• S.M. Gierman, P.R. Bolton, W.J. Corbett, G.R. Hays, F. King, R.E. Kirby, J.F. Schmerge, J.J. Sebek
  SLAC, Menlo Park, California

Funding: Supported by US DOE under contract DE-AC03-76SF00515.

The Stanford Synchrotron Radiation Laboratory operates a thermionic radio-frequency gun as part of its injector for the SPEAR 3 storage ring. In order to generate the high bunch charge required for top-off injection, it may be advantageous to operate the thermionic cathode as a photo-emitter. In this note we report on measurements of the wavelength dependence of the quantum efficiency of a tungsten dispenser cathode in a low-field environment, and on high-power tests of the injector in photoemission mode.

• J.A. Safranek, W.J. Corbett, X. Huang, J.J. Sebek
  SLAC, Menlo Park, California
• W.X. Cheng
  BNL, Upton, Long Island, New York

Funding: Work supported by the US Department of Energy, Office of Basic Energy Sciences.

In the past, SPEAR3 has had typically 50 to 70% injection efficiency. Much of the lost injected beam hit the small gap vacuum chambers at the insertion devices. We are now implementing injection with photon beamline shutters open, so these losses create Bremsstrahlung down the photon beamlines, increasing radiation levels on the photon experimental floor. In this paper, we describe work done to better control the booster to SPEAR (BTS) transport line beam so as to reduce losses during injection. We have used new BTS BPM electronics to control the transport line trajectory. The trajectory response on these BPMs has been used to correct the BTS optics. We use turn-by-turn BPM readings of the injected beam in SPEAR to optimize the BTS trajectory in all six transverse and longitudinal coordinates. We use turn-by-turn profile measurements of the injected beam to verify the BTS optics correction. The stainless steel windows have been removed from the BTS vacuum system to reduce the transverse dimensions of the injected beam.

• W.J. Corbett, W.X. Cheng, X. Huang
  SLAC, Menlo Park, California

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

Recent experimental results and advances in the theory of short-bunch dynamics have lead to an improved understanding of the parameters and limitations of short-bunch operation in storage rings. In this paper the measurement and analysis of short bunches under a variety of operational parameters is reported for SPEAR3.

• J.A. Safranek, W.J. Corbett, X. Huang, J.J. Sebek, A. Terebilo
  SLAC, Menlo Park, California

Funding: Work supported by the US Department of Energy, Office of Basic Energy Sciences.

We present nonlinear dynamics measurements and tracking for the SPEAR3 storage ring. SPEAR3 does not have a vertical pinger magnet, so we have developed a method of measuring (x, y) frequency maps by exciting vertical oscillations using a strip line driven with a swept frequency. When the vertical oscillations reach the desired amplitude, the drive is cut, and an injection kicker excites horizontal oscillations. The subsequent free horizontal and vertical betatron oscillations are digitized turn-by-turn. We have used measured and tracked frequency maps in (x, y) and (x, energy) to characterize and optimize the dynamic aperture, injection and lifetime of the SPEAR3 low emittance optics.

• 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.