A new ground level neutron monitor for space weather assessment
We report on a new ground-level neutron monitor design for studying cosmic rays and fluxes of solar energetic particles at the Earth’s surface. The first-of-its-kind instrument, named the NM-2023 after the year it was standardised and following convention, will be installed at a United Kingdom Meteorological Office observatory (expected completion date December 2023) and will reintroduce such monitoring in the UK for the first time since ca. 1984. The Monte Carlo N-Particle (MCNP ®) transport code is used for the development and application of parameterised radiation transport models to investigate alternative neutron detectors, their location and bulk material geometry in a realistic CR neutron field. Benchmarked against a model of the current and most widespread design standardised in 1964 (the NM-64), two main parameterisation studies are conducted; a parameterisation of a simplified standard model and a concept slab parameterisation. We show that the NM-64 standard is well optimised for the intended large-diameter boron trifluoride (BF3) proportional counters but not for multiple smaller diameter counters, and that the new design (based on a slab arrangement) produces comparable counting efficiencies to an NM-64 with six BF3 counters, but is more compact, lower cost and avoids the use of highly toxic BF3.