High-performance, imaging, thermal neutron detectors

Existing and planned spallation neutron sources require two-dimensional detectors for many experiments. Unlike the requirements for steady-state neutron sources, it is essential that these detectors possess good time resolution to determine neutron energy. A range of detectors based on gas proportional chambers, with low-noise encoding electronics, has been fabricated at this laboratory, with properties well suited for use at spallation sources. These high-performance detectors possess outstanding qualities in terms of dynamic range and stability of both recorded neutron positions and response (efficiency), in addition to normal attributes such as good position resolution, high detection efficiency and insensitivity to γ-rays. We review here some of the major characteristics of the detectors, describe recent advances, and illustrate their high level of performance with neutron scattering results. While relatively few such detectors are required world wide, specialized efforts are required for their development. The additional opportunities provided by new spallation sources will need continued advances in detector performance. (author)