COSMIC RAY INTENSITY AT SEA-LEVEL IN SINGAPORE

Abstract

In this work initially a non-focussing Cerenkov counter was designed and applied to the detection and recording of total cosmic ray intensity at sea-level. Subsequently, with certain modification to the existing instruments, an experiment was carried out to investigate and improve, if possible, the counting performance of paraffin scintillator developed very recently. The improved scintillator was then used for cosmic ray counting and a comparison was made with respect to water-radiator. Chapter 1 of this text summarises the historical, theoretical and experimental background of cosmic radiation, and also the recent developments in its study. The geophysical and astrophysical factors influencing the variation of cosmic ray intensity are also dealt with as a matter of relevance to this work. The recent theories on the origin of cosmic radiation are briefly surveyed. The experiment on the detection and registration of cosmic ray intensity by means of a non-focussing and all-directional Cerenkov counter is contained in Chapter 2. This Chapter begins with a survey on the theoretical aspect of Cerenkov radiation, principles of Cerenkov counters, and various types of counters in current use. A fairly detailed description is devoted to the design and construction of instruments and their technical data. This is followed by cosmic ray intensity data, and observation and inference made with respect to the characteristics of the intensity variation. Chapter 3 concerns with the investigation into the performance of medicinal paraffin scintillators with a hope to achieve further improvement in efficiency. A summary is given to the scintillation processes both in organic and inorganic scintillators, the working principles of scintillation counters and the background of medicinal paraffin scintillators. This is followed by a description of instruments and experimental details. The observational data are critically analysed and inferences arc made with respect to the selection of a new scintillator with better performance for subsequent cosmic ray works. The experiment on the detection of cosmic ray intensity with a now scintillation counter of improved efficiency is given in Chapter 4. It includes an analysis of the observational data of intensity variation of cosmic rays, a comparison of performance of cosmic ray detection by the scintillator and water radiator, and is concluded by an analysis of the diurnal frequency-distribution of cosmic ray showers. A General Conclusion on this research work as a whole and a discussion of possible further works by the extension of the present instruments are also appended. The numerical suffixes in the text refer to the specific literature in the REFERENCES commencing from page 123.