Design and Performance of a Broad Band Focusing Cherenkov Counter

We have designed and constructed a broad band (.95<ß<1.00) focusing Cherenkov counter with large angular acceptance (±40) for use in particle identification in a double armed spectrometer experiment at the Brookhaven National Laboratory AGS. To achieve this large angular acceptance while maintaining a resolution in particle velocity of ¿ß~.015 we have employed a new method of light collection. This light collection scheme will be discussed and general applications of this method to improve the velocity resolution of existing differential Cherenkov counters will be presented.