Author: Wootton, K.P.
Paper Title Page
TUPF18 Vertical Undulator Emittance Measurement: A Statistical Approach 543
 
  • K.P. Wootton, R.P. Rassool
    The University of Melbourne, Melbourne, Australia
  • M.J. Boland, B.C.C. Cowie, R.T. Dowd
    SLSA, Clayton, Australia
 
  Direct measurement of low vertical emittance in storage rings is typically achieved via interferometric techniques. Proof of low vertical emittance is demonstrated by the measurement of a null radiation field, which is also the crux of the vertical undulator emittance measurement. Here we present strategies to improve the sensitivity to low vertical emittance beams. We move away from photon spectrum analysis to a statistical analysis of undulator radiation, showing the measured increase in signal-to-background. Reproducing simulations of previous work, we demonstrate that photon beam polarisation extends the linearity of the technique by several decades in emittance. These statistical and polarisation improvements to the signal-to-background allow realistic measurement of smallest vertical emittance.  
poster icon Poster TUPF18 [2.090 MB]  
 
TUPF19 APPLE-II Undulator Magnetic Fields Characterised from Undulator Radiation 546
 
  • K.P. Wootton, R.P. Rassool
    The University of Melbourne, Melbourne, Australia
  • M.J. Boland, B.C.C. Cowie
    SLSA, Clayton, Australia
 
  The spatial profile of APPLE-II undulator radiation has been measured at high undulator deflection parameter, high harmonic and very small emittance. Undulators are typically designed to operate with small deflection parameter to push the fundamental mode to high photon energies. This unusual choice of parameters is desirable for measurement of vertical emittance with a vertical undulator. We present 1-D and 2-D measured profiles of undulator radiation, and show that this is reproduced in numerical models using the measured magnetic field of the insertion device. Importantly these measurements confirm that for these parameters, the spatial intensity distribution departs significantly from usual Gaussian approximations, instead resembling a double-slit diffraction pattern. This could be an important consideration for photon beamlines of ultimate storage ring light sources.  
poster icon Poster TUPF19 [2.364 MB]  
 
TUPF20 Low Noise and High Dynamic Range Optical Interferometer Beamsize Measurements 550
 
  • M.J. Boland
    SLSA, Clayton, Australia
  • T.M. Mitsuhashi
    KEK, Ibaraki, Japan
  • K.P. Wootton
    The University of Melbourne, Melbourne, Australia
 
  The technique of optical interferometry to measure beam sizes requires a low noise and high dynamic range digitisation system to push the performance to ultra low emittance on storage rings. The next generation of camera sensor Scientific CMOS (sCMOS) promises to provide the technology to improve optical interferometry. A series of measurements was performed on the Australian Synchrotron storage ring using a sCMOS and a intensity imbalance optical interferometer. The coupling in the storage ring was varied from maximum to minimum using the skew quadrupoles and the beam size at the optical diagnostic beamline was varied from over 100 microns to around 1 micron. A comparison is made between interferometer measurements using the sCMOS with and without an intensity imbalance and with previous measurements using a CCD system.