Diagnostics for Lepton Accelerators

Paper Title Page
RPAE043 Beam Position Monitor for Undulator by Using SR Monitor Technique 2789
  • T. Mitsuhashi, M.T. Tadano
    KEK, Ibaraki
  A beam position monitor for the undulator by using the optical SR monitor technique has been tested in the Photon Factory. A visible SR in far tail of the undurater spectrum is extracted by a water-cooled beryllium mirror. The extraction mirror has a hole in the center for passing through the central peak of the undulator radiation which has an opening angle of 1/gamma. Extracted visible light in large opening angle has exactly same optical axis of the undulator radiation, because of it’s a far tail of the spectrum of same radiation. We applied focusing system to observe the beam position in the undulator through the optical image of beam. The results show us this method is applicable to monitor a position of beam in the undulator, and gap change of undulator has no effect of beam position monitoring. We can easily measure the angle of visible ray, this method is applicable not only beam position monitor but also monitoring the angular deviation of undulator radiation.  
RPAE054 Beam Stability at the Advanced Photon Source 3268
  • G. Decker, O. Singh
    ANL, Argonne, Illinois
  Funding: This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.

The Advanced Photon Source has been in operation since 1996. Since that time, extensive incremental improvements to orbit stabilization systems have been made. This includes the addition of 80 channels of narrowband rf beam position monitors (bpm's), 40 channels of bending magnet photon bpm's, and most recently the inclusion of 36 insertion device photon bpm's into the orbit correction response matrix. In addition, considerable improvements have been made in the area of power supply regulation, both for the main multipole magnets and the steering corrector magnets. The present status of overall performance will be discussed, including long term pointing stability, reproducibility, and AC beam motion.

RPAT047 Preliminary Design of a Femtosecond Oscilloscope 2944
  • E.D. Gazazyan, K.A. Ispirian, A.T. Margaryan
    YerPhI, Yerevan
  • D.K. Kalantaryan
    YSU, Yerevan
  • E.M. Laziev
    CANDLE, Yerevan
  The calculations on motion of electrons in a finite length electromagnetic field of linearly and circularly polarized laser beams have shown that one can use the transversal deflection of electrons on a screen at a certain distance after the interaction region for the measurement of the length and longitudinal particle distribution of femtosecond bunches. In this work the construction and preliminary parameters of various parts of a device that may be called femtosecond oscilloscope are considered. The influence of various factors, such as the energy spread and size of the electron bunches, are taken into account. For CO2 laser intensity 1016 W/cm2 and field free drift length 1m the deflection is 5.3 and 0.06 cm, while the few centimeters long interaction length between 2 mirrors requires assembling accuracy 6 mm and 1.3 micron for 20 MeV to 50 keV, respectively.  
RPAT048 An X-Ray BPM and Accompanying Electronics 3019
  • S.R. Marques, O.R. Bagnato, Bombacini, F.O. Bombacini, M.J. Ferreira, H. J. Onisto
    LNLS, Campinas
  Recent experiments at the LNLS Ultra Violet and X-Ray beam lines are pushing on the Synchrotron Radiation beam position stability requirements. In the direction of having photon Beam Position Monitor integrated to the orbit closed loop control system, we developed a staggered blades XR BPM and a four channel current measurement electronics. The BPM mechanical design was based on the SR masks previously developed and currently in use at the beam lines front end. By this design reuse, in addition to using an already available and well-tested, low cost construction technique, we expect to have a simple replacement of the SR masks by the XR BPMs in most of the beam lines, shortening the downtimes and the number of line parts to be replaced. We describe the design and the resulting performance of the XR BPM and the accompanying electronics.  
RPAT049 Numerical Studies on the Electro-Optic Sampling of Relativistic Electron Bunches 3070
  • S. Casalbuoni, H. Schlarb, B. Schmidt, B. Steffen
    DESY, Hamburg
  • P. Schmüser, A. Winter
    Uni HH, Hamburg
  Ultraviolet and X ray free electron lasers require sub-picosecond electron bunches of high charge density. Electro-optic sampling (EOS) is a suitable diagnostic tool for resolving the time structure of these ultrashort bunches. The transient electric field of the relativistic bunch induces a polarization anisotropy in a nonlinear crystal which is sampled by femtosecond laser pulses. In this paper, the EOS process is studied in detailed numerical calculations. The THz and the laser pulses are treated as wave packets which are propagated through the zinc telluride resp. gallium phosphide crystals. The effects of signal broadening and distortion are taken into account. The time resolution is limited by the lowest lattice oscillation frequency which amounts to 5.3 THz in ZnTe and 11 THz in GaP. The shortest bunch length which can be resolved with moderate distortion is about 200 fs (FWHM) in ZnTe and 100 fs in GaP.  
RPAT050 Electro Optic Bunch Length Measurements at the VUV-FEL at DESY 3111
  • B. Steffen, S. Casalbuoni, E.-A. Knabbe, H. Schlarb, B. Schmidt
    DESY, Hamburg
  • P. Schmüser, A. Winter
    Uni HH, Hamburg
  For the operation of a SASE FEL, the longitudinal bunch length is one of the most critical parameters. At the superconducting linac of the VUV-FEL at DESY, we have installed an electro optic sampling (EOS) experiment to probe the time structure of the electric field of the bunches to better than 100 fs rms. The field-induced birefringence of a ZnTe crystal is detected by a femtosecond laser pulse (TiSa) and the time structure is measured by scanning the relative timing of the electron bunch and the TiSa pulse. A synchronization stability of better than 50 fs between laser and accelerator RF has been achieved. First results on the synchronization measurements and for the bunch length as function of the linac parameters are presented.  
RPAT051 Measurement of Dynamic Beam-Beam Effects on Horizontal Beam Size at KEKB Using SR Interferometer Equipped with Retrofocus Optics 3150
  • J.W. Flanagan, H. Fukuma, S. Hiramatsu, T. Mitsuhashi
    KEK, Ibaraki
  Transverse beam-size enlargement due to dynamic beta and beam-beam effects has been observed in the KEKB Low Energy Ring (LER) and High Energy Ring (HER). In order to observe these effects, a retrofocus optics system has been developed and installed in the horizontal SR interferometers at the HER and LER. This system allows us to vary the apparent beam size to match the dynamic range of the interferometer. We report on the retrofocus optics system and measurement results, and compare the measured effects with those expected from dynamic beta simulations.  
RPAT052 Vertical Beam Size Measurement by Streak Camera under Colliding and Single Beam Conditions in KEKB 3194
  • H. Ikeda, J.W. Flanagan, H. Fukuma, Y. Funakoshi, S. Hiramatsu, T. Mitsuhashi, K. Ohmi, S. Uehara
    KEK, Ibaraki
  Beam behavior of KEKB was studied by measurement of the beam size using a streak camera. Effect of the electron-cloud and the parasitic collision on the vertical beam size was examined in beam collision. We intentionally injected a test bunch of positrons after 2 rf buckets of a bunch to enhance the electron cloud effect and changed electron beam conditions to see the beam-beam effect. The beam size was also measured with a single positron beam and compared with that during collision. The result of the measurement is reported in this paper.  
RPAT053 Movement of BPMs Due to Thermal Stress in KEKB 3253
  • M. Tejima, A. Arinaga, H. Fukuma, S. Hiramatsu, T. Ieiri, I. Ishii, M. Tobiyama
    KEK, Ibaraki
  Movement of Beam Position Monitors (BPM) due to thermal stress in high beam current operation is observed in KEKB. For high luminosity operation of KEKB, the beam current as high as 1.6A is accumulated in the positron ring and a precise control of the beam orbit based on the BPM system is required. Though the every BPM chamber is fixed firmly on a support of each quadrupole magnet, the BPM chamber moves several hundred microns from the setting position depending on the beam current due to beam pipe heating by strong synchrotron light irradiation. Such movement introduces an unavoidable offset error in the BPM measurement, and is a serious problem not only for KEKB but also for the next generation of B-factory operated with extremely high beam current. We report the measurement of the movement by distance sensors and an attempt to correct the BPM offset error in real-time operation.  
RPAT054 Beam Position Monitor at the PLS BTL 3289
  • S.-C. Kim, M.-H. Chun, Y.J. Han, J.Y. Huang, D.T. Kim, W.W. Lee
    PAL, Pohang, Kyungbuk
  Funding: Work supported by the Ministry of Science and Technology, Korea.

Electron Linac at the Pohnag Accelerator Laboratory (PAL) has been operated continuously as the full energy injector for storage ring. Linac and storage ring energy has been 2.0 GeV since Dec. 1994, and 2.5 GeV since Oct. 2002. In Aug. 2004, thirteen BPMs are newly installed at BTL(Beam Transport Line) for beam trajectory measurement and feedback. These BPMs consist of 100mm strip-line electrodes in 150mm long chamber, and 500MHz log-ratio signal processing circuits. BPM data acquisition system is developed as EPICS IOC using NI S-series data acquisition board and NI LabView 7.1. BTL BPMs will be used for optic correction and beam energy feedback for PLS beam injection. This paper describes on design, test results, installation and data acquisition system of the PLS BTL BPM.

RPAT058 The IEEE-1394 Digital Camera Application in the Taiwan Light Source
  • C.H. Kuo, K.-T. Hsu, M.-H. Wang
    NSRRC, Hsinchu
  The CCD camera with digital interface has been adopted for the diagnostics purpose recently. The long distance transmission with digital interface eliminates image distortion. Without frame grabber in the computer that is also another benefit. These applications include screen monitor and optical transition radiation monitor image for injection study, synchrotron radiation monitor of the booster synchrotron and storage ring. An intensified gated CCD camera is also applied for transient profile study. Wider dynamic range and the flexibility of the newly camera provide various functional enhancements for the diagnostics purpose. The effort and achievement will be summary in this report.  
RPAT059 The SRI Beam Size Monitor Developed at NSRRC 3465
  • T.C. Tseng, J.-R. Chen, H.C. Ho, C.-K. Kuan, C.J. Lin, S.Y. Perng, D.-J. Wang, J. Wang
    NSRRC, Hsinchu
  A beam size monitor based on the synchrotron radiation interferometer (SRI) was installed in the NSRRC TLS. This monitor consists of a simple diagnostic beamline with a water-cooled beryllium mirror inside and a detecting optical system for both vertical and horizontal beam size measurement. The beam sizes measured are 48 micron and 160 micron respectively and are more close to the theoretical values than the synchrotron image monitor. Comparing with other monitors, at least 1 micron beam size variation is detectable. To minimize the thermal effect, the mirror is located far away from the source point and closed to the detecting optical system. The thermal distortion of the mirror is quite small measured by a portable long trace profiler (LTP) and agrees with the simulating analysis. The detailed monitor system design and testing results are presented in this paper.  
RPAT061 New Electron Beam Position Monitoring and Feedback System Upgrades for the Synchrotron Radiation Source at Daresbury Laboratory 3538
  • R.J. Smith, M. Dufau, B.G. Martlew
    CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • G. Cox
    CCLRC/DL, Daresbury, Warrington, Cheshire
  Funding: ASTeC Department, CCLRC Daresbury Laboratory.

The installation of a new APPLE/II undulator with user controlled polarisation has necessitated the upgrade of the Electron Beam Position Monitoring (EBPM) detector electronics and position feedback systems. The upgraded installation will utilise commercially available multiplexed detection electronics, coupled with a two phase control system interface replacement. Phase one involves the replacement of the existing G-64 based read-back system with direct analogue connections to the VME beam steering and Feedback system. This allows existing monitoring and feedback software to work with improved update rates (~ 1Hz -> ~ 8Hz). Phase two will see the installation of new high-performance control system front ends and will allow real-time monitoring at up to 100Hz and provide snapshots with resolution of 1-10 KHz.

RPAT062 Design and Operation of a Radiative Bhabha Luminosity Monitor for CESR-c 3564
  • M.A. Palmer, D. L. Rubin, J.C. Smith
    Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
  • M. Cravey, J. Napalitano
    RPI, Troy, New York
  • V. Crede
    Cornell University, Department of Physics, Ithaca, New York
  • K.L. Dooley
    Vassar, Poughkeepsie, New York
  • H. Vogel
    CMU, Pittsburgh, Pennsylvania
  Funding: Work supported by the National Science Foundation.

The CLEO-c experiment at the Cornell Electron Storage Ring (CESR) is presently embarking on a multi-year exploration of charm and QCD physics in the 3-5 GeV center-of-mass energy range. In order to facilitate rapid optimization of machine parameters over this energy range, a luminosity monitor based on the measurement of radiative-bhabha photons coming from the CLEO-c interaction point (IP) has been designed and installed in the CESR ring. Key design criteria of the device include: better than 1% statistical measurements of the luminosity with a 1 Hz update rate over the full range of CESR-c operating conditions; bunch-by-bunch measurement capability; a large horizontal aperture to enable measurements under conditions ranging from single-bunch head-on collisions to multi-bunch collisions with a horizontal crossing angle of up to 4~mrad; and, a segmented readout to provide direct information on beam characteristics at the IP. We review the design and performance of this device and discuss its application to machine tuning and performance studies.

RPAT063 A Bunch-By-Bunch and Turn-By-Turn Instrumentation Hardware Upgrade for CESR-c 3597
  • M.A. Palmer, J. Dobbins, C.R. Strohman, E. Tanke
    CESR-LEPP, Ithaca, New York
  Funding: Work supported by the National Science Foundation.

A key factor in the colliding beam performance of the Cornell Electron Storage Ring (CESR) is the impact of parasitic beam-beam interactions between bunches in the two beams as they follow their electrostatically separated orbits in a single vacuum chamber. In order to better investigate the differential performance of bunches in CESR, instrumentation electronics has been developed to allow acquisition of turn-by-turn data from multiple bunches simultaneously. The electronics consists of a standardized digital board centered around an Analog Devices TigerSHARC family digital signal processor, a communications interface, and an interface to the CESR Precision Timing System. Mated to these components is an analog front end and digitizer board which is customized for the particular diagnostic device of interest. Front ends have been developed for beam position monitor, luminosity monitor, and beam profile monitor applications. We describe the design and characterization of this new hardware.

RPAT064 Beam-Based Calibration of the Electron Energy in the Fermilab Electron Cooler 3638
  • S. Seletsky
    Rochester University, Rochester, New York
  • A.V. Shemyakin
    Fermilab, Batavia, Illinois
  Electron cooling of 8.9 GeV antiprotons in the Fermilab’s Recycler ring requires precise matching of electron and antiproton velocities. While the final match can be done by optimization of the cooling process, for the very first cooling one should rely on the knowledge of absolute values of electron and antiproton energies. The upper limit for the energy uncertainty of both beams is determined by the Recycler’s momentum aperture and is equal to 0.3%. The paper discusses a method of the electron energy calibration that is based on the measurement of the electron’s Larmor wavelength in the field of the cooling section solenoid. The method was tested in an 18 m long cooling section prototype with 3.5 MeV electrons. An accuracy of 0.3% was demonstrated.  
RPAT065 A Wire Scanner Design for Electron Beam Profile Measurement in the Linac Coherent Light Source Undulator 3667
  • J.L. Bailey, T.W. Buffington, B.X. Yang
    ANL, Argonne, Illinois
  Funding: Work supported by U. S. Department of Energy, Office of Basic Energy Sciences under Contract No. W-31-109-ENG-38.

The Linac Coherent Light Source (LCLS), currently under design, requires beam diagnostic instruments between the magnets in the beam undulator section. Ten wire scanners are planned as one of the primary instruments to characterize electron beam properties. The development of these wire scanners presents several design challenges due to the need for high accuracy and resolution of the wire motion (3 microns tolerance, typical) and the high intensity of the beam (3400 A over an area of 30 micron rms radius). In this paper, we present the technical specification and design criteria for the scanners. We will also present the mechanical design of the UHV-compatible drive and its engineering analysis. Lastly, we present the wire card design and discuss associated thermal and mechanical issues originating from the highly intense x-ray and electron beams.

RPAT067 Beam Angle Measurement Using Cherenkov Radiation 3742
  • T. Watanabe, M. Babzien, K. Kusche, V. Yakimenko
    BNL, Upton, Long Island, New York
  A simple beam angle monitor utilizing observation of far-field Cherenkov radiation is being developed. The monitor is independent of beam energy as well as position and requires only modest camera sensitivity. Since the wavefront of Cherenkov radiation is not spherical but planar, the far-field image is supposed to be infinetesimally small in one-dimensional geometrical optics, which may result in high angular resolution. In a practical experiment, however, beam scattering in a radiator and diffraction from a finite size radiation source determine the resolution. Numerical analysis shows that the angular resolution with a 100-um thickness fused silica radiator is 0.8 mrad. The experimental results with 2-mm and 100-um thickness fused silica are shown. The possibility of non-destructive measurement is also discussed.  
RPAT068 Proposed Diagnostics for the NSLS-II 3760
  • I.P. Pinayev, S.L. Kramer, J. Rose, T.V. Shaftan
    BNL, Upton, Long Island, New York
  Funding: The U.S. Department of Energy under contract No. DE-AC02-98CH10886.

The National Synchrotron Light Source is performing R&D of a new 3 GeV electron storage ring to be used for the facility upgrade. To satisfy the demands for the brightness and stability of the future light source a state-of-the-art diagnostics system is a necessity. We present our preliminary design with focus on the requirements for instrumentation and technical solutions to achieve them.

RPAT069 Electron Beam Size Measurements in a Cooling Solenoid 3801
  • T.K. Kroc, T.B. Bolshakov, A.V. Burov, A.V. Shemyakin
    Fermilab, Batavia, Illinois
  • S. Seletsky
    Rochester University, Rochester, New York
  Funding: Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy.

The Fermilab Electron Cooling Project requires a straight trajectory and constant beam size to provide effective cooling of the antiprotons in the Recycler. A measurement system was developed using movable appertures and steering bumps to measure the beam size in a 20 m long, nearly continuous, solenoid. This paper discusses the required beam parameters, the implimentation of the measurement system and results for our application.

RPAT070 Mechanical and Thermal Design of the CEBAF Hall A Beam Calorimeter 3819
  • M.E. Bevins, A.R. Day, P. Degtiarenko, L.A. Dillon-Townes, A. Freyberger, R. Gilman, A. Saha, S. Slachtouski
    Jefferson Lab, Newport News, Virginia
  Funding: DOE.

A calorimeter has been proposed to provide 0.5% - 1.0% absolute measurements of beam current in the Hall A end station of the Thomas Jefferson National Accelerator Facility (JLab) CEBAF machine. Silver and copper calorimeters built in the 1960’s achieved precisions of about 1%. Modern powder metallurgy processes have produced high density, high thermal conductivity tungsten-copper composite materials that will minimize beam loss while maintaining a rapid thermal response time. Heat leaks will be minimized by mounting the mass in vacuum on glass ceramic mounts. A conduction cooling scheme utilizes an advanced carbon fiber compliant thermal interface material. Transient finite difference and finite element models were developed to estimate heat leaks and thermal response times.

RPAT071 Digital Beam Position Monitor for the Happex Experiment 3841
  • S.R. Kauffman, H. Dong, A. Freyberger, L. Kaufman, J. Musson
    Jefferson Lab, Newport News, Virginia
  Funding: This work was supported by DOE contract No. DE-AC05-84ER40150.

The proposed HAPPEX experiment at CEBAF employs a three cavity monitor system for high-precision (1 mm), high-bandwidth (100 kHz) position measurements. This is performed using a cavity triplet consisting of two TM110-mode cavities (one each for X and Y planes) combined with a conventional TM-010-mode cavity for a phase and magnitude reference. Traditional systems have used the TM010 cavity output to directly down convert the BPM cavity signals to base band. The Multi-channel HAPPEX digital receiver simultaneously I/Q samples each cavity and extracts position using a CORDIC algorithm. The hardware design consists of a digital receiver daughter board and digital processor motherboard that resides in a VXI crate. The daughter board down converts 1.497 GHz signals from the TM010 cavity and X and Y signals from the TM110 cavities to 4 MHz, and extracts the quadrature digital signals. The motherboard processes this data and computes beam intensity and X-Y positions with a resolution of one mm, 100 kHz output bandwidth, and overall latency of ten microseconds. The results are available in both analog and digital format.

RPAT072 The General ElectroN Induced Emission (GENIE) System 3877
  • M.A. Epps, R. Kazimi
    Jefferson Lab, Newport News, Virginia
  • P.L. Gueye
    Hampton University, Hampton, Virginia
  A real time beam diagnostic system is proposed for the Jefferson Lab injector region. The General ElectroN Induced Emission System (GENIE) is a package that includes both hardware (beam monitoring devices) and software (for 3D or 4D visualization of the beam transport). This beam diagnostic tool relies primarily on the use of (very small) scintillating fibers placed in different planes to extract the beam profile, beam position, beam current and beam emittance in real time. Accuracies in position and angle could be at the sub- μm and μrad levels, respectively. The beam current could be reconstructed within a few percent. A combined Geant4/Parmela simulation will be developed for beam optic studies. While Parmela offers the power of beam transport with phase matching capabilities (among others), Geant4 provides the power for tracking secondary particles, as well as 3D & 4D visualization. A phase I investigation of GENIE using a 100 keV beam line is discussed in this document.  
RPAT074 PEP-II Transverse Feedback Electronics Upgrade 3928
  • J.M. Weber, M.J. Chin, L.R. Doolittle
    LBNL, Berkeley, California
  • R. Akre
    SLAC, Menlo Park, California
  Funding: Supported by the U.S. Department of Energy under contract No. DE-AC03-76SF00098 (LBNL) and DE-AC03-76SF00515 (SLAC).

The PEP-II B Factory at the Stanford Linear Accelerator Center (SLAC) requires an upgrade of the transverse feedback system electronics. The new electronics require 12-bit resolution and a minimum sampling rate of 238 Msps. A Field Programmable Gate Array (FPGA) is used to implement the feedback algorithm. The FPGA also contains an embedded PowerPC 405 (PPC-405) processor to run control system interface software for data retrieval, diagnostics, and system monitoring. The design of this system is based on the Xilinx® ML300 Development Platform, a circuit board set containing an FPGA with an embedded processor, a large memory bank, and other peripherals. This paper discusses the design of a digital feedback system based on an FPGA with an embedded processor. Discussion will include specifications, component selection, and integration with the ML300 design.

RPAT075 Optical Synchronization Systems for Femtosecond X-Ray Sources 3958
  • R.B. Wilcox, J.W.  Staples
    LBNL, Berkeley, California
  • R. Holzwarth
    Menlo Systems GmbH, Martinsried
  Funding: This work was supported by the Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under the Department of Energy Contract No. DE-AC03-76SF00098.

In femtosecond pump/probe experiments using short x-ray and optical pulses, precise synchronization must be maintained between widely separated lasers in a synchrotron or FEL facility. We are developing synchronization systems using optical signals for applications requiring different ranges of timing error. For the sub-100fs range we use an amplitude modulated CW laser at 1GHz to transmit RF phase information, and control the delay through a 100m fiber by observing the retroreflected signal. Initial results show 40fs peak-to-peak error above 10Hz, and 200fs long term drift, mainly due to amplitude sensitivity in the analog mixers. For the sub-10fs range we will lock two single-frequency lasers separated by several teraHertz to a master modelocked fiber laser, transmit the two frequencies over fiber, and lock two comb lines of a slave laser to these frequencies, thus synchronizing the two modelocked laser envelopes. For attosecond synchronization we propose a stabilized, free space link using bulk lens waveguides and high peak power ultrashort pulses.

RPAT076 Smith Purcell Radiation Bunch-Length Measurement
  • S.E. Korbly, A.S. Kesar, R.A. Marsh, R.J. Temkin
    MIT/PSFC, Cambridge, Massachusetts
  Funding: This work was supported by the Department of Energy, High Energy Physics, under contract DE-FG02-91ER40648.

Measurements of Coherent Smith-Purcell Radiation (SPR) were performed at the 17 GHz high-gradient accelerator built by Haimson Research Corporation at the MIT Plasma Science and Fusion Center. SPR is a promising radiation source because the radiation intensity is enhanced by the number of grating periods. The radiation produced obeys the SP resonance condition correlating the radiation frequency at each observation angle, allowing SPR to be exploited as a bunch-length measurement. For a 15 MeV 150 mA 125 ns beam in short and long pulse modes, bunch-lengths of 0.6 ps and 1 ps were measured with this method, respectively, with an error of ± 0.1 ps. Frequency measurements were also performed using a double Heterodyne system. Heterodyne measurements revealed frequency-locking, which gave a power level enhancement of 1000 at integer multiples of the Accelerator RF frequency. Frequencies up to 514 GHz were measured with a bandwidth of 25 MHz.

RPAT077 Beam Test Proposal of an ODR Beam Size Monitor at the SLAC FFTB 4015
  • Y. Fukui, D. Cline, F. Zhou
    UCLA, Los Angeles, California
  • A. Aryshev, V. Karataev, T. Muto, M. Tobiyama, J.U. Urakawa
    KEK, Ibaraki
  • P.R. Bolton, M.C. Ross
    SLAC, Menlo Park, California
  • R. Hamatsu
    TMU, Hatioji-shi,Tokyo
  • G.A. Naumenko, A. Potylitsyn, A. Sharafutdinov
    Tomsk Polytechnic University, Physical-Technical Department, Tomsk
  We design a single bunch transverse beam size monitor which will be tested to measure the 29 GeV electron/positron beam at the SLAC FFTB beam line.The beam size monitor uses a CCD camera to make images of the interference pattern of the optical diffraction radiation from conductive slit target which are placed close to the beam path. In this method, destruction of the accelerated electron/positron beam bunches due to the beam size monitoring is negligible, which is vital to the operation of the Linear Collider project. A dis-phased conductive slit target and a lens system allow us to recover the sensitivity of the transverse beam size with a small photon yield ratio at the valley to that at the peak due to the large gamma*λ, and with the near field effect due to the large λ*gamma**2. A solution for non-negligible divergence at the SLAC FFTB is also discussed.  
RPAT078 Bunch Length Measurements Using Coherent Radiation 4027
  • R. Ischebeck, C.D. Barnes, I. Blumenfeld, F.-J. Decker, M.J. Hogan, R.H. Iverson, P. Krejcik, R. Siemann, D.R. Walz
    SLAC, Menlo Park, California
  • C.E. Clayton, C. Huang, D.K. Johnson, W. Lu, K.A. Marsh
    UCLA, Los Angeles, California
  • S. Deng, E. Oz
    USC, Los Angeles, California
  • N.A. Kirby
    Stanford University, Stanford, Califormia
  Funding: Work supported by Department of Energy contracts DE-AC02-76SF00515 (SLAC), DE-FG03-92ER40745, DE-FG03-98DP00211, DE-FG03-92ER40727, DE-AC-0376SF0098, and National Science Foundation grants No. ECS-9632735, DMS-9722121 and PHY-0078715.

The accelerating field that can be obtained in a beam-driven plasma wakefield accelerator depends on the current of the electron beam that excites the wake. In the E-167 experiment, a peak current above 10kA will be delivered at a particle energy of 28GeV. The bunch has a length of a few ten micrometers and several methods are used to measure its longitudinal profile. Among these, autocorrelation of coherent transition radiation (CTR) is employed. The beam passes a thin metallic foil, where it emits transition radiation. For wavelengths greater than the bunch length, this transition radiation is emitted coherently. This amplifies the long-wavelength part of the spectrum. A scanning Michelson interferometer is used to autocorrelate the CTR. However, this method requires the contribution of many bunches to build an autocorrelation trace. The measurement is influenced by the transmission characteristics of the vacuum window and beam splitter. We present here an analysis of materials, as well as possible layouts for a single shot CTR autocorrelator.

RPAT079 Resolution of Transverse Electron Beam Measurements Using Optical Transition Radiation 4042
  • R. Ischebeck, F.-J. Decker, M.J. Hogan, R.H. Iverson, P. Krejcik, R. Siemann, D.R. Walz
    SLAC, Menlo Park, California
  • C.E. Clayton, C. Huang, W. Lu
    UCLA, Los Angeles, California
  • S. Deng, E. Oz
    USC, Los Angeles, California
  • M. Lincoln
    Stanford University, Stanford, Califormia
  Funding: Work supported by Department of Energy contracts DE-AC02-76SF00515 (SLAC), DE-FG03-92ER40745, DE-FG03-98DP00211, DE-FG03-92ER40727, DE-AC-0376SF0098, and National Science Foundation grants No. ECS-9632735, DMS-9722121 and PHY-0078715.

In the plasma wakefield acceleration experiment E-167, optical transition radiation is used to measure the transverse profile of the electron bunches before and after the plasma acceleration. The distribution of the electric field from a single electron does not give a point-like distribution on the detector, but has a certain extension. Additionally, the resolution of the imaging system is affected by aberrations. The transverse profile of the bunch is thus convolved with a point spread function (PSF). Algorithms that deconvolve the image can help to improve the resolution. Imaged test patterns are used to determine the modulation transfer function of the lens. From this, the PSF can be reconstructed. The Lucy-Richardson algorithm is used to deconvolute this PSF from test images.

RPAT080 The SPEAR 3 Diagnostic Beamlines 4057
  • W.J. Corbett, C. Limborg-Deprey, W.Y. Mok, A. Ringwall
    SLAC, Menlo Park, California
  Funding: Work supported in part by DOE contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences.

SPEAR 3 is equipped with an x-ray pinhole camera and a visible/UV beam line to evaluate electron beam properties. The pinhole camera has a 30 x 25 micron Ta aperture and 60% image demagnification on a phosphor screen. The image is captured by a National Instruments frame-grabber on a remote computer with a parallel video signal for control room monitoring. The visible/UV beam line features a horizontal ± 0.3 mrad ‘cold finger’ to remove the x-ray core of the beam. The remaining visible/UV light is deflected 18 degrees onto an optical bench where it is focused via refractive Cassegrain optics. The beam is then split into parallel optics for gated- and streak camera measurements. This paper describes the experimental set up and preliminary measurements obtained with both systems.

RPAT081 Initial Scraper Measurements in SPEAR 3
  • W.J. Corbett, J.A. Safranek, A. Terebilo
    SLAC, Menlo Park, California
  Funding: Work supported by Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences.

Horizontal and vertical scraper assemblies have been installed in a standard straight section of SPEAR 3 (beta-x=10.2 m, beta-y=4.8 m, epsx=18 nm-rad, 0.1% coupling). Each scraper has stepper motor accuracy and transductor resolution on the order of 1 micron and a MATLAB/EPICS interface to simplify data acquisition. In this paper we present initial scraper measurements and analysis of the results. Of particular importance are comparison of measured dynamic aperture and momentum acceptance with model and measurement of vertical acceptance for future beam lines.

RPAT082 Coherent Transition Radiation To Measure the SLAC Electron Bunch Length 4102
  • P. Muggli
    USC, Los Angeles, California
  • C.D. Barnes, M.J. Hogan, P. Krejcik, R. Siemann, D.R. Walz
    SLAC, Menlo Park, California
  • R. Ischebeck, H. Schlarb
    DESY, Hamburg
  Funding: Work supported by U.S. DOE.

Ultrashort electron bunches are now available at Stanford Linear Accelerator Center and are use mainly to produce short bursts of x-rays in a magnetic undulator and for plasma wakefield acceleration experiments. The shortest bunches have an rms longitudinal width of ˜10 microns, and a peak current of about 30 kA. Methods to measure such short bunch lengths include electro-optic modulation of a short laser pulse in a nonlinear crystal and coherent transition (CTR) autocorrelation. The transition radiation spectrum emitted by the bunches when traversing a 1 micron thin titanium foil is coherent for wavelengths longer that the bunch length and extends into the millimeter wavelength range. A CTR far-infrared autocorrelator was used to measure the bunch length as a function of the accelerator. The results obtained with this autocorrelator are the only measurements of the SLAC ultra-short bunches to date. Experimental results, as well as the limitations of the measurements and the future improvements to the autocorrelator will be presented.

RPAT083 Beam Profile Measurements and Simulations of the PETRA Laser-Wire 4123
  • J. Carter, I.V. Agapov, G.A. Blair, G.E. Boorman, C.D. Driouichi, F. Poirier, M.T. Price
    Royal Holloway, University of London, Surrey
  • K. Balewski, H.-C. Lewin, S. Schreiber, K. Wittenburg
    DESY, Hamburg
  • S.T. Boogert, S. Malton
    UCL, London
  • N. Delerue, D.F. Howell
    OXFORDphysics, Oxford, Oxon
  • T.  Kamps
    BESSY GmbH, Berlin
  The laser-wire will be an essential diagnostic tool at the International Linear Collider and advanced light sources. It uses a finely focussed laser beam to measure the transverse profile of electron bunches by detecting the Compton-scattered photons (or electrons) downstream of where the laser beam intersects the electron beam. Such a system has been installed at the PETRA storage ring at DESY, which uses a piezo-driven mirror to scan the laser light across the electron beam. Latest experimental results are presented and compared to detailed simulations using Geant4.  
RPAT084 Design of the APS RF BPM Data Acquisition Upgrade 4156
  • R.M. Lill, F. Lenkszus, E. Norum, A. Pietryla
    ANL, Argonne, Illinois
  Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.

The Advanced Photon Source (APS) is a third-generation synchrotron light source in its tenth year of operation. The storage ring employs three different types of beam position monitor (BPM) systems to measure and control beam motion. The monopulse radio frequency (rf) BPM is a broadband (10 MHz) system, which is considered to be the backbone of orbit control. The rf BPM system was designed to measure single-turn and multi-turn beam positions. The rf BPMs are presently suffering from an aging data acquisition system. By replacing only the data acquisition we will revitalize this system for another decade and demonstrate a cost-effective approach to improved beam stability, reliability, and enhanced postmortem capabilities. In this paper we present the design of an eight-channel ADC/digitizer VXI board with a sampling rate of 88 MHz (per channel) and 14-bit resolution coupled with a field-programmable gate array and embedded central processing. We will discuss the upgrade system specifications, design, and prototype test results.

RPAT085 Initial Imaging of 7-GeV Electron Beams with OTR/ODR Techniques at APS 4162
  • A.H. Lumpkin, W. Berg, N. Sereno, C. Yao
    ANL, Argonne, Illinois
  Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38.

The development of nonintercepting (NI) diagnostics continues to be of interest at the Advanced Photon Source (APS) as well as elsewhere. In the three rings of the APS facility we use optical synchrotron radiation generated as the electron beam transits the dipole magnetic fields as an NI mechanism to image the beam during top-up operations. However, in the straight transport lines an alternative method is needed. Optical diffraction radiation (ODR) is under investigation to monitor 7-GeV beam trajectory and potentially transverse shape in the booster-to-storage ring (BTS) beamline during top-up operations. We have performed our initial measurements with an Al blade/mirror that served as an optical transition radiation (OTR) monitor when fully inserted into the beam and as an ODR monitor when the beam passed near the edge. In the case of ODR, appreciable signal is emitted by the metal when gamma times the reduced ODR wavelength is comparable to the impact parameter, where gamma is the Lorentz factor. Visible light optics and a standard CCD camera could thus be used for a few-mm impact parameter. We attribute the near-field signal for 1.5- to 3.0-mm impact parameters predominately to the ODR mechanism.

RPAT086 Dual-Sweep Streak Camera Measurements of the APS User Beams 4185
  • A.H. Lumpkin, B.X. Yang
    ANL, Argonne, Illinois
  • F. Sakamoto
    UTNL, Ibaraki
  Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences under Contract Number W-31-109-ENG-38.

The Advanced Photon Source (APS) is a hard x-ray user facility based on a 7-GeV storage ring (SR). To accommodate the requests of the diverse user community, the APS normally runs with a 24-singlets fill pattern, a hybrid fill with a singlet and eight septuplets, or a 324-singlet fill pattern. In all cases the total stored beam current is 100 mA, with the lattice providing a natural emittance of about 2.5 nm rad. The first two patterns are used with a top-up mode that involves injection of one pulse of ~2.5 nC every two minutes into the designated SR bucket. Since the partition of bunch current varies for the different fills as well as the loading of the rf cavities, dual-sweep streak camera measurements (Hamamatsu model C5680) have been performed to characterize the average and individual bunch lengths in the fill patterns and the phase slew that occurs within the patterns. The bunch lengths vary from 32 ps (σ) within the septuplet to 50 ps (σ) for the singlet in the hybrid fill. The phase slew is significant in the hybrid fill across the eight septuplets. Example streak images of each pattern will be presented and discussed.

RPAT087 Design of a High-Resolution Optical Transition Radiation Imager System for the Linac Coherent Light Source Undulator 4209
  • B.X. Yang, J.L. Bailey, S.J. Stein, D.R. Walters
    ANL, Argonne, Illinois
  Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. W-31-109-ENG-38.

The Linac Coherent Light Source (LCLS), a free-electron x-ray laser, is under design and construction. Its high intensity electron beam, 3400 A in peak current and 46 TW in peak power, is concentrated in a small area (30 micrometer rms in both horizontal and vertical directions) inside its undulator. Ten optical transition radiation (OTR) imagers are planned between the undulator segments for the characterization of the transverse profiles of the electron beam. In this paper, we present the performance requirements and technical requirements of the OTR imagers. We will discuss in detail the design of the OTR screen, the arrangement and modeling of the imaging optics, and the mechanical design and analysis of the compact camera module. Through a unique optical arrangement, this imager will achieve a fine resolution (12 micrometer rms or better) over the entire field of view (5 mm × 5 mm). The compact camera module will fit in the limited space available with remote focus adjustment. A digital camera will be used to read out the beam images in a programmable region (5 mm × 0.5 mm) at the full beam repetition rate (120 Hz), or over the entire field at a lower rate (15 Hz).

RPAT088 Energy-Spread-Feedback System for the KEKB Injector Linac 4212
  • M. Satoh, K.  Furukawa, T. Suwada
    KEK, Ibaraki
  New energy-spread feedback system using nondestructive energy-spread monitors have been developed in order to control and stabilize the energy spreads of single-bunch electron and positron beams in the KEKB injector linac. The well-controlled feedback systems of the injector linac are successfully working in dairy operation not only for keeping the injection rate higher along with the beam-orbit and energy feedback systems but also for reducing a background level to the high-energy B-factory experiment. The energy spreads of the injection beams are well stabilized within 0.2%, 0.5% and 0.3% for the electron beam, the positron beam, and the high-current primary electron beam for positron production, respectively, through the energy-spread feedback system under the nominal operation condition. In this paper, we will report in detail the energy-spread feedback system using the nondestructive energy-spread monitors with multi-strip-line electrodes and their performance in the KEKB operation.  
RPAT089 Advances in Optical Transition and Diffraction Radiation Emittance Diagnostics 4224
  • R.B. Fiorito, A.G. Shkvarunets
    IREAP, College Park, Maryland
  • T. Watanabe, V. Yakimenko
    BNL, Upton, Long Island, New York
  Funding: Office of Naval Research and the DOD Joint Technology Office.

We have performed a series of experiments using Optical Transition Radiation and Optical Diffraction Radiation Interferometry to measure the two orthogonal (x,y) rms divergences of the Brookhaven National Laboratory’s Advanced Test Facility electron beam operating at an energy of 50 MeV. Measurement of the rms divergences at the (x,y) beam waist conditions, together with corresponding measurements of the rms beam sizes allows a determination of the rms x and y emittances. A comparison of the results using OTRI and ODTRI are presented.

RPAT090 The Study of New Signal Processing Technique in Photon Beam Position Monitors 4239
  • S.F. Lin, H. Gao, P. Lu, B. Sun, J. Wang
    USTC/NSRL, Hefei, Anhui
  A log-ratio signal processing technique in photon beam position monitors (PBPM) was presented in this paper. The main performances (e.g. sensitivity, position offset and linearity range) of split PBPM and a pair of wires PBPM were analyzed , and the result of the measurement fit well with the theory. An inexpensive logarithmic amplifier chip which can measure photon currents from 0.1nA to 3.5mA was used in electronic circuits. The logarithmic ratio of the signal amplitudes from the PBPM provides a real-time analog signal that has wider linearity range and higher bandwidth than signal processing technique.

Supported by Natural Science Foundation of China (10275062) and CAS Knowledge Innovation Project (KY4206).

RPAT091 Longitudinal Electron Bunch Diagnostics Using Coherent Transition Radiation 4254
  • D. Mihalcea, C.L. Bohn
    Northern Illinois University, DeKalb, Illinois
  • U. Happek
    UGA, Athens, Georgia
  • P. Piot
    Fermilab, Batavia, Illinois
  The longitudinal charge distribution of electron bunches in the Fermilab A0 photo-injector was determined by using the coherent transition radiation produced by electrons passing through a thin metallic foil. The auto-correlation of the transition radiation signal was measured with a Michelson type interferometer. The response function of the interferometer was determined from measured and simulated power spectra for low electron bunch charge and maximum longitudinal compression. Kramers-Kroning technique was used to determine longitudinal charge distribution. Measurements were performed for electron bunch lengths in the range from 0.3 to 2 ps (rms).  
RPAT092 Conceptual Design of an Insertion Device for Non-Destructive Beam Diagnostics of a Low-Emittance Synchrotron Light Source 4275
  • M. Masaki
    JASRI/SPring-8, Hyogo
  An insertion device is proposed to measure small vertical angular divergence and energy spread (dE/E) of electron beam in a low-emittance synchrotron light source. In accelerators such as the SPring-8 storage ring operated on the small emittance-coupling ratio, vertical divergence of spectral photon flux produced by electron beam in a conventional undulator of several meters long will be dominated by natural divergence of the undulator radiation. Therefore, the divergence of spectral flux is not useful for vertical emittance diagnostics. The proposed insertion device consists of N short undulator sections as x-ray radiators cascaded through vertical deflective sections to make a half-period cosine-like electron trajectory. Two radiation parts of the upper and lower sides are formed due to up-and-down electron orbit by the deflective sections. X-rays emitted from the two radiation parts interfere at observation point far from the insertion device. It was numerically studied that the vertical angular divergence in the sub-micro radian range and the energy spread of the 1·10-3 order could be measured by visibility and envelope width of an observed interference pattern, respectively.  
RPAT093 Libera Electron Beam Position Processor 4284
  • R. Ursic, A. Kosicek
    Instrumentation Technologies, Solkan
  Libera is a product family delivering unprecedented possibilities for either building powerful single station solutions or architecting complex feedback systems in the field of accelerator instrumentation and controls. This paper presents functionality and field performance of its first member, the electron beam position processor. It offers superior performance with multiple measurement channels delivering simultaneously position measurements in digital format with MHz kHz and Hz bandwidths. This all-in-one product, facilitating pulsed and CW measurements, is much more than simply a high performance beam position measuring device delivering micrometer level reproducibility with sub-micrometer resolution. Rich connectivity options and innate processing power make it a powerful feedback building block. By interconnecting multiple Libera electron beam position processors one can build a low-latency high throughput orbit feedback system without adding additional hardware. Libera electron beam position processor is ideally suited for the Third and the Fourth generation light sources.  
RPAT094 Femtosecond Synchronisation of Ultrashort Pulse Lasers to a Microwave RF Clock 4299
  • A. Winter
    Uni HH, Hamburg
  • N. Ignashin, A. Simonov, S. Sytov
    IHEP Protvino, Protvino, Moscow Region
  • E.-A. Knabbe, S. Simrock, B. Steffen
    DESY, Hamburg
  A precise synchronization between the laser repetition rate and the linac-RF is mandatory for electro-optic sampling or pump-probe experiments. The level of stability is usually determined by measuring of the spectral noise power density of the feedback signal when the system is locked. However, an independent measurement is needed to confirm this. In this paper, we present an approach exploiting electronic techniques to synchronize a TiSa laser to the RF of the DESY VUVFEL with sub-50 fs stability. The remaining time jitter is measured by an RF monitoring system independent of the locking PLL.  
RPAT095 Time Resolved X-Ray Spot Size Diagnostic 4302
  • R.A. Richardson, F.W. Chambers, S. Falabella, G. Guethlein, B.A. Raymond, J.T. Weir
    LLNL, Livermore, California
  Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

A diagnostic was developed for the determination of temporal history of an X-ray spot. A pair of thin (0.5 mm) slits image the x-ray spot to a fast scintillator which is coupled to a fast detector, thus sampling a slice of the X-Ray spot. Two other scintillator/detectors are used to determine the position of the spot and total forward dose. The slit signal is normalized to the dose and the resulting signal is analyzed to get the spot size. The position information is used to compensate for small changes due to spot motion and misalignment. The time resolution of the diagnostic is about 1 ns and measures spots from 0.5 mm to over 3 mm. The theory and equations used to calculate spot size and position are presented, as well as data. The calculations assume a symmetric, Gaussian spot. The spot data is generated by the ETA II accelerator, a 2kA, 5.5 MeV, 60ns electron beam focused on a Tantalum target. The spot generated is typically about 1 mm FWHM. Comparisons are made to an X-ray pinhole camera which images the XRay spot (in 2D) at four time slices.

RPAT096 High-Precision Resonant Cavity Beam Position, Emittance and Third-Moment Monitors 4311
  • N. Barov, J.S. Kim, A.W. Weidemann
    Far-Tech, Inc., San Diego, California
  • R.H. Miller, C.D. Nantista
    SLAC, Menlo Park, California
  Funding: Work supported by the U.S. Dept. of Energy.

Linear colliders and FEL facilities need fast, nondestructive beam position and profile monitors to facilitate machine tune-up, and for use with feedback control. FAR-TECH, Inc. is developing a resonant cavity diagnostic to simultaneously measure the dipole, quadrupole and sextupole moments of the beam distribution. Measurements of dipole and quadrupole moments at multiple locations yield information about beam orbit and emittance. The sextupole moment can reveal information about beam asymmetry which is useful in diagnosing beam tail deflections caused by short range dipole wakefields. In addition to the resonance enhancement of a single-cell cavity, use of a multi-cell standign-wave structure further enhances signal strength and improves the resolution of the device. An estimated rms beam size resolution is sub micro-meters and beam position is sub nano-meter.

RPAT097 2-D Low Energy Electron Beam Profile Measurement Based on Computer Tomography Algorithm with Multi-Wire Scanner 4323
  • N.J. Yu, K.Y. Gong, Q. F. Li, C.-X. Tang, S. Zheng
    TUB, Beijing
  A new method for low energy electron beam profile measurement is advanced, which presents a full 2-D beam profile distribution other than the traditional 2-D beam profile distribution given by 1-D vertical and horizontal beam profiles. The method is based on the CT (Computer Tomography) algorithm. Multi-sets of data about the 1-D beam profile projections are attained by rotating the multi-wire scanner. Then a 2-D beam profile is reconstructed from these projections with CT algorithm. The principle of this method is presented. The simulation and the experiment results are compared and analyzed in detail.