Fast neutron detectors based on solid-state single crystalline and multilayer composite scintillators

We report on the development and analysis of two types of fast neutron and neutron-gamma detection media: (1) large volume inorganic oxide crystalline scintillators; and (2) large-area multilayer composite structures consisting of dispersed granules of small-crystalline scintillators contained in a transparent plastic matrix. The first type is based on solid-state single crystal CWO, BGO and ZWO scintillators of large size (diameter 30-50 mm, length up to 100 mm). For these large crystals, we have experimentally confirmed previous results demonstrating very high efficiency for fast neutron detection (up to 50%), which were obtained earlier on small-sized samples of smaller (about 10-12 cm 3 ) volume. Such larger-size scintillators are needed in order to increase detector sensitivity for the detection of very small quantities of neutron-emitting radioactive materials. In our subsequent search for new efficient and cost effective solid-state neutron detectors, we have developed and studied the second type of detection media: large area multi-layer composite detectors (named ZEBRA). We measured the sensitivity of a 40×100×100 mm multilayer ZEBRA detector (with a total thickness 40 mm, and a scintillator cross sectional layer of area 100 cm2) comprised of dispersed GSO(Ce) and found it to be comparable to the normal sensitivity of a 3He-detector with an area of 4000 cm 2 . The efficiency of ZEBRA detectors is not lower than 50%, i.e., approximately at the same level of detection achieved by single crystal scintillators. The cost of such composite detectors is projected to be substantially lower than that of neutron/gamma detectors based on conventional single crystals.