In this article, construction, operation, and performance of the RICH detector of Fermilab experiment 781 (SELEX) are described. The detector utilizes a matrix of 2848 phototubes for the photocathode to detect Cherenkov photons generated in a 10 m neon radiator. For the central region an N0 of 104 cm-1, corresponding to 13.6 hits on a β = 1 ring, was obtained. The ring radius resolution measured is 1.6%25.
