Performance of the PHENIX EM Calorimeter

The PHENIX Electromagnetic Calorimeter is a large 15,552 channel lead/scintillator sampling calorimeter based on the shish-kebab optical readout technique. In this report we summarize studies leading to an optimal design for measurement of photons and electrons in the 1 GeV momentum range within the high multiplicity environment expected for events at RHIC. Timing resolutions of /spl sim/100 ps and a sampling dominated energy resolution of 8% at 1 GeV are featured. We also present a novel scheme for monitoring gain and timing of our entire system. Test results with a 144 channel preproduction "super-module" exposed to electron and hadron beams at the AGS are described. The calorimeter is currently under construction in Russia and the US and will be fully installed at RHIC during 1998.