Studies of the cosmic radiation using a neutron monitor

Abstract

This thesis is concerned with the production of evaporation neutrons in neutron monitors by the charged particle components of the cosmic radiation at sea level and their detection. The evaporation neutron detection efficiency of a modified I6Y - type monitor is measured using a novel technique which uses stopping negative muons as a source of neutrons, and the result is compared with that expected from previous measurements of other monitors. Use is made of this result in an experimental study of neutron production by unaccompanied cosmic ray protons, pions and muons in the momentum range 1-30 GeV/c. The experiment has, employed an air-gap magnet spectrograph in conjunction with the monitor, and the results of this study are compared with previous work. They confirm previous findings that the yield of evaporation neutrons in monitors from protons and pions is significantly overestimated by the only available theoretical model, and suggestions, are made to account for this discrepancy. Within fairly large statistical errors, the measured neutron production by fast muons agrees with the theoretical predictions. An examination is made of the possibility of using a neutron monitor in conjunction with an air shower detection array to measure the changes in slope of the nuclear active particle (NAP) energy spectrum in extensive air showers (HAS) of energy l0(^17)eV at sea level which may arise due to primary particles of different atomic mass number and fluctuations in the longitudinal development of proton induced showers. Using NAP spectra predicted by a mathematical model of the EAS development it is found that monitors of conventional design are unlikely to be sensitive to these changes although the total neutron yield per shower could be used as a measure of the expected differences in the NAP flux.