Photo-electron and ionization chamber position monitors for CHESS

Abstract

In order to provide positional information of the CHESS (Cornell High Energy Synchrotron Source) photon beams, we have constructed two positionsensitive devices. The first, located approximately at the 7 m point in the ultra-high vacuum of CESR (Cornell Electron Storage Ring), is a split photoelectron detector. The second detector, which is located outside the CESR vacuum at approximately the 11 m point, will be in the helium-filled beam pipe. This is a split ionization chamber composed of two pairs of collector plates on either side of the 14 mrad beam. Positional sensitivity of the photoelectron monitor to better than 0.1 mm was demonstrated over a range of 2 mm.