Author: Tian, K.
Paper Title Page
MOPPR001 Resonant Spin Depolarisation Measurements at the SPEAR3 Electron Storage Ring 771
  • K.P. Wootton, R.P. Rassool
    The University of Melbourne, Melbourne, Australia
  • M.J. Boland, Y.E. Tan
    ASCo, Clayton, Victoria, Australia
  • W.J. Corbett, M.H. Donald, X. Huang, R.R. Ortiz, J.A. Safranek, K. Tian
    SLAC, Menlo Park, California, USA
  Accurate electron beam energy measurements are valuable for precision lattice modelling of high-brightness light sources. At SPEAR3 the beam energy was measured using the resonant spin depolarisation method with striplines to resonantly excite the spin tune and a sensitive NaI scintillator beam loss monitor was used to detect resulting changes in Touschek lifetime. Using the combined apparatus an electron beam energy of 2.997251(7) GeV was measured, giving a relative uncertainty better than 3x10-6. The measured momentum compaction factor was found to be in close agreement with the numerical model value using rectangular defocussing gradient dipoles with measured magnetic field map profiles. In this paper we outline the chosen experimental technique, with emphasis on its applicability to electron storage rings in general.  
WEOAA01 Injected Beam Imaging at SPEAR 3 with a Digital Optic Mask 2116
  • H.D. Zhang, R.B. Fiorito, A.G. Shkvarunets
    UMD, College Park, Maryland, USA
  • W.J. Corbett, A.S. Fisher, K. Tian
    SLAC, Menlo Park, California, USA
  Funding: *This work is partially funded by the Office of Naval Research and the DOD Joint Technology Office.
At SPEAR3, the light source operates in top-up injection mode with 273nC charge circulating in the storage ring (350mA). Each individual injection pulse contains only 40pC, or a contrast ration of 1:6800. In order to monitor injected beam dynamics during User operations, it is desirable to optically image the injected charge distribution on a turn-by-turn basis in the presence of the bright stored beam. The measurement is made by re-imaging visible synchrotron radiation onto a 1024x768 pixel Digital-Micro-Array mirror device (DMD) which is used to 'mask' light from the central stored beam while observing the weak injected beam signal on an intensified, fast-gated CCD camera. Complex beam dynamics are observed after only a few 10's of turns around the synchrotron. In this paper we report on the DMD optical configuration, masking considerations, measurement timing and initial tests imaging the injected beam in the presence of stored beam.
slides icon Slides WEOAA01 [1.874 MB]