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No description available.

No description available.

No description available.

No description available.

No description available.

The origin of cosmic-rays is one of the long-standing problems in astro physics. In recent years, strong evidence has been found that certain classes of object contain and are able to accelerate particles to high energies. In this thesis the origin problem is addressed in two different ways. Firstly, two different regions of the Galaxy are studied using γ-ray observations from the COSB satellite combined with atomic and molecular gas measurements. The Vela region contains a pulsar and a supernova remnant and is particularly valuable location for cosmic-ray studies because of its proximity, the association of the two objects, and the intensity of the γ -ray flux it produces. At greater longitudes, the region around the peculiar object η Carinae is also studied. It is rich in potential sources of cosmic rays including active stars and a spiral arm seen at a tangent at l ~ 282º .Analysis of the Vela region reveals strong evidence for cosmic ray production at all energies observed by COSB. The supernova remnant seems the most likely candidate, but the possibility of the pulsar itself producing some of the particles cannot be ruled out. The excess γ -ray emission from around η Carinae does not appear correlated with the active stars but seems to becoming predominantly from the spiral arm. This is the first time evidence has been presented for cosmic-ray acceleration by the spiral shock in a particular, known spiral arm which is observed as a feature in the gas. The γ -rays are produced in the gas clouds associated with this arm. The second approach to the cosmic-ray origin problem involves a model for cosmic-ray production in supernova remnants and is used in association with a Monte-Cailo simulation of their occurrence in the Galaxy. Unlike earlier models (Bhat et al 1987), the motion of the Sun is also taken into account and the supernova explosions occur mainly in spiral arms. The results are in the form of a time sequence of energy density values and tire compared in detail with (^10)Be results. It is found that the model accounts for the long-term rise in the concentration of this radioisotope and does not predict large excursions from the mean energy density that beset older models. Thus the cosmic ray production by supernova remnants seems to be consistent with the radioisotope data.

This thesis reports measurements made on the longitudinal cascade of high energy cosmic ray showers using observations of atmospheric Cerenkov light. The lateral distribution of the Cerenkov light shower has been shown to be one of the measurable ground parameters which is sensitive to cascade development. The interpretation of such measurements together with other depth sensitive parameters in recorded showers has allowed inferences to be made about the mass distribution of the primary particles and about the nature of the high energy interactions which govern the generation of the cascade through the atmosphere. Measurements of atmospheric Cerenkov light from showers between 10(^15) – 10(^18) eV were made at Dugway Proving Grounds, Utah, U.S.A. between October 1977 and March 1980, using an array of fast photo multipliers to record both the lateral distribution of light density and the time structure of the light pulses. This thesis concerns the detailed analysis and interpretation of the lateral distribution data. These results were subsequently combined with those from pulse timing measurements to present composite results on the gross feature of shower development, the depth of cascade maximum. Analysis techniques have been developed to determine both the average characteristics of the lateral distribution and the fluctuations in the data which could be attributed to intrinsic fluctuations in cascade development. The results of these analyses were then related, through the results of computer simulations of shower development, to the depth of cascade maximum. A change in the elongation rate and the magnitude of fluctuations between 10(^16) and 10(^17) eV has been observed and this is interpreted as a change in primary mass composition from predominantly heavy particles ~ 10(^16) eV to include a greater proportion of light nuclei ~ 2 x 10(^17) eV. The combined measurement of the mean and fluctuations in the depth of maximum has allowed certain interaction models to be rejected. These were those involving scaling in the central region or using an interaction cross section which remains constant with energy. Results from other observations of cosmic ray showers show further indication of the change in primary mass composition between ~ 10(^16) eV and ~ 2 x 10(^17) eV. At higher energies these other results indicate a mass composition changing little with energy.

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Previous work on the muon component of extensive air showers is described and reviewed with particular reference to the muon heights of origin with respect to the main cascade. Thu mechanical and operating details of a specialist experiment to determine the heights of origin of muons are described together with the results from detailed computer simulations which are tailored to resemble the characteristics of the equipment. The raw experimental data are examined in detail as a precursor to interpreting the data from the equipment. The final results from the experiment are given in detail and their relevance to air shower cascade development discussed. Suggestions are made for future work in this and related fields.