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Title: The measurement of fast neutron spectra with semiconductor detectors
Author: Rickard, Ian Charles
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1971
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The importance of reactor physics measurements in the study of fast reactors is discussed. It is seen that in order to meet the stringent target accuracies the existing experimental methods must be refined and the sources of experimental error identified and, where possible, eliminated. The construction and physical principles of the lithium-6 semi-conductor sandwich detector are discussed. It is shown how the results from this technique can be used to measure fast neutron spectra in the energy range (10 KeV - 7 MeV). The life-span of the detectors is severely limited by fast neutron radiation damage in the silicon diodes. A measurement of the relative efficiency of the detector, from which values of the 6 Li(n,04)T cross-section have been inferred in the energy range (150 KeV - 4. MeV), has enabled. the technique to reach the target accuracies in the range (1 - 4. MeV). Other sources of experimental error have been isolated enabling improvements to be incorporated into the existing electronics system. In a measurement of the Uranium-235 fission spectrum a value of 1.36 (+.04) MeV has been obtained for the Maxwellian fission temperature. It has been shown that reproducible spectrum measurements can be obtained from detectors having different fractions of background events. Fast neutron spectra have been measured in three ZEBRA assemblies in the energy range (10 KeV - 6 MeV) and their accuracies assessed. The experimental results are compared with results from competing experimental techniques and with theoretical predictions made using current methods and data. It is concluded that the results provide a sufficiently accurate overlap with existing techniques to provide an accurate measurement of the fast neutron spectrum above 1 MeV.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available