A High Efficiency GEM Neutron Detector for the SNS

72488-Current neutron detectors will not be able to adequately handle the expected instrument data rates at the DOE¿s new neutron beam research facilities, nor do they have sufficient position and time resolution. This project will develop a new class of neutron detectors that employ the gaseous electron multiplier (GEM). These detectors not only will have significantly better position and time resolution than current instruments, they also will be easier to build. In Phase I, a 10 cm x 10 cm, three-element prototype GEM neutron detector was fabricated and tested at a pulsed neutron source, in order to evaluate its efficiency, gamma sensitivity, and position and time resolution. Computational tools were developed to evaluate the secondary electron production of candidate neutron converter geometries. These accomplishments have led to changes in the fundamental geometry of the device. Phase II will develop single-module, double-sided GEM detectors with neutron converters fabricated as CsI-Gd-Kapton-Gd-CsI sandwiches. The design will improve detector efficiency while retaining the time-of-flight and position resolution advantages of the GEM. The device will be optimized by iterative fabrication and testing cycles using reactor- and spallation-source neutrons and offered as a stand-alone detector product. In addition, multiple double-sided GEM detector modules will be combined as a means of substantially improving the neutron detection efficiency. Commercial Applications and Other Benefits as described by awardee: The GEM neutron detector should find a market at neutron bean research installations worldwide. The device appears to be particularly well suited to the most demanding of detector applications at the Spallation Neutron Source at Oak Ridge National Laboratory. In addition, the device could be re-configured for other sources, say x-rays, by changing the central neutron-electron conversion element to a radiation-electron converter optimized for x-rays. Because these devices could be made economically in large sizes, it also is likely that they would find use in Homeland Security applications as efficient, large area radiation detectors.