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wire scanner

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PM12 Cavity Mode Related Wire Breaking of the SPS Wire Scanners And Loss Measurements of Wire Materials diagnostics, instrumentation, radio-frequency 119
 
  • F. Caspers, B. Dehning, E. Jensen, J. Koopman, J.F. Malo, F. Roncarolo
    CERN, Geneva, Switzerland
  During 2002 SPS running with the high intensity LHC type beam the breaking of several of the carbon wires in the wire scanners has been observed. This damage occurred with the scanners in their parking position. The observation of large changes in the wire resistivity and thermionic electron emission indicated clearly a strong RF beam induced heating and its bunch length dependence. A subsequent analysis in the laboratory, simulating the beam by a RF-powered wire, showed two main problems. The housing of the wire scanner acts as a cavity with a mode spectrum starting around 350 MHz and high impedance values around 700 MHz. The carbon wire used appears to be an excellent RF absorber and thus dissipates a significant part of the beam-induced power. The classical cavity mode technique is used to determine the complex permittivity and permeability of different samples. As a resonator, a rectangular TE01N type device is used. Different materials such as silicon carbide (SiC), carbon and quartz fibres as well as other samples were measured, since no data for these materials was available. In particular SiC properties are of interest, since SiC bulk material is often used as a microwave absorber. As a result, the carbon wire will be replaced by a SiC wire, which shows much less RF losses. Placing ferrite tiles on the inner wall of the wire scanner housing considerably reduces the impedance of the cavity modes. The reduction of the Q values of these modes is confirmed by laboratory measurements.  
 
PM15 First Experimental Results And Improvements On Profile Measurements With The Vibrating Wire Scanner halo, tail, diagnostics, instrumentation 128
 
  • S.G. Arutunian, K.H. Bakshetyan, N.M. Dobrovolski, M.R. Mailian, H.E. Soghoyan, I.E. Vasiniuk
    YPI, Yerevan Physics Institute, Armenia
  • K. Wittenburg
    DESY, Deutsches Elektronen-Synchrotron, Hamburg, Germany
  The paper presents the first experimental results of transverse profile scans using a wire scanner based on a vibrating wire (vibrating wire scanner - VWS). The measurements were performed at the injector electron beam (6 nA) of the Yerevan synchrotron. The beam profile information is obtained by measuring the wire natural oscillations that depend on the wire temperature. This first experiments on weak electron beam proved this new method as a very sensitive tool, even suitable for tail measurements. Additional, improvements were tested to overcome some problems connected with signal conditioning and signal transfer in the presence of electromagnetic noise. As a result the noises were neatly separated and reduced. A mathematical method for rejection of distorted data was developed. Experiments with the scanner at the PETRA accelerator at DESY are planned for measurements of beam tails.  
 
PM16 Wire Scanner Beam Profile Measurement For ESRF beam profile, transfer line, emittance, ESRF 131
 
  • A.B. El-Sisi
    NRC, Atomic Energy Authority, NRC, Plasma and Nuclear Fusion Dept., Cairo, Egypt
  Method of beam transverse profile measurement in accelerator by wire scanner is wide spread in accelerator field. The wire scanner is used in beam transfer lines of European Synchrotron Radiation Facility (ESRF) to provide data for beam profiles, which is being used in emittance measurements. The beam energy in the first transport line is 200 MeV and the peak current is 25 mA. The purpose of the scanner is to provide horizontal and vertical beam profiles. This work will discuss the operation of the wire scanner, and the first results of the scanner in ESRF. By changing the value of focus quad at (de focus quad = 18 A) we get the emittance value for the vertical plane. The value is 1.5·10-6 mrad. When we used this value to simulate our result we find that the simulation gives good fitting with real values of vertical plane. Also by changing the value of the focus quad at (focus quad = 10.46 A) we get the emittance value for the horizontal plane. The value is 2·10-7 mrad. And we find that the simulation gives good fitting with real values.