AVALANCHE PHOTODIODES FOR SCINTILLATING FIBER DETECTORS

A HIGH SPEED, HIGH SENSITIVITY AVALANCHE PHOTODIODE (APD) ARRAY IS BEING INVESTIGATED TO MEET THE STRINGENT REQUIREMENTS OF DETECTORS FOR HIGH ENERGY PHYSICS EXPERIMENTS SUCH AS THE CENTRAL TRACKER VERTEX DETECTOR AND CALORIMETERS WHICH ARE BEING DESIGNED FOR EXISTING AND PROPOSED PARTICLE PHYSICS DETECTORS. THESE DETECTORS WILL HAVE UNPRECEDENTED PERFORMANCE CHARACTERISTICS TO BE USED AS READOUTS FOR THE VERY LOW LIGHT LEVELS PRODUCED IN SCINTILLATING PLASTIC FIBERS WHICH RESULT FROM CHARGED PARTICLE INTERACTIONS AT VERY HIGH RECYCLE RATES. THE APPROACH TAKEN IS TO MODIFY EXISTING APD DESIGNS TO YIELD A DEVICE WITH LOWER DARK CURRENT, INCREASED SENSITIVITY AT SHORT WAVELENGTHS, AND FASTER CYCLE TIMES WHEN OPERATED IN THE SINGLE PHOTON GEIGER MODE. CONSIDERATION WAS GIVEN TO ADAPTABILITY OF THE APD TO ACTIVE QUENCHING CIRCUITRY. CONSTRUCTING HIGH GAIN DEVICES THAT FULFILL DETECTOR NEEDS FOR PROPORTIONAL MODE OPERATION SUCH AS THOSE REQUIRED FOR HIGH DYNAMIC RANGE CALORIMETRY MEASUREMENTS IS ALSO BEING INVESTIGATED. THE DATA GATHERED DURING THIS WORK WILL BE USED TO PRODUCE AN APD ARRAY WITH THE REQUIRED COMBINATION OF CHARACTERISTICS TO BE USED IN HIGH SPEED, LOW LIGHT LEVEL APPLICATIONS ENVISIONED AT MODERN DETECTORS SUCH AS THE SSC, DO AT FERMILAB, AND L3 AT CERN.