Abstract:
Background Efficient neutron detectors are widely used in national security, neutron scattering, and nuclear energy development. The 3He proportional tube, a commonly used neutron detector, faces a global shortage of 3He resources. Meanwhile, existing alternative detectors like BF3 proportional tubes have low efficiency and toxicity, and most large-area boron-lined gas detectors adopt a flow-gas design requiring gas cylinders, causing inconvenience in use and maintenance.
Purpose To address the above issues, this study aims to develop a sealed large-area neutron detector based on a boron-lined multi-wire proportional chamber (MWPC) for nuclear environment safety monitoring and fusion pulsed neutron measurement.
Methods The Geant4 software with the FTFP_BERT_HP physics library was used to simulate the effect of boron coating thickness on detection efficiency, energy deposition of secondary particles in the working gas, and γ-ray sensitivity. A double-layer sealed detector with a 1.6 μm boron coating and a 10 cm×10 cm effective area was fabricated. Performance tests (pulse height spectrum and neutron detection efficiency) were conducted at the 20th beamline (BL20) of the China Spallation Neutron Source (CSNS), using a self-developed readout electronics system and a standard 3He tube as a reference.
Results Simulation showed that thermal neutron detection efficiency was 1%−7% when boron coating thickness was 0.1−2.5 μm, and γ-ray sensitivity was less than 5×10−6 at a 100 keV energy threshold. Experimental results indicated that the detector’s pulse height spectrum matched the simulated energy deposition. After background subtraction, its detection efficiencies for 0.18 nm, 0.29 nm, and 0.48 nm neutrons were 4.2%, 6.0%, and 9.4%, respectively, consistent with the 10B neutron absorption cross-section law.
Conclusions The developed sealed large-area boron-lined MWPC neutron detector avoids complex gas circulation systems. Future optimization of boron coating thickness and conversion layer number can further improve efficiency, providing a new solution for nuclear safety monitoring and fusion pulsed neutron measurement.
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