Visible-light beam size monitors using synchrotron radiation at CESR

Abstract

A beam profile monitor utilizing visible synchrotron radiation (SR) from a bending magnet has been designed and installed in Cornell Electron-Positron Storage Ring (CESR). The monitor employs a double-slit interferometer to measure both the horizontal and vertical beam sizes over a wide range of beam currents. By varying the separation of the slits, beam sizes ranging from 50 to 500 um can be measured with a resolution of approximately 5 um. To measure larger beam size (> 500 um), direct imaging can be employed by rotating the double slits away from SR beam path. By imaging the pi-polarized component of SR, a small vertical beam size (~70 um) was measured during an undulator test run in CESR, which was consistent with the interferometer measurement. To measure the bunch length, a beam splitter is inserted to direct a fraction of light into a streak camera setup. This beam size monitor measures the transverse and longitudinal beam sizes simultaneously, which is successfully used for intrabeam scattering studies. Detailed error analysis is discussed.