Further studies of a ferrous iron doped synthetic kaolin: dosimetry of X-ray induced defects

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Abstract
The structure of kaolin has been examined together with aspects of dosimetry and energy loss mechanisms of radiation to explain the formation of g = 2 EPR centres. The analysis points to the formation of a trapped hole on the ‘inner layer’ oxygen atoms of kaolin located at the boundaries between divalent ion and trivalent ion ‘cells’, in particular at the boundaries with excess negative charge. Direct interaction of X-rays with atoms and the possibility of proton recoil are eliminated. The means of production appears to be by transfer of charge following ionization of atoms by secondary electrons, with transfer of vacancies ultimately to the oxygen ions. Mechanisms which result in a decrease in signal strength with increase in concentration are examined. It is concluded that the cell mechanisms discussed are consistent with the rates of production and that at 20 Mrad (air) the number of centres should be reaching saturation.