Abstract
We are developing thin tile scintillator detectors with silicon photomultiplier (SiPM) readout for use in a multi-layer fast-neutron tracker. The tracker is based on interleaved Timepix and plastic scintillator layers. The thin 15 × 15 × 2 mm plastic scintillators require suitable optical readout in order to detect and measure the energy lost by energetic protons that have been recoiled by fast neutrons. Our first prototype used dual SiPMs, coupled to opposite edges of the scintillator tile using light-guides. An alternative readout geometry was designed in an effort to increase the fraction of scintillation light detected by the SiPMs. The new prototype uses a larger SiPM array to cover the entire top face of the tile. This paper details the comparative performance of the two prototype designs. A deuterium-tritium (DT) fast-neutron source was used to compare the relative light collection efficiency of the two designs. A collimated UV light source was scanned across the detector face to map the uniformity. The new prototype was found to have 9.5 times better light collection efficiency over the original design. Both prototypes exhibit spatial non-uniformity in their response. Methods of correcting this non-uniformity are discussed.
Highlights
Fast neutron detection often relies on measuring the energy deposited in a detector by elastically recoiled nuclei
The thin 15 x 15 x 2 mm plastic scintillators require suitable optical readout in order to detect and measure the energy lost by energetic protons that have been recoiled by fast neutrons
This paper describes work to optimise the design of the plastic scintillator component of the tracker
Summary
Fast neutron detection often relies on measuring the energy deposited in a detector by elastically recoiled nuclei. The plastic scintillators provide a hydrogenous target in which fast neutrons may elastically collide with hydrogen nuclei (protons), with some recoiling protons escaping the plastic and being measured by the neighbouring Timepix detector. Timepix is a single-quantum counting pixellated silicon detector [3] In the tracker it operates in time-over -threshold mode, where the charge deposited in each individual pixel is measured. Two different readout geometries are compared, with the aim in improving the proportion of scintillation photons reaching the SiPM active area. This quantity is described as the light collection efficiency (LCE)
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