• K.J. Bertsche, R.C. Field, A.S. Fisher, M.K. Sullivan
  SLAC, Menlo Park, California
• A. Drago
  INFN/LNF, Frascati (Roma)

Funding: Work supported by the Department of Energy under contract number DE-AC03-76SF00515.

We present a possible design for a fast luminosity feedback for the Super-B Interaction Point (IP). The design is an extension of the fast luminosity feedback installed on the PEP-II accelerator. During the last two runs of PEP-II and BaBar (2007-2008), we had an improved luminosity feedback system that was able to maintain peak luminosity with faster correction speed than the previous system. The new system utilized fast dither coils on the High-Energy Beam (HEB) to independently dither the x position, the y position and the y angle at the IP, at roughly 100 Hz. The luminosity signal was then read out with three independent lock-in amplifiers. An overall correction was computed based on the lock-in signal strengths and beam corrections for position in x and y and in the y angle at the IP were simultaneously applied to the HEB. With the 100 times increase in luminosity for the SuperB design, we propose using a similar fast luminosity feedback that can operate at frequencies between DC and 1 kHz, high enough to be able to follow and nullify any vibrational beam motion from the final focusing magnets.

• W.X. Cheng, W.J. Corbett, A.S. Fisher, X. Huang, J.A. Safranek, A. Terebilo
  SLAC, Menlo Park, California
• W.Y. Mok
  Life Imaging Technology, Palo Alto, California

Funding: Work sponsored by U.S. Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences.

An intensified, fast-gated CCD camera was recently installed on the visible diagnostic beam line in SPEAR3. The ~2nS electronic gate capability, ability to make multiple-exposure images and to acquire sequences of images provides good diagnostic potential. Furthermore, the addition of a rotating mirror just upstream of the photocathode provides the ability to optically ‘streak’ multiple images across the photocathode. In this paper, we report on several fast-gated camera studies including (1) resonant excitation of vertical bunch motion, (2) imaging of the injected beam with and without emittance-spoiling windows in the upstream transfer line, (3) injection kicker tuning to minimize perturbations to the stored beam and (4) images of short-bunch ‘bursting’ in the low momentum-compaction mode of operation.

• W.J. Corbett, W.X. Cheng, A.S. Fisher, E. Irish
  SLAC, Menlo Park, California
• T.M. Mitsuhashi
  KEK, Ibaraki
• W.Y. Mok
  Life Imaging Technology, Palo Alto, California

Funding: Work sponsored by U.S. Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences.

A two-slit interferometer has been installed in the SPEAR3 diagnostic beam line to measure vertical beam size at a dipole source point. The diagnostic beam line accepts unfocused, visible light in a 3.5 x 6.0 mrad aperture so that at the slit location 17 m from the source, the vertical extent of the beam is 100mm. For typical source sizes of sigy~15 um (0.1% emittance coupling) a slit separation of 80 mm produces fringe visibility of order V=0.5. Hence a significant plot of fringe visibility vs. slit separation can be generated to infer source size via Fourier transformation. In this paper we report on the interferometer construction, beam size measurement and potential deficiencies of the system, and compare with theoretical results.