Calorimeter

calorimeter design for GLAST produces flashes of light that are used to determine how much energy is in each gamma-ray. A calorimeter ("calorie-meter") is a device that measures the energy (heat: calor) of a particle when it is totally absorbed. CsI(Tl) bars, arranged in a segmented manner, give both longitudinal and transverse information about the energy deposition pattern. Once a gamma ray penetrates through the anticoincidence shield, the silicon-strip tracker and tungsten converter planes, it then passes into the cesium-iodide calorimeters. This causes a scintillation reaction in the cesium-iodide, and the resultant light flash is photoelectrically converted to a voltage. This voltage is then digitized, recorded and relayed to earth by the spacecraft's onboard computer and telemetry antenna. Cesium-iodide blocks are arranged in two perpendicular directions, to provide additional positional information about the shower.