High Spatial Resolution Detectors for Single Crystal Diffractometers

Proportional Technologies, Inc. PTI) proposes the development of a neutron detector based on boron-coated rectangular channels, to satisfy the requirements of single crystal diffractometers, like MaNDi and TOPAZ at the SNS. Detectors for these instruments require high spatial resolution on the order of 300-600 μm, efficiencies greater than 60% at 1Å, gamma rejection on the order of 10-6 or better, and count rate capability of 100 kcps. Additionally, the detectors should allow near 4π coverage with minimal dead area, and little parallax. PTI will develop a boron-coated structure that satisfies the above requirements in a close-packed array of rectangular cells, sealed inside a single thin Al housing. Each cell will be fabricated by squashing a round boron-coated straw BCS) into a rectangular shape, lined on all 4 sides with enriched boron carbide 10B4C). Cell dimensions will be 0.5 mm  2.5 mm  150 mm. A 3006 array of cells will form a 150150 mm2 detector panel. Resistive wires tensioned at the center of each cell will be read out individually, in order to decode the cell ID. Charge division will be used to decode the event position along the length of the wire. The array will be oriented such that neutrons are incident at an angle θ=11.3. This angle, equal to the arctangent of the cell dimensions ratio, θ=arctan0.5/2.5), ensures that neutrons always traverse one long side of the cell they hit. Thus, they go through the 2 coating layers of that side at a very steep angle. The detection efficiency of a 6 layer-deep array, will reach 61% for 1-Å neutrons. The array will have a gamma discrimination on the order of 10-7, previously demonstrated in BCS detectors, and fast signals of 100 ns, for a count rate capability of 1000 kHz. If our proposed SBIR project objectives meet the challenge, society will benefit from inexpensive, high sensitivity panels for use in Single Crystal Spectrometers at SNS as well as around the world. The increased speed of completion and quality of crystal studies is expected to provide great public benefit in diverse fields ranging from superconductivity to effective development of new drugs for cancer treatment.