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The topics covered in this dissertation are all areas of study involving observations at low radio frequencies. There are three main subject areas: a study of the twin-tailed radio galaxy 3C3.1; a study of both an old and a new sample of radio sources that exhibit very steep radio spectra at low frequency; the design and construction of a new radio telescope operating at low radio frequency together with the making of a new radio source survey. 3C3.1 has been studied by other authors but new high angular resolution, high sensitivity observations at low radio frequency have allowed further progress to be made in understanding the behaviour of this source. It has been thought that 3C3.1 type sources would be responsible for most (if not all) of the very steep spectrum radio sources. 3C3.1 is relatively close, hence easy to study. A model has been developed which explains the previously not understood brightness distribution along the long luminous jets. In order to quantify the predicted behaviour more precisely a set of simple numerical simulations was performed. Very steep spectrum radio sources are by their nature easier to detect at low radio frequencies. In the past, it has been shown that most, if not all, very steep spectrum sources are associated with clusters of galaxies. Both optical and further radio observations of a sample of sources prepared by the author, and a sample prepared by other workers were undertaken. The optical observations of high sensitivity have greatly strengthened the hypothesis that all of such sources are indeed associated with clusters of galaxies. The radio observations, both performed at high and low radio frequencies, have shown that such sources seem to have in general evolved from conventional sources with both 'tailed' and 'double' radio structure. A serious limitation for further work at low radio frequencies is the availibility of high sensitivity, high resolution instruments. A twenty five element interferometer with a one mile baseline operating at 38 MHz was designed and constructed. This allowed an appraisal of the operating conditions at such low frequency. A deep radio survey of the north pole was performed and a new sample of very steep spectrum constructed.

The horn plays an elemental role in the make up of a radio-telescope. The focus of this research is on one particular type of horn – the diagonal horn. An analysis of the diagonal horn is made using the Fourier method. The analysis begins from Maxwell’s equations, as the basic building block, and describes the steps involved in developing the radiation pattern. Based on the theory, a program was written that produces the theoretical graphs referred to throughout the thesis. A diagonal horn was manufactured and the radiation patterns were measured. A comparison of these measured patterns is made against the theoretically generated patterns. Further research was carried out to demonstrate the effects on the radiation patterns when the horn is fitted with a dielectric plug. This practice may enhance the directivity of the horn at the cost of introducing new losses / Master of Engineering (Hons)

The NOMAD experiment is a neutrino oscillation experiment, capable of identifying \nm, \nmb, \nel, \neb\ and \nt\ for use in oscillation analyses. A search for \mutoe\ oscillations is conducted, emphasising the development of two separate beam simulators, to provide the background, (no oscillation), \nel\ signal. Both beam descriptions include fits to the results of the SPY experiment that measured hadron production from a 450~GeV proton beam on beryllium target. An independent analysis of the raw SPY data to produce the particle yield is reported. A series of criteria are described for the selection and classification of neutrino events. These produce the data samples necessary for both tuning the beam simulation and determining the oscillation signal. The development of a GEANT and FLUKA based Monte Carlo beam simulator is presented, providing good agreement to the measured neutrino beam. This simulation method has sizeable variations depending on the beamline geometry, which is not known precisely. This causes large systematic errors. An empirical parametrisation is proposed and used for the first time in a NOMAD oscillation search. It uses the measured neutrino spectra at NOMAD, except the \nel, to infer the meson production at the target, and then predict the \nel\ spectrum. This method has good agreement with the data and is also insensitive to alterations of the beamline geometry, resulting in much smaller systematic errors. The reduction of the systematic errors allows the \mutoe\ oscillations search to be performed with much greater precision. Comparisons of the \nel/\nm\ ratio between the empirical parametrisation and data yields no evidence for \mutoe\ oscillations, setting a limit on the mixing parameter, $sin^2(2 \theta) &lt 1.9 \times 10^{-3} \mbox{(90\% CL)}$ at high $\Delta m^2$. The present sensitivity of the analysis on the mixing parameter is 0.0017.

In radio astronomy wider observing bandwidths are constantly desired for the reasons of improved sensitivity and velocity coverage. As observing frequencies move steadily higher these needs become even more pressing. In order to process wider bandwidths, components that can perform at higher frequencies are required. The chief limiting component in the area of digital spectrometers and correlators is the digitiser. This is the component that samples and quantises the bandwidth of interest for further digital processing, and must function at a sample rate of at least twice the operating bandwidth. In this work a range of high speed digitiser integrated circuits (IC) are designed using an advanced InP HBT semiconductor process and their performance limits analysed. These digitiser ICs are shown to operate at up to 10 giga-samples/s, significantly faster than existing digitisers, and a complete digitiser system incorporating one of these is designed and tested that operates at up to 4 giga-samples/s, giving 2 GHz bandwidth coverage. The digitisers presented include a novel photonic I/O digitiser which contains an integrated photonic interface and is the first digitiser device reported with integrated photonic connectivity. In the complementary area of analogue correlators the limiting component is the device which performs the multiplication operation inherent in the correlation process. A 15 GHz analogue multiplier suitable for such systems is designed and tested and a full noise analysis of multipliers in analogue correlators presented. A further multiplier design in SiGe HBT technology is also presented which offers benefits in the area of low frequency noise. In the effort to process even wider bandwidths, applications of photonics to digitisers and multipliers are investigated. A new architecture for a wide bandwidth photonic multiplier is presented and its noise properties analysed, and the use of photonics to increase the sample rate of digitisers examined.

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

The NOMAD experiment is a neutrino oscillation experiment, capable of identifying \nm, \nmb, \nel, \neb\ and \nt\ for use in oscillation analyses. A search for \mutoe\ oscillations is conducted, emphasising the development of two separate beam simulators, to provide the background, (no oscillation), \nel\ signal. Both beam descriptions include fits to the results of the SPY experiment that measured hadron production from a 450~GeV proton beam on beryllium target. An independent analysis of the raw SPY data to produce the particle yield is reported. A series of criteria are described for the selection and classification of neutrino events. These produce the data samples necessary for both tuning the beam simulation and determining the oscillation signal. The development of a GEANT and FLUKA based Monte Carlo beam simulator is presented, providing good agreement to the measured neutrino beam. This simulation method has sizeable variations depending on the beamline geometry, which is not known precisely. This causes large systematic errors. An empirical parametrisation is proposed and used for the first time in a NOMAD oscillation search. It uses the measured neutrino spectra at NOMAD, except the \nel, to infer the meson production at the target, and then predict the \nel\ spectrum. This method has good agreement with the data and is also insensitive to alterations of the beamline geometry, resulting in much smaller systematic errors. The reduction of the systematic errors allows the \mutoe\ oscillations search to be performed with much greater precision. Comparisons of the \nel/\nm\ ratio between the empirical parametrisation and data yields no evidence for \mutoe\ oscillations, setting a limit on the mixing parameter, $sin^2(2 \theta) &lt 1.9 \times 10^{-3} \mbox{(90\% CL)}$ at high $\Delta m^2$. The present sensitivity of the analysis on the mixing parameter is 0.0017.

In radio astronomy wider observing bandwidths are constantly desired for the reasons of improved sensitivity and velocity coverage. As observing frequencies move steadily higher these needs become even more pressing. In order to process wider bandwidths, components that can perform at higher frequencies are required. The chief limiting component in the area of digital spectrometers and correlators is the digitiser. This is the component that samples and quantises the bandwidth of interest for further digital processing, and must function at a sample rate of at least twice the operating bandwidth. In this work a range of high speed digitiser integrated circuits (IC) are designed using an advanced InP HBT semiconductor process and their performance limits analysed. These digitiser ICs are shown to operate at up to 10 giga-samples/s, significantly faster than existing digitisers, and a complete digitiser system incorporating one of these is designed and tested that operates at up to 4 giga-samples/s, giving 2 GHz bandwidth coverage. The digitisers presented include a novel photonic I/O digitiser which contains an integrated photonic interface and is the first digitiser device reported with integrated photonic connectivity. In the complementary area of analogue correlators the limiting component is the device which performs the multiplication operation inherent in the correlation process. A 15 GHz analogue multiplier suitable for such systems is designed and tested and a full noise analysis of multipliers in analogue correlators presented. A further multiplier design in SiGe HBT technology is also presented which offers benefits in the area of low frequency noise. In the effort to process even wider bandwidths, applications of photonics to digitisers and multipliers are investigated. A new architecture for a wide bandwidth photonic multiplier is presented and its noise properties analysed, and the use of photonics to increase the sample rate of digitisers examined.

Thesis (M.S.)--Brigham Young University. Dept. of Electrical and Computer Engineering, 2006. / Includes bibliographical references (p. 77-79).

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