TUCC —  Contributed Talk in Tuesday-C   (02-Oct-12   13:50—15:50)
Electron Storage Ring as a Single Shot Linac Beam Monitor
  • Y. Shoji, K. Takeda
    LASTI, Hyogo, Japan
  • T. Asaka, Y. Minagawa, S. Suzuki, Y. Takemura
    JASRI/SPring-8, Hyogo-ken, Japan
  The SPring-8 linac has been operated as an injector to the electron storage ring, NewSUBARU. Because of the small acceptance of the ring, fine parameter tuning is required for the stable top-up injection. In that process, some single shot linac beam measurements were necessary to understand the shot-by-shot fluctuation of the injection efficiency. We used the electron ring itself as a linac beam monitor. The time-resolving visible light monitor in the ring records the profiles of the injected linac beam for many revolutions. The pulse width for the single rf bucket (500MHz) of the ring is normally 1 ns, which contains 3 linac bunches (2856MHz). The time profile in the ring gives the energy profile at after 1/4 of the synchrotron oscillation period. The spatial profile of several revolutions, recorded by a double-sweep streak camera or ICCD gated camera, gives a beam emittance of a single-shot. The streak camera enables the bunch by bunch measurement. The effective resolution depends on the beta function of the ring, which can easily be changed. For the vertical emittance, our spatial resolution of 0.3 mm FWHM at βy = 17 m was good enough to identify the quadrupole mismatch.  
Design and Expected Performance of the New SLS Emittance Monitor
  • N. Milas, M. Rohrer, A. Saa Hernandez, V. Schlott, A. Streun
    PSI, Villigen, Switzerland
  • Å. Andersson, J. Breunlin
    MAX-lab, Lund, Sweden
  The vertical emittance minimization campaign at SLS, realized in the context of the TIARA WP6, has already achieved the world's smallest vertical emittance of 0.9 pm in a synchrotron light source. The minimum value reached for the vertical emittance is only five times bigger than the quantum limit of 0.2 pm. However, the resolution limit of the present SLS emittance monitor has also been reached thus, to further continue the emittance minimization program the construction of an improved second monitor is necessary. In this paper we present the design and studies on the performance of this new monitor based on the image formation method using vertically polarized synchrotron radiation in the vis-UV spectral regimes. This monitor includes a new feature, providing the possibility of performing full interferometric measurement by the use of a set of vertical obstacles that can be driven on the light path. Simulations results are used to investigate the possible source of errors and their effects on imaging and the determination of the beam height. We also present the expected performance, in term of emittance accuracy and precision, and discuss possible design limitations.  
Measurement of Nanometer Electron Beam Sizes with Laser Interference using IPBSM
  • J.N. Yan
    University of Tokyo, Tokyo, Japan
  At ATF2, the Local Chromaticity Correction focusing scheme is to be verified through realizing its design vertical e- beam size (σy ) of 37 nm. The 'IPBSM', installed at ATF2's virtual IP, is the only existing beam size monitor capable of measuring σy < 100 nm, making it indispensable for ATF's goals and R&D at future LCs. This owes to a novel technique of colliding e- beam against laser interference fringes. σy is derived from the modulation depth of resulting Compton photons, which is large for small σy. The measurable range from O(10) nm ~ a few μm, is controlled by switching between laser crossing angles θ = 174° , 30°, and 2° - 8° . In early 2011, measuring σy < 300 nm was hindered by an immense earthquake and heavy signal jitters. The ensuing recovery and upgrades stabilized the laser system and improved resolution to 5%. In spring 2012, we commissioned advanced crossing angle modes by consistently measuring σy ≥ 150 nm. Our goals for the autumn 2012 run is to stably measure σy < 50 nm. Major hardware upgrades during the summer aim at more reliable alignment and optimization of specialized functions to suppress bias factors.