The distribution of cosmic ray neutrons in the atmosphere.
An introduction to the demography of cosmic ray neutrons including a detailed description of neutron diffusion theory with special reference to diffusion in the atmosphere. The design and performance of the detectors, flight unit electronics, telemetry system and receiving and recording equipment ar...
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| Format: | Thesis |
| Language: | English |
| Published: |
1966
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| Online Access: | https://eprints.utas.edu.au/19972/ https://eprints.utas.edu.au/19972/1/whole_GreenhillJohnGilbert1967_thesis.pdf |
| Summary: | An introduction to the demography of cosmic ray neutrons including a detailed description of neutron diffusion theory with special reference to diffusion in the atmosphere. The design and performance of the detectors, flight unit electronics, telemetry system and receiving and recording equipment are described. The theory of frequency division multiplexing methods is described and applied to the optimisation of the telemetry system used in the experiments. The experiments are described and smoothed for curve counting rate dataAa number of the balloon ascents tabulated. The energy sensitivity of the neutron detectors is discussed. Experimental data on the background and directional response of the detectors are presented and analysed. The contribution to the counting rate of neutrons produced in the detector materials is estimated for various altitudes and latitudes. An increase in the neutron counting rate at high altitudes over Macquaries Island is described. This event occured at a time of high geophysical activity and was accompanied by intense bursts of auroral X-rays. Possible causes of the increase are discussed and the neutron flux is estimated on the assumption that the event was genuine. The flux of protons, required to produce the neutrons by interactions with air nuclei, is estimated and shown to be barely compatible with riometer and other observations at the time of the event. Possible sources of such a proton flux increase are discussed'. The results of the latitude survey measure- ments in August-October 1964 are described and compared with other experimental and theoretical data. Good agreement is obtained with the theoretical results of Newkirk (1963). Time variations in the neutron flux over Wilkes and Mildura are discussed and evidence is presented for a decrease between 1962 and 1964 in the absorption length of the neutron producing radiation over Macquarie Island. Differences between the neutron flux, measured in simultaneous flights from Wilkes and Macquarie Island, are discussed. The latitude dependence of the neutron leakage flux is estimated from the count rate variation at 15gm cm-2 and compared with various experimental and theoretical results. It is shown that the latitude distributions of the slow neutron density are essentially the same as the counting rate distributions for our detectors. These distributions are compared with the results of Lingenfelter (1963) and Soberman (1956) and significant differences are found to exist. The absolute neutron density distributions are evaluated by nornalising our data to those of Miles (1964). The results are compared with other experimental and theoretical data and a value for the global average carbon 14 production rate is obtained. An anomaly: in the literature on the efficiency of slow neutron detectors is discussed. |
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