.
IHEP Beijing, Beijing
BEPCII is the upgrade project of the Beijing Electron Positron Collider (BEPC) with its design luminosity of 1x1033cm-2s-1 @1.89 GeV. The construction of BEPCII was completed in May 2008. The collider has been operated for high energy physics experiments since February 2009 with 1/5 of design luminosity at psi(3680). The luminosity has been steadily increased during the operation. Status and updated performance of BEPCII will be reported.
KEK, Ibaraki
This presentation will cover the development of the tuning methods, beam stabilization and reliability, and instrumentation including laser wires, high resolution BPMs and fast feedback, to achieve the beam of a few nano meters size required for the ILC final focus.
SINAP, Shanghai
The Shanghai Synchrotron Radiation Facility (SSRF), a 3.5GeV storage ring based third generation light source, started its user operation with 7 beamlines in May 2009. During the passed year, the facility reliably operated about 4000 hours for user experiments. This paper presents the operational status of the SSRF in the first year and its future performance improvement plans.
LBNL, Berkeley, California
SLAC, Menlo Park, California
Electron clouds impose limitations on current accelerators that may be more severe for future machines, unless adequate measures of mitigation are taken. Recently, it has been proposed to use feedback systems operating at high frequency (in the GHz range) to damp single-bunch transverse coherent oscillations that may otherwise be amplified during the interaction of the beam with ambient electron clouds. We have used the simulation package WARP-POSINST to study the growth rate and frequency patterns in space-time of the electron cloud driven transverse instability in the CERN SPS accelerator with, or without, an idealized feedback model for damping the instability. We will present our latest simulation results, contrast them with actual measurements and discuss the implications for the design of the actual feedback system.
ASCo, Clayton, Victoria
The Australian Synchrotron has been running normal operations for beamlines since April 2007. The high degree of beam availability has allowed for an extensive accelerator physics program to be developed. The main points of this program will be presented, including student involvement at different levels and developments being made in anticipation of moving to top-up mode injections.
SOLEIL, Gif-sur-Yvette
The SOLEIL synchrotron light source is now delivering photons to 20 beamlines with a current of 400 mA in top-up mode. The long and short term H and V beam position stabilities are in the range of one micron thanks to the efficient slow and fast orbit feedbacks, and to the improved tunnel temperature regulation. The bunch by bunch transverse feedback is running with two independent H and V loops. To enable canted undulator implementations, a 3 magnet chicane has been installed in a medium straight whereas an additional triplet of quadrupole was inserted in the middle of a long straight to create a double low vertical beta. 17 insertion devices are now installed in the storage ring, 2 will be added early 2010, 8 are under construction, including a cryogenic undulator. Following the significant progression of the vacuum conditioning, the lifetime is now mainly Touchek limited. An electron bunch slicing set-up is also being installed to provide 100 fs long X-rays pulses to two existing beamlines. ~4500 hours will have been delivered in 2009 to the Beamlines with an availability above 96 % thanks to the very reliable operation of the unique SOLEIL RF system.
KEK, Ibaraki
A hybrid fill mode has been tested at the Photon Factory storage ring (PF-ring). The hybrid fill mode consists of a train of low-current bunches and a high-current single bunch. Since a bunch-by-bunch feedback system was not available because of the high contrast of currents between the bunch train and the single bunch, we suppressed multibunch instabilities in the transverse and longitudinal planes by using the octupole magnets and RF phase modulation, respectively. We also suppressed single-bunch instabilities by controlling ring chromaticity. As a result, we successfully stored a 450 mA current with the hybrid fill mode: 1/2 filling (2.56 mA/bunch × 156) + 1 single bunch opposite to the bunch train (50 mA/bunch). The distribution of vacuum pressures along the ring was similar for the hybrid fill and the typical single-bunch mode. In this conference, we will present the results of this test experiment as well as some future subjects to be solved for the user operation.
SINAP, Shanghai
The SSRF (Shanghai Synchrotron Radiation Facility) storage ring consisting of 20 Double Bend Achromatic cells with four super-periods is designed with a low emittance of 3.9nm.rad on 3.5GeV beam energy. Commissioning of the storage ring began on Dec. 21st 2007, and the beam was stored within sixty hours. After one and a half years commissioning, all specifications of the storage ring were reached in 2009. In this paper, study of beam dynamics in the SSRF storage ring is presented. Results of the measurement are given in detail, such as model calibration, orbit stability, etc.
KEK, Ibaraki
Mitsubishi Electric TOKKI Systems, Amagasaki, Hyogo
Gazing at SuperKEKB project, a new control subsystem was designed and implemented to upgrade the low level RF system of the KEKB accelerator based on Experimental and Industrial Control System (EPICS). The new control subsystem comprises a uTCA, a PLC, and an industrial PC. Each card plugged in the uTCA chassis and the PLC function as an embedded Input / Output Controller (IOC) by running the EPICS core program on the Linux operating system. The industrial PC runs Extensible Display Manger on Linux to serve as an Operator Interface (OPI). This paper describes the details of the design and the implementation of the fully embedded EPICS-based low level RF control subsystem for SuperKEKB.
ESS-Bilbao, Zamudio
ESS Bilbao, Bilbao
University of the Basque Country, Faculty of Science and Technology, Bilbao
The use of distributed control systems for improving control system's performance is a hot research topic. Thus, the importance of developing control systems across networked environment is rising, a lot of research is focused on developing middleware based solutions. On the other hand, EPICS is an extended control system middleware, which is based on TCP/UDP protocol. This protocol has non-deterministic characteristics, limiting its use for networked control systems. Despite of these characteristics, the interest on TCP based networks in industrial field has been increasing due to its advantages in cost and easy integration. In this work, EPICS as a networked control system is analyzed in order to develop strategies to improve its performance. For this purpose, an EPICS based networked control scheme is presented, where control loop is closed over the net. As opposed to usual way of working with EPICS, two IOCs are used located in different hosts. The first one performs data acquisition, while the second one calculates the control signal. The analysis and control performance study of such scheme is presented by using periodic sampling, as well as event based sampling approach.
NSRRC, Hsinchu
To enhance waveform and spectrum remote access supports in the Taiwan Light Source (TLS), development of the EPICS support of Ethernet-based oscilloscope and spectrum analyzer for the TLS is under way. The EPICS platforms which built to interface these instruments could access the waveform and spectrum through the PV (Process Variable) channel access. By using remote operations of waveform and spectrum acquisition, long distance cabling could be eliminated and signal quality be improved. The EDM (Extensible Display Manager) tool is used to implement the operation interface of control console and provide waveform display. According to specific purpose use, different graphical user interfaces to integrate waveform and spectrum acquisition are built. This project is the preparation for future control room integration with the Taiwan Photon Source control room. The efforts will be described at this report.
NSRRC, Hsinchu
Implementation of the Control system for the Taiwan Photon Source (TPS) is on going. The TPS control system will provide versatile environments for machine commissioning, operation, and to do accelerator experiments. The control system is based on EPICS toolkits. Test-bed has set up for various developments. The open architecture will facilitate machine upgrade, modification easily and minimize efforts for machine maintenance. Performance and reliability of the control system will be guaranteed from the design phase. Development status will be summary in this report.
Melbourne
ASCo, Clayton, Victoria
The Australian Synchrotron storage ring has a resistive wall instability in the vertical plane. Presently this instability is being controlled by increasing the vertical chromaticity. However new in-vacuum insertion devices that significantly increase the ring impedance may demand chromatic corrections beyond the capabilities of the sextupole magnets. A transverse bunch-by-bunch feedback system has been commissioned to combat the vertical instability* and provide beam diagnostics**. A high frequency narrow band mode that could not be damped was initial encountered with IVUs at minimum gap preventing the system from being implemented during user beam. Tuning of the bunch fill pattern, the digital filters and mapping out the system response lead to a configuration for user mode operations.
* Spencer, M.J. et. al. EPAC'08, Genoa, Italy
** Peake, D.J. et. al. PAC'09, Vancouver, Cananda
SOLEIL, Gif-sur-Yvette
JASRI/SPring-8, Hyogo-ken
In this paper we introduce and discuss the recent developments made in our digital transverse bunch by bunch feedback system at SOLEIL, which is routinely in service since the first user operation in both the high average current and high bunch current modes. The above includes installation of a third chain with a dedicated 4-electrode stripline intended to operate in the horizontal plane, an attempt to sample the BPM signal directly at the RF frequency without down-converting to the baseband following the success at SPring-8, a refined tuning procedure by measuring the feedback damping times as a function of the band frequency, as well as exploration of different digital filters ensuring a larger working range in terms of betatron tunes or a faster response against single bunch instabilities. The achieved performance and results are described. The observed evolution of the machine impedance and instabilities shall also be presented.
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
In view of increased processing bandwidth at demanding experiments and the need for rapid compensation of noise spikes and new, yet unknown excitations a fast orbit feedback aiming at noise suppression in the 1Hz-50Hz range has become mandatory for the 3rd generation light source BESSY II. As a first step the fast setpoint transmission plus the replacement of all corrector power supplies is foreseen. Later - in combination with top-up operation - orbit stability can be further improved by replacing today's multiplexed analog beam position monitors by parallel processing fast digital units. This paper describes how the pilot installation of a small subset of fast corrector power supplies already allows to tune performance and study the benefits for today's most sensible experiments.
DELTA, Dortmund
A stable beam orbit is essential for safe operation of particle accelerators. This applies to electron machines and even more to hadron machines running high beam currents. Based on developments at DELTA, basic designs of fast orbit feedbacks systems for the FAIR rings SIS18 and HESR (planned) and COSY at the Forschungszentrum Jülich are presented.
DELTA, Dortmund
Dimtel, San Jose
DELTA is a 1.5-GeV synchrotron radiation source at the TU Dortmund University with 2 ns bunch spacing. At nominal operating currents, the beam exhibits significant longitudinal centroid motion due to coupled-bunch instabilities. Two techniques were successfully used at DELTA to damp such instabilities: RF phase modulation, which also improves the beam lifetime, and bunch-by-bunch feedback. Using diagnostic data from the bunch-by-bunch feedback system, modal spectra and growth rates of the longitudinal instabilities were characterized. We also present a preliminary characterization of transverse coupled-bunch oscillations observed at the highest beam currents.
ELETTRA, Basovizza
FERMI@Elettra is a new 4th-generation light source based on a single pass free electron laser. It consists of a 1.5-GeV normal-conducting linac working at 50 Hz repetition rate and two chains of undulators where the photon beams are produced with a seeded laser multistage mechanism. A number of control loops, some of them working on a shot by shot basis, are required to stabilize the crucial parameters of the beams. For this purpose, a generalized real-time framework integrated in the control system has been designed to flexibly and easily implement feedback loops using several monitoring and control variables. The paper discusses the requirements of the control loops and the implementation of the feedback framework. The first closed loop results and the experience gained in the operation of the feedbacks during the first phase of the machine commissioning will also be presented.
INFN/LNF, Frascati (Roma)
SLAC, Menlo Park, California
Rome University La Sapienza, Roma
The SuperB project has the goal to build in the Frascati or Tor Vergata area, an asymmetric e+/e- Super Flavor Factory to achieve a peak luminosity > 1036 cm-2 s-1. The SuperB design is based on collisions with extremely low vertical emittance beams. A source of emittance growth comes from the bunch by bunch feedback systems producing high power correction signals to damp the beams. To limit any undesirable effect, a large R&D program is in progress, partially funded by the INFN Fifth National Scientific Committee through the SFEED (SuperB feedback) project approved within the 2010 budget. One of the first steps of the R&D program consists in the upgrade and test of new 12-bit feedback systems in the vertical plane of the DAΦNE main rings. The systems are the direct evolution of the previous 8-bit system design by a KEK/SLAC/LNF collaboration, yielding a good compatibility with the powerful diagnostics and analysis programs developed in the past. Studies on their effects in the longitudinal plane are also in progress.
KEK, Ibaraki
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
Transverse bunch by bunch feedback systems for J-PARC MR accelerator has been designed and tested. Bunch positions are detected by Log-ratio position detection systems with center frequency of 12 MHz. The digital filter which consists of two LLRF4 boards samples the position signal with 64 times of RF frequency. Up to four sets of 16 tap FIR filter with one-turn delay and digital shift gain can be used. Preliminary results of beam test of the system are also shown.
Tokyo City University, Tokyo
KEK, Ibaraki
Miyazaki University, Miyazaki
NIRS, Chiba-shi
Tsukuba University, Ibaraki
J-PARC is a new accelerator facility to produce MW-class high power proton beams. From the main ring (MR) high energy protons are extracted in a slow extracted mode for hadron experiments. The beam is required with as small ripple as possible to prevent pileup events in particle detectors or data acquisition systems. We took beam tests at HIMAC using a prototype signal processing unit. In these beam tests we had recognized the improvement of the extracted beam structure by using the feedback algorithm whose parameters were changed according to the beam characteristics. We have developed a new signal processing unit for the spill feedback control of J-PARC. The unit consists of three signal input ports (gate, spill intensity and residual beam intensity), three signal output ports (spill control magnets), two DSPs (power spectrum analysis and spill feedback control), dual port memories, FPGAs and a LAN interface (remote control with SUZAKU-EPICS). From October 2009, this unit is being used in the beam study of J-PARC MR to check the performance of digital filtering, phase-shift processing, servo feedback control, real-time power spectrum analysis and adoptive control.
JAI, Oxford
IFIC, Valencia
The commissioning of the ATF2 final focus test beam line facility is currently progressing towards the achievement of its first goal: to demonstrate a transverse beam size of about 40 nm at the focal point. In parallel, studies and R&D activities have already started towards the second goal of ATF2, which is the demonstration of nanometer level beam orbit stabilization. These two goals are important to achieve the luminosity required at future linear colliders. Beam-based intra-train feedback systems will play a crucial role in the stabilization of multi-bunch trains at such facilities. In this paper we present the design and simulation results of beam-based intra-train feedback systems at the ATF2: one system located in the extraction line at the entrance to the final focus, and another at the interaction point. The requirements and limitations of these systems are also discussed.
CERN, Geneva
UMIT, Hall in Tirol
One of the major challenges of the CLIC main linac is the preservation of the ultra-low beam emittance. The dynamic effect of ground motion would lead to a rapid emittance increase. Orbit feedback systems (FB) have to be optimized to efficiently attenuate ground motion (disturbance), in spite of drifts of accelerator parameters (imperfect system knowledge). This paper presents a new FB strategy for the main linac of CLIC. It addresses the above mentioned issues, with the help of an adaptive control scheme. The first part of this system is a system identification unit. It delivers an estimate of the time-varying system behavior. The second part is a control algorithm, which uses the most recent system estimate of the identification unit. It uses H2 control theory to deliver an optimal prediction of the ground motion. This approach takes into account the frequency and spacial properties of the ground motion, as well as their impact on the emittance growth.
CERN, Geneva
The LHC deploys a comprehensive suite of beam-based feedbacks for safe and reliable machine operation. This contribution summarises the commissioning and early results of the LHC feedback control systems on orbit, tune, chromaticity, and energy. Their performance – strongly linked to the associated beam instrumentation, external beam perturbation sources and optics uncertainties – is evaluated and compared with the feedback design assumptions.
NSRRC, Hsinchu
As the latest generation light source, TPS (Taiwan Photon Source) has stringent requirements to perform submicron beam stability with low emittance. The slow and fast correctors of integrated orbit feedback system have been designed for TPS project, therefore some feedback system designed based on them an operation experiences from TLS. This report will present performance simulation and the initial design of system infrastructure for large scale calculation and wide bandwidth communication. To perform this requirement, FPGA-based platform will be implemented to achieve low latency and fast computation. Some studies of integrated feedback loop, communication structure, devices control such as BPM electronics and corrector power supplies are also described.
JAI, Oxford
We present the design and beam test results of a prototype beam-based digital feedback system for the Interaction Point of the International Linear Collider. A custom analogue front-end signal processor, FPGA-based digital signal processing boards, and kicker drive amplifier have been designed, built, deployed and tested with beam in the extraction line of the KEK Accelerator Test Facility (ATF2). The system was used to provide orbit correction to the train of bunches extracted from the ATF damping ring. The latency was measured to be approximately 140 ns.
JAI, Oxford
The design luminosity of the future linear colliders requires transverse beam size at the nanometre level at the interaction point (IP), as well as stabilisation of the beams at the sub-nanometre level. Different imperfections, for example ground motion, can generate relative vertical offsets of the two colliding beams at the IP which significantly degrade the luminosity. In principle, a beam-based intra-train feedback system in the interaction region can correct the relative beam-beam offset and steer the beams back into collision. In addition, this feedback system might considerably help to relax the required tight stability tolerances of the final doublet magnets. For CLIC, with bunch separations of 0.5 ns and train length of 156 ns intra-train feedback corrections are specially challenging. In this paper we describe the design and simulation of an intra-train feedback system for CLIC. Results of luminosity performance simulation are presented and discussed.
Diamond, Oxfordshire
We present our observations of the medium term and long term stability of the photon beams at Diamond Light Source. Drift of the Electron Beam Position Monitors results in real X-ray beam movements, observed by both Front End X-ray Beam Position Monitors and beamline scintillator screens on some beamlines. We discuss how we are using these diagnostics tools to measure and characterise the drift. Medium term movements related to top-up cycles are seen, believed to be caused by changes to single bunch charge, and the long term drift of the electron beam position over several days and weeks is examined. A slow feedback system using X-ray Beam Position Monitors has been shown to successfully correct this drift. The results of these trials are presented.
ANL, Argonne
The Advanced Photon Source (APS) real-time orbit feedback system is complex and faults are difficult to diagnose. This paper presents a diagnostic method based on fault tree analysis (FTA). The fault tree is created based on more than ten years operating experience of the system. The method is described to analyze the fault tree. The operator interface to the diagnostic tool is discussed.
ANL, Argonne
A bunch-by-bunch feedback system was installed at the APS in 2008. Close-loop tests were conducted and improvements have been made to the system that include two 500-watt amplifiers, a new location for the horizontal drive stripline, a two-blade new horizontal stripline, and upgrade of front-end electronics. With these improvements we are able to stabilize beam with a reduced chromaticity of 0.45 in the horizontal plane and 2.5 in the vertical plane for the 24-singlet bunch pattern. Beam lifetime has increased from 8.5 hours to 15 hours. We did not observe any obvious increase in the effective beam emittance and rms beam motion. More studies will be performed to explore the potential of improving beam performance of the hybrids fill pattern, which has a 16-mA leading bunch. We report the system improvements and the results of our test results.
cyao@aps.anl.gov
SLAC, Menlo Park, California
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
CERN, Geneva
The SPS at high intensities exhibits transverse single-bunch instabilities with signatures consistent with an Ecloud driven instability. We present recent MD data from the SPS, details of the instrument technique and spectral analysis methods which help reveal complex vertical motion that develops within a subset of the injected bunch trains. The beam motion is detected via wide-band exponential taper striplines and delta-σ hybrids. The raw sum and difference data is sampled at 50 GHz with 1.8 GHz bandwidth. Sliding window FFT techniques and RMS motion techniques show the development of large vertical tune shifts on portions of the bunch of nearly 0.025 from the base tune of 0.185. Results are presented via spectrograms and rms bunch slice trajectories to illustrate development of the unstable beam and time scale of development along the injected bunch train. The study shows that the growing unstable motion occupies a very broad frequency band of 1.2 GHz. These measurements are compared to numerical simulation results, and the system parameter implications for an Ecloud feedback system are outlined.
ORNL RAD, Oak Ridge, Tennessee
ORNL, Oak Ridge, Tennessee
The prototype of an analog transverse (vertical and horizontal) feedback system to actively damp the electron-proton (e-p) instability has been developed and tested on the ORNL Spallation Neutron Source (SNS). We will describe the principle components, system configuration, and review several experimental studies geared towards understanding the current performance and limitations of the system.
BNL, Upton, Long Island, New York
CERN, Geneva
The SPS exponential coupler stripline are used to study single bunch instabilities. An accurate description of the response of the pickup is required to obtain high resolution measurements of the bunch vertical motion along the longitudinal axis. In this study we present the results of the comparison between dedicated beam experiments and electromagnetic simulations of a geometrical model of the stripline.
Uni HH, Hamburg
PSI, Villigen
DESY, Hamburg
After its upgrade, the free-electron laser in Hamburg (FLASH) will start operating with an exchanged RF-gun driven by an improved photoinjector laser. Since the SASE FEL process is very sensitive to the RF gun phase it is highly desirable to implement phase stabilization feedback, which, in turn, requires an arrival-time stabilization of the photoinjector laser pulses. In this paper we report on the synchronization of the photoinjector laser system to the optical timing reference using an optical cross-correlation scheme. This enables not only the measurement of the timing jitter, but also the stabilization using adaptive feed-forward algorithms acting on an EOM incorporated in the laser's pulse train oscillator. First results from the commissioning and future plans for a feedback system are discussed.
KEK, Ibaraki
Crab cavities were installed in KEKB in 2007. The function of the cavity is to tilt the bunch of the beam in the longitudinal direction. But if the RF phase gets out of control, the cavity kicks the beam like a steering magnet. To avoid this unwanted kick, the RF phase must be controlled well. In beam operation, some disturbances may occur such as a discharge, a quench, etc. When such disturbances occur, it is very difficult to control the RF phase precisely. We can't trust measured RF phase at that time. In KEKB, beam is aborted quickly when a disturbance is detected. Beam behavior before detect the disturbances has been investigated. We discuss following items. (1)How fast should the beam be aborted after detecting disturbances? (2)How fast should RF be turned off after detecting disturbances? (3)What a kind of disturbance is harmful? (4)Is the beam abort necessary at all? (Is just to turn RF off OK?)
KEK, Ibaraki
Kyoto ICR, Uji, Kyoto
Tohoku Gakuin University, Miyagi
Nine 1.3 GHz 9-cell superconducting cavities (MHI-01 ~ 09) for International Linear Collider (ILC) project were fabricated from 2005 to 2009 at KEK-STF. The vertical test (with temperature and X-ray mapping) and optical inspection using by high resolution camera system for nine cavities were carried out from 2006 to 2009 for STF Phase-I project and S1-Global project at KEK. The cavities were separated to three series. The first series is MHI-01 ~ 04 (fabricated at 2005). They were made the Centrifugal barrel polishing (CBP) at initial surface treatment. The second series is MHI-05 and 06 (fabricated 2008). The third series is MHI-07 ~ 09 (fabricated at 2009). The surface treatments of second and third series cavity were made only Electro Polishing (EP) process (without CBP), because of the EBW seams of equator and iris were improved by the feedback of optical inspection method. A good correlation has been so far observed between the hot spots localized by thermometry measurements in the vertical test and the positions of surface defects found by this system. The result of optical inspection will be reported in this paper.
KEK, Ibaraki
At PF-AR, a bending magnet power supply was updated in 2007. The converter works in the 3 pulsed PWM. A trouble caused by higher harmonics above 40th had occurred. We manufactured filters and installed in 6.6kV ac lines in 2008. Furthermore, a QF magnet power supply was updated in 2009. This paper reports on the update of PF-AR main magnet power supplies.
PSI, Villigen
In accelerator applications, high precision high speed power supplies (PSs) for magnets are needed to guarantee the high beam quality. These PSs are the main purpose of the presented second generation of a Digital Power Electronic Control System (DPC) which has been designed and successfully applied at the Paul Scherrer Institute PSI. The main components of the DPC are the controller board (DPC_CC) and the high precision analogue to digital converter board (DPC_AD). Compared to the first generation the properties such as precision, acquisition rate, processing power and functionality have been improved considerably. This allows faster control cycles and/or more complex control algorithms. The controller board now features 12 standard precision (16 bit) ADC channels and allows the simultaneous control of multiple power supplies. High precision requirements are met by adding the DPC_AD to the system. In conclusion, the modular and flexible design allows well-matched solutions for the typically heterogeneous accelerator power supplies.
NSRRC, Hsinchu
CMS/ITRI, Hsinchu
Based on the requirement of beam stability for the third-generation synchrotron radiation light source is more stringent, lower ripple and higher bandwidth of output current of corrector magnet power converters should be developed to implement the closed orbit correction of Taiwan Photo Source (TPS). The ±10A/±50V corrector magnet power converter uses a full bridge configuration, the switching frequency of power MOSFET is 40 kHz, in that each bridge leg has its own independent PWM controller and the output current bandwidth is 1 kHz when connected with the corrector magnet load. Using a DCCT as the current feedback component the output current ripple of this converter could be lower than 5 ppm. In this paper, we will describe the hardware structure and control method of the corrector magnet power converter and the test results will be demonstrated.
NSRRC, Hsinchu
We design and implement a power convert to supply dc power bus for the MCOR30 correction supply. The dc power supply's characteristics were variable frequency at heavy and medium/light load. These characteristics matched with the correction supply working requirement. The dc power bus has a relaxation oscillator generating a symmetrical triangular waveform, which MOSFET's switching is locked to. The frequency of this waveform is related to a current that will be modulated by feedback circuitry. As a result, the tank circuit driven by half-bridge will be stimulated at a frequency dictated by the feedback loop to keep the output voltage regulated, thus exploiting its frequency-dependent transfer characteristics. The high performance characteristics of the resonant dc power bus are illustrated in this paper.
NSRRC, Hsinchu
This paper presents an implementation of a precision corrector magnet power converter using the digitally controlled pulse width modulation method. The output current precision of this ±10A/±50V corrector magnet power converter is within ±10ppm. The digital control circuit of the power converter is implemented with using a high speed ADS8382 18-bits analog-to-digital converter and a TMS320F28335 digital signal processor. The converter uses a full bridge configuration, the switching frequency of power MOSFET is 40 kHz and the control resolution is 17-bits. Using a DCCT as the current feedback component the output current ripple of this converter could be lower than 5 ppm that is beyond the requirement of TLS corrector power converter and suitable to be used in TPS.
ANL, Argonne
The DC/DC converters in the Advanced Photon Source storage ring are more than 15 years old, and an upgrade is underway to resolve the aging and obsolescence issues. In the upgrade, an 18-bit resolution for current regulation is desired. This paper describes a digital control system to achieve this goal. The system uses a serializer chip, TI TLK2541, combined with a ∑-Δ modulator to realize a 21-bit digital pulse width modulation (DPWM). Analog and digital filters are implemented to block the ripple currents and to reduce the EMI noises. Deployed with filter circuits, a digital compensator has been designed to meet the requirements of output current regulation. Furthermore, a voltage feed forward is employed to compensate for input bus voltage variations. A prototype digital controller using a field-programmable-gate-array development board has been developed. The resolution of the current regulation, and the effect of noises into the digital controlled power converter system have been tested and analyzed.
Kyoto ICR, Uji, Kyoto
KEK, Ibaraki
A prototype of a permanent magnet quadrupole lens for ILC final focus doublet is fabricated. In order to demonstrate the feasibility, it will be tested in a real beam line. Such practical experiences include its shipping, storage, handling, installation, alignment technique, and so on. Because permanent magnets cannot be switched off in contradistinction to electromagnets, they should be evacuated from beam lines when no interference is desired and the process should be quick with enough reproducibility. The magnetic center and strength stability including reproducibility are also important issues during the beam test. In order to reduce interferences with current ongoing testing items at ATF2, the magnet will be installed at a further upstream position of the ATF2 beam line. The installation and test plan will be described.
CERN, Geneva
Cockcroft Institute, Warrington, Cheshire
Fermilab, Batavia
JAI, Oxford
The CLIC BDS tuning, alignment and feedbacks studies have been typically performed independently and only over particular sections of the BDS. An effort is being put to integrate all these procedures to realistically evaluate the luminosity performance.
INFN/LNF, Frascati (Roma)
BINP SB RAS, Novosibirsk
In DAΦNE, the Frascati e+/e- collider, the crab waist collision scheme has been successfully implemented in 2008 and 2009. During the collision operations for Siddharta experiment, an unusual synchrotron damping effect has been observed. Indeed, with the longitudinal feedback switched off, the positron beam becomes unstable with beam currents in the order of 200-300 mA. The longitudinal instability is damped by bringing the positron beam in collision with a high current electron beam (~2A). Besides, we have observed a shift of ≈600Hz in the residual synchrotron sidebands. Precise measurements have been performed by using a commercial spectrum analyzer and by using the diagnostics capabilities of the DAΦNE longitudinal bunch-by-bunch feedback. This damping effect has been observed in DAΦNE for the first time during collisions with the crab waist scheme. Our explanation is that beam collisions with a large crossing angle produce a longitudinal tune shift and a longitudinal tune spread, providing Landau damping of synchrotron oscillations.
JASRI/SPring-8, Hyogo-ken
NewSUBARU/SPring-8, Laboratory of Advanced Science and Technology for Industry (LASTI), Hyogo
RIKEN Nishina Center, Wako
Transverse beam instabilities were suppressed with chromaticity modulation (CM)* in the electron storage ring, New SUBARU. The horizontal and vertical betatron tune spread inside a bunch were introduced by CM with synchrotron oscillation frequency driven by an AC sextuple magnet**, to obtain Landau damping of the coherent bunch motion. The tune spread in a bunch is usually introduced by octupole field, however, its high nonlinearity reduces the dynamic aperture. And usual feedback against instabilities work only on m=0 mode and it is not easy to be applied to hadron synchrotrons because of their varying revolution period. The CM scheme has not such disadvantages. The damping time of coherent motion excited by external kick was measured and was found as less than 1ms, one order faster than that without CM. To observe the effect on instabilities, we intentionally tuned an HOM in a cavity to excite a horizontal multi-bunch instability. The instability peak in the spectrum of the beam motion was vanished with CM turned on and the instability was suppressed. We also observed the increase of the threshold current of the vertical single-bunch mode-coupling instability by factor 3 with CM.
* T. Nakamura, Proc. of PAC'95, p.3100 (1995).
** T. Nakamura, et al., Appl. Superconduct., IEEE Trans. Vol. 18, p.326 (2008).
CERN, Geneva
In the CTF3 accelerator, the RF produced by each of ten 3 GHz klystrons goes through waveguides, RF pulse compressors and splitters. The RF phase and power transformation of these devices depend on their temperature. The quantitative effect of the room temperature variation on the RF was measured. It is the major source of undesired changes during the CTF3 operation. An RF phase-loop and a compressor temperature stabilization are developed to suppress the phase fluctuation and the power profile change due to the temperature variation. The implementation is transparent for operators it does not limit anyhow the flexibility of RF manipulations. Expected and measured suppression characteristics will be given. As well RF measurement dependence on the temperature will be mentioned.
IUAC, New Delhi
Superconducting Linac at Delhi was partly established and commissioned with one linac cryomodule to house 8 quarter wave niobium cavities along with buncher and rebuncher cryomodule. Two more linac cryomodules are designed, developed and integrated with beam line and cryo distribution line recently. Design of present modules are modified based on the feedback from earlier modules. Present paper will be highlighting the modified design along with thermal and vacuum performance of the present modules w.r.t earlier module.
NIRS, Chiba-shi
The betatron tune fluctuation due to the current ripple of power supplies brings the beam spill ripple through the stable area variation in resonant slow extraction. The effect becomes dominant especially in the case of the low beam rate extraction. The RF-knockout slow extraction method is insensitive to the tune ripple compared to the ordinary one because it uses the diffusion with the transverse RF field. However, the ripple effect appears even in the beam spill extracted by it. The amount of the separatrix fluctuation due to the tune ripple depends on the difference between the bare and the resonant tune, and the sextupole magnetic strength. We measured the correlation between the beam spill and the tune ripple which was the artificially generated with low and high frequency components of 67 Hz and 1167 Hz near those of the real current ripple. We confirmed the reduction of the beam spill ripple by setting the tune away from the resonance while keeping the separatrix area. The comparison between the experimental results, the analytical calculation and the simulation will be reported.
KEK, Ibaraki
J-PARC, KEK & JAEA, Ibaraki-ken
University of Fukui, Faculty of Engineering, Fukui
Tokyo City University, Tokyo
Tsukuba University, Ibaraki
JAEA/J-PARC, Tokai-mura
High power protons from the J-PARC main ring is slowly extracted using the third integer resonance and delivered to the experimental hall for various nuclear and particle physics experiments. The slow extraction device comprises two electro static septa (ESS),ten magnetic septa, four bump magnets, eight resonant sextupole magnets and their power supply. One of the critical issue of the slow extraction is radiation caused by the beam loss during the slow extraction. We have developed the electrostatic and magnetic septa with thin septum thickness. A unique scheme with large step size and small angular spread of the extracted beam enables hit rate on the ESS less than 1% level. In January 2009, first 30 GeV proton beam has been successfully delivered to the fixed target. Quadrupole magnets and a DSP feedback control system to obtain a uniform beam spill structure were implemented in 2009 summer shutdown period. We will report the extraction efficiency, extracted beam profiles and spill structure obtained by the beam commissioning so far. We will also mention a upgrade plan based on some new ideas to aim a higher performance.
KEK, Tsukuba
Miyazaki University, Miyazaki
Tokyo City University, Tokyo
NIRS, Chiba-shi
The slow extraction beam from the J-PARC Main Ring (MR) to the Hadron Experimental Facility is used in various nuclear and particle physics experiments. A flat structure and low ripple noise are required for the spills of the slow extraction. The spill control system has been developed for the J-PARC slow extraction to make a flat structure and small ripple. It consists of the extraction quadrupole magnets and feedback device. The extraction magnets consist of two kinds of quadrupole magnets, EQ (Extraction Q-magnet) which make flat beam and RQ (Ripple Q-magnet) which reject the high frequent ripple noise. The feedback system, which is using Digital Signal Processor (DSP), makes a ramping pattern for EQ and RQ from spill beam monitor. The extraction magnets and feedback device were installed in September 2009, and spill feedback study were successfully started from the beam time in October 2009. Here we report the operation status of magnets and first study of beam commissioning with spill feedback.
Fermilab, Batavia
Muons, Inc, Batavia
Typically, high power sources for accelerator applications are multi-megawatt microwave tubes that may be combined together to form ultra-high-power localized power stations. The RF power is then distributed to multiple strings of cavities through high power waveguide systems which are problematic in terms of expense, efficiency, and reliability. Magnetrons are the lowest cost microwave source in dollars/kW, and they have the highest efficiency (typically greater than 85%). However, the frequency stability and phase stability of magnetrons are not adequate, when magnetrons are used as power sources for accelerators. Novel variable frequency cavity techniques have been developed which will be utilized to phase and frequency lock magnetrons, allowing their use for either individual cavities, or cavity strings. Ferrite or YIG (Yttrium Iron Garnet) materials will be attached in the regions of high magnetic field of radial-vaned, π−mode structures of a selected ordinary magnetron. A variable external magnetic field that is orthogonal to the magnetic RF field of the magnetron will surround the magnetron to vary the permeability of the ferrite or YIG material.
NSRRC, Hsinchu
Previously, the Taiwan Light Source (TLS) has proven that the temperature stability of de-ionized cooling water is one of the most critical factors of electron beam stability. A series of efforts were devoted to these studies and promoted the temperature stability of the de-ionized cooling water system within ±0.1°C. Further, a high precision temperature control ±0.01°C has been conducted to meet the more critical stability requirement. Using flow mixing mechanism and specified control philosophy can minimize temperature variation effectively. The paper declares the mechanism through simulation and verifies the practical influences. The significant improvement of temperature stability between cooling devices and de-ionized water are also presented.
INFN-Ferrara, Ferrara
UNIFE, Ferrara
Univ. degli Studi di Padova, Padova
INFN/LNL, Legnaro (PD)
JINR, Dubna, Moscow Region
Channeling in bent crystals is a technique with high potential to steer charged-particle beams for several applications in accelerators physics. Revisited methods of silicon micromachining techniques allowed one to realize a new generation of crystals. Characterizations using x-ray diffraction, atomic force microscopy, high resolution transmission electron microscopy and ion beam analysis techniques, showed high quality of the crystals. A specifically designed holder allowed to mechanically bend a crystal at given curvature and remove unwanted torsion. Characterization of such crystals with 400 GeV at CERN H8 external line highlighted 85% single-pass efficiency. A selected crystal has been installed inside the SPS ring in the environment of the CERN experiment UA9 and successfully employed for collimation of the circulating beam.
On behalf of UA9 collaboration
Euclid TechLabs, LLC, Solon, Ohio
Fermilab, Batavia
AES, Medford, NY
Use of a superconducting travelling wave accelerating (STWA) structure with a small phase advance per cell rather than a standing wave structure may provide a significant increase in the accelerating gradient in the ILC linac. For the same surface electric and magnetic fields the STWA achieves an accelerating gradient 1.2 larger than TESLA-like standing wave cavities. In addition, the STWA allows longer acceleration cavities, reducing the number of gaps between them. However, the STWA structure requires a SC feedback waveguide to return the few hundreds of MW of circulating RF power from the structure output to the structure input. A test single-cell cavity with feedback was designed and manufactured to demonstrate the possibility of a proper processing to achieve a high accelerating gradient. The first results of high-gradient tests of a prototype 1.3 GHz single-cell cavity with feedback waveguide will be presented.
PSI, Villigen
The filling pattern can have a big impact in the effective bunch lengthening of a passive 3rd harmonic system and as a consequence in the Touschek component of the beam lifetime. Using a longitudinal dynamics tracking code, in which the effects of the accelerating system and the 3rd harmonic system are taken into account, we can calculate the synchronous phase drift caused by the transient beam-loading and thus the effective bunch increase for several different filling patterns. In this paper we present a comparison between simulation and measurements for the SLS.