A BEAM INTENSITY PROFILE MONITOR BASED ON SECONDARY-ELECTRON EMISSION

Two dual function intensity profile monitors have been designed for a measurement of parity violation in right arrow over p-p scattering at about 230 MeV using longitudinally polarized protons. Each device contains a set of split secondary electron emission (SEM) foils to determine the median of the beam current distribution (in x and y). The split foils, coupled through servoamplifiers and operational amplifiers to upstream aircore steering magnets, have demonstrated the ability to hold the beam position stable to +/- 5-mu-m for beam position fluctuations up to 1000 Hz. These monitors also contain a set of foil strip planes giving information on the intensity distribution projected onto the two orthogonal axes, x and y. Data were acquired using 0.008 mm thick, 0.90 mm wide aluminum foil strips at 1.00 mm centers. The foil strip planes were able to determine the beam centroid to within +/- 3-mu-m after one hour of data taking with a 100 nA, 15 mm FWHM Gaussian beam.