Neutron detectors are used in a variety of applications, such as particle physics experiments, instrumentation at nuclear reactors, radiation safety, cosmic ray detection, and border security. Accurate detection of neutrons and their corresponding kinetic energy can be difficult since neutrons have no charge. This makes it difficult to direct neutrons toward a detector to facilitate detection. Neutrons also do not ionize atoms directly, so gaseous ionization detectors are usually ineffective. Additionally, there is typically a relatively high level of background noise. The main component of background noise in neutron detection is high-energy photons. It can be difficult to determine in certain types of detectors whether neutrons or photons are being detected. Both register similar signals after interacting in the detector.
Homogenous capture-gated neutron spectrometers have been utilized for several years. Homogeneous detectors are composed of a single, uniform mixture of appropriate chemicals that include a hydrogenous scintillator and a high-capture-cross-section component that provides the neutron-capture signal. A typical capture material consists of boron enriched in the B-10 isotope.
Heterogeneous capture-gated neutron spectrometers offer several advantages over the homogeneous class of spectrometers. However, heterogeneous detectors are typically composed of relatively expensive materials. A typical heterogeneous detector contains two or more separate materials placed in intimate contact with each other, forming a single, optically transparent body. Characteristic capturing materials may include Li-6, B-10, or both types of nuclei. For example, current detectors can include thick sheets of plastic scintillator interspersed with relatively thin sheets of lithium-glass scintillator, with the lithium enriched in the Li-6 isotope. This type of heterogeneous detector requires an efficient scintillator that incorporates the capturing nuclei, since the capture byproducts of the Li-6 or B-10 isotopes are heavy, short-range charged particles such as tritons and alpha particles that do not escape the capturing scintillator. This type of scintillator can be quite expensive, thereby increasing the overall cost of the detector.
The above factors have limited the use of neutron detectors to small, niche markets. A relatively small, inexpensive neutron detector can create new markets for neutron detectors in medicine, nuclear science, and homeland security.
Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.