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Abstract
The aim of this dissertation is to prepare and develop a locally thermoluminescence detector (TLD). Calcium sulphate doped by dysprosium CaSO4:Dy and Calcium sulphate doped by dysprosium & gadolinium (CaSO4:Dy,Gd) have been prepared under laboratory controlled condition. This dissertation consisted of six chapters; Introduction, Theoretical background, Experiments, Result & discussion, TL-Kinetics and conclusions.
The first chapter, Introduction, gives a brief summary about luminescence and thermoluminescence phenomenon. Historical review of some previous works has been mentioned. The application of TL-phenomena to the measurement of absorbed radiation dose and general requirements of TLD material has been discussed. Several of TL-material properties have been investigated in some details as: effect of doping concentration on the TL response, effect of thermal treatment, effect of gamma dose in TL-response, effect of UV on TL-phototransfer, storage time effect on the TL rate of fading, determination of TL parameters and application of the new made dosimeters as personal and area monitoring.
The second chapter exhibits Theoretical Background to the TL-phenomena by using the band theory; traps and recombination centers. Simple model which is based on the energy band model and in fact it became well enough accepted to enable a quantitative theory of the kinetics of thermoluminescence to be developed.
Thermoluminescence analysis has been studied by using the means of the trap emptying. Methods of analysis; partial curve analysis, peak shape method and peak position method have been mentioned.
The third chapter discusses the methods of experiments, material, apparatus and irradiation sources. Two standard techniques were used during the course of this work to achieve the optimum concentration of the activators Dy and Gd. The prepared samples were thermally treated to improve its sensitivity as well as its stability. The samples CaSO4:Dy and CaSO4:Dy,Gd have been exposed to pre-irradiation of high gamma dose for TL-sensitization. Grain size effect on the sensitivity of TL-material has been studded. Pre-annealing and fading of phosphor have been tested. The TL response as a function of the Gamma dose (for CaSO4:Dy and CaSO4:Dy,Gd) and neutron response (for CaSO4:Dy,Gd) were studded. Ultra violet effect and dose re-estimation has been achieved.