ABSTRACT
The effects of ionisation density on the structure of the glow curve of LiF:Mg,Ti (TLD-100) are briefly reviewed and discussed within the framework of the spatially correlated TC/LC model and localised recombination. The effects of 'slow-cooling' on the structure of composite peak 5 following low-ionisation density beta/gamma irradiation are described and analysed in both 'slow-cooled' and 'normally cooled' samples. It is demonstrated that 'slow-cooling' using a cooling rate of 30 degrees C h(-1) increases the relative intensity of glow peak 5a to composite glow peak 5 from approximately 0.1 to approximately 2, thereby greatly improving the precision of measurement of the ratio 5a/5. The improved precision removes a hurdle impeding the development of the ionisation density discrimination properties of the peak 5a/5 nanodosimeter.
Subject(s)
Fluorides/chemistry , Fluorides/radiation effects , Lithium Compounds/chemistry , Lithium Compounds/radiation effects , Neutrons , Thermoluminescent Dosimetry/instrumentation , Dose-Response Relationship, Radiation , Equipment Design , Equipment Failure Analysis , Ions , Magnesium/chemistry , Magnesium/radiation effects , Radiation Dosage , Reproducibility of Results , Sensitivity and Specificity , Thermoluminescent Dosimetry/methods , Titanium/chemistry , Titanium/radiation effectsABSTRACT
The effects of 'slow-cooling' on the structure of composite peak 5 following low-ionisation density beta/gamma irradiation are described and analysed in both 'slow-cooled' and 'normally-cooled' samples. Computerised glow curve deconvolution is employed with constrained 'peak-shape' parameters deduced from anciliary studies using 4 eV and 5 eV optical excitation.
Subject(s)
Fluorides/chemistry , Fluorides/radiation effects , Lithium Compounds/chemistry , Lithium Compounds/radiation effects , Neutrons , Radiation Protection/instrumentation , Thermoluminescent Dosimetry/instrumentation , Equipment Design , Equipment Failure Analysis , Radiation Dosage , Radiation Protection/methods , Reproducibility of Results , Sensitivity and Specificity , Thermoluminescent Dosimetry/methodsABSTRACT
In this paper some of the many theoretical models dealing with characteristics of TL materials are discussed. Special attention is given to some of the models dealing with the effects of ionisation density, that is Modified Track Structure Theory (MTST) and Microdosimetric Track Structure Theory (MTT) for the calculation of Heavy Charged Particle relative TL efficiencies, as well as solid-state models based on conduction band/valence band theory. Failures, successes, conflicts and trends are highlighted as well as a peek into future avenues of research for dosimetric TL materials.
Subject(s)
Equipment Failure Analysis , Materials Testing , Models, Theoretical , Thermoluminescent Dosimetry/instrumentation , Thermoluminescent Dosimetry/trends , Computer Simulation , Computer-Aided Design , Dose-Response Relationship, Radiation , Equipment Design , Forecasting , Radiation Dosage , Reproducibility of Results , Sensitivity and Specificity , Technology Assessment, Biomedical , Thermoluminescent Dosimetry/methodsABSTRACT
It is demonstrated experimentally that optical excitation of irradiated LiF:Mg,Ti (TLD-100) by 4 eV photons has the same effect for both alpha particle (high-ionisation density) irradiation and photon/electron irradiation. In both cases, peak 5a converts to peak 4 causing peak 4 to increase following the bleach. Such an observation is consistent with the major premise of track structure theory that radiation effects following heavy changed particle (HCP)/neutron irradiation are due exclusively to the interaction of the secondary electrons created by the HCP slowing down.
Subject(s)
Alpha Particles , Beta Particles , Fluorides/chemistry , Fluorides/radiation effects , Lithium Compounds/chemistry , Lithium Compounds/radiation effects , Models, Chemical , Thermoluminescent Dosimetry/instrumentation , Thermoluminescent Dosimetry/methods , Computer Simulation , Dose-Response Relationship, Radiation , Equipment Design , Equipment Failure Analysis , Light , Magnesium/chemistry , Magnesium/radiation effects , Materials Testing , Radiation Dosage , Titanium/chemistry , Titanium/radiation effectsABSTRACT
The optical absorption (OA) and thermoluminescence (TL) of dosimetric LiF:Mg,Ti (TLD-100) as well as nominally pure LiF single crystal have been studied as a function of irradiation dose, thermal and optical bleaching in order to investigate the role of the 4.45 eV OA band in low temperature TL. Computerised deconvolution was used to resolve the absorption spectrum into individual gaussian bands and the TL glow curve into glow peaks. Although the 4.45 eV OA band shows thermal decay characteristics similar to the 4.0 eV band its dose filling constant and optical bleaching properties suggest that it cannot be associated with the TL of composite peaks 4 or 5. Its presence in optical grade single crystal LiF further suggests that it is an intrinsic defect or possibly associated with chance impurities other than Mg, Ti.
