DEVELOPMENT OF INSTRUMENTATION FOR IMAGING SCATTERED COLD NEUTRONS AND X-RAYS

THE LONG RANGE STRUCTURE OF MATERIALS IS CURRENTLY BEING STUDIED USING SMALL ANGLE SCATTERING OF SLOW ("COLD") NEUTRONS AND X-RAYS. LOCAL ORDER IS STUDIED BY DIFFRACTION.WITH THE ADVENT OF STRONGER SOURCES OF COLD NEUTRONS, AND THE CURRENT SITUATION WITH X-RAY SOURCES, THERE IS A NEED FOR MUCH HIGHER SPEED OF RESPONSE IN LARGE AREA ARRAYS. PRESENT ION-CHAMBER WIRE ARRAYS ARE LIMITED TO ABOUT 40,000 CTS/S TOTAL WITH 10% DEADTIME. RATIOS OF 10,000 IN COUNT RATE BETWEEN PEAK AND BACKGROUND RATES ARE NEEDED IN MANY EXPERIMENTS. OBTAINING 100,000 CTS/S PER PIXEL, WITH LITTLE CROSS-TALK, WOULD "AMOUNT TO A REVOLUTION IN COLD-NEUTRON PHYSICS". CURVED DETECTORS ARE IMPRACTICAL WITH STRETCHED WIRES. THE USE OF SEMICONDUCTOR SUB-ARRAYS, 5 CM SQUARE, WITH 5 MM SQUARE ELEMENTS, WOULD ALLOW SUBSTANTIALLY SPHERICAL ARRAY SYSTEMS. THE PRESENT PROJECT WOULD DEVELOP FAST, EFFICIENT SUB-ARRAYS COMPRISING A CONVERTER LAYER WITH 100 DETECTORS, 100 AMPLIFIER CHAINS AND100 SCALER/READOUT REGISTERS LOCATED ON A FEW SLICES OF SILICON. THE PRESENT PROPOSAL WILL TEST THE DETECTOR PORTION OF THE SYSTEM AND STUDY THE FEASIBILITY OF THE COMPLETE SYSTEM. THE PROPOSER BELIEVES THIS APPROACH IS TECHNICALLY FEASIBLE AND MAY WELL BE ECONOMICALLY VIABLE.