  The resolution of a conventional telescope used to image visible-light
synchrotron radiation is often limited by diffraction effects. To improve
resolution, the double-slit interferometer method was developed at KEK and has
since become popular around the world. Based on the Van Cittert-Zernike theorem
relating transverse source profile to transverse spatial coherence, the
particle beam size can be inferred by recording fringe contrast as a function
of interferometer slit separation. In this paper, we describe the SPEAR3
double-slit interferometer, develop a theoretical framework for the
interferometer and provide experimental results. Of note the double-slit system
is 'rotated' about the beam axis to map the dependence of photon beam coherence
on angle.

Accelerator Physics;High Energy Physics - Experiment