The separation of neutron and gamma signals through exploitation of the pulse shape discrimination (PSD) phenomena is a trusted technique, but with the advent of PSD sensitive plastic scintillators the prospect for mass deployment in homeland security or environmental radiation scenarios is increased. In an equally progressive technological advance the silicon photomultiplier (SiPM) is rapidly becoming a replacement for the traditional PMT. The combination of plastic scintillator with multiple SiPMs has enabled the development of a compact neutron-sensitive detector for deployment in, say, an environmental radioactivity situation where position sensitivity is required.
A monolithic piece of scintillator is optically coupled to four SensL J-series SiPM arrays at each corner of the scintillator and secured by a 3D-printed housing. We use triangulation methods from the four readout channels to measure the position of the radiation interaction within the scintillator tile, and assess the performance of this method as a low cost position-sensitive neutron/gamma detector. By design, the nature of the detector is such that swift replacement of components is possible allowing exploitation of the PSD capable plastic EJ299-33 or the fast timing properties of the alternative EJ200 plastic scintillator.
We report the testing of this device with standard radioisotopes (22-Na, 60-Co, 137-Cs), the response when exposed to the mixed radiation field of an AmBe neutron source, and its suitability for locating “unknown” sources under laboratory conditions.