Developments in OTR/ODR Imaging Techniques for 7-GeV Electron Beams at APS

We have continued our investigations on imaging 7-GeV electron beams in a transport line at the Advanced Photon Source (APS) using optical transition radiation (OTR) and optical diffraction radiation (ODR) emitted from an Al blade. In our experiments appreciable visible wavelength ODR is emitted for impact parameters of 1 to 2 mm, values that are close to /2. We have now upgraded our imaging system to include an optical transport that provides either near-field or far-field imaging, and we have performed initial experiments. The OTR far-field images indicate that beam divergence effects at the 30-70 microrad regime are detectable, and these are some of the first recorded for this regime. An analytical model predicts beam-size sensitivity in the 20-50 micron regime, while beam position resolution to 10 microns with a smaller beam and higher optical magnification should be feasible with near-field ODR imaging. Although originally developed to support top-up operations at APS, the ODR imaging techniques for nonintercepting relative beam size and position monitoring should also be applicable to high-energy accelerator beams that drive x-ray FELs, energy-recovering linacs for light sources, and the proposed ILC.