The BaBar cesium iodide electromagnetic calorimeter

The BABAR Cesium Iodide Electromagnetic Calorimeter is currently in the technical design stage. The calorimeter consists of approximately 10,000 individual thallium-doped cesium iodide crystals arranged in a near-hermetic barrel and endcap structure. Taking previous cesium iodide calorimeters as a benchmark, we hope to build a system with roughly two times better energy resolution. This will be achieved by a combination of high quality crystal growing, precision mechanical processing of crystals and support structure, highly efficient light collection and low noise readout electronics. The calorimeter described here represents the current state of the design and we are undertaking an active period of optimization before this design is finalized. We discuss here the physics motivation, the current design and options for optimization.