Prototyping a Neutron Detector for Dark Matter Experiments

Neutrons can produce signals in liquid scintillator detectors that are indistinguishable from those expected from weakly interacting massive particles (WIMPs). In underground experiments, neutrons arise from radiogenic and cosmogenic sources, making their effective identification and vetoing crucial for rare-event detection. Accurate characterization of both the ambient neutron background and the detector response is therefore essential for dark matter searches.

We are developing a boron-loaded liquid scintillator detector for neutron tagging and background characterization. The detector employs a scintillator cocktail composed of pseudocumene as the primary scintillator, trimethyl borate for boron loading, and a wavelength shifter. The prompt signal from neutron thermalization and the delayed signal from neutron capture on boron enable efficient neutron identification.

This work presents a prototype instrumented with silicon photomultipliers (SiPMs), which offer improved stability, compactness, lower operating voltage, and reduced cost compared to traditional photomultiplier tubes. We also explore alternative scintillator mixtures and multiple wavelength shifters to enhance light yield and overall performance.