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radiation

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IT03 Beam Loss Monitors at the ESRF beam-losses, vacuum, injection, synchrotron 3
 
  • B. Joly, U. Weinrich, G.A. Naylor
    ESRF, The European Synchrotron Radiation Facility, Grenoble, France
  The European Synchrotron radiation facility is a third generation x-ray source providing x-rays on a continuous basis. As a facility available to external users, the monitoring of radiation caused by the loss of high-energy stored beam is of great concern. A network of beam loss monitors has been installed inside the storage ring tunnel so as to detect and localize the slow loss of electrons during a beam decay. This diagnostic tool allows optimization of beam parameters and physical aperture limits as well as giving useful information on the machine to allow the lifetime to be optimized and defects localized.  
 
IT07 Bunch Length Measurements electron, laser, linac, gun 19
 
  • M. Geitz
    DESY, Deutsches Elektronen Synchrotron, Hamburg, Germany
  An rf photo-injector in combination with a magnetic bunch compressor is suited to produce high-charged sub-picosecond electron bunches required for electron-drive linacs for VUV and X-ray FELs. This report summarizes time- and frequency domain bunch length measurement techniques with sub-picosecond resolution.  
 
IT12 Use of Superimposed Alternating Currents in Quadrupoles to Measure Beam Position with Respect to their Magnetic Centre quadrupole, electron, storage-ring, lattice 38
 
  • N. Marks
    CLRC, Daresbury Laboratory, Warrington, UK
  The positional stability of the electron beam in a modern state-of-the-art synchrotron radiation source is critical, as the many experimental users require consistency in the position and dimensions of the incoming photon beams which are incident on their experimental samples. At the Daresbury Synchrotron Radiation Source (SRS), inaccuracies in the measurements of the positions of both beam position monitors and the lattice quadrupoles can be overcome by measuring the position of the electron beam with respect to the magnetic centres of the quadrupoles. This was achieved by superimposing an alternating ('ripple') current on the direct current excitation of a single lattice quadrupole and examining the resulting beam oscillations at remote positions in the storage ring. If the electron beam is then subjected to a local distortion at the position of this quadrupole, the amplitude of the beam oscillation induced by the superimposed current is minimised (nominally zero) when the beam is at the quadrupole's magnetic centre. This paper presents details of the electrical circuit developed to inject an alternating current into the coils of individual quadrupoles and gives details of the results achieved to date.  
 
CT08 Adaptive Optics for the LEP 2 Synchrotron Light Monitors synchrotron, extraction, synchrotron-radiation, optics 77
 
  • G. Burtin, R.J. Colchester, G. Ferioli, J.J. Gras, R. Jung, J.M. Vouillot
    CERN, Geneva, Switzerland
  The image obtained with the LEP synchrotron radiation telescopes deteriorates, giving multiple and deformed images, when the beam energy goes beyond 80 GeV at beam currents above 2 mA. This problem is due to the deformation of the light extracting beryllium mirror, by as little as 1 mm, and had been predicted at the design stage. To overcome this problem, several changes together with an adaptive optics set-up have been introduced. These essentially consist of a cylindrically deformable mirror to compensate the cylindrical deformation of the beryllium mirror and a movable detector to compensate the spherical deformation. Both components are continuously adjusted as a function of beam current and energy.  
 
CT10 Real Time Display of the Vertical Beam Sizes in LEP Using the BEXE X-Ray Detector and Fast VME Based Computers positron, electron, luminosity, synchrotron 87
 
  • R. Jones, A. Manarin, G. Pignard, E. Rossa, H. Schmickler, M. Sillanoli, C. Surback
    CERN, Geneva, Switzerland
  Fast X-ray detectors based on CdTe photoconductors have been installed in LEP since the beginning of its operation in 1989. The angular divergence of the high energy photons from the synchrotron radiation (x-rays) and the narrow spacing of the 64 photoconductors of the detector allow a good measurement of vertical beam profiles down to an rms beam size of 300 mm. This paper presents some specific parameters and experimental results of an upgrade program in which the local processing power of the front-end electronics has been increased by a factor 50. Such a powerful tool has allowed a real time display of the time evolution of the vertical beam sizes. An online correlation plot between the electron and positron beam sizes (turn by turn) is also displayed. These online video images are available in the LEP control room and are used in daily operation for luminosity optimisation.  
 
PS15 Beam profile measurements at 40 MHz in the PS to SPS transfer channel injection, proton, ion, kicker 135
 
  • G. Ferioli, J.J. Gras, H. Hiller, R. Jung
    CERN, Geneva, Switzerland
  Bunch to bunch beam profile measurements provide a valuable tool to control the injection lines to the SPS. A fast profile monitor based on a 2.5μm Mylar coated with Aluminium Optical Transition Radiation (OTR) radiator, has been developed, installed and tested in the transfer line between the PS and SPS. The OTR beam image is focused onto a fast Linear Multianode Photo Multiplier Tube and the associated electronics sample and store profiles every 25ns. The paper describes the detector design, the electronic processing, and presents the results of different measurements made with bunches of 109-1011 protons at 26 GeV, and bunches of 106 Pb82+ ions at 5.11 GeV/u.  
 
PT04 Radiation protection system installation for the accelerator production of tritium/low energy demonstration accelerator project (APT/LEDA) radio-frequency, controls, beam-transport, rfq 162
 
  • J.E. Wilmarth, M.T. Smith, T.L. Tomei
    LANL, Los Alamos National Laboratory, Los Alamos, NM, USA
  The APT/LEDA personnel radiation protection system installation was accomplished using a flexible, modular proven system which satisfied regulatory orders, project design criteria, operational modes, and facility requirements. The goal of providing exclusion and safe access of personnel to areas where prompt radiation in the LEDA facility is produced was achieved with the installation of a DOE-approved Personnel Access Control System (PACS). To satisfy the facility configuration design, the PACS, a major component of the overall radiation safety system, conveniently provided five independent areas of personnel access control. Because of its flexibility and adaptability the Los-Alamos Neutron- Science-Center-(LANSCE)-designed Radiation Security System (RSS) was efficiently configured to provide the desired operational modes and satisfy the APT/LEDA project design criteria. The Backbone Beam Enable (BBE) system based on the LANSCE RSS provided the accelerator beam control functions with redundant, hardwired, tamper-resistant hardware. The installation was accomplished using modular components.  
 
PT16 Status of the delta synchrotron light-monitoring-system synchrotron, synchrotron-radiation, shielding, emittance 196
 
  • U. Berges, K. Wille
    DELTA, Institute for Accelerator Physics and Synchrotron Radiation, University of Dortmund, Germany
  A synchrotron radiation source like DELTA needs an optical monitoring system to measure the beam size at different points of the ring with high resolution and accuracy. The measurements with the present synchrotron light monitors show that beam sizes larger than 250 μm can be measured. The measured emittance is of the order of the theoretical values of the optics and goes down to 8 nm rad. The magnification of the system can simply be increased by adding another lens to measure smaller emittances and beamsizes down to 100 μm. In this case you still have an optical image of the beam available, but sometimes the position of the camera has to be adapted due to the great magnification of the optical system. The image processing system which is based on a VME Framegrabber makes a two dimensional gaussian fit to the images from different synchrotron light-monitors. First tests with monochromatic components of the synchrotron radiation (500 nm and 550 nm) and with short time cameras (shutter time down to 1/10000 s) have been performed. A two-dimensional PSD has been installed to measure slow beam motion. To measure small beam sizes, especially in the vertical plane, diffraction elements will be used. This paper gives an overview over the present installation and the results.  
 
PT17 Role of pre-wave zone effects in TR-based beam diagnostics diagnostics, electromagnetic-fields, linac, background 199
 
  • V.A. Verzilov
    INFN-LNF, Laboratori Nazionali di Frascati dell'INFN, Frascati, Italy
  Transition radiation (TR) is nowadays intensively exploited by a number of techniques to characterize different beam parameters. These methods are based, sometimes implicitly, on standard formulae, and used often without paying due attention to their applicability. In particular, standard expressions are only first-order asymptotic, i.e., strictly speaking, valid at infinity. In this paper TR is examined in a spatial domain where conventional results are no more exact and variations in radiation properties are observed. Under certain conditions, for example, at long wavelengths or very high energies the effect is so considerable that should be taken into account in accurate beam measurements.