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emittance

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IT04 Review of Emittance and Stability Monitoring Using Synchrotron Radiation Monitors instrumentation, diagnostics, synchrotron-radiation, synchrotron 16
 
  • K. Holldack, J. Feikes, W.B. Peatman
    BESSY, Berlin, Germany
  Different techniques of emittance and stability monitoring using bend magnet and undulator radiation will be reviewed. Besides imaging methods for emittance monitoring , the problem of XBPM's used for the measurement of the centre of mass position of the undulator beams will be treated in detail. The key feature of these monitors is a careful electron optical design to take account of gap dependent changes of the shape and photon energy of the undulator beam as well as spurious signals from dipoles and high heat load. The reason for the fact that these monitors work well on low energy machines like BESSY II but often fail due in high energy machines will be demonstrated by experimental results obtained on different types of BESSY II insertion devices such as undulators, wavelength shifters, multipole wigglers and electromagnetic undulators. Experimental results of global and local orbit monitoring and a proof of principle of a XBPM-based local feedback will be shown.  
 
IT06 Measurement of Small Transverse Beam Size Using Interferometry instrumentation, diagnostics, brillance 26
 
  • T. Mitsuhashi
    KEK, High Energy Accelerator Research Organization, Oho, Tsukuba, Ibaraki, Japan
  The principle of measurement of the profile or size of small objects through the spatial coherency of the light is known as the van Cittert-Zernike theorem. We developed the SR interferometer (interferometer for synchrotron radiation) to measure the spatial coherency of the visible region of the SR beam, and we demonstrated that this method is able to measure the beam profile and size. Since the small electron beam emits a SR beam which has a good spatial coherency, this method is suitable for measuring a small beam size. In this paper, the basic theory for the measurement of the profile or size of a small beam via the spatial coherency of the light, a design of the SR interferometer, and the results of beam profile measurement, examples of small beam size measurements and recent improvements are described.  
 
IT10 6-D Electron Beam Characterisation Using Optical Transition Radiation and Coherent Diffraction Radiation instrumentation, diagnostics, linear-collider 46
 
  • M. Castellano, V. Verzilov
    INFN-LNF, Laboratori Nazionali di Frascati, Frascati, Italy
  • L. Catani, A. Cianchi
    INFN-Roma2, Roma, Italy
  • G. D'Auria, M. Ferianis, C. Rossi
    ELETTRA, Sincrotrone Trieste, Trieste, Italy
  The development of non-intercepting diagnostics for high charge density and high energy electron beams is one of the main challenge of beam instrumentation. Diffraction Radiation based diagnostics, being non-intercepting, are among the possible candidates for the measurements of beam properties for the new generation linacs. At the 1 GeV Sincrotrone Trieste linac, we are performing the first measurements of beam transverse parameters using Diffraction Radiation emitted by the electron beam passing through a 1 mm slit opened on a screen made of aluminium deposited on a silicon substrate. The analysis of the angular distribution of the Diffraction Radiation for a given wavelength, slit aperture and beam energy gives information about the beam size and its angular divergence.  
 
IT12 Investigations of Longitudinal Charge Distribution in Very Short Electron-Bunches instrumentation, diagnostics, linear-collider 56
 
  • M. Hüning
    RWTH-Aachen, III. Physik Institut, Aachen, Germany
  Electro-optical-sampling is a powerful technique to measure the longitudinal charge distribution of very short electron bunches. The electrical field moving with the bunch induces an optical an-isotropy in a ZnTe crystal which is probed by a polarized laser pulse. Two measurement principles are possible. In the first one a short laser pulse of lengths <50 fs is used directly to scan the time varying optical properties of the crystal. In the second method the laser pulse is frequency chirped and the temporal information is encoded into the time ordered frequency spectrum, which can be recovered by an optical grating and a CCD camera. A resolution in the 100 fs regime can also be achieved with longitudinal phase space tomography. Acceleration on the slope of the rf wave at different phases and measurements of the energy profiles are sufficient for a reconstruction algorithm based on maximum entropy methods. The longitudinal phase space distribution can be obtained without artifacts due to the limited angular range of the projections.  
 
CT05 Beam-Profile Instrumentation for a Beam-Halo Measurement: Overall Description, Operation, and Beam Data
Work supported by the US Department of Energy 		instrumentation, diagnostics 76
 
  • J.D. Gilpatrick, D. Barr, L. Day, D. Kerstiens, M. Stettler, R. Valdiviez
    LANL, Los Alamos National Laboratory, Los Alamos, NM, USA
  • M. Gruchalla, J. O'Hara
    HC, Honeywell Corporation, USA
  • J. Kamperschroer
    GAC, General Atomics Corporation, San Diego, CA, USA
  The halo experiment presently being conducted at the Low Energy Demonstration Accelerator (LEDA) at Los Alamos National Laboratory (LANL) has specific instruments that acquire horizontally and vertically projected particle-density beam distributions out to greater than 105:1 dynamic range. We measure the core of the distributions using traditional wire scanners, and the tails of the distribution using water-cooled graphite scraping devices. The wire scanner and halo scrapers are mounted on the same moving frame whose location is controlled with stepper motors. A sequence within the Experimental Physics and Industrial Control System (EPICS) software communicates with a National Instrument LabVIEW virtual instrument to control the movement and location of the scanner/scraper assembly. Secondary electrons from the wire scanner 33 μm carbon wire and protons impinging on the scraper are both detected with a lossy-integrator electronic circuit. Algorithms implemented within EPICS and in Research Systems Interactive Data Language (IDL) subroutines analyse and plot the acquired distributions. This paper describes the beam profile instrument, describes our experience with its operation, compares acquired profile data with simulations, and discusses various beam profile phenomenon specific to the halo experiment.  
 
CT07 Excitation of Large Transverse Beam Oscillations without Emittance Blow-Up Using the "AC-Dipole" Principle instrumentation, diagnostics, SPS 82
 
  • O. Berrig, W. Höfle, R. Jones, J. Koopman, J.-P. Koutchouk, F. Schmidt
    CERN, Geneva, Switzerland
  The so-called "AC-Dipole" principle allows the excitation of transverse oscillations to large (several σ) excursions without emittance blow-up. The idea was originally proposed and tested at BNL for resonance crossing with polarized beams, using an orbit corrector dipole with an excitation frequency close to the betatron tune, hence "AC-Dipole". This method of beam excitation has several potential applications in the LHC, such as phase advance and β-measurements, dynamic aperture studies and the investigation of resonance strengths. The technique was recently tested in the CERN-SPS using the transverse damper as an "AC-Dipole" providing the fixed frequency excitation. results from this experiment are presented, along with an explanation of the underlying principle.  
 
CT08 Measuring Beta-Functions with K-Modulation instrumentation, diagnostics, SPS 85
 
  • O. Berrig, C. Fischer, H. Schmickler
    CERN, Geneva, Switzerland
  The precise measurement of the local value of the beta-function at the place of a beam size monitor is necessary for the precise determination of the beam emittance. We developed a new method for the measurement of the beta-function by using of continuous square-wave modulation of the force of the quadrupole and by continuous tune tracking. Measurements were performed at LEP in order to evaluate the precision that can be achieved with this method in the LHC. The paper describes the method and discusses in details the results obtained at LEP for colliding and non-colliding beams.  
 
CT09 X-Ray Interference Methods of Electron Beam Diagnostics instrumentation, diagnostics, synchrotron-radiation, ESRF 88
 
  • O. Chubar, A. Snigirev, S. Kuznetsov, T. Weitkamp
    ESRF, Grenoble, France
  • V. Kohn
    RRC, Russian Research Center 'Kurchatov Institute', Moscow
  Electron beam diagnostics methods based interference and diffraction of synchrotron radiation (SR) in hard X-ray range will be discussed. Two simple optical schemes providing X-ray interference patterns highly sensitive to transverse size of the emitting electron beam, will be considered. For each scheme, the visibility of fringes in the pattern depends on transverse size of the electron beam. However, the pattern is also determined by the scheme geometry, shape and material of diffracting bodies. Therefore, for correct interpretation of the experimental results, high-accuracy computation of SR emission and propagation in the framework of physical optics should be used. Examples of practical measurements and processing of the results are presented.  
 
PS02 Bench Test of a Residual Gas Ionization Profile Monitor (Rgipm)
Work supported by U.S. Department of Energy 		instrumentation, diagnostics, brillance, LANL 102
 
  • W.C. Sellyey, J.D. Gilpatrick
    LANL, Los Alamos National Laboratory, Los Alamos, NM, USA
  • R. Senior
    GAC, General Atomics Corporation, San Diego, CA, USA
  An RGIPM has been designed, constructed and bench tested to verify that all components are functioning properly and that the desired resolution of about 50μm× rms can be achieved. This paper will describe some system details and it will compare observed results to detailed numerical calculations of expected detector response.  
 
PS04 Design of a Magnetic Quadrupole Pick-Up for the CERN PS instrumentation, diagnostics, pick-up, CERN-PS 108
 
  • A. Jansson, L. Søby, D.J. Williams
    CERN, Geneva, Switzerland
  A quadrupole pick-up is sensitive to the quantity σ2x - σ2y, where σx and σy are the horizontal and vertical r.m.s. beam sizes. Since it is a non-invasive device, it is potentially very useful for matching and emittance measurements. A magnetic quadrupole pick-up has been developed for the CERN PS. By coupling to the radial component of the magnetic field around the beam, it was possible to eliminate the common-mode problem, which is usually a limiting factor in the use of quadrupole pick-ups. This paper presents the final pick-up design, which is the result of a series of simulations and test prototypes. The performance of the pick-up and its associated electronics is discussed. Preliminary results from the two pick-ups recently installed in the PS machine are also presented.  
 
PS05 Measurement of the Time-Structure of the 72 MeV Proton Beam in the PSI Injector-2 Cyclotron instrumentation, diagnostics, PSI 111
 
  • R. Dölling
    PSI, Paul Scherrer Institut, Villigen, Switzerland
  The time-structure monitor at the last turn of the 72MeV Injector-2 cyclotron has been improved in order to meet the stringent time-resolution requirement imposed by the short bunch length. Protons scattered by a thin carbon-fibre target pass through a first scintillator-photomultiplier detector and are stopped in a second one. The longitudinal bunch shape is given by the distribution of arrival times measured with respect to the 50 MHz reference signal from the acceleration cavities. From a coincidence measurement, the time resolution of the detectors has been determined to be 51 ps and 31 ps fwhm. Longitudinal and horizontal bunch shapes have been measured at beam currents from 25μA to 1700μA. Approximately circular bunches were observed with diameter increasing with current. The shortest observed proton bunch length was 38 ps fwhm.  
 
PS06 Laser Profile Measurements of an H-Beam instrumentation, diagnostics, SNS 114
 
  • R. Connolly, P. Cameron, J. Cupolo, M. Grau, M. Kesselmann, C-J. Liaw, R. Sikora
    BNL, Brookhaven National Laboratory, Upton, NY, USA
  A non-intercepting beam profile monitor for H--beams is being developed at Brookhaven National Lab. An H- ion has a first ionization potential of 0.75eV. Electrons can be removed from an H--beam by passing light from a near-infrared laser through it. Experiments have been performed on the BNL linac to measure the transverse profile of a 750keV beam by using a Nd:YAG laser to photoneutralize narrow slices of the beam. The laser beam is scanned across the ion beam neutralizing the portion of the beam struck by the laser. The electrons are removed from the ion beam and the beam current notch is measured.  
 
PS09 Transverse Beam Profile Measurements Using Optical Methods instrumentation, diagnostics, GSI, linac 123
 
  • A. Peters, P. Forck, A. Weiss, A. Bank
    GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
  Two different systems are currently under development at GSI's heavy ion facility to measure transverse beam profiles using optical emitters. At the GSI-LINAC for energies up to 15 MeV/u residual gas fluorescence is investigated for pulsed high current beams. The fluorescence of N2 is monitored by an image intensified CCD camera. For all ion species with energies above 50 MeV/u slowly extracted from the synchrotron SIS a classical viewing screen system is used. Three different target materials have been investigated and their behavior concerning efficiency, saturation and timing performance is evaluated. Both systems (will) use CCD cameras with a digital read out using the IEEE 1394 standard.  
 
PS10 Control and Data Analysis for Emittance Measuring Devices instrumentation, diagnostics, controls, GSI 126
 
  • T. Hoffmann
    GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
  • D.A. Liakin* (work done at GSI)
    ITEP, Institute for Theoretical and Experimental Physics, Moscow, Russia
  Due to the wide range of heavy ion beam intensities and energies in the GSI linac and the associated transfer channel to the synchrotron, several different types of emittance measurement systems have been established. Many common devices such as slit/grid or dipole-sweep systems are integrated into the GSI control system. Other systems like the single shot pepper pot method using CCD-cameras or stand-alone slit/grid set-ups are connected to personal computers. An overview is given about the various systems and their software integration. Main interest is directed on the software development for emittance front-end control and data analysis such as evaluation algorithms or graphical presentation of the results. In addition, special features for improved usability of the software such as data export, project databases and automatic report generation will be presented. An outlook on a unified evaluation procedure for all different types of emittance measurement is given.  
 
PS13 A Zone Plate Based Beam Monitor for the Swiss Light Source instrumentation, diagnostics, PSI 133
 
  • C. David
    PSI-LMN, Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, Villigen, Switzerland
  • V. Schlott, A. Jaggi
    PSI-SLS, Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland
  At the Swiss Light Source, a source imaging set-up is planned on a dedicated dipole magnet beam-line. A transmission Fresnel Zone Plate will be used to generate a demagnified image of the source at a photon energy in the 1.8 keV range. The image will be acquired by scanning a pinhole in the image plane. A diffraction limited spatial resolution of approximately 2 microns can be anticipated. The concept has the advantage of having no components operated in reflection, and no components inside the frontend.  
 
PS14 Microwave Pickups for the Observation of Multi GHz Signals Induced by the ESRF Storage Ring Electron Bunches instrumentation, diagnostics, pick-up, ESRF, storage-ring 136
 
  • E. Plouviez
    ESRF, European Synchrotron Radiation Facility, Grenoble, France
  The length of the bunches stored in ESRF lies in the 30 ps to 120 ps range (FWHM). The observation of single bunch phenomena like transverse or longitudinal oscillations or bunch length variation requires the acquisition and analysis of signals at frequencies higher than 10 GHz. A set of microwave cavity pick ups operating at 10 GHz and 16 GHz together with the appropriate electronics has been implemented on the ESRF storage ring; it detects the wall currents on the vacuum chamber due to the electron beams circulation. We describe the design of these cavities, give the result and analysis of measurements performed with the pick ups and indicate how we plan to use these devices as beam diagnostics  
 
PS15 A New Wirescanner Control Unit instrumentation, diagnostics, controls, DESY 139
 
  • M. Werner, K. Wittenburg
    DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
  Wires scanners are standard instruments for beam size measurements in storage rings: A wire is crossing the beam at a given speed and the secondary emission current of the wire and/or the photomultiplier signals produced from Bremsstrahlung or particles scattered at the wire are recorded together with the wire positions. The control unit described here is based on a previous CERN design. It now has additional features: Triggered fast scans (1m/s) with a trigger uncertainty below ±30μs (mechanics + electronics) used at the TTF Linac and at the proton synchrotron DESY III, Slow scans (e.g. 50μm/s) for the TTF Linac, Positioning of the wire within ±3μm for tail scans at the storage rings PETRA and HERA, A 10.5MHz data acquisition rate for bunch-by-bunch acquisitions in the accelerators at DESY. Another important design goal was the compatibility with CERN scanners; it is foreseen to operate them at LHC with the new control unit. First measurements with the new control unit at TTF and HERA will be presented.  
 
PS17 Beam Size Measurement of the Spring-8 Storage Ring by Two-Dimensional Interferometer instrumentation, diagnostics, synchrotron-radiation, SPring-8 142
 
  • M. Masaki, S. Takano
    SPring, Japan Synchrotron Radiation Research Institute SPring-8, Japan
  Two-dimensional interferometer using visible synchrotron radiation was developed in order to measure beam sizes at a source point in a bending magnet of the SPring-8 storage ring. The theoretical background of this method is described in the framework of wave-optics. Assuming designed optics parameters, transverse emittance was evaluated from measured beam size.  
 
PS18 Planned X-Ray Imaging of the Electron Beam at the SPRING-8 Diagnostics Beamline BL38B2 instrumentation, diagnostics, synchrotron-radiation, SPring-8 145
 
  • S. Takano, M. Masaki, H. Ohkuma, S. Sasaki, M. Shoji, K. Tamura
    SPring, Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo, Japan
  X-ray imaging observation of the electron beam is planned at the SPring-8 storage ring diagnostics beamline BL38B2 to evaluate small vertical emittance. The resolution target is 1 micron of electron beam size (1s). The synchrotron radiation from a dipole magnet source will be imaged by a single phase zone plate. Monochromatic X-ray with energy of 8keV will be selected by a double crystal monochromator. The magnification factor of the zoneplate is 0.27, and an X-ray zooming tube will be used as a detector to compensate for demagnification.  
 
PS21 Diagnostics for the Photon Injector Test Facility in Desy Zeuthen instrumentation, diagnostics, PITZ, free-electron-laser, linac 154
 
  • J. Bähr, I. Bohnet, D. Lipka, H. Lüdecke, F. Stephan, Q. Zhao
    DESY-Zeuthen, Deutsches Elektronen-Synchrotron, Zeuthen, Germany
  • K. Flöttmann
    DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
  • I. Tsakov
    NRNE, Institute for Nuclear Reseach and Nuclear Energy of the Bulgarian Academy of Science, Sofia, Bulgaria
  A Photo Injector Test facility (PITZ) is under construction at DESY-Zeuthen. The aim is to develop and operate an optimized photo injector for future free electron lasers and linear accelerators. This concerns especially minimal transverse emittances and proper longitudinal phase space. The commissioning of the photo injector will take place in summer 2001. In the rst phase the energy of the produced electrons is about 5 MeV. A short description of the setup and beam parameters are given. Optimization of an electron gun is only possible based on an extended diagnostics system. The diagnostics system for the analysis of the transversal and longitudinal phase space will be described. It consists of a measurement system of the transversal emittance, a TV-based image measurement system, a streakcamera measurement facility, a spectrometer using a dipole magnet and further detectors. Problems of the measurement of the longitudinal phase space are discussed in detail.  
 
PM11 Injection Matching Studies Using Turn-By-Turn Beam Profile Measurements in the CERN PS instrumentation, diagnostics, pick-up, injection, CERN-PS 189
 
  • M. Benedikt, Ch. Carli, Ch. Dutriat, A. Jansson, M. Giovannozzi, M. Martini, U. Raich
    CERN, Geneva, Switzerland
  The very small emittance beam needed for the LHC requires that the emittance blow-up in its injector machines must be kept to a minimum. Mismatch upon the beam transfer from one machine to the next is a potential source of such blow-up. The CERN PS ring is equipped with 3 Secondary Emission Grids (SEM-Grids) which are used for emittance measurement at injection. One of these has been converted to a multi-turn mode, in which several tens of consecutive beam passages can be observed. This allows the study of mismatch between the PS-Booster and the PS. This paper describes the instrument and experimental results obtained during the last year.  
 
PM15 Sensitivity Studies with the SPS Rest Gas Profile Monitor instrumentation, diagnostics, CERN-SPS 201
 
  • G. Ferioli, C. Fischer, J. Koopman, M. Sillanoli
    CERN, Geneva, Switzerland
  During the SPS run in the year 2000 further test measurements were performed with the rest gas monitor. First, profiles of single circulating proton bunches were measured and the bunch charge progressively reduced, in order to determine the smallest bunch intensity which can be scanned under the present operating conditions. The image detector in this case was a CMOS camera. Using a multi-anode strip photo-multiplier with fast read-out electronics, the possibility to record profiles on a single beam passage and on consecutive turns was also investigated. This paper presents the results of these tests and discusses the expected improvements for the operation in 2001. Moreover, the issue of micro channel plate ageing effects was tackled and a calibration system based on electron emission from a heating wire is proposed. The gained experience will be used for the specification of a new monitor with optimised design, to be operated both in the SPS and in the LHC.  
 
PM18 Beam Diagnostics for Low-Intensity Radioactive Beams instrumentation, diagnostics, isotope-production, EXCYT 210
 
  • L. Cosentino, P. Finocchiaro
    INFN-LNS, Laboratori Nazionali del Sud, Catania, Italy
  In order to perform imaging, profiling and identification of low intensity (Ibeam<105 pps) Radioactive Ion Beams (RIB), we have developed a series of diagnostics devices, operating in a range of beam energy from 50 keV up to 8 MeV/A. These characteristics do them especially suitable for ISOL RIB facilities.  
 
PM20 A High Dynamic Range Bunch Purity Tool instrumentation, diagnostics, ESRF, synchrotron-radiation 216
 
  • B. Joly, G.A. Naylor
    ESRF, Grenoble, France
  The European synchrotron radiation facility uses a stored electron beam in order to produce x-rays for the study of matter. Some experiments make use of the time structure of the x-ray beam which is a direct reflection of the time structure in the electron beam itself. Avalanche photo-diodes have been used in an x-ray beam in a photon counting arrangement to measure the purity of single or few bunch filling modes. Conventional techniques measuring the photon arrival times with a time to analogue converter (TAC) achieve dynamic ranges in the 10-6 range. We report here the use of a gated high count rate device achieving a measurement capability of 10-10. Such high purity filling modes are required in synchrotron light sources producing x-ray pulses for experiments looking at very weak decay signals as seen in M”ssbauer experiments..  
 
DS02 Emittance Measurement Techniques
Session 2: Monday Afternoon (16:30--18:00 Hrs) 		diagnostics 226
 
  • O. Chubar
    ESRF, Grenoble, France
  I. Physical questions.

Short review of the existing techniques, methods and approaches (imaging, interference, projection, betatron coupling) with their advantages and limitations. New promising methods of emittance diagnostics (short contributions/messages from participants are expected). How to go from beam profile (size, divergence, etc.) measurements to emittance? Problems of indirect measurements.

II. Practical questions.

Emittance, brightness (brilliance), luminosity are very important "passport" characteristics of an accelerator. In practice, however, lack of time, man-power, sometimes low priority, make it not so easy to construct and maintain a good, reliable emittance diagnostic system. How this situation can be improved? What can be shared (ideas, software, hardware, personnel)? How to shorten a long way from a bright idea to a reliable system? Can final beam users (e.g. SR users) contribute/share their diagnostics systems or data?