Author: Fiorito, R.B.
Paper Title Page
MOPG58 Coherent Diffraction Radiation Imaging Methods to Measure RMS Bunch 198
  • R.B. Fiorito, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • C.I. Clarke, A.S. Fisher
    SLAC, Menlo Park, California, USA
  • A.G. Shkvarunets
    UMD, College Park, Maryland, USA
  The measurement of the RMS bunch length with high resolution is very important for latest generation light sources and also a key parameter for the optimization of the final beam quality in high gradient plasma accelerators. In this contribution we present progress in the development of novel single shot, RMS bunch length diagnostic techniques based on imaging the near and far fields of coherent THz diffraction radiation (CTHzDR) that is produced as a charged particle beam interacts with a solid foil or an aperture. Recent simulation results show that the profile of a THz image of the coherent point spread function (CSF) of a beam whose radius is less than the PSF, i.e. the image produced by a single electron, is sensitive to bunch length and can thus be used as a diagnostic. The advantages and disadvantages of near field and far field imaging are examined and the results of a recent high energy (20 GeV) CTHzDR experiments at SLAC/FACET are presented. Plans for experiments to further validate and compare these imaging methods for both moderate and high energy charged particle beams are also discussed.  
poster icon Poster MOPG58 [1.067 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-MOPG58  
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WEPG80 Optical Effects in High Resolution and High Dynamic Range Beam Imaging Systems 844
  • J. Wolfenden, R.B. Fiorito, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • M. Bergamaschi, R. Kieffer, T. Lefèvre, S. Mazzoni
    CERN, Geneva, Switzerland
  • P. Karataev, K.O. Kruchinin
    JAI, Egham, Surrey, United Kingdom
  Optical systems are used to transfer light in beam diagnostics for a variety of imaging applications. The effect of the point spread function (PSF) of these optical systems on the resulting measurements is often approximated or misunderstood. It is imperative that the optical PSF is independently characterised, as this can severely impede the attainable resolution of a diagnostic measurement. A high quality laser and specially chosen optics have been used to generate an intense optical point source in order to accomplish such a characterisation. The point source was used to measure the PSFs of various electron-beam imaging systems. These systems incorporate a digital micro-mirror array, which was used to produce very high (>105) dynamic range images. The PSF was measured at each intermediary image plane of the optical system; enabling the origin of any perturbations to the PSF to be isolated and potentially mitigated. One of the characterised systems has been used for optical transition radiation (OTR) measurements of an electron beam at KEK-ATF2 (Tsukuba, Japan).  
poster icon Poster WEPG80 [1.851 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG80  
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