published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / abstract / Physics / Master / Master of Philosophy

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Gamma-ray astronomy is generally viewed as an adjunct to cosmic ray physics. As such, the observation of very high energy gamma-rays will allow a new and complementary means of examining the origin and evolution of cosmic rays. However, at present the atmospheric Cerenkov technique (the technique by which very high energy gamma-rays are observed) is seriously hampered by limited flux sensitivity. Monte Carlo simulations suggest that the application of imaging to the atmospheric Cerenkov technique will provide a much needed increase in sensitivity. The successful application of imaging to very high energy gamma-ray observations of the Crab nebula will be discussed, as will improved techniques for calibration and noise rejection. These observations permit an improved estimate of the nebular magnetic field strength.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / by David Hopkins Shoemaker. / M.S.

Cosmic rays measured by the fluorescence detectors of the Pierre Auger Observatory contain two large sources of error; the degree of scatter created by the atmosphere and the amount of Cherenkov contamination that has been recorded by a detector. When an event is viewed in stereo, these two sources of error can be accounted for directly by using the light profiles calculated by the two detectors. In this thesis accounting for the atmospheric scatter was explored by the use of a program called AerosolMin described in Chapter 5. This program could reconstruct the scattering parameters of the atmosphere by comparing the two profiles of the light produced by an air shower, as calculated by two detectors, as they should be identical in size. When using AerosolMin it was found that only the highest energy events ( > 10 [superscipt 20] eV ) could use this technique and that for the event that occurred at the GPS second of 799137161 a layer of fog was present that could not be accounted for with the simplistic atmospheric profile currently used by the reconstruction software. In Chapter 6 the Cherenkov profiles that had been miscalculated by a detector were replaced to increase the reconstruction statistics. The program that performed this replacement, FdCherenkovReplacer was most successful on events that had recorded a large amount of direct Cherenkov light. The event that occurred at the GPS second of 772256331 is explored in Chapter 7. The Coihueco detector that recorded this event was contaminated by direct Cherenkov light, but when replaced by FdCherenovReplacer it was found to have miscalculated the geometry of the event by 0.4 °. / Thesis (M.Sc.)--School of Chemistry and Physics, 2007.

Bibliography : leaves 187-205. / xi, 209 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1994?

This thesis describes several aspects of cosmic ray composition studies using the Utah Fly's Eye and High Resolution Fly's Eye (HiRes) detectors. The Fly's Eye detector utilises the atmospheric fluorescence technique to measure the development of cosmic ray cascades as they pass through the atmosphere. This is complementary to the surface array technique, as used by the Akeno experiment in Japan, which measures the electromagnetic and muon content of air showers at a single observation level. For some time it was thought that Fly's Eye and Akeno gave inconsistent composition results. In Chapter 4 I show that the inconsistency is due, for the most part, to a difference in the assumptions made about hadronic interactions. In Chapter 5 I present analysis of the composition between 10^17 and 10^18 eV using the prototype High Resolution Fly's Eye (HiRes) detector in coincidence with the Michigan Muon Array (MIA). The hybrid nature of these measurements gives us more information about cosmic ray showers than either technique on its own. The consistency or otherwise of the composition measured by the two detectors is discussed. Finally, in Chapter 6, I discuss a method of extracting the total proton-proton cross section from the cosmic ray data. This information is of interest because it is derived at centre of mass energies much higher (by at least an order of magnitude) than those currently accessible by collider experiments. I present a preliminary calculation of the cross section using the HiRes/MIA hybrid data set. / Thesis (Ph.D.)--Department of Physics and Mathematical Physics, 2001.

When astronauts travel in space, they are exposed to high energy cosmic radiations. The cosmic ray spectrum contains very high energy particles, generally up to several GeV per nucleon. Currently NASA is funding research on the effects, such as acute radiation sickness, of cosmic radiation. Animal models are used to conduct the studies of radiation effects of particles in the range of several MeV/nucleon to about 1000 MeV/nucleon. In order to compare different radiations, the biological effectiveness relative to a specific radiation is usually used. For low energy heavy ions and neutrons 250 keV photons are usually used for the reference radiation but their depth dose distribution is very different from that for cosmic rays. In this research, the advantages of using high energy electrons as the reference radiation for research on cosmic radiation were demonstrated. The conclusion is based on the evaluation of the dose distributions and microdosimetric spectra of the electrons and high energy protons as a function of depth in a tissue equivalent absorber as determined by Geant4 simulation.

published_or_final_version / Physics / Doctoral / Doctor of Philosophy