Novel Large Area High Resolution Neutron Detector for the Spallation Neutron Source

The Spallation Neutron Source (SNS) facility, due for completion at Oak Ridge National Laboratory in 2006, will push available thermal neutron flux at least an order of magnitude above that achievable at any other neutron science facility. The markedly increased deliverable flux imposes extreme requirements on imaging detectors at many of the target stations. This project will develop a new detector technology, based on the 10-boron thin-film conversion of neutrons and the detection of reaction products in the gas of a thin straw detector. By using dense packed arrays of such straws, which can be as long as 1 meter, efficient high-resolution imaging can be achieved, with a quantum leap in integral and differential counting rate. Phase I developed a 150-element sub-array of detectors with the full 1 meter length and the required depth for the SNS. The sub-array was configured so that a 1 meter square detector can be constituted by replicating the single sub-array. The sub-array was thoroughly tested in a thermal neutron beam to determine all operating specifications, including spatial resolution, differential and integral counting rate, gamma rejection, and neutron sensitivity. Phase II will design and construct a complete, 1 square meter, neutron imaging detector, which will provide an integral rate capability approaching 2 x 107 cps, a differential rate capability of at least 2000 cps per pixel, spatial resolution of 7 mm x 4 mm x 4 mm (depth encoded), sensitivity of 70% for thermal neutrons, and a capability of operating in gamma radiation fields approaching 1 R/hr. The device will be installed at an appropriate test site and thoroughly evaluated in an activity that simulates the demands of SNS operations. Commercial Applications and other Benefits as described by the awardee: The large area neutron detector for the SNS should benefit many fields, including, for example, the development of improved drug therapies and materials that are stronger, longer-lasting, and more impact-resistant. In addition to the SNS, the detector should find application in nuclear terrorism detection and nuclear waste remediation.