  The PHENIX collaboration has designed a conceptually new Hadron Blind
Detector (HBD) for electron identification in high density hadron environment.
The HBD will identify low momentum electron-positron pairs to reduce the
combinatorial background in the mass region below 1 GeV/c^2. The HBD shall be
installed in PHENIX during the 2007 physics run. The HBD is a windowless
proximity focusing Cherenkov detector with a radiator length of 50 cm, CsI
photocathode and three layers of Gas Electron Multipliers (GEM) for gas
amplification. Pure CF_4 serves both as a radiator and as a detector gas. The
radiation budget of the device is less than 3% of a radiation length.
