Hadron Blind Detector for the PHENIX Experiment at RHIC
  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. 
A. Milov (for the PHENIX Collaboration)