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.Comment: 26 pages, 13 figure
A new primary mirror for a visible-light beam size monitor (vBSM) was designed and installed in the Cornell Electron-Positron Storage Ring (CESR). The vertical angular acceptance of the mirror was doubled to allow double-slit interferometry with large slit separation (>12 mm). In addition, the diffraction associated with the first generation mirror has been eliminated. The resolution of the vertical beam size measurements has been dramatically improved but is ultimately limited by the beam motion. Two fast-response detectors, a Photomultiplier Tube (PMT) array and a gated camera, were employed to study the beam motion. The advantages and limitations of both devices are discussed in this paper. The gated camera was also used to measure single-shot beam width and motion of each bunch in a multi-bunch train. We measured significantly more horizontal motion of electron as compared to positron bunch trains in otherwise identical machine condition. This difference may be a signature for the difference between electron cloud build-up for positron bunch trains versus ions effects characteristic of electron bunch trains.
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