Cosmic-Ray Neutron Energy Spectrum

The cosmic-ray neutron energy spectrum in the equilibrium region of the atmosphere has been measured with several different calibrated detectors from thermal energies to about 1 Bev at 44° north magnetic latitude and up to 40 000 feet. By combination of the data from these measurements with those from other experiments, a complete differential energy spectrum is obtained which shows the characteristic maximum near thermal energies and a roughly $\frac{1}{E}$ variation up to about 100 kev. The presence of a second maximum in the spectrum near 1 Mev is attributed to the evaporation neutrons from stars, and above this energy up to 800 Mev the spectrum falls off as $E^{-1.4\mathrm{}}$.