| Paper | Title | Page |
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| FRPMN002 | Preliminary Studies for Top-up Operations at the Australian Synchrotron | 3856 |
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| The Australian Synchrotron is now a fully commissioned synchrotron light source providing beam for users. With the facility now fully operational, the next major advancement in machine operations will be top-up mode. The advantages of running top-up are well documented by other third generation light sources; in broad terms it leads to a better quality beam for users and better experimental results. An overview will be given of the top-up runs that have been conducted and the instrumentation that was used. It has been demonstrated that top-up operation is possible, however improvements in injection efficiency and beam stability during injection are required before this can become a routine mode of operation. | ||
| FRPMN003 | Measurements of Impedance and Beam Instabilities at the Australian Synchrotron | 3859 |
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| In this paper we present the first measurements of machine impedance and observed beam instabilities at the Australian Synchrotron. Impedance measurements are made by studying the single bunch behaviour with beam current, using optical and X-ray diagnostic beamlines. An observed coupled-bunch instability, its cause and cure is also discussed. | ||
| FRPMN004 | Storage Ring Turn-By-Turn BPMs At The Australian Synchrotron | 3865 |
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| The Australian Synchrotron's Storage Ring is equipped with a full compliment of 98 Libera Electron Beam Position Processors from I-Tech (EBPPs) [1]. The EBPPs are capable of measuring beam position data at turn-by-turn (TBT) rates and have long history buffers. TBT data from the EBPPs has been used to determine the linear optics of the storage ring lattice using techniques developed at other facilities. This is a useful complement to other methods of determining the linear optics such as LOCO. Characteristics of the EBPPs such as beam current dependence have been studied during commissioning and will also be presented. | ||
| FRPMN005 | Design of Button Beam Position Monitor for the Brazilian Synchrotron Light Source | 3871 |
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| We present the electric and mechanical design of a button beam position monitor (BPM) recently developed and installed in the UVX electron storage ring at the Brazilian Synchrotron Light Laboratory (LNLS). The first commissioning results will also be presented. This development started when we observed strong correlation between false stripline BPM readings and the external temperature of this BPM. Simulations indicate that the temperature gradient in the BPM body can cause deformations that could explain the false readings in some BPMs. The small dimension of the button compared to the stripline and the better thermal isolation between the button and the BPM body should contribute to minimize this problem. | ||
| FRPMN007 | Image Charge Effects in Dynamics of Intense Off-Axis Beams | 3880 |
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Funding: CNPq, Brasil. This paper analyzes the combined envelope-centroid dynamics of magnetically focused high-intensity charged beams surrounded by conducting walls. Similarly to the case were conducting walls are absent, we show that the envelope and centroid dynamics decouples from each other. Mismatched envelopes still decay into equilibrium with simultaneous emittance growth, but the centroid keeps oscillating with no appreciable energy loss. Some estimates are performed to analytically obtain some characteristics of halo formation seen in the full simulations. |
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| FRPMN008 | Wave Breaking and Particle Jets in Inhomogeneous Beams | 3886 |
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Funding: CNPq, Brasil and AFOSR under grant FA9550-06-1-0345. We analyze the dynamics of inhomogeneous, magnetically focused high-intensity beams of charged particles. While for homogeneous beams the whole system oscillates with a single frequency, any inhomogeneity leads to propagating transverse density waves which eventually result in a singular density build up, causing wave breaking and jet formation. The theory presented in this paper allows to analytically calculate the time at which the wave breaking takes place. It also gives a good estimate of the time necessary for the beam to relax into the final stationary state consisting of a cold core surrounded by a halo of highly energetic particles. |
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| FRPMN009 | Transition from isotropic to anisotropic beam profiles in a uniform linear focusing channel. | 3892 |
| This paper examines the transition from isotropic to anisotropic beam profiles in a uniform linear focusing channel. Considering a high-intensity ion beam in space-charge dominated regime and large beam size-rms mismatched initially, observe a fast anisotropy situation of the beam characterized for a transition of the transversal section round to elliptical with a coupling of transversal emittance driven for collective instabilities of nonlinear space-charge forces. | ||
| FRPMN010 | Emittance Measurements at the 100 keV Beam Stage of the Injector Linac of the IFUSP Microtron | 3898 |
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Funding: Work supported by FAPESP and CNPq In this work we describe the determination of the beam emittance for the 100-keV injector of the IFUSP racetrack microtron. We measured the beam spot diameter at a fluorescent screen located 40 cm after a 3-mm diameter collimator (placed at the entrance to the first chopper cavity). A solenoid lens located upstream to the collimator was used to produce a beam waist at the fluorescent screen position. We used the collimator and the beam waist sizes to calculate the emittance for 80 and 90 keV beams. Results showed no dependence with energy, indicating that the collimator is limiting the beam emittance at 2.32(5) ??mm?mrad. |
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| FRPMN011 | Studies of Dipole Field Quality for the Beta-Beam Decay Ring | 3904 |
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Funding: European Community under the FP6 - Research Infrastructure Action - Structuring the European Research Area - EURISOL DS Project Contract no. 515768 RIDS. The aim of the beta-beams is to produce highly energetic beams of pure electron neutrino and anti-neutrino, coming from beta-decays of the 18Ne10+ and 6He2+, both at γ=100, directed towards experimental halls situated in the Frejus tunnel. The high intensity ion beams are stored in a ring until the ions decay. The beta decay products have a magnetic rigidity different from the one of the parent ions and are differently deflected in the 6T superconducting dipoles. Consequently, all the injected ions are lost anywhere in the ring, generating a high level of irradiation. So, the dipole apertures need to be large enough to avoid the decay products hitting their walls, which may worsen the field quality. A study on its tolerances has been carried out. Since the decay ring has to accept the beam during a large number of turns, the chosen criteria is the size of the dynamic aperture that the multipolar defects in the dipoles may shrink. Tolerances on the systematic and random errors of these defects have been investigated. In order to relax the tolerances, a routine was written which enlarges automatically the dynamic aperture in presence of field errors. |
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| FRPMN012 | Bias on Absolute Luminosity Measurements at the ILC from Beam-Beam Space Charge Effects | 3907 |
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| A way to determine luminosity at the International Linear Collider (ILC) is to measure the Bhabha event rate in a finely segmented calorimeter (LumiCal) at very low polar angles in the very forward region of the detector. An absolute precision between 10-4 and 10-3 is needed for a number of key physics measurements. Besides theoretical uncertainties on the Bhabha cross section and experimental errors when identifying Bhabha events in the LumiCal, the very strong beam-beam space charge effects which characterise the ILC e+e- collisions lead to a major bias in the counting rate, which drastically limits the luminosity measurement if uncorrected. In this paper, Bhabha event samples produced with the BHLUMI generator are used in the context of the GUINEA-PIG beam-beam simulation to study how beamstrahlung radiation and electromagnetic deflections affect the proposed experimental selections. A corrective method based on determining the luminosity spectrum within the LumiCal is suggested to minimise the resulting errors. The expected residual uncertainty after correction is estimated based on simulations with realistic beam conditions. | ||
| FRPMN013 | Precise Tune Measurements from Multiple Beam Position Monitors | 3913 |
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Funding: Work supported by the Marie Curie Intra-European Fellowship No MEIF-CT-2006-025678 One of the main limitations for precise tune measurements using kicked turn-by-turn data is the beam decoherence, which can limit the available signal to a reduced number of turns. Applying Laskar's frequency analysis, on measurements from several beam position monitors, a fast and accurate determination of the real tune is possible. The efficiency of the method is demonstrated when applied in turn-by-turn data from the ESRF storage ring and CERN's Super Proton Synchrotron. Estimates from tracking simulations and analytical considerations are further compared with the experimental results. |
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| FRPMN014 | 3D Simulation of Coherent Instabilities in Long Bunches Induced by the Kicker Impedances in the FAIR Synchrotrons | 3919 |
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Funding: Work supported by the European Community under the FP6 programme: Structuring the European Research Area - Specific Support Action - DESIGN STUDY (contract 515873 - DIRACsecondary-Beams). 3D simulation studies of the transverse impedance budget for long bunches in the FAIR synchrotrons have been started. Important transverse instability driving sources are the thin resistive wall and the kicker impedances. Major concerns are the required low momentum spreads and the additional loss of Landau damping due to the space charge tune shift. The simulation code PATRIC has been extended in order to predict coherent instability thresholds with space charge and for broadband impedance sources. Examples of code benchmarking using the numerical Schottky noise, analytical stability boundaries and comparisons with other codes will be discussed. The improvement of transverse stability in long bunches relative to a coasting beam is analyzed for different rf wave forms. Conclusions for the impedance budget in the FAIR synchrotrons are drawn. |
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| FRPMN015 | Simulation of Synchrotron Radiation at the First Bunch Compressor of FLASH | 3925 |
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Funding: This project is supported by the Helmholtz Association under contract HGF-VH-FZ-006 One method to measure the bunch shape at the FLASH facility at DESY, Hamburg is based on the observation of synchrotron radiation generated at the first bunch compressor. For the correct interpretation of the results it is mandatory to know how various parameters of the real setup, in contrast to theoretical assumptions, influence the observed spectrum. The aim of this work therefore is to calculate the generation of synchrotron radiation of a moving point charge inside the bunch compressor with the emphasis of including the effects of the vertical and horizontal vacuum chamber walls in the vicinity of the last dipole magnet. Because of the small wavelength in comparison with the chamber geometries this is a demanding task. One idea to cope with the difficulties is to use optical methods such as the uniform theory of diffraction (UTD). In this paper the applicability and limitations of the proposed method are discussed. Furthermore a comparison of simulated and new measured fields is shown. |
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| FRPMN016 | Wake Field Computations for the PITZ Photoinjector | 3931 |
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Funding: This work is supported in part by the EU under contract number RIDS-011935 (EUROFEL). The computation of wake fields excited by ultra short electron bunches in accelerator components with geometrical discontinuities is a challenging problem, as an accurate resolution for both the small bunch and the large model geometry are needed. Several computational codes (PBCI, ROCOCO, CST PARTICLE STUDIO etc.) have been developed to deal with this type of problems. Wake field simulations of the RF electron gun of the Photoinjector Test Facility at DESY Zeuthen (PITZ) are performed whith different specialized codes. Here we present a comparison of the wake potentials calculated numerically obtained from the different codes. Several structures of the photoinjector are considered. |
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| FRPMN017 | Beam Position Monitor Calibration at the FLASH Linac at DESY | 3937 |
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| In the FLASH (Free electron LASer in Hamburg) facility at DESY more than 60 beam position monitors (BPM) with single bunch resolution are currently installed, and more are planned for future installation. Their calibration has been initially made by measuring each electronics board in the RF laboratory. However the ultimate calibration of each monitor is made by measuring its response to beam movement. This is a time-consuming procedure depending on the availability and accuracy of other components of the machine such as corrector magnets. On the other hand it has the advantage of getting in one measurement the answer of the monitor with all its components and of being independent of the monitor type. The calibration procedure and particularities for various types of BPMs in various parts of the linac will be discussed. A procedure based on the response matrices is also now under study. This would significantly speed up the calibration procedure, which is particularly important in larger accelerators such as the European XFEL (X-ray Free Electron Laser), to be built at DESY. | ||
| FRPMN018 | Wake Computations for Undulator Vacuum Chambers of PETRA III | 3943 |
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| At DESY it is planned to convert the PETRA ring into a synchrotron radiation facility, called PETRA III. The wake fields of a tapered transition from the standard vacuum chamber to the small gap chamber of the insertion devices contribute significantly to the impedance budget of PETRA III. The computer codes MAFIA and PBCI have been used to determine the loss and kick parameter of the tapered transition. PBCI is a recently developed parallelized, fully 3D wake field code, which is using a purely explicit, split-operator scheme to solve the Maxwell equation in the time domain. | ||
| FRPMN019 | The Regular and Random Multi-Pole Errors Influence on the HESR Dynamic Aperture | 3949 |
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| The High Energy Storage Ring has the racetrack lattice, where each arc has the even number of super-periods S and the tune with one unit smaller ν=S-1 in both planes. Due to this fundamental feature the total n-order multi-pole is entirely cancelled and the regular errors can be fully compensated inside of one arc. In case of the random multi-pole errors the dynamic aperture is determined by the structure resonances excitation. We consider both regular and random multi-pole influence on the dynamic aperture and the possible correction scheme. | ||
| FRPMN020 | Beam Profile Measurements Based on Light Radiation of Atoms Excited by the Particle Beam | 3955 |
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Funding: Supported by BMBF and NRF, project-code SUA06/003 Diagnostics of intense particle beams requires development of new nondestructive beam monitoring methods. There are several kinds of diagnostic devices based on registration of products of accelerated beam particles interaction with atoms and molecules of residual gas in an accelerator vacuum chamber. Usually these devices used as beam profile monitors, which register electrons or/and ions produced in collisions of beam particles with residual gas. Some attempts were performed in application of light radiation of excited atoms. However, up to now this direction in the beam diagnostics was not developed properly. Nondestructive method of beam diagnostic system based on light radiation of atoms excited by the beam particles has the advantages - insensitivity to external magnetic and electric fields and, as a consequence, to the beam space charge fields. It allows to get higher spatial and time resolution. Measurements under different conditions at COSY-Juelich and in a cyclotron beamline at I'Themba LABS are presented and the pro and contra of the method is discussed |
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| FRPMN021 | Investigation of the Injection into the ANKA Storage Ring by a Turn by Turn BPM System | 3958 |
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| Modern BPM Electronics allow turn by turn acquisition of the position for both the injected and stored beam. This offers additional opportunities for diagnostics. In addition to the slow acquisition system installed at ANKA, two LIBERA ELECTRON units (www.i-tech.si) have been installed. I. E. the system was used to investigate and optimize the Injection. The stray field of the Septum causes a bump of the stored beam. The settings of the Kicker could be optimized for minimized the orbit distortion. By measuring the phase space of the injected beam the injection efficiency will be improved. | ||
| FRPMN022 | Analysis of Multi-Turn Beam Position Measurements in the ANKA Storage Ring | 3964 |
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The observation of betatron oscillations following a deflection by a kicker pulse offers the possibility to study various machine parameters. The damping of the centre-of-charge signal's amplitude for one bunch, for example, depends chromaticity, energy loss, momentum compaction factor and impedance. A new multi-turn acquisition system based on LIBERA ELECTRON units (http://www.i-tech.si) has been installed in the ANKA storage ring. First analyses of the thus acquired data for different machine conditions reveal systematic limitations in the current ANKA multi-turn setup. Measurements preformed under varying conditions are presented and discussed with respect to the influence on future analysis.
* http://www.i-tech.si |
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| FRPMN023 | New Beam Diagnostic Developments at the Photo-Injector Test Facility PITZ | 3967 |
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Funding: This work has partly been supported by the European Community, contracts RII3-CT-2004-506008 and 011935, and by the "Impuls- und Vernetzungsfonds" of the Helmholtz Association, contract VH-FZ-005. The Photo-Injector Test Facility at DESY in Zeuthen (PITZ) is an electron accelerator which was built to develop and optimize high brightness electron sources suitable for SASE FEL operation. Currently, in parallel to the operation of the existing setup, a large extension of the facility and its research program is ongoing. The beam line which has a present length of about 13 meters will be extended up to about 21 meters within the next two years. Many additional diagnostics components will be added to the present layout. Two high-energy dispersive arms, an RF deflecting cavity and a phase space tomography module will extend the existing diagnostic system of the photo injector and will contribute to the full characterization of new electron sources. We will report on the latest developments of the beam diagnostics at PITZ. |
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| FRPMN024 | Trapped modes analysis for the ELETTRA booster DCCT installation | 3970 |
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| In the new Elettra full energy injector, bunch charge measurements will be performed by different types of current transformers (CT), depending on their position (single pass or multi pass sections). In the single pass sections (Linac and Transfer lines) a new type of current transformer (in-flange CT by Bergoz) will be used. Main advantage of this device is a compact and reliable design; they are also specially suited in space critical application. For the booster ring a standard DC current transformer will be used to measure the DC component of the circulating beam current. The housing has been developed in house, including the magnetic shield and the ceramic gap in the vacuum chamber. Furthermore, calculations of the trapped modes in the current monitor housing are described. Longitudinal coupling impedance and loss factors for these resonant modes are estimated and we showed that dissipated power is not critical with ELETTRA booster parameters. | ||
| FRPMN025 | Review of the Longitudinal Impedance Budget of the ELETTRA Storage Ring | 3976 |
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| Changes in the longitudinal impedance budget occur due to the changes in the machine structure. In this paper we update the longitudinal impedance budget of Elettra following the installation of the new vacuum chambers in the last three years. The measurements are performed by mapping the horizontal closed orbit deviation in single bunch operation mode, taking full advantage of the newly installed high resolution BPM electrons system. The current results are compared with those of the previous measurements. | ||
| FRPMN027 | Non-Intercepting Electron Beam Transverse Diagnostics with Optical Diffraction Radiation at the DESY FLASH Facility | 3982 |
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Funding: Work supported by the European Comunity Infra-structure Activity under the FP6 Structuring the European Research Area program (CARE, contract number RII3-CT-2003-506395) The characterization of the transverse phase space for high charge density and high energy electron beams is a fundamental requirement in many particle accelerator facilities, since knowledge of the characteristics of the accelerated beams is of great importance for the successful development of the next generation light sources and linear colliders. The development of suitable beam diagnostics, non-invasive and non-intercepting, is therefore necessary to measure the properties of such beams. Optical Diffraction Radiation (ODR) is considered the most promise candidate, as testified by the interest of many laboratories all around the world. An experiment based on the detection of ODR has been set up at DESY FLASH Facility to measure the electron beam transverse parameters. The radiation is emitted by a 700 MeV-energy electron beam passing through a slit of 0.5 mm or 1 mm aperture depending on the beam size. The slit is opened by chemical etching on a screen made of aluminum deposited on a silicon substrate. Radiation is then detected by a air-cooled high sensitivity CCD camera. The status of the experiment and preliminary results are reported. |
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| FRPMN028 | Design and E. M. Analysis of the New DAFNE Interaction Region | 3988 |
| A new interaction region (IR) vacuum chamber has been designed for the DAFNE upgrade aimed at testing of the crabbed waist collision scheme. Compared to the existing IR vacuum chamber, the new one has a simplified design and consists essentially of the confluence of straight tubes, having a double Y shape. Sharp discontinuities have been avoided to limit the beam impedance of the structure. However, the study of the electromagnetic interaction with the beam is necessary in order to avoid excessive power loss due to eventual higher order modes (HOM) trapped in the Y-shape chamber. With HFSS the first design of the chamber has been analyzed and HOMs have been found and characterized. On the basis of these results some modifications in the geometry of the IR chamber have been introduced to eliminate or attenuate these trapped resonances. The results of these simulations are presented. | ||
| FRPMN030 | RF measurements results of the final brazed SPARC RF Deflector | 3994 |
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The longitudinal phase space and the horizontal beam slice emittance measurements of the SPARC 150MeV-1nC electron beam, foresee the use of a RF deflector. The device is a five cells standing wave structure operating on the TM110-like dipole mode at 2.856GHz and allows reaching a longitudinal resolution of 12μm with 2MW of peak input power. In the paper we illustrate the RF measurements on the final copper device.
This work has been partially supported by the EU in the sixth framework program, Contract no. 011935 EUROFEL-DS1. |
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| FRPMN031 | Commissioning and Status of New BPM Electronics for COD Measurement at the SPring-8 Storage Ring | 3997 |
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| At SPring-8 storage ring, a signal processing circuit for closed orbit measurement and a part of its control system were replaced during summer shutdown period of 2006. In the new circuit, one of four beam signals at the frequency of 508.58 MHz, which is the acceleration frequency of the SPring-8, is selected by a multiplexer and down-converted to IF frequency. The IF signal is sampled by 2 MSPS 16-bit ADC and detected with DSP. On the DSP, spurious frequencies are eliminated by digital filter and effective band-width can be changed by averaging. During the commissioning of the new circuit after the summer shutdown, DSP parameters such as number of averaging were decided to measure beam positions at all BPMs in 3 seconds, although the new circuit was designed with a target repetition of a few 10 Hz or around 100 Hz with resolution of sub-microns. With the DSP parameters, position resolution of less than 0.5 micron is achieved. In this paper, we also describe long term stability, current dependence and beam filling pattern dependence of the new circuit compared with the old one in addition to the position resolution and measurement repetition. | ||
| FRPMN032 | On Skew Nonlinear Resonance in the SPring-8 Storage Ring | 4003 |
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| Recently we accomplish the matrix formulation for the canonical perturbation theory of the linear betatron coupling resonance. By merging the perturbation theory with the matrix formalism, we manifest the symplectic structure of the former theory, and conversely derive the analytical representation for the latter. The formulation for the coupled betatron motion implies that the linear coupling causes the excitation of skew resonances by nonlinear fields with mid-plane symmetry. This effect is visible in the vicinity of the linear coupling resonance, which is observed in the SPring-8 storage ring, for example, as the blow-up of the vertical beam size on the third order skew coupling resonance. For the purpose of studying the impacts of the skew nonlinear resonance on the beam dynamics, we investigate the characteristic behavior of the resonance expected by the matrix formulation. | ||
| FRPMN033 | Adiabatic Damping During Acceleration in the Induction Synchrotron | 4009 |
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Damping in a bunch length during the acceleration in the induction synchrotron experiment *, where a single proton bunch injected from the KEK 500 MeV Booster and trapped by the barrier voltages is accelerated to 6 GeV, has been observed. Such a damping may be regarded as the adiabatic damping, as found in a conventional RF synchrotron. A technique to analytically deal with this phenomenon is well established in the RF synchrotron. A WKB solution is employed for the small amplitude synchrotron oscillation. However, a simple WKB approach is not available for the present barrier bucket acceleration, because longitudinal motion always depends on the oscillation amplitude. This paper discusses a novel technique capable of quantitatively predicting the adiabatic phenomenon which has been newly developed. The analytical results were worked out and verified using simulations for ideal conditions. Theoretical approach tells us that a bunch length in the barrier bucket acceleration never continues to shrink but achieves a constant value corresponding to the time duration between the barrier voltage pulses.
* K. Takayama et al., "Experimental Result of the Induction Synchrotron", appear in Phys. Rev. Lett. (2007) and in this conference. |
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| FRPMN035 | Crabbing Angle Measurement by Streak Camera at KEKB | 4018 |
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| Crab cavities will be installed in the KEKB rings in order to increase luminosity. We measure the crabbing angle using a streak camera and show the results in this paper. | ||
| FRPMN036 | Resonance Correction systems for JPARC Main Ring | 4024 |
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| The injection time for the JPARC Main Ring for the basic scenario is about 120ms, which corresponds to about 20,000 turns. The particle losses at the Main Ring collimator should be less than 1% from the expected maximum beam power at the injection energy. To keep the particle losses for the Main Ring operation below the limit, the correction systems have been suggested to eliminate possible resonance excitation. The proposed correction schemes allow us to suppress linear and nonlinear resonances. The calculated and/or measured field data for main magnets of the ring has been taken into account for this study. | ||
| FRPMN037 | Ion Instability in the ILC Damping Ring | 4030 |
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| Ions created by electron beam trapped in a bunch oscillate with a certain frequency, with the result that the beam oscillate with the same frequency. Recent high intensity and low emittance rings, the growth rate of this ion instability is very rapid. Super B factory and ILC damping ring, which are similar design parameter, are extremely low emittance. We discuss the ion instability for these rings. | ||
| FRPMN038 | Simulation of Synchro-betatron Sideband Instability caused by Electron Clouds at KEKB | 4033 |
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| Electron cloud causes a fast head-tail instability above a threshold density. Experiments at KEKB showed synchro-betatron sideband, which indicates the head-tail instability. The sideband appears near νy+kνs, where 1<k<2, that differs from ordinary instability seen near νy-νs. We investigate the origin of the sideband using a computer simulation. | ||
| FRPMN039 | Measurement of Quadrupolar Tune Shifts After the Reconstruction of the Photon Factory Storage Ring | 4039 |
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The tune shift of transverse quadrupolar oscillations is a measure of a quadrupolar component of wakefields in the storage ring*. By measuring both dipolar and quadrupolar tune shifts, one can estimate the dipolar and the quadrupolar components of wakefields (exactly, kick factors) independently. We carried out such measurements before and after the upgrade of the Photon Factory storage ring. The results showed the change in the tune shifts which were caused by the replacement of many (about two-thirds of the ring) vacuum chambers.
* S. Sakanaka, T. Mitsuhashi, and T. Obina, Phys. Rev. ST Accel. Beams 8, 042801 (2005). |
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| FRPMN041 | Study on the Longitudinal Impedance of BPM for KEKB and Super KEKB | 4048 |
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| The longitudinal impedance of the KEK B-factory (KEKB) button-type beam position monitors (BPMs) was recalculated by MAFIA in preparation for a future plan to increase the beam current. The diameter and the gap of the button electrode were 12 mm and 1 mm, respectively. For High Energy Ring (HER), an asymmetric structure was applied to extract the TE110 mode into the coaxial cable. The Q-value and shunt impedance were estimated at 91 and 17 Ω (at 7.6 GHz) respectively, and the beam current limit for longitudinal multi-bunch instability was 2.6 A. On the other hand, the electrode of Low Energy Ring (LER) BPM had a symmetric structure and the Q-value and shunt impedance were estimated at 133 and 8 Ω (at 7.6 GHz). In this case, the current limit was 1.7 A. Based on the experiences at the KEKB, the new BPM was designed for the Super KEKB, a future high-intensity B-factory at KEK. In order to reduce the impedance the electrode diameter was cut down to 6 mm from 12 mm. The Q-value and shunt impedance were estimated at 23 and 2 Ω (at 13 GHz). The current limit was expected to be about 7 A in full bucket operation (5120 bunches), and more than 10 kA in 4-bucket spacing operation. | ||
| FRPMN042 | Continued Study on Photoelectron and Secondary Electron Yield of TiN Coating and NEG (Ti-Zr-V) Coatings at the KEKB Positron Ring | 4054 |
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In order to investigate a way to mitigate the electron-cloud instability (ECI), the secondary electron and photoelectron yields (SEY and PEY) of a TiN coating and a NEG (Ti-Zr-V) coating have been studied at the KEK B-Factory (KEKB) positron ring. Following the previous study at an arc section*, the test chambers were installed a straight section, where the line density was less than 1/10 of that at the arc section. The number of electrons around the beam orbit was measured up to a stored beam current of about 1.7 A (1389 bunches). The electron current of the NEG-coated and TiN-coated chambers were about 60% and 30% of that for a copper chamber, respectively. The difference between the copper and the NEG coating was clearer than the measurement at the arc section, where the intense SR obscured the effect of SEY. The evaluated max values for the TiN coating, the NEG coating and the copper were 0.9 - 1.0, 1.0 - 1.1 and 1.3 - 1.4, respectively, which were almost consistent with the previous results. The experiments using a beam duct with ante-chambers are also briefly touched upon.
* Y. Suetsugu et al., NIM-PR-A, Vol.556 (2006) 399. |
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| FRPMN043 | Measurement of Beam Position Monitor Using HOM Couplers of Superconducting Cavities | 4060 |
| The offset beam from the axis induces the HOMs in the cavities. These HOMs in superconducting cavities are usually damped by HOM couplers to suppress the beam instability. The induced HOM power is proportional to the beam offset and can be used to measure the beam position inside the cavity. The shifter magnet is installed to the JAEA superconducting ERL-FEL to vary the beam position. The HOM power from the HOM coupler with various beam position is measured. The result of the beam test is presented. | ||
| FRPMN044 | Measurement of Ultra-short Electron Bunch Duration by Coherent Radiation Analysis in Laser Plasma Catode | 4066 |
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| Laser plasma accelerator can recently generate monochromatic and low-emittanced electron bunchs. Its pulse duration is femtoseconds, 40fs by the PIC simulation and about 250fs by measurement at University of Tokyo. But in such measurements only time-averaged spectrum and pulse duration were obtained by a few bolometers and coherent transition radiation (CTR) interferometer. Since the electron generation and acceleration are not stable yet, we need to know shot-by-shot behavior to improve its mechanism. Here we introduce the polychromator with ten channel-sensors for the single shot measurement. By this polychromator, we can obtain such a discrete spectrum of CTR by a single shot, thus the bunch duration can also be obtained shot-by-shot. This polychromator has ten channels to observe infrared radiation, and is mainly sensitive for the wavelengths around 1~2mm. We select this range of wavelength as the measurement tool, because the electron bunch duration changes shot-by-shot during traveling along the distance between the plasma and Ti foil (CTR emitter) due to their energy spectrum fluctuation. Further results and discussion will be presented on the spot. | ||
| FRPMN045 | Beam Position Monitor and its Calibration in J-PARC LINAC | 4072 |
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| The beam commissioning of J-PARC linac has been started in November 2006. Beam Position Monitors (BPMs) which have been calibrated on the bench setup with a scanning wire, utilize beam based calibration to relate the BPM center and the center of Q magnet. In this presentation, detail of installed BPM and the calibration methods are described. | ||
| FRPMN046 | Effects of Magnetic Field Tracking Errors on Beam Dynamics at J-PARC RCS | 4078 |
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| The 3-GeV Rapid-Cycling Synchrotron (RCS) of J-PARC aims at providing a 1-MW proton beam at a repetition rate of 25 Hz for an injection energy of 400 MeV. In this paper, we discuss influences of field tracking errors between dipoles and quadrupoles and between different families of quadrupoles on beam dynamics in combination with effects of the space charge and intrinsic nonlinear fields for the J-PARC RCS. | ||
| FRPMN047 | Development of a Beam Induced Heat-Flow Monitor for the Beam Dump of the J-PARC RCS | 4084 |
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| A beam induced heat-flow monitor (BIHM) will be installed in front of the beam dump of the RCS (Rapid Cycling Synchrotron) at J-PARC (Japan Particle Accelerator Research Complex), where a power limitation of the beam dump is 4 kW. The purposes of this monitor are to observe a beam current injected into the beam dump and to generate an alarm signal for the main control system of the RCS. At the BIHM the beams penetrate a carbon plate of 1.5 mm in thickness, where the plate is supported by four rods on the monitor chamber. The heat generated by the interactions between the beam and the carbon plate propagates to the outer edge of the plate, and then to the monitor chamber through the four rods. By measuring the temperature differences between upstream and downstream ends of each rod, the total heat flow can be measured. The beam current can be determined by the measured heat flow with the help of the calculated stopping power of a proton in a carbon material. The design of the BIHM and test results of a prototype will be described. | ||
| FRPMN050 | Multiple parameter characterizations for electron beam with diffraction radiation | 4096 |
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There are growing interests in developing non-intercepting method for real-time monitoring electron beam parameters for International linear collider and X-ray free electron lasers. In this paper we present both theorectical considerations and experimental demonstration of the ability of diffraction radiation for measuring electron beam profile, divergence, emittance and bunch length*. The possibility of using optical diffraction radiation to direct image electron beam profile is studied**.A new method for bunch length measurement with diffraction radiation deflector is also proposed and analysed***.
* Dao Xiang and Wen-Hui Huang, Nucl. Instr. and Meth. in Phys. Res. B, 254 (2007) 165.** Dao Xiang and Wen-Hui Huang, Nucl. Instr. and Meth. in Phys. Res. A, 570 (2007) 357.*** Dao Xiang and Wen-Hui Huang, Phys. Rev. ST-AB, 10 (2007) 012801. |
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| FRPMN051 | Design of S-band Cavity BPM for HLS | 4102 |
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Funding: Supported by 985 Project of USTC 173123200402002 For the development of accelerators we require increasingly precise control of beam position. Cavity BPMs promise a much higher position resolution compared to other BPM types and manufacture of cavity BPMs is in general less complicated. The cavity BPM operating at S-band for HLS (Hefei Light Source) was designed. It consists of two cavities: a position cavity tuned to TM110 mode and a reference cavity tuned to TM010 mode. To suppress the monopole modes we use waveguides as pickups. Superheterodyne receivers are used in electronics for many cavity BPMs while we decide to use chip AD8302 produced by Analog Devices to process the signals. To simulate and calculate the electromagnetic field we use MAFIA. |
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| FRPMN052 | Bunch Length Measurement in Time Domain for HLS | 4108 |
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Funding: Supported by the Natural Science Foundation of China (10675118) and by Knowledge Innovation Project of CAS A simple measurement method of beam bunch length in time domain for HLS (Hefei Light Source) has been proposed. The Bunch length measurement system is composed of an optical system, a high speed photo-receiver and a wide bandwidth oscilloscope. The photo-receiver which is made by FEMTO has high sensitivity and high bandwidth, which converts the synchrotron radiation light into electronic signal. The oscilloscope which is made by Tektronix is TDS7704B, which has a high bandwidth up to 7GHz and show the bunch length in time domain. The measurement results of the bunch length and its analysis are given. We compare the results with that determined by the conventional method using a streak camera. |
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| FRPMN053 | Beam Instability and Correction for "DRAGON-I" | 4114 |
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| 'Dragon-I' is a high current pulse electron linear induction accelerator designed and constructed in IFP/CAEP. It generates a 20MeV, 2.5kA, 60ns pulse electron beam. The whole facility has three parts: injector; accelerator and beam focus system. The accelerator consists of 72 induction cells and 18 connection cells. A solenoid was installed inside each cell forming beam transport sysem. During the initial beam test both high frequency and low frequency oscillation were found. A lot of simulation and experiment investigations were done to get the transverse impedance of the cells and the corkscrew motion of the electron beam. Details of both the simulation and the experimental methods to correct the instability are presented. | ||
| FRPMN054 | The Design Study of IP-BPM for the ILC | 4120 |
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| Beam position monitors (BPMs) with a resolution in a few nanometers range are required to control beams in the locations that are close to the interaction point (IP) of the International Linear Collider (ILC). ATF2 at KEK has considered as a test facilitiy to investigate this requirement. We have performed the design study for IP-BPM by using of the electromagnetic simulation program MAFIA and HFSS. The designed IP-BPM consists of one cell sensor cavity and one cell reference cavity. The results of the design studies showed signal decay time of 20 ns and orbit sensitivity of a few nm. The signal voltage from sensor cavity showed increasing of a factor of 3 and 2 in horizontal and vertical directions, respectively, than the IP-BPM that was installed ATF extraction beam line. We present the results of design studies in which include effects of common mode contamination in the IP-BPM. | ||
| FRPMN055 | Proton Beam Energy Measurement Using Semiconductor Detectors at the 45MeV Test Beam Line of PEFP | 4126 |
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Funding: This research was supported by MOST (Ministry of Science and Technology) of Korea as a sub-project of PEFP (Proton Engineering Frontier Project). The test beam line was installed at the MC-50 cyclotron of KIRAMS (Korea Institute of Radiological And Medical Sciences). It has been supporting many pilot and feasibility studies on the development of beam utilization technologies of PEFP (Proton Engineering Frontier Project). The energy measurement with high accuracy is very important for the some experiments such as radiation hardness test of semiconductor devices, nuclear physics, detector test, etc. SSB and Si(Li) detector was used as del-E and E detector and the thickness of detectors are 2mm and 5mm each. The available energy range is 10MeV~39MeV and the flux was controlled not to be exceed 1·10+05/cm2-sec using a 0.5mm diameter collimator. |
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| FRPMN056 | Beam Current and Energy Measurement of the PEFP 20 MeV Accelerator | 4129 |
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Funding: This work is supported by the 21C Frontier R&D program in the Ministry of Science and Technology of the Korean government. The beam test of the Proton Engineering Frontier Project (PEFP) 20 MeV proton linear accelerator started again, after the upgrade of the RF control system, One of the important goals of the test is to increase the beam current to the design level. Tuned current transformers were installed along the DTL tanks to measure the beam current itself and possible beam loss along the accelerator. Because there were no empty drift tubes, the current transformers should be installed between DTL tanks. Therefore, the tuning plans were developed to obtain the desired beam properties with the limited number of beam diagnostic devices. Also two BPMs for the time of flight measurement and energy degrader were installed at the end of the 20 MeV accelerator to measure the beam energy. In this paper, the overall test results including beam current and energy measurement are presented. |
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| FRPMN060 | Beam Loss Simulation of SNS LINAC | 4138 |
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Funding: SNS is managed by UT-Batelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy. We are developing a sophisticated system of beam loss pattern evaluation and residual radiation estimation. We have installed a number of Neutron Detectors and Ionization Chambers along LINAC. In this paper we present our implementation and simulation of the losses by inserting Faraday Cups, using Beam Stops and running Wire Scanners at different energies. The measured losses are simulated by 3-D transport codes (GEANT4, SHIELD, MCNPX). We compare two different sets of Beam Loss Monitors: Ionization Chambers (detecting X-ray and gamma radiation) and Photo-Multiplier Tubes with a neutron converter (detecting neutrons) and outline that such a combination is a better way to measure beam losses than relying on detectors of one type. We interpret the loss signal in terms of beam current lost in the SNS LINAC with accurate longitudinal loss distribution and plan to automate beam steering according to loss monitors readings by using vast Loss Pattern Database developed by simulating different loss scenarios with the transport codes. |
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| FRPMN062 | OTR Interferometry Diagnostic for the A0 Photoinjector | 4144 |
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Funding: Operated by Universities Research Association, Inc. for the U. S. Department of Energy under contract DE-AC02-76CH03000. OTR interferometry (OTRI) is an attractive diagnostic for investigation of relativistic electron beam parameters. The diagnostic is currently under development at the A0 Photoinjector. This diagnostic is applicable for NML accelerator test facility that will be built at Fermilab. The experimental setups of the OTR interferometers for the Photoinjector prototype are described in the report. Results of simulations and measurements are presented and discussed. |
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| FRPMN063 | Superconducting RF Gun Cavities for large Bunch Charges | 4150 |
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| The first electron beam of the RF gun with a 3.5 cell superconducting cavity is expected in July 2007 in FZD. This cavity has been designed for small bunch charges. In the paper we present the design of a similar cavity and of 1.5 cell gun cavities for large bunch charges. For a charge of 2.5 nC, which is the design value of the BESSY-FEL, and a bunch length of 21 ps a projected transverse emittance less then 1 π mm mrad has been obtained (without thermal emittance). | ||
| FRPMN064 | Applications of Cherenkov Radiation in Dispersive and Anisotropic Metamaterials to Beam Diagnostics | 4156 |
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Funding: US Department of Energy Cherenkov radiation (CR) is extensively used for detection of charged particles. The prompt nature of the radiation is one major advantage for diagnostics that measure temporal properties of the beam. However, low signal levels and small angles of radiation with respect to the particle trajectory present limitations on the use of traditional detector media. Using modern artificial metamaterials as Cherenkov radiators can provide essential advantages. As a rule metamaterials are characterized by strong dispersion and anisotropy that can be engineered to the requirements of the detector. We present theoretical and numerical analyses of CR in bulk anisotropic and dispersive media and in waveguides. The properties exhibited by these materials (large angles of radiation, two maxima in the angular distributions, etc.) allow the design of detectors with unusual characteristics, like a detector that registers almost all moving particles, and simultaneously only particles with velocity exceeding a predetermined threshold. We consider the case of a material that is approximately equivalent to an isotropic left-handed medium that also presents advantages as a Cherenkov medium. |
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| FRPMN065 | Fast Vertical Single-Bunch Instability at Injection in the CERN SPS - An Update | 4162 |
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| Following the first observation of a fast vertical instability for a single high-brightness bunch at injection in the SPS in 2003, a series of detailed measurements and simulations has been performed in order to assess the resulting potential intensity limitations for the SPS, as well as possible cures. During the 2006 run, the characteristics of this instability were studied further, extending the intensity range of the measurements, and comparing the experimental data with simulations that take into account the latest measurements of the transverse machine impedance. In this paper, we summarize the outcome of these studies and our understanding of the mechanisms leading to this instability. The corresponding intensity limitations were also determined. | ||
| FRPMN067 | Collision Rate Monitors for LHC | 4171 |
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| Collision rate monitors are essential in bringing particle beams into collision and optimizing the performances of a collider. In the case of LHC the relative luminosity will be monitored by measuring the flux of small angle neutral particles produced in the collisions. Due to the very different luminosity levels at the four interaction regions (IR) of LHC two different types of monitors have been developed. At the high luminosity IR (ATLAS and CMS) fast ionization chambers will be installed while at the other two (ALICE and LHC-b) solid state polycrystalline Cadmium Telluride (CdTe) detectors will be used. The ionization chambers are being developed by Lawrence Berkeley National Lab (Berkeley CA, USA) while the CdTe monitors are being developed by CERN and CEA-LETI (Grenoble, FR) This paper describes the system with particular emphasis on the monitors based on CdTe detectors, detailed description of the ionisation chambers being available in separate papers. | ||
| FRPMN068 | The 4.8 GHz LHC Schottky Pick-up System | 4174 |
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Funding: LARP The LHC Schottky observation system is based on traveling wave type high sensitivity pickup structures operating at 4.8 GHz. The choice of the structure and operating frequency is driven by the demanding LHC impedance requirements, where very low impedance is required below 2 GHz, and good sensitivity at the selected band at 4.8 GHz. A sophisticated filtering and triple down-mixing signal processing chain has been designed and implemented in order to achieve the specified 100 dB instantaneous dynamic range without range switching. Detailed design aspects for the complete systems and test results without beam are presented and discussed. |
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| FRPMN069 | Longitudinal Coupled-Bunch Instabilities in the CERN PS | 4180 |
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Funding: Work supported by EU Design Study DIRACsecondary-Beams (contract 515873). Longitudinal coupled bunch instabilities in the CERN PS represent a major limitation to the high brightness beam delivered for the LHC. To identify possible impedance sources for these instabilities, machine development studies have been carried out. The growth rates of coupled bunch modes have been measured, and modes have been identified using mountain range data. Growth rate estimations from coupled bunch mode theory are compared to these results. It is shown that the longitudinal impedance of the broad resonance curve of the main 10 MHz RF system can be identified as the most probable source. Possible methods to improve the beam stability are analyzed together with the performance of a damping system. |
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| FRPMN070 | Controlled Longitudinal Emittance Blow-up in the CERN PS | 4186 |
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| The longitudinal emittance of the bunches in the CERN PS must be increased before transition crossing to avoid beam loss due to a fast vertical instability. This controlled blow-up is essential for all high-intensity beams in the PS, including those for transfer to the LHC. The higher harmonic 200 MHz RF system (six cavities) used for this blow-up has to generate a total RF voltage which, for the most demanding blow-up, is comparable to the voltage of the main RF cavities. The system is presently subject to a major upgrade and a possible reduction in the number of higher harmonic RF cavities installed is under consideration. To determine the minimum required, detailed simulations and machine development studies to optimize the longitudinal blow-up have been performed. Further options to produce the required longitudinal emittance using other RF systems are also analyzed. The results obtained for the different scenarios for the longitudinal blow-up are presented and compared in this paper. | ||
| FRPMN071 | The LHC Beam Loss Measurement System | 4192 |
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| One of the most important elements for the protection of CERN's Large Hadron Collider (LHC) is its beam loss monitoring system. It aims to prevent the super conducting magnets from quenching and to protect the machine components from damages, as a result of critical beam losses. This contribution reviews the design requirements: a high reliability to insure a safe protection and a high availability, a high dynamic range required by the beam dump trigger generation and beam tuning and finally a high radiation tolerance to be able to install the front-end electronics in the LHC tunnel. Examples of the reliability studies using the reliability ISOGRAPH fault tree software package are shown to explain the particular design. Measurement results from the LHC beam loss system installed at HERA (DESY) and at the SPS (CERN) are given to demonstrate its functionality. The detector design of the ionisation chambers and the secondary emission monitors are summarized and measurements with high and low intensity beams as well as with continuous and pulsed proton, muon and neutron beams are discussed. | ||
| FRPMN072 | LHC Beam Loss Detector Design: Simulations and Measurements | 4198 |
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| The LHC beam loss monitoring system must prevent the super conducting magnets from quenching and protect the machine components from damage. 4000 gas filled ionization chambers are installed all around the LHC ring. They probe the far transverse tail of the hadronic shower induced by lost beam particles. Secondary emission chambers are placed in very high radiation areas for their lower sensitivity. This paper focuses on the signal response of the chambers to various particle types and energies and the simulated prediction of the hadronic shower tails. Detector responses were measured with continuous and bunched proton and mixed particle beams of 30 MeV to 450 GeV at PSI and CERN. Additional test measurements with 662 keV gammas and 174 MeV neutrons were performed on the ionization chamber. The measured signal speed, shape and absolute height are compared to GEANT4 and Garfield simulations. Aging data of SPS ionization chambers are shown. The far transverse tail of the hadronic shower induced by 40 GeV and 920 GeV protons impacting on the internal beam dump of HERA at DESY have been measured and compared to GEANT4 simulations. | ||
| FRPMN073 | The FPGA-based Continuous FFT Tune Measurement System for the LHC and its Test at the CERN SPS | 4204 |
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| A base band tune (BBQ) measurement system has been developed at CERN. This system is based on a high-sensitivity direct-diode detection technique followed by a high resolution FFT algorithm implemented in an FPGA. The system allows acquisition of continuous real-time spectra with 32-bit resolution, while a digital frequency synthesiser (DFS) can provide an acquisition synchronised chirp excitation. All the implemented algorithms support dynamic reconfiguration of processing and excitation parameters. Results from both laboratory measurements and tests performed with beam at the CERN SPS are presented. | ||
| FRPMN074 | Simulation Study of the Horizontal Head-Tail Instability Observed at Injection of the CERN Proton Synchrotron | 4210 |
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| For many years, a horizontal head-tail instability has been observed at the CERN Proton Synchrotron during the long 1.2 s injection flat-bottom. This slow instability has been damped using linear coupling only, i.e. with neither octupoles nor feedbacks. Using the nominal machine and beam parameters for LHC, the sixth head-tail mode number is usually observed. Several other modes were also observed in the past by tuning the chromaticity, and these observations were found to be in good agreement with Sacherer's formula. The purpose of this paper is to present the results of assessing the effect of chromaticity and linear coupling on this slow head-tail instability using the HEADTAIL simulation code, and to compare these simulations with both measurements performed over the last few years, and theoretical calculations. | ||
| FRPMN075 | Resistive-Wall Impedance of an Infinitely Long Multi-Layer Cylindrical Beam Pipe | 4216 |
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| The resistive wall impedance of cylindrical vacuum chambers was first calculated more than forty years ago under some approximations. Since then many papers have been published to extend its range of validity. In the last few years, the interest in this subject has again been revived for the LHC graphite collimators, for which a new physical regime is predicted. The first unstable betatron line in the LHC is at 8 kHz, where the skin depth for graphite is 1.8 cm, which is smaller than the collimator thickness of 2.5 cm. Hence one could think that the resistive thick-wall formula would be about right. It is found that it is not, and that the resistive impedance is about two orders of magnitude lower at this frequency, which is explained by the fact that the skin depth is much larger than the beam pipe radius. Starting from the Maxwell equations and using field matching, a consistent derivation of the transverse resistive wall impedance of an infinitely long cylindrical beam pipe is presented in this paper. The results, which should be valid for any number of layers, beam velocity, frequency, conductivity, permittivity and permeability, have been compared to previous ones. | ||
| FRPMN076 | Nominal LHC Beam Instability Observations in the CERN Proton Synchrotron | 4222 |
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| The nominal LHC beam has been produced successfully in the CERN Proton Synchrotron since 2003. However, after having restarted the CERN PS in spring 2006, the LHC beam was set-up and observed to be unstable on the 26 GeV/c extraction flat top. An intensive measurement campaign was made to understand the instability and to trace its source. This paper presents the observations, possible explanations and the necessary measures to be taken in order to avoid this instability in the future. | ||
| FRPMN078 | Improved Algorithms to Determine Non-Linear Optics Model of the SPS from Non-Linear Chromaticity | 4231 |
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Funding: This work is partially supported by the U. S. DOE In recent years several measurements of the SPS non-linear chromaticity have been performed in order to determine the non-linear optics model of the SPS machine at injection energy for different cycles. In 2006 additional measurements have been performed at injection and during the ramp for the cycle used to accelerate the LHC beam. New and more robust matching algorithms have been developed in 2006 to fit the model to the measurements up to arbitrary chromatic order. In this paper we describe the algorithms used in the analysis of the data and we summarize and compare the results from all experiments. |
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| FRPMN079 | Two-Beam Resistive-Wall Wake Field | 4237 |
| In all storage-ring colliders, two beams propagating in opposite direction share a common beam pipe over parts or all of the ring circumference. The resistive-wall wake field coupling bunches of these two beams is different from the conventional single-beam wake field, as the magnetic force and the longitudinal electric force experienced by a probe bunch invert their sign, while the transverse electric force does not. In addition, the distance between driving and probing bunches is not constant, but the net wake field must be obtained via an integration of the force experienced over the drive-probe distance. We derive the two-beam resistive-wall wake field for a round beam pipe. | ||
| FRPMN081 | A Preliminary Study of Beam Instabilities in Top-up Operation at Taiwan Light Source | 4246 |
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| The storage ring of Taiwan Light Source started to operate fully in top-up mode since October 2005. The beam current has been gradually increased to 300 mA in routine user operation. Phenomena of collective effects were observed at 300 mA in top-up operation mode. Active feedback systems were implemented to stabilize the beam in top-up mode. Results of beam observation and analysis will be presented. | ||
| FRPMN082 | Diagnostic and Timing Supports for Top-Up Injection Operation for the TLS | 4252 |
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| Routine top-up operation of Taiwan Light Source (TLS) was started from October 2005 after high efficiency multi-bunch instabilities suppression system put into service. To support the top-up operation, various diagnostics and timing supports are needed. These include diagnostics for injection efficiency, filling pattern of the storage ring, tune, instability, loss pattern measurement. Timing control of the injection process are also needed. Design consideration and details of these efforts will be summary in this report. Further possible improvement will be also discussed. | ||
| FRPMN083 | RF Feed-Forward Control Experiments for the 50 MeV Linear Accelerator at TLS | 4258 |
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| Performance of an electron linear accelerator is very important for synchrotron light source application. Its performance will decide the reproducibility of filling pattern in the booster synchrotron. The filling pattern of the booster synchrotron will affect filling pattern control of the storage ring. The RF feed-forward control can improve performance of linear accelerator deistically. Design consideration and details of the implementation will be summary in this report. | ||
| FRPMN084 | Beam Trip Event Diagnostic System for the TLS | 4264 |
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| The beam trip event diagnostic system includes several eight channels high-speed digitizer for data acquisition, PC base computer and optical fibre network applies to capture data. The PC are also to serve signal processing, beam trip event analysis and archive. This system can integrate beam trip, interlock signal of SRF, waveform of the injection kicker, quench and interlock signal of the superconducting insertion device, and instability of the stored beam. This diagnostic system can be routine monitor signal and record beam trip event. Design consideration and details of the implementation will be summarized in this report. | ||
| FRPMN085 | Application of the IEEE-1394 and the GigE Vision Digital Cameras for Diagnostics in Taiwan Light Source | 4270 |
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| Digital camera has been adopted for the booster, storage ring and transport-line diagnostic recently at the Taiwan Light Source. The system provides low image distortion and lossless image transmission over long distances. The system is integrated with commercial software in the control system. The fully remote control supports various operations and application that is useful. These applications include of screen monitor equip in the booster and storage ring, wider dynamic range sensor and highly flexibility control for the emittance measurement in the transport line, booster and linac. System configuration and present status will be summarized in this report. | ||
| FRPMN086 | Beam Position Monitoring System Upgrade for the TLS | 4276 |
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| Taiwan light source (TLS) equips with 59 beam position monitors (BPM). Existing Bergos's type multiplexing BPM electronics are working well during last decade. To improve the functionality of the BPM system, new type of BPM electronics (Liberal Electron) will be replace some existing multiplexing BPM electronics. Seamless integration of two kinds of electronics is via reflective memory. The high precision closed orbits were measured by multiplexing BPM via multi-channel PMC form factor 16-bits ADC modules and gigabit Ethernet fast access channel of Libera Electron. Turn-by-turn beam position measurement is also supported by new BPM electronics. Tune measurement is also possible by spectra analysis of the turn-by-turn beam position data. The preliminary version of the orbit data was sampled every millisecond. Fast orbit data were shared by reflective memory network to support fast orbit feedback application. Averaged data were updated to control database at a rate of 10 Hz. The system structure, software environment and preliminary beam test of the BPM system are summarized in this report. | ||
| FRPMN089 | Facility Wide Real-Time Beam Loss Monitoring & Control using FPGA Technology | 4282 |
| The ISIS facility based at Rutherford Appleton Laboratory, Chilton, Didcot, UK is currently the worlds brightest pulsed Neutron Spallation Source producing a beam to target power of 160kW. It is critical during machine operation to reduce activation of machine components by monitoring and controlling beam losses. Beam loss detection is provided using a total of 82 gas ionisation chambers distributed throughout the Injector, 800MeV Synchrotron, the Extracted Proton Beamline and the new Extracted Proton Beamline for TS2. This paper outlines the design of a new Beam Loss Display and Beam Trip Unit which uses a high speed FPGA design to provide real time monitoring, beam loss data logging and increased beam trip reaction time. | ||
| FRPMN090 | A Prototype Energy Spectrometer for the ILC at End Station A in SLAC | 4285 |
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| The main physics programme of the international linear collider requires a measurement of the beam energy with a relative precision on the order of 10-4 or better. To achieve this goal a magnetic spectrometer using high resolution beam position monitors (BPM) has been proposed. A prototype spectrometer chicane using 4 dipole magnets is currently under development at the End Station A in SLAC, intending to demonstrate the required stability of this method and investigate possible systematic effects and operational issues. This contribution reports on the successful commissioning of the beam position monitor system and the resolution and stability achieved. Also, the initial results from a run with a full spectrometer chicane are presented. | ||
| FRPMN091 | Simulation of HOM Wakefields in the Main ILC Cavities | 4288 |
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| We investigate the electromagnetic field (e.m.) excited by a train of multiple bunches in the main superconducting linacs of the ILC. These e.m. fields are represented as a wake-field. Detailed simulations are made for the modes which constitute the long-range wake-field in new high gradient cavity structures. In particular, we focus our study on the modes in re-entrant and low loss Ichiro cavities. Modes trapped within a limited number of cells can give rise to a significant diminution in the emittance of the beam and we pay particular attention to these modes. Beam tracking simulations on the resulting emittance dilution over the entire length of the linac are made in order to provide details on the damping which is necessary for modes with particularly large kick factors. | ||
| FRPMN092 | Beam Coupling Impedance Simulations and Laboratory Measurements for the LHC FP420 Detector | 4294 |
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The FP420 collaboration* aims at designing forward proton tagging detectors to be installed in the LHC sectors 420 meters downstream of the ATLAS detector and/or CMS detector. The experiment requires modification of the beam pipe material and geometry with a consequent impact on the LHC impedance budget and the circulating beam stability. This paper describes numerical simulations and laboratory measurements carried out to characterize the coupling impedance (longitudinal and transverse) and the associated loss factor of each insertion. The detectors are located in pockets of the beam tube. We study both single and multi-pocket configurations with a view to characterizing the impact on the beam dynamics. In addition, results are compared to available analytical calculations for the resistive wall impedance.
* Cox, Brian et al., "FP420 : An R&D Proposal to Investigate the Feasibility of Installing Proton Tagging Detectors in the 420 m Region of the LHC", CERN-LHCC-2005-025 |
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| FRPMN094 | Beam Profile Measurements with the 2-D Laser-Wire at PETRA | 4303 |
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Funding: Work supported by the PPARC LC-ABD collaboration and the Commission of the European Communities under the 6th Framework Programme Structuring the European Research Area, contract number RIDS-011899. The current PETRA II Laser-Wire system, being developed for the ILC and PETRA III, uses a piezo-driven mirror to scan laser light across an electron bunch. This paper reports on the recently installed electron-beam finding system, presenting recent horizontal and vertical profile scans with corresponding studies. |
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| FRPMN098 | Compact PCI/PXI Based High Voltage Cards. | 4312 |
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Funding: BiRa Systems, Albuquerque, New Mexico High voltage power modules find uses in many applications like the Photo multiplier Tubes (PMT), Ionization chambers, CRT systems testing, high voltage biasing for Avalanche Photodiodes, Photo detectors, X-ray tubes, Pulse generators which are used in radars, lasers, EMC testing and other imaging applications. Providing high voltage, to these applications, which can be remotely controlled in a small, confined area, is a problem many laboratories around the world face. The LV and the HV series of high voltage systems from BiRa Systems present experimenters with voltages ranging from several hundreds upto ± 5kV in a rugged CompactPCI / PXI chassis, running National Instruments' LabView. The CompactPCI architecture offers modularity, tight integration and low cost. Apart from that, the deterministic and real time nature of the operating system also allows these modules to be remotely controlled and monitored over the Ethernet. The high voltage cards can be easily custom tailored to a particular voltage and current requirement |
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| FRPMN099 | Equilibrium Fluctuations in an N-Particle Coasting Beam: Schottky Noise Effects | 4318 |
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Funding: Supported by DOE grant DE-FG02-99ER41104
We discuss the longitudinal dynamics of an unbunched beam with a collective effect due to the vacuum chamber and with the discretness of an N-particle beam (Schottky noise) included. We start with the 2N equations of motion (in angle and energy) with random initial conditions. The 2D phase space density for the N-Particles is a sum of delta functions and satisfies the Klimontovich equation. An arbitrary function of the energy also satisfies the Klimontovich equation and we linearize about a convenient equilibrium density taking the initial conditions to be independent, identically distributed random vaiables with the equilibrium distribution. The linearized equations can be solved using a Laplace transform in time and a Fourier series in angle. The resultant stochastic process for the phase space density is analyzed and compared with a known result*. Work is in progress to study the full nonlinear problem. To gain further insight we are studying three alternative approaches: (1) a BBGKY approach, (2) an approach due to Elskens and Escande** and (3) the 'three-level-approach' of Donsker and Varadhan (see "Entropy, Large Deviations and Statistical Mechanics'', by R. S. Ellis).
* V. V. Parkhomchuk and D. V. Pestrikov, Sov. Phys. Tech. Phys. 25(7), July 1980 ** "Microscopic Dynamics of Plasmas and Chaos", Y. Elskens and D. Escande, IoP, Series in Plasma Physics, 2003. |
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| FRPMN102 | An Instrument Design for the Accurate Determination of the Electron Beam Location in the Linac Coherent Light Source Undulator | 4324 |
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Funding: Work supported by U. S. Department of Energy, under Contract Nos. DE-AC02-06CH11357 and DE-AC03-76SF00515. The Linac Coherent Light Source (LCLS), currently under design, requires accurate alignment between the electron beam and the undulator magnetic centerline. A Beam Finder Wire (BFW) instrument has been developed to provide beam location information that is used to move the undulators to their appropriate positions. A BFW instrument is mounted at each of the 33 magnets in the undulator section. Beam detection is achieved by electrons impacting two carbon fiber wires and then sensing the downstream radiation. The wires are mounted vertically and horizontally on a wire card similar to that of a traditional wire scanner instrument. The development of the BFW presents several design challenges due to the need for high accuracy of the wires' location and the need for removal of the wires during actual operation of the LCLS (30 microns repeatability is required for the wire locations). In this paper, we present the technical specification, design criteria, mechanical design, and results from prototype tests for the BFW. |
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| FRPMN103 | Single-Bunch Instability Estimates for the 1-nm APS Storage Ring Upgrade with a Smaller Vacuum Chamber | 4330 |
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Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
We recently studied a lattice achieving 1-nm emittance at the APS storage ring*. The successful design required very strong sextupoles in order to tune the machine to the desired positive chromaticity. A preliminary design of such magnets indicated saturation in the poles unless the vacuum chamber gets smaller by a factor of two compared to the existing APS chamber. Since the resistive wall impedance scales as 1/b3, where b is the radius of the chamber, we questioned how much current we can store in a single bunch at the 1-nm storage ring. In order to answer this question quantitatively, we calculated all wake potentials of impedance elements of the existing APS storage ring with the transverse dimension properly scaled but with the longitudinal dimension kept unchanged. With the newly calculated impedance of a smaller chamber, we estimated the single-bunch current limit. It turned out that the ring with a smaller chamber would not diminish the single-bunch current limit substantially. We present both wake potentials of 1-nm and the existing rings followed by the simulation results carried out for determining the accumulation limit to the ring.
* A. Xiao, "A 1-nm Lattice for the APS Storage Ring" these proceedings. |
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| FRPMN104 | Impedance Database II for the Advanced Photon Source Storage Ring | 4336 |
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Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The first Impedance Database* constructed at the Advanced Photon Source was successfully used in reproducing the main characteristics of single-bunch instabilities observed in the storage ring. However, the finite bandwidth of the corresponding impedance model was limited to 25 GHz, which happens to be the resolution limit of the density modulation observed in the microwave instability simulation. In order to resolve simulation results never verified in the experiments, we decided to extend the calculated bandwidth of impedance to 50 GHz by recalculating the wake potentials excited by a shorter bunch. Since low-order electromagnetic code requires 20-40 grid points per wavelength, reducing the bunch length required a large number of grids for the 3D structure. We used bunch lengths of 1- and 2-mm in the Gaussian distribution in the Impedance Database II project. For the large-scale computation we used the 3D electromagnetic code GdfidL ** for wake potential calculation at the cluster equipped with 240 GB of memory. The resultant wake potential excited by the short bunch together with application to the storage ring for collective effects is presented in the paper.
* Y.-C. Chae, "The Impedance Database and Its Application to the APS Storage Ring" Proc. 2003 PAC, p. 3017.** http://www.gdfidl.de |
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| FRPMN105 | The Wakefield Effects of Pulsed Crab Cavities at the Advanced Photon Source for Short-X-ray Pulse Generation | 4339 |
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Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
In recent years we have explored the application to the Advanced Photon Source (APS) of Zholents' crab-cavity-based scheme for production of short x-ray pulses. As a near-term project, the APS has elected to pursue a pulsed system using room-temperature cavities*. The cavity design has been optimized to heavily damp parasitic modes while maintaining large shunt impedance for the deflecting dipole mode**. We evaluated a system consisting of three crab cavities as an impedance source and determined their effect on the single- and multi-bunch instabilities. In the single-bunch instability we used the APS impedance model as the reference system in order to predict the overall performance of the ring when the crab cavities are installed in the future. For multi-bunch instabilities we used a realistic fill pattern, including hybrid-fill, and tracked multiple bunches where each bunch was treated as soft in distribution. To verify the electrical design, the realistic wake potential of the 3D structure was calculated using GdfidL and this wake potential was used in the multi-bunch simulations.
* M. Borland et al., "Planned Use of Pulsed Crab Cavities at the APS for Short X-ray Pulse Generation," these proceedings.** V. Dolgashev et al., "RF Design of Normal Conducting Deflecting Structures for the APS," these proceedings. |
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| FRPMN106 | Progress toward a Hard X-ray Insertion Device Beam Position Monitor at the Advanced Photon Source | 4342 |
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Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Long-term pointing stability at synchrotron light sources using conventional rf-based particle beam position monitoring is limited by the mechanical stability of the pickup electrode assembly. Photoemission-based photon beam position monitors for insertion device beams suffer from stray radiation backgrounds and other gap-dependent systematic errors. To achieve the goal of 500-nanoradian peak-to-peak pointing stability over a one-week period, the development of a photon beam position detector sensitive only to hard x-rays (> several keV) using copper x-ray fluorescence has been initiated. Initial results and future plans are presented. |
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| FRPMN107 | Observations of Rising Tune During the Injection Instability of the IPNS RCS Proton Bunch | 4345 |
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Funding: This work is supported by the U. S. DOE under contract no. W-31-109-ENG-38. In the IPNS RCS, a single proton bunch (h=1) is accelerated from 50 MeV to 450 MeV in 14.2 ms. The bunch experiences an instability shortly after injection (<1 ms). During the first 1 ms, the beam is bunched but little acceleration takes place; thus, this period of operation is similar to that of a storage ring. Natural vertical oscillations (assumed to be tune lines) show the vertical tune to be rising toward the bare tune value, suggesting neutralization of space charge and a reduction of its detuning effects. Neutralization time near injection ranges from 0.25 ms - 0.5 ms, depending on the background gas pressure. Oscillations move from the LSB to the USB before disappearing. Measurements made with a recently installed pinger system show the horizontal chromaticity to be positive early but approaching zero later in the cycle. The vertical chromaticity is negative throughout the cycle. During pinger studies, two lines are observed, suggesting the formation of islands. Neutralization of the beam space charge implies the generation of plasma in the beam volume early in the cycle which may then dissipate as the time-varying electric fields of the beam become stronger. |
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| FRPMN108 | Coupled-Bunch Instability Study of Multi-cell Deflecting Mode Cavities for the Advanced Photon Source | 4348 |
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Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The short-pulse X-ray project at the Advanced Photon Source (APS) uses three room-temperature nine-cell 2.815 GHz deflecting-mode cavities in a straight section. Undamped, these cavities' higher-order and lower-order resonator modes will cause multi-bunch instabilities in longitudinal and transverse planes for any bunch pattern of a 1'000mA store. Damping of these modes must be part of the design of the cavities. We report calculations of instability growth rates and tracking simulations that were essential in specifying the rf design of the damping structures. We used various operating bunch patterns and scanned levels of damping of the cavities. Because one of the operating bunch patterns is not symmetric, we used a normal mode analysis * implemented in the APS code clinchor. Our calculation included random sampling of resonator frequencies in a reasonable range. We found that staggering of frequencies is only effective for modes that could not be heavily damped.
* K. Thompson and R. Ruth, PAC 1989 |
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| FRPMN109 | 200-mA Studies in the APS Storage Ring | 4354 |
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Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source storage ring is normally operated with 100 mA of beam current. A number of high-current studies were carried out to determine the multibunch instability limits. The longitudinal multibunch instability is dominated by the rf cavity higher-order modes (HOMs), and the coupled-bunch instability (CBI) threshold is bunch-pattern dependent. We can stably store 200 mA with 324 bunches, and the CBI threshold is 245 mA. With 24 bunches, several components are approaching temperature limits above 160 mA, including the HOM dampers. We do not see any CBI at this current. The transverse multibunch instabilities are most likely driven by the resistive wall impedance; there is little evidence that the dipole HOMs contribute. Presently, we rely on the chromaticity to stabilize the transverse multibunch instabilities. When we stored beam up to 245 mA, we used high chromaticity, and the beam was transversely stable. The stabilizing chromaticity was studied as a function of current. We can use these experimental results to predict multibunch instability thresholds for various upgrade options, such as smaller-gap or longer ID chambers and the associated increased impedance. |
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| FRPMN110 | Transverse Multibunch Bursting Instability in the APS Storage Ring | 4360 |
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Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The horizontal bursting instability was first observed in a single bunch in the APS in 1998, soon after operation began. Above the instability threshold, the bursting is characterized by exponentially growing bunch centroid oscillations that saturate, then decay, repeating quasi-periodically. More recently, bursting was also observed with multiple bunches in both the horizontal and vertical planes, showing that this is not purely a single-bunch phenomenon. On the other hand, the multibunch instability threshold is strongly dependent on bunch spacing, and the dependence is markedly different for the two transverse planes. Depending on the bunch spacing, the bunch-to-bunch oscillations are sometimes coupled, sometimes not. In this paper, we discuss the threshold in terms of the chromaticity required to stabilize the beam. We present instability imaging data using a streak camera that shows the bunch-to-bunch oscillation phase, and turn-by-turn beam position histories that give the bursting time dependence for different bunch spacings. Finally, we discuss the machine impedance and measured tune shift with current. |
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| FRPMN111 | Design and Performance of the LCLS Cavity BPM System | 4366 |
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Funding: Work supported by U. S. Department of Energy under Contract Nos. DE-AC02-06CH11357 and DE-AC03-76SF00515 In this paper we present the design of the beam position monitor (BPM) system for the LCLS undulator, which features a high resolution X-band cavity BPM. Each BPM has a TM010 monopole reference cavity and a TM110 dipole cavity designed to operate at a center frequency of 11.384 GHz. The signal processing electronics features a low-noise single-stage three-channel heterodyne receiver that has selectable gain and a phase locking local oscillator. We will discuss the system specifications, design, and prototype test results. |
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| FRPMN112 | Far-Field OTR and ODR Images Produced by 7-GeV Electron Beams at APS | 4372 |
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Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 We have investigated the angular distribution patterns (far-field focus) of optical transition radiation (OTR) and optical diffraction radiation (ODR) generated by 7-GeV electron beams passing through and near an Al metal plane, respectively. The 70-μrad opening angles of the OTR patterns provide calibration factors for the system. Effects of the upstream quadrupole focusing strength on the patterns as well as polarization effects were observed. The OTR data are compared to an existing OTR single-foil model, while ODR profile results are compared to expressions for single-edge diffraction. ODR was studied with impact parameters of about 1.25 mm, close to the gamma λ?bar value of 1.4 mm for 628-nm radiation. We expect angle-pointing information along the x axis parallel to the mirror edge is available from the single-lobe ODR data as well as divergence information at the sub-100-μrad level. Experimental and model results will be presented. |
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| FRPMN113 | Initial Far-Field OTR Images Generated by 120-GeV Protons at FNAL | 4378 |
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Funding: Work supported by U. S. Department of Energy, Office of Science,under Contract No. DE-AC02-06CH11357 and by U. S. Department of Energy under Contract No. DE-AC02-CH03000. We have successfully imaged for the first time the angular distribution patterns of optical transition radiation (OTR) generated by 120-GeV proton beams passing through an Al metal plane. These experiments were performed at FNAL with the same chamber, foil, and camera design as with the near-field experiments previously reported. In this case the lens-to-CID-chip separation was remotely adjusted to provide the focus-at-infinity, or far-field optical imaging. The ~8-mrad opening angle of OTR patterns confirm/provide the calibration factors for the system. We also used linear polarizers to select the orthogonal polarization components of the radially polarized OTR. The OTR angular distribution results are compared to an existing analytical model. We show angle pointing information is available from the single-foil OTR data at the sub-mrad level and divergence information at about the 1-mrad level. Data have been obtained in transport lines both before the antiproton production target and before the NuMI target with particle intensities of about 5 to 22 x ·1012. A two-foil interferometer calculation was also performed. Single-foil experimental and modeling results will be presented. |
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| FRPMN114 | Feasibility of Near-field ODR Imaging of Multi-GeV Electron Beams at CEBAF | 4381 |
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Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 and U. S. DOE Contract No. DE-AC05-06OR23177. We have evaluated the feasibility of using the optical diffraction radiation (ODR) generated as a 1- to 6-GeV CW electron beam passes nearby the edge of a single metal conducting plane as a nonintercepting (NI) relative beam size monitor for CEBAF. Previous experiments were successfully done using near-field imaging on the lower-current, 7-GeV beam at APS, and an analytical model was developed for near-field imaging. Calculations from this model indicate sufficient beam-size sensitivity in the ODR profiles for beam sizes in the 30-50 micron regime as found in the transport lines of CEBAF before the experimental targets. With anticipated beam currents of 100 microamps, the ODR signal from the charge integrated over the video field time should be ~500 times larger than in the APS case. These signal strengths will allow a series of experiments to be done on beam energy dependencies, impact parameters, polarization effects, and wavelength effects that should further elucidate the working regime of this technique and test the model. Plans for the diagnostics station that will also provide reference optical transition radiation (OTR) images will also be described. |
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| FRPMN115 | A Novel FPGA-Based Bunch Purity Monitor System at the APS Storage Ring | 4384 |
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Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 Bunch purity is an important source quality factor for the magnetic resonance experiments at the Advanced Photon Source. Conventional bunch-purity monitors utilizing time-to-amplitude converters are subject to dead time. We present a novel design based on a single field-programmable gate array (FPGA) that continuously processes pulses at the full speed of the detector and front-end electronics. The FPGA provides 7778 single-channel analyzers (six per RF bucket). The starting time and width of each single-channel analyzer window can be set to a resolution of 178 ps. A detector pulse arriving inside the window of a single-channel analyzer is recorded in an associated 32-bit counter. The analyzer makes no contribution to the system dead time. Two channels for each RF bucket count pulses originating from the electrons in the bucket. The other four channels on the early and late side of the bucket provide estimates of the background. A single-chip microcontroller attached to the FPGA acts as an EPICS IOC to make the information in the FPGA available to the EPICS clients. |
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| FRPMN116 | Status of the RF BPM Upgrade at the Advanced Photon Source | 4390 |
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Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source (APS), a third-generation synchrotron light source, has been in operation for twelve years. The monopulse radio frequency (rf) beam position monitor (BPM) is one of three BPM types now employed in the storage ring at the APS. It is a broadband (10 MHz) system designed to measure single-turn and multi-turn beam positions, but it suffers from an aging data acquisition system. The replacement BPM system retains the existing monopulse receivers and replaces the data acquisition system with high-speed analog-to-digital converters (ADCs) and a field-programmable gate array (FPGA) that performs the signal processing. A first article system has been constructed and is currently being evaluated. This paper presents the results of testing of the first article system as well as the progress made in other areas of this upgrade effort. |
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| FRPMN117 | Pepper-pot Based Emittance Measurements of the AWA Photoinjector | 4393 |
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| The Argonne Wakefield Accelerator (AWA) RF photocathode gun is a 1.5 cell, L-band, RF photocathode gun operating at 80 MV/m, with an emittance compensating solenoid, and a magnesium photocathode and generates an 8 MeV, 1 nC - 100 nC beam. In this paper, we report on a parametric set of measurements to characterize the transverse trace space of the 1 nC electron beam directly out of the gun. The entire experiment is simulated with PARMELA, from the photocathode, through the pepper pot, and to the imaging screen. The transverse trace-space is sampled with a 2-D pepper pot which allows for simultaneous, single-shot measurements, of both the x and y distributions. A series of pepper pots were available during the experiment to increase the dynamic range of emittance measurements. Realistic particle distributions are used for the simulations and are derived from actual laser profiles, which were captured from a virtual cathode and generated with MATLAB-based particle generator. We report both the second moment (emittance) and the detailed phase space distribution over a gun launch phase range of approximately 50 degrees. | ||
| FRPMN118 | LCLS-S1 Optical Transition Radiation Monitor | 4396 |
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Funding: Work supported by the U. S. Department of Energy, under Contract Nos. DE-AC02-06CH11357 and DE-AC03-76SF00515. ANL has developed a high-resolution optical transition radiation (OTR) imaging monitor system for the LCLS injection linac at SLAC. The imaging station, OTR-S1, will be located at the S1 spectrometer with a beam energy of 135 MeV. The system will be used to acquire 2-D transverse beam distributions of the accelerated photocathode-gun-generated electron beam. We anticipate an average beam current of 0.2-1 nC and nominal beam spot size of σ-x 130 microns, σ-y 100 microns. The imaging system was designed for a field of view h/v: 10x7.5 mm. The spatial resolution of ~12 microns was verified over the central 5x4 mm region in the visible. A 12-bit digital camera acquires the image and a Mac-based digital frame capturing system was employed for the initial lab-based performance testing of the device. We are reporting on system development, image capture system, testing methodology, and test data analysis. Commissioning results will be reported as they become available. |
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| FRPMN119 | Vector Processing Enhancements for Real-Time Image Analysis | 4399 |
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Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. A real-time image analysis system was developed for beam imaging diagnostics. An Apple Power Mac G5 with an Active Silicon LFG frame grabber were used to capture video images that were processed and analyzed. Software routines were created to utilize vector processing hardware to reduce the time to process images as compared to conventional methods. These improvements allow for more advanced image processing diagnostics to be performed in real time. |
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| FRPMN120 | Tuning the Narrow-band Beam Position Monitor Sampling Clock to Remove the Aliasing Errors in APS Storage Ring Orbit Measurements | 4402 |
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Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source storage ring employs a real-time orbit correction system to reduce orbit motion up to 50 Hz. This system uses up to 142 narrow-band rf beam position monitors (Nbbpms) in a correction algorithm by sampling at a frequency of 1.53 kHz. Several Nbbpms exhibit aliasing errors in orbit measurements, rendering these Nbbpms unusable in real-time orbit feedback. The aliasing errors are caused by beating effects of the internal sampling clocks with various other processing clocks residing within the BPM electronics. A programmable external clock has been employed to move the aliasing errors out of the active frequency band of the real-time feedback system (RTFB) and rms beam motion calculation. This paper discusses the process of tuning and provides test results. |