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Borate Phosphors for Radiation Dosimetery
Published in S. K. Omanwar, R. P. Sonekar, N. S. Bajaj, Borate Phosphors, 2022
‘Retrospective dosimetry' is the term used when determining the dose of absorbed radiation to environmental or locally available materials in situations where conventional, synthetic dosimeters were not in place at the time of radiation exposure. Two major categories exist: dating and accident dosimetry. In the luminescence dating, if one wishes to establish the dose delivered to natural materials during exposure to natural radiation over the lifetime of the sample in a certain environment. The other category is accident dosimetry, where one is interested in the determination of absorbed dose due to a radiation accident or other event, over and above the normal background radiation. OSL is proving to be a useful tool in these applications [175].
Persistent Luminescence: Cerium-Doped Phosphors
Published in Sanjay J. Dhoble, B. Deva Prasad Raju, Vijay Singh, Phosphors Synthesis and Applications, 2018
A good LLP material possesses the following properties:The first property is the initial afterglow intensity and the afterglow duration. While the initial intensity is an important factor for safety signage applications, the afterglow duration can be defined as the duration below which the photopic intensity decreases to an eye-perceivable intensity value of 0.32 mcd/m2.The activation energy of traps that store charges (electrons/holes) must be between 0.5 and 1.0 eV, which can be emptied continuously at room temperature. The activation energy can be measured using the thermoluminescence (TL) technique [18]. The traps with activation energy greater than 1.0 eV are suitable for storage devices and for luminescence dating. The traps require additional energy for charge release, which can be supplied by either thermal energy or optical energy [18,19]. TL glow curves responsible for persistent luminescence and the effective technique of phototransfer are shown in Fig. 2.2.The frequency factor or an attempt to escape frequency (s, in sec−1) is another parameter for good LLP materials. The delay in phosphorescence is generally due to the time spent by the charges (e.g., electrons) in the electron traps. The mean time spent in a trap at temperature T is given by Eq. 2.1
Luminescence dating of Quaternary alluvial successions, Sellicks Creek, South Mount Lofty Ranges, southern Australia
Published in Australian Journal of Earth Sciences, 2020
R. P. Bourman, D. Banerjee, C. V. Murray-Wallace, S. Buckman, D. K. Panda, A. P. Belperio, C. L. Jayawardena
Luminescence dating techniques (Aitken, 1985, 1998; Bateman, 2019) represent a significant advance in Quaternary geochronology, as luminescence ages do not require calibration, the age range of the methods span several hundred thousand years, and in geological contexts, the event dated corresponds with the time of sedimentation, representing the last time that mineral particles (quartz and feldspar) were exposed to sunlight. Luminescence methods are based on electron capture, involving the progressive storage of free electrons within mineral lattice defects and electron traps owing to exposure to ionising radiation and cosmic rays during the burial history of sediment. The luminescence quantified in samples during laboratory stimulation is proportional to the dose accumulated in the natural environment. The equivalent dose (De) represents the inferred naturally accumulated dose. The luminescence age of sediments is obtained by dividing the equivalent dose (De) by the dose rate (D) for the same sample.