Lunar radio detection of ultra-high-energy particles.
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Date
2013
Authors
Bray, Justin D.
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Advisors
Protheroe, Raymond John
Ekers, Ronald David
Ekers, Ronald David
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Abstract
Ultra-high-energy cosmic rays, and their expected counterpart neutrinos, are the most energetic particles in nature, and their origin remains unknown. The detection of these particles is key to identifying their origin, but is complicated by their low flux, which necessitates the use of extremely large detectors. The largest potential aperture for detecting the most energetic of these particles is offered by the lunar radio technique, which makes use of the Moon as a detector, using ground-based radio telescopes to search for nanosecond-scale radio pulses from particles interacting in the lunar regolith, and it is this technique that is the subject of this thesis. In this thesis I present a description of the most sensitive lunar radio experiment to date, conducted in 2010 with the Parkes radio telescope as part of the LUNASKA project, including a comprehensive test of the purpose-built Bedlam backend used in this experiment. The signal-processing strategy is explored in great detail, with an extensive discussion of the statistics of stochastic signals, and an optimal strategy is described which compensates both for known effects such as ionospheric dispersion and for previously-unidentified effects such as phase ambiguity from frequency downconversion. A series of cuts is outlined which successfully removes all anthropogenic radio interference, the first time this has been accomplished for a lunar radio experiment without the benefit of a coincidence filter operating between multiple channels. After these cuts, no radio pulses are observed; this null detection allows limits to be placed on the fluxes of ultra-high-energy cosmic rays and neutrinos. To place this experiment in context, I perform a review of the null detections published for previous lunar radio experiments, including detailed analyses of their experimental techniques, based on the rigorous treatment applied in the above work. In several cases, I find previously-unidentified problems which significantly limit the sensitivity of previous experiments. Finally, I improve on existing analytic models for calculating the sensitivity of lunar radio experiments to ultra-high-energy cosmic rays and neutrinos, allowing a comparison with a range of possible future experiments, and comment on future prospects for this technique.
School/Discipline
School of Chemistry and Physics
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2013
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This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals