Radiation Hard Detector Array for Visible Light, Gamma Rays and

NEW TECHNOLOGIES ARE REQUIRED FOR THE DETECTION AND IMAGING OF VISIBLE LIGHT, GAMMA RAYS AND NEUTRONS IN HIGH RADIATION ENVIRONMENTS SUCH AS THOSE ENCOUNTERED IN SPACE. CURRENTLY AVAILABLE, CRYSTALLINE SILICON DETECTOR ARRAYS SUCH AS CHARGE COUPLED DEVICES (CCD) ARE EXTREMELY SUSCEPTIBLE TO RADIATION DAMAGE AND A FEW KILORADS OF HIGH ENERGY PROTONS CAN SERIOUSLY DEGRADE PERFORMANCE IN A MATTER OF WEEKS OR MONTHS. NEWLY DEVELOPED, HYDROGENATED AMORPHOUS SILICON (a-Si:H) PIXEL ARRAYS HOLD GREAT PROMISE FOR IMAING APPLICATIONS IN HIGH RADIATION ENVIRONMENTS. RECENT RESEARCH HAS SHOWN THAT MOSFET'S MADE WITH a-Si CAN WITHSTAND 5 MRAD OF GAMMA RAYS AND ARE AT LEAST 25 TIMES LESS SENSITIVE TO GAMMA RAYS THAN SIMILAR CRYSTALLINE SILICON DEVICES. OTHER RESEARCH HAS SHOWN THAT PROTOTYPE a-Si:H PIXEL ARRAYS CAN WITHSTAND 10oC RADS OF HIGH ENERGY PHOTONS WITH ONLY A 1.3% DROP IN SIGNAL OUTPUT. THIS DAMAGE CAN BE COMPLETELY REVERSED WITH MODEST HEATING TO 130oC. THESE ARRAYS CAN BE SUITABLE SCINTILLATOR, USED FOR IMAGING EITHER GAMMA RAYS OR FAST NEUTRONS. A PHASE I PROGRAM IS PROPOSED THAT WILL QUANTIFY THE IMAGING CAPABILITIES OF A PROTOTYPE a-Si:H PIXEL ARRAY FOR VISIBLE LIGHT, GAMMA RAYS AND FAST NEUTRONS. THE RADIATION HARDNESS OF THE PIXEL COMPONENTS WITH REQUEST TO HIGH ENERGY PROTONS AND ELECTRONS WILL ALSO BE EVALUATED. 219 SENSORS ASSOCIATED WITH AERLY-WARNING SYSTEMS MUST DETECT BALLISTIC MISSILES, WHICH APPEAR AS MOVING POINT TARGETS. TRACKING TECHNIQUES BASED ON CONVENTIONAL SIGNAL OR IMAGE PROCESSING ALGORITHMS REQUIRE SIGNIFICANT COMPUTATIONAL RESOURCES, PROVIDED BY DIGITAL PROCESSORS THAT ARE REMOTE FROM THE FOCAL PLANE. WE PROPOSE HERE A NOVEL METHOD FOR MOTION DETECTION THAT CAN BE IMPLEMENTED ON-BOARD THE FOCAL PLANE. THIS METHOD, CALLED THE WAVE PROCESS, IS A VELOCITY BANDPASS FILTER FOR TWO-DIMENSIONAL STARING MOSAIC FOCAL PLANES DETECTING MOVING POINT TARGETS. IT IS RESILIENT TO BACKGROUND VARIATIONS, PLATFOR JITTER, AND SLIGHT CHANGES IN TARGET SPEED AND DIRECTION. IT IS A DISTRIBUTED ARCHITECTURE, ALLOWING IT TO IDENTIFY MANY SIMULTANEOUS REGIONS OF MOTION WITHOUT SUFFERING A SLOWDOWN. IT IS EFFICIENTLY IMPLEMENTED IN SUBTHRESHOLD VLSI WHICH ALLOWS ON-FOCAL-PLANE APPLICATION REDUCING SYS