  A Ring Imaging \v{C}erenkov detector built for the BRAHMS experiment at the
Brookhaven RHIC is described. This detector has a high index of refraction gas
radiator. \v{C}erenkov light is focused on a photo-multiplier based photon
detector with a large spherical mirror. The combination of momentum and ring
radius measurement provides particle identification from 2.5 GeV/c up to 35
GeV/c for pions and kaons and well above 40 GeV/c for protons during runs that
had the radiator index of refraction set at $n-1=1700 \times 10^{-6}$.
