Two-Dimensional Scintillation Neutron Detectors for the Extension of SENJU Diffractometer

Two-dimensional neutron detectors were developed for the extension of SENJU time-of-flight Laue single crystal neutron diffractometer in J-PARC MLF. The detectors are installed at the additional detector bank for the SENJU instrument. The detector module is made based on ZnS scintillator and wavelength-shifting fiber technology, where each detector module maintains a neutron-sensitive area of 256 × 256 mm with a pixel size of 4 × 4 mm. To meet the tight space limitation in the instrument, the detector was designed as compact as possible. The detector has a depth of 170 mm, which is about 40% smaller than that of the original SENJU detector. Moreover, new comparator electronics cards are implemented, which pick up signals with smaller heights and narrower time widths than the original ones. These cards help decrease in the applied PMT voltage and they improved count uniformity. All four produced detector exhibited similar detector performances: detection efficiency 50-60% for 2-Å neutron,
⁶⁰
Co gamma-ray sensitivity 1×10
^-5
, count uniformity 3-6%.