Measurement of the flux and energy spectrum of cosmic-ray induced neutrons on the ground

Abstract

New ground-based measurements of the cosmic-ray induced neutron flux and its energy distribution have been made at several locations across the United States using an extended-energy Bonner sphere spectrometer. The data cover over twelve decades of neutron energy, from meV to GeV. An expression to scale the flux to other locations has been developed from a fit to the altitude dependence of our measurements and an expression from the literature for the geomagnetic and solar-activity dependence of neutron monitor rates. In addition, an analytic expression is provided which fits the neutron spectrum above about 0.4 MeV. The neutron flux is important for estimating the soft-error rate in computer memories and recent computer logic devices.