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photon

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CT03 500 fs Streak Camera for UV-Hard X-Rays in 1 kHz Accumulating Mode with Optical 'Jitter Free' Synchronisation laser, accumulation, acceleration, optics 54
 
  • K. Scheidt, G.A. Naylor
    ESRF, The European Synchrotron Radiation Facility, Grenoble, France
  The development at the ESRF of a jitter-free, laser triggered Streak Camera has now yielded time resolution results as short as 460 fs while operating in accumulating mode. The so-called jitter-free synchronisation between the laser light and the Streak Camera is performed through a GaAs photo-switch in a simple HV circuit that connects directly to the Streak tube’s deflection plates. The novelty of this technique permits to obtain excellent dynamic range measurements in a shot-to-shot accumulation of ultra fast (laser stimulated) events at up to 1kHz without degrading the time resolution. Important insight was obtained on the quality of this optical synchronisation and its dependence on the laser characteristics, the switch circuit, and the structure of the GaAs switch itself. This permitted to suppress the jitter causes and today the 500 fs limitation is imposed by the streak tube’s intrinsic time resolution. This work was done by measuring (with Au or Pd photo-cathodes) the 3rd harmonic (i.e. 267 nm) of a 100 fs Ti:Saph laser. Also important progress was made with the reliability of the photo-switch and problems of HV break-down and structural degradation have been completely resolved. Since the principal use of this system at the ESRF is in ultra-fast X-ray diffraction experiments the exchangeable photo-cathode structure of this tube covers the entire UV-to-X-rays spectrum. The QE of various photo-cathode materials was measured in the 8-30 keV range.  
 
CT04 Bunch Length Measurements in LEP pick-up, synchrotron, impedance, monitoring 59
 
  • A.J. Burns, H. Schmickler
    CERN, Geneva, Switzerland
  For many years a streak camera has been used for observing the longitudinal distribution of the particles in any LEP e+ or e- bunch (5-50 ps r.m.s. length) on a turn by turn basis, using synchrotron light. In 1996, a comparison made with the longitudinal vertex distributions of 3 LEP experiments allowed the identification and elimination of certain systematic errors in the streak camera measurements. In 1997, a new bunch length measurement technique was commissioned that uses the high frequency slope of the bunch power spectrum from a button pickup. In 1998, this new method was confronted with measurements from the streak camera and the LEP experiments. The measurements made in 1996 and 1998 are presented, with emphasis on the calibration of the two instrumental methods and their respective precision and limitations.  
 
CT05 Daresbury SRS Positional Feedback Systems feedback, dipole, multipole, wiggler 64
 
  • S.L. Smith, S.F. Hill
    CLRC, Daresbury Laboratory, Warrington, UK
  The Daresbury SRS is a second generation synchrotron radiation source which ramps from its injection energy of 600 MeV to 2.0 GeV. Beam orbit feedback systems have been in routine operation on the SRS since 1994 and are now an essential element in delivering stable photon beams to experimental stations. The most recent enhancements to these systems have included the introduction of a ramp servo system to provide the orbit control demanded by the installation of two new narrow gap insertion device and development of the vertical orbit feedback system to cope with an increasing number of photon beamlines. This paper summaries the current status of these systems and briefly discusses proposed developments.  
 
CT12 Preliminary Test of a Luminescence Profile Monitor in the CERN SPS proton, vacuum, ion, injection 95
 
  • J. Camas, R.J. Colchester, G. Ferioli, R. Jung, J. Koopman
    CERN, Geneva, Switzerland
  In order to satisfy the tight emittance requirements of LHC, a non-intercepting beam profile monitor is needed in the SPS to follow the beam emittance evolution during the acceleration cycle from 26 to 450 GeV. Beyond 300 GeV, the synchrotron light monitor can be used. To cover the energy range from injection at 26 GeV to 300 GeV, a monitor based on the luminescence of gas injected in the vacuum chamber has been tested and has given interesting results. This monitor could also be used in LHC, where the same problem arises. Design and results are presented for the SPS monitor.  
 
PS19 Photon counting detectors for fill structure measurements at visible wavelengths storage-ring, single-bunch, diagnostics, electron 144
 
  • H.L. Owen
    CLRC, Daresbury Laboratory, Warrington, UK
  When making accurate measurements of the relative populations of electron bunches in a storage ring, notably in light sources operating with only a single bunch filled, the method of time-correlated single photon counting gives the greatest dynamic range. The timing resolution and background noise level of the photon detector employed is critically important in determining the overall performance of the system; hitherto the best performance has been obtained detecting X-ray photons using avalanche photodiodes. On the SRS at Daresbury a visible light diagnostic station offers greater ease of access to instrumentation and operational advantages. A review is given of the detector types which have been employed, and the performances which can be obtained using visible light.