Boron-coated straw detector efficiency comparison with 3He proportional counters — A prospect for cosmic ray neutron monitoring

This paper benchmarks two Proportional Technologies, Inc. (PTI) boron-coated straw (BCS) detector offerings against commercial helium-3 ( 3He) detectors for ground-level neutron monitoring. This study aims to assess if BCS-based detectors are a viable detector choice for the construction of a cosmic ray neutron monitor (NM) that is less expensive, smaller and produces comparable results to the 6-tube NM-64, typically used in the existing global NM network. The experimental methodology, data and analysis for the observed detection efficiency of the PTI-110 BCS module as a function of distance are presented. The PTI-204 BCS detector tube is benchmarked against a 7.5atm 3He-filled cylindrical proportional counter using a high-density polyethylene (HDPE) moderating test rig. Monte Carlo N-Particle (MCNP) models are validated against the experimental data. The experimental and simulation data for PTI-110 BCS unit detection efficiency agreement is within 4.5%. This confirms that the response of charged particles from the B4C layer is accounted for. The measured 3He tube detection efficiency was nearly three times greater than the PTI-204 detector. A trade-off analysis of 3He (at various fill pressures) versus BCS-based detector options, with supporting experimentally validated MCNP calculations, is used to provide confidence in the calculation of the 4 atm 3He tube-based ground-level NM design.