An Ionization Profile Monitor for the Brookhaven AGS

A non-destructive internal emittance device has been built for the AGS, with separate units to measure the horizontal and vertical profiles of the circulating beam. Positive ions from collisions of the beam with background gas are collected in a 3-kV/cm electric field onto a 64-channel parallel strip detector. Because positive ions rather than electrons are collected, profile broadening due to space charge is small. Tests indicate that a quantitative, reproducible and accurate measurement of beam size throughout the acceleration cycle is provided.