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Novel Avalanche Photodiode Arrays for Scintillating Fiber Readout--Radiation Monitoring Devices, Inc., 44 Hunt Street, Watertown, MA  02472-4699; 617-926-1167

Dr. Michael R. Squillante, Principal Investigator, msquillante@rmdinc.com 

Dr. Gerald Entine, Business Official, gentine@rmdinc.com 

DOE Grant No. DE-FG02-00ER83085

Amount:  $750,000

High energy physics is replete with complex detector systems that record interaction positions, energy deposition, and timing information from thousands of individual elements.  Fiber optic tracking is a potentially simpler and less expensive method for large volume detectors that use conventional photomultiplier tubes coupled to scintillators.  The key technology that needs to be linked to these trackers is a compact, high density photodetector that can provide sufficient readout of low light signals.   This project will adapt a benchmark avalanche photodiode (APD) technology to the precise requirements found only in high energy physics.  To accomplish this, small, sub-millimeter pixilated arrays must be fabricated, radiation hardness must be improved, lower noise thresholds must be reached, and quantum efficiency must be maximized.  The planar processed APD arrays produced in Phase I met or exceeded all expectations.  Multielement APD arrays with small pixels (< 1mm²) were couple to fibers and evaluated for gain, noise, cross-talk, and detection efficiency.   Crucial tests of radiation hardness validated that the arrays can withstand fluences of 10¹² n/cm² without degradation.  Phase II will produce larger arrays, integrate packaging, continue the evaluation of radiation hardness, and add pulse processing electronics.  A prototype system to more fully demonstrate the technology will be designed.  

Commercial Applications and Other Benefits as described by the awardee: Combined fiber optic/APD detectors will largely remain in the realm of high energy physics, but many more applications are available for the APD arrays themselves.  As radiation detectors (and combined with scintillators), position sensitive APDs should find use in other scientific disciplines and in medical imaging.  As purely optical detectors, the low light levels that APDs can record make them an attractive alternative to photomultiplier tubes in a whole host of photonic devices (LIDAR, LADAR, spectrometers, etc.).