Scintillating materials are commonly used in radiation detectors. Such materials typically indicate the presence of a neutron flux by the emission of scintillation photons. Recent developments have allowed these scintillating materials to be drawn into optical fibers. The light-guide property of the fiber collects the scintillation light generated over the entire length of the fiber and delivers it to the fiber end facets, where it is gathered for analysis in photomultiplier tubes. A fiber-optic scintillation detector typically allows for the creation of a relatively inexpensive, robust, and versatile large-area radiation detector.
Many fiber-based scintillation neutron detectors contain layers of closely-packed fibers for planar coverage. However, in this configuration, a Compton electron (which may be generated from a gamma ray) may cross through multiple fibers in the fiber bundle. While the scintillation light generated by the Compton electron in a single fiber is small, the total scintillation light accumulated in the fiber bundle is often large enough to mimic a neutron event. Thus, this configuration suffers from a poor ability to reject gamma rays, which interfere with the neutron signal. In fact, the ability to reject gamma rays when the fibers are closely packed in a bundle compares unfavorably with competing technologies.
The gamma rejection ratio of these closely-packed fiber-based scintillation neutron detectors can be increased as high as approximately 104:1, but at the cost of added system complexity and reduced neutron sensitivity. Alternatively, electronic logic circuitry may be employed in these detectors to distinguish neutron-induced scintillation light from that induced by other events, such as the presence of gamma rays. However, such an approach again increases the system's cost and adds to its complexity.
A variety of approaches have been employed in a variety of different contexts in an attempt to separate individual fibers in order to optimize the detection of neutrons. The materials employed to separate the fibers in these previous approaches have, however, proved ineffective at or inappropriate for increasing the gamma rejection ratio.
As such, needs exist for an improved fiber-based scintillation neutron detector.