Differentials or integrals: pluses and minuses in their application to additive dose techniques
Retrospective radiation dosimetry is based on the growth of radiation sensitive defects. In Electron Paramagnetic Resonance (EPR), the peak-to-peak measurement of the differential of the absorption spectrum is used, whereas in luminescence dosimetry, the response of the sample to irradiation is traditionally determined by the height or the integral of the emission spectrum. It has been shown experimentally and can be proved mathematically that, except in special cases, the environmental dose estimate (De) depends on which parameter is used to measure radiation response. Since integral methods are directly related to the number of radiation-produced defects, it is increasingly assumed that they will give the best estimates of De in EPR as well as in luminescence dosimetry. We show that the disparity in De is not due to any inherent superiority of a particular method, but is rather due to the different degree of interference between wide and narrow peaks in the different methods. In spite of their conceptual nicety, integral methods do not necessarily give the best estimate of De. This is demonstrated by computer simulation and guidelines are also given on selecting the best method in any particular case. Differential techniques might be very profitably applied to luminescence dosimetry as well as EPR dosimetry. The differential spectrum not only shows detail which may be obscured in the integral curve, but also provides a very simple graphical means of isolating a preferred spectral component. This leads to the possibility of extending the range of substances which may be reliably used for dosimetry or dating by luminescence techniques.
Lyons
RG
Department of Physics, The University of Auckland, New Zealand.
Tan
SM