A Velocity-of-Light' Gas Cerenkov Calorimeter for the region beyond HF in CMS

A gas Cerenkov calorimeter for the very forward region of CMS beyond HF, 5<eta<7, looks promising as a rad-hard and inexpensive alternative to a quartz fiber calorimeter in the extremely high radiation environment near the beam. Using Xe gas at one atmosphere results in a Cerenkov photon yield four times higher than the yield from pure quartz. Using isobutane increases the yield by nearly a factor of three over Xe, and at pressure P the yield goes up like P. A particular design has been tested in the H4 beam at CERN in September 1999.