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Bravin, E.

Paper Title Page
MOPLS020 Rad-hard Luminosity Monitoring for the LHC 580
 
  • A. Ratti, J.-F. Beche, J.M. Byrd, K. Chow, S. De Santis, P. Denes, B. Ghiorso, H.S. Matis, M. T. Monroy, W.C. Turner
    LBNL, Berkeley, California
  • E. Bravin
    CERN, Geneva
  • P.F. Manfredi
    Pavia University, Engineering faculty, Pavia
  • W. Vandelli
    Pavia University, Pavia
 
  Luminosity measurements at the high luminosity points of the LHC are very challenging due to the extremely high radiation levels in excess of 1 GGy/yr. We have designed an ionization chamber that uses a flowing gas mixture and a combination of metals and ceramics. With such a choice, an additonal challenge is achieving the necessary speed to be able to resolve bunch-by-bunch luminosity data. We present the design, analysis and experimental results of the early demonstration tests of this device.  
TUPCH083 Time-resolved Spectrometry on the CLIC Test Facility 3 1205
 
  • T. Lefevre, C.B. Bal, H.-H. Braun, E. Bravin, S. Burger, R. Corsini, S. Doebert, C.D. Dutriat, F. Tecker, P. Urschütz, C.P. Welsch
    CERN, Geneva
 
  The high charge (>6microC) electron beam produced in the CLIC Test Facility 3 (CTF3) is accelerated in fully loaded cavities. To be able to measure the resulting strong transient effects, the time evolution of the beam energy and its energy spread must be measured with at least 50MHz bandwidth. Three spectrometer lines were installed all along the linac in order to control and tune the beam. The electrons are deflected by a dipole magnet onto an Optical Transition Radiation (OTR) screen, which is observed by a CCD camera. The measured beam size is then directly related to the energy spread. In order to provide time-resolved energy spectra, a fraction of the OTR photons is sent onto a multichannel photomultiplier. The overall set-up is described, special focus is given to the design of the OTR screen with its synchrotron radiation shielding. The performance of the time-resolved measurements are discussed in detail. Finally, the limitations of the system, mainly due to radiation problems, are discussed.  
TUPCH088 High Dynamic Range Beam Profile Measurements 1217
 
  • C.P. Welsch, E. Bravin, B. Burel, T. Lefevre
    CERN, Geneva
  • T. Chapman, M.J. Pilon
    Thermo, Liverpool, New York
 
  In future high intensity, high energy accelerators, beam loss has to be minimized to maximize performance and minimize activation of accelerator components. It is imperative to have a clear understanding of the mechanisms that can lead to halo formation and to have the possibility to test available theoretical models with an adequate experimental setup. Measurements based on optical transition radiation (OTR) provide an interesting opportunity for high resolution measurements of the transverse beam profile. In order to be applicable for measurements within the beam halo region, it is of utmost importance that a high dynamic range is covered by the image acquisition system. The existing camera system as it is installed in the CLIC Test Facility (CTF3) is compared to a step-by-step measurement with a photo multiplier tube (PMT) and measurements with a cooled charge injection device (CID) camera. The latter acquisition technique provides an innovative and highly flexible approach to high dynamic range measurements and is presented in some detail.  
TUPCH089 Investigations of OTR Screen Surfaces and Shapes 1220
 
  • C.P. Welsch, E. Bravin, T. Lefevre
    CERN, Geneva
 
  Optical transition radiation (OTR) has proven to be a flexible and effective tool for measuring a wide range of beam parameters, in particular the beam divergence and the transverse beam profile. It is today an established and widely used diagnostic method providing linear real-time measurements. Measurements in the CLIC Test Facility (CTF3) showed that the performance of the present profile monitors is limited by the optical acceptance of the imaging system. In this paper, two methods to improve the systems' performance are presented and results from measurements are shown. First, the influence of the surface quality of the OTR screen itself is addressed. Several possible screen materials have been tested to which different surface treatment techniques were applied. Results from the measured optical characteristics are given. Second, a parabolic-shaped screen support was investigated with the aim of providing an initial focusing of the emitted radiation and thus to reduce the problem of aperture limitation. Measured and calculated emission distributions are presented.