Fiber multilayered ZnS position-sensitive neutron detector with high detection efficiency

Abstract

A fiber multilayered ZnS position-sensitive (FMZP) neutron detector that combines wavelength shift fibers and ZnS/LiF (ZnS) scintillators is developed. The FMZP detector consists of four ZnS scintillators of 0.45 mm thickness sandwiched by five fiber planes. It achieves a detection efficiency of 76% for thermal neutrons. Eight pieces of detection elements of 5 cm length are arranged in close contact in a row, and form a position detector of length 40 cm. Because the elements can also be arranged as bent or two-dimensional structures, various forms of construction are possible. The detector can be downsized using a multipixel photon counter (MPPC), which is a silicon light sensor. However, the MPPC needs several control circuits for stable operation. The system readout circuit performs gain-adjustment and temperature-compensation functions. Each detection element signal is digitized to a waveform by a high-speed analog-to-digital converter, and the waveform is analyzed to detect only neutron signals, eliminating narrow pulses such as the gamma ray noise of the fiber. The proposed FMZP detector can be used as an alternative for 3He neutron detectors.