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quadrupole

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IT12 Use of Superimposed Alternating Currents in Quadrupoles to Measure Beam Position with Respect to their Magnetic Centre electron, storage-ring, lattice, radiation 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.  
 
PS04 Influence of transverse beam dimensions on beam position monitor signals pick-up, emittance, synchrotron, instrumentation 106
 
  • A. Jankowiak, T. Weis
    DELTA, Institute for Accelerator Physics and Synchrotron Radiation, University of Dortmund, Germany
  In this paper we will evaluate the influence of transverse beam dimensions on the signal functions of a beam position monitor (BPM) with capacitive pick-up electrodes. The error which occurs in the determination of the beam position when disregarding these effects is calculated as an example for the DELTA1 BPM. The possibility to use this effect for the measurement of the beam size / emittance is discussed.  
 
PS09 Beam Steering With Image Processing In The Cryring Injection Beamline injection, ion, focusing, synchrotron 118
 
  • A. Källberg, A. Simonsson
    MSI, Manne Siegbahn Laboratory Of Physics, Stockholm, Sweden
  By varying six quadrupoles and observing how the beam spot moves on three fluorescent screens the beam is aligned in the injection beamline. The method is now automated and upgraded by using image processing of the picture to get the position of the beam.  
 
PT01 Closed-orbit correction using the new beam position monitor electronic of Elsa Bonn closed-orbit, electron, resonance, alignment 153
 
  • J. Dietrich, I. Mohos, J. Keil
    IKP, Forschungszentrum Jülich GmbH, Jülich, Germany
  RF and digital electronics, developed at the Forschungszentrum Jülich/IKP were integrated to form the new beam position monitor (BPM) system at the Electron Stretcher Accelerator (ELSA) of the University of Bonn. With this system the preservation of the polarization level during acceleration was currently improved by a good correction of the closed-orbit. All BPM offsets relative to the magnetic quadrupole centers were determined by the method of beam-based alignment. The optics functions measured by the BPM system are in good agreement with theoretical predictions.  
 
PT05 First results on closed-loop tune control in the CERN-SPS feedback, simulation, acceleration, controls 165
 
  • L. Jensen, O.R. Jones, H. Schmickler
    CERN, Geneva, Switzerland
  This paper presents the first measurements performed with the SPS Qloop. The emphasis will be laid on the model used for designing the regulation loop and how well it fits reality.  
 
PT10 Emittance and dispersion measurements at TTF emittance, dipole, linac, acceleration 180
 
  • M. Castellano, A. Cianchi, V.A. Verzilov
    INFN-LNF, Laboratori Nazionali di Frascati dell'INFN, Frascati, Italy
  It is well known that beam dispersion , along with the Twiss parameters and emittance, contributes to the beam spot size. So that, in general, anomalous dispersion is an undesirable event and must be minimized by careful tuning the machine. If not, when the spot size is used to infer beam emittances, as it is the case of the "quadrupole scan" method, basically employed at TTF, the unknown dispersion can lead to overestimated values for the emittance. This paper presents the first attempt to determine the dispersion function at several points of the TTF Linac and to separate its contribution to the local emittance measurement, performed by means of the OTR imaging technique.  
 
PT14 Experience with stripline beam position monitors on the TESLA test facility LINAC linac, alignment, lattice, beam-transport 190
 
  • P. Castro, P. Patteri, F. Tazzioli
    DESY, Deutsches Elektronen Synchrotron, Hamburg, Germany
  Measurement and correction of beam position are very important for the optimization of beam characteristics and alignment in the Tesla Test Facility (TTF) linac. We describe and present measurements with beam of the performance of the stripline beam position monitors (BPMs) in operation and in order to determine the beam response.