The momentum spectrum of nuclear active particles in the cosmic radiation

Abstract

This thesis describes studies of nuclear active particles (NAPs) in the cosmic radiation over the momentum range 1-30 GeV/c. Both unaccompanied particles and NAPs in extensive air showers (EAS) are studied near sea level at Durham using an air-gap magnet spectrograph in conjunction with a neutron monitor. Details are given of the design of the spectrograph, neutron monitor and associated equipment as used for measurements on unaccompanied NAPs (Chapter 2), and the techniques used for derivation of the momentum spectra from the basic data are described in Chapter 3. The results, in the form of momentum spectra of unaccompanied protons and negative pions, and the limited analysis of NAPs in EAS are presented in Chapter 4 where they are compared with the results of other workers. Measurements of the momentum of NAPs in EAS were found to be difficult and the data are mainly concerned with the response of the neutron monitor to EAS. A model of the propagation of cosmic rays through the atmosphere, which was mainly intended for predictions of the properties of large EAS, is described and used to predict the momentum spectra of unaccompanied particles at sea level. The results of this prediction are compared with the experimental data (Chapter 5) and the results of other model predictions (Chapter 6). It is shown that no single model, when combined with a reasonable spectrum of primary cosmic rays, can adequately explain all the data on unaccompanied particles at sea level. It is also shown that the spectra of high energy protons and pions are likely to be the sea level measurements which are most sensitive to the form of the primary cosmic ray spectrum.