Typescript (photocopy) / 89 leaves, [48] leaves of : 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 Applied Mathematics, 1982

Investigations of the cosmic ray flux around the " knee " in the all - particle energy spectrum can provide information on the origin of this steepening. Studies of air shower development in this region are especially informative, although experiments in recent years have produced some conflicting results. Some report an unusually rapid development of showers, which has been interpreted in terms of an increased proportion of heavy nuclei in the flux, compared with the directly measured low energy composition. This thesis describes measurements of the lateral distribution of Cerenkov light associated with air showers with sea level sizes between ~ 10 ^ and 1O7 particles. It is shown that the slope of the lateral distribution is sensitive to air shower development and that the shape is in agreement with the results of recent calculations. These calculations are used to assign depths of maximum to the showers observed. A comprehensive simulation of the selection biases present in the experiment is used in the interpretation of the results on the depth of shower maximum. The data are shown to be consistent with a cosmic ray composition rich in iron in the energy region studied. / Thesis (Ph.D.)--Department of Physics, 1985.

Thesis (M. Sc.)--University of Adelaide, 1987. / Transparency in pocket. Includes bibliographical references (leaves 108-115).

Thesis (Ph. D.)--University of Adelaide, Dept. of Physics, 1985. / Includes bibliographical references.

Thesis (Ph.D.) -- University of Adelaide, Department of Physics, 1979.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Applied Mathematics, 1982. / Typescript (photocopy).

Thesis (M. Phil.)--University of Hong Kong, 1994. / Includes bibliographical references (leaves 115-117).

Thesis (Ph. D.)--University of Chicago, Dept. of Physics, March 2000. / Includes bibliographical references. Also available on the Internet.

A novel detector for ultra-high energy cosmic rays, and its prototype are discussed. It detects events with primary energy greater than 100 PeV. (1 PeV = 1000 TeV; 1EeV = 1000 PeV.) The detector operates by sensing the near-ultraviolet scintillation light of ionized nitrogen molecules created by the passage of ionizing particles in extensive air showers. (The concept is loosely based on the highly successful Fly's Eye detector situated at Dugway, Utah.) Typical events should consist of 1 to 100 EeV primary energy showers, with near-vertical cores, passing through the detector's field-of-view at distances of 1 to 20 km. The optical field of view of the hypothetical detector would be 60 degrees wide by several (≈ 3) degrees high and would look in a near-horizontal direction at a distant mountain range or other suitably dark background roughly 20 Ian away. A typical good location would be the rim of a canyon, looking slightly downward at the other side. The field-of-view would be subdivided into 3 or more thinner ''wedges'', 60 degrees wide by, perhaps, 1 degree high. A single detector provides timing and brightness information only. Three widely-separated detectors with overlapping fields-of-view provide sufficient data to determine the core location, the zenith and azinruthal angles of the core axis, and the absolute luminosity of the cascade. Interpretation of the luminosity data would be a challenge, but it should be possible to estimate primary energy from it. The advantage of this new scheme is the enormous effective detector area per relatively low-cost detector module. Each triplet of detectors "sees" 300 square km with a typical core axis acceptance of roughly 1 sr. The construction and testing of a prototype unit has been accomplished. The field-of-view was 41 degrees wide by 2 degrees high. Light was collected by a 4.7 square meter mirror and focused onto a wave-shifter PMT system. 8 events with primary energies in the 0.1 to 1 EeV range were observed in an 8.5 hour period. Representative events are shown and preliminary data analysis is discussed.

We have conducted an extensive experimental study on the subject of near ground atmospheric electricity. The main objective was to gain more understanding of this particular aspect of atmospheric phenomena, while testing the possible application to cosmic ray research. The results in atmospheric electricity show that there are certain patterns in ion grouping such as the size and lifetime. The average lifetime of ion group is 0.7 seconds and the average size is about 10 meters at our experimental site. Ultrahigh energy cosmic ray air showers should create sizable slow atmospheric electric pulses according to our theoretical calculations. Preliminary studies on air showers with total particle number N equal or greater than 10⁵ (10¹⁵ eV) have yielded strong evidence that slow atmospheric current pulses are associated with air showers. The theory and the experiment agree with each other fairly well when we average over large numbers of events. With our current experimental arrangement, when the air shower exceeds a certain size, the system response saturates. Therefore it is extremely desirable in future research that the counter array be designed for a much higher threshold level, since this prototype experiment indicates that interesting data would be obtained. Another reason for further experimental research being directed toward ultrahigh energy, e.g., N ≥ 10⁷ (10¹⁷ eV) and higher, is to establish a calibration of the slow atmospheric electric signals generated by cosmic rays as a function of primary cosmic ray energy and core location. This type of slow atmospheric electric signal, if fully understood and calibrated, offers a new and potentially less expensive technique to observe ultrahigh energy cosmic ray events, which hold some fundamental keys to the knowledge of the universe on a large scale.