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Single crystals of Li 2 B 4 O 7 (LTB) with varying Ag content were grown using the Czochralski technique and studied for their optical absorption, photo-luminescence (PL) and thermally stimulated luminescence (TSL) properties. The optimum Ag concentration in the LTB was found to be about 500 ppm for the best TSL properties. A TSL readout set-up has been described that uses a solar blind photo-multiplier tube (PMT) to match the emission from Ag which is in the UV region (peak at 270 nm). This has significantly improved the performance of the TSL set-up by lowering dark counts and enhancing the signal due to a better matching between the emission from Ag ions and PMT response. In addition, the use of the solar blind PMT also minimized the thermal noise generated from heating of sample in the TSL set-up. Radiation doses lower than 5 μGy could be measured using this set-up with small LTB:Ag crystal samples (100 mg). The lower detection limit has been estimated to be 500 nGy. [ABSTRACT FROM AUTHOR]

Abstract: Single crystals of Li2B4O7 (LTB) doped with Cu and Ag and Cu, Ag co-doped have been grown using the Czochralski technique. Luminescence studies revealed a sensitizer role of Ag in the LTB:Cu,Ag crystal. It is found that, despite an energy transfer from Ag+ to Cu+ centers, emission from both the centers participate in the thermally stimulated luminescence (TSL) of co-doped. We propose that the LTB:Cu,Ag crystal will be a better and efficient material for dosimeters [TSL as well as optically stimulated luminescence (OSL)] compared to singly doped LTB crystals in a photo-readout system having a maximum response in the 200nm to 600nm range. [Copyright &y& Elsevier]

Abstract: An optically transparent ceramic of CaF2:Mn has been prepared by hot pressing of nano-phase powders under vacuum conditions. The transmission recorded for a 1mm thick sample at 800nm was about 50%. A scanning electron micrograph exhibited a pore-free structure without any secondary phases at the grain boundaries. The doping concentration of Mn and its oxidation state as determined using secondary ion mass spectrometry and X-ray photoemission spectroscopy were 1.5at.% and Mn2+, respectively. The photo-luminescence properties of these ceramics were studied and their application as a thermo-luminescent dosimeter has been established. These ceramics were able to measure low level doses down to about 3mGy and exhibited a linear output up to 100mGy. [Copyright &y& Elsevier]

Abstract: Results of photoluminescence in conjunction with photoconductivity properties of NaBi(WO4)2 crystal are presented and explained with the help of calculated electronic and optical properties. Crystals were annealed in air/vacuum to change the local environment near (WO4)2− complex and consequently two emission bands near 470 and 520nm could be separated for excitation at different energies. The activation energy for thermal quenching of emission was calculated to be 160meV. The role of excitons and localization of charge carriers is explained on the basis of photoconductivity of these crystals that has been observed only intrinsically in contrast to iso-structurally PbWO4. [Copyright &y& Elsevier]

Abstract: Large size, transparent and crack-free single crystals of pure and 0.1mol% Ce doped Li6Gd(BO3)3 have been grown using the Czochralski technique. The photoluminescence and decay kinetics in millisecond range were investigated in the 77–300K temperature range. In the case of Ce doped single crystals a broad emission band at 400nm corresponding to 5d→4f transitions of Ce3+ centers has been observed near room temperature. This emission band splits into two peaks at 386nm and 414nm below 200K. The temperature dependence of Ce3+ emission corresponding to excitation bands at 312 and 345nm were studied. It was observed that for an excitation at 345nm (corresponding to the Ce3+ ions alone) the emission intensity decreases with increasing temperatures while it remains constant for the excitation of Ce3+ at 312nm that coincides with the Gd3+ energy level at the same wavelength. This suggests the participation of a temperature dependent energy transfer mechanism between Gd3+ and Ce3+ ions in the Li6Gd(BO3)3 matrix. The mechanism has been explained by studying the temperature dependence of Gd3+ emission at 312nm in the doped and undoped crystals. [Copyright &y& Elsevier]

The molten salt of Strontium Iodide (SrI 2 ) and Europium Iodide (EuI 2 ) was filtered by specially designed dual chamber quartz ampoule using micro frit filter. Eu 2+ doped SrI 2 single crystal was grown by modified transparent vertical Bridgman technique. Photoluminescence (PL) excitation and emission (PLE) were recorded for the grown crystal. The characteristic emission of Eu 2+ was observed at 432 nm. Similar emission was observed at 435 nm, when the sample was excited by X-ray source also. Scintillation properties of the SrI 2 :Eu 2+ crystal were checked by the gamma ray spectrometer using 137 Cs, 57 Co and 60 Co gamma sources. The energy resolutions of the grown crystal were found to be 4.6% at 662 KeV, 7.5% at 122 KeV and 9.8% at 1332 KeV. The Scintillation decay profile was also analyzed. The scintillation decay time of Eu 2+ ion was calculated to be 1.26 μs for SrI 2 :Eu 2+ single crystal. [ABSTRACT FROM AUTHOR]

Abstract: Lithium tetraborate (Li2B4O7) is a tissue equivalent material and single crystals of this material doped with Cu are promising for dosimetric applications. In the present study highly transparent single crystals of lithium tetraborate (Li2B4O7) doped with Cu (0.5wt%) have been grown using the Czochralski technique. The Li2B4O7:Cu crystals were studied using photoluminescence, X-ray diffraction (XRD), UV–vis transmission, time resolved fluorescence and thermoluminescence (TL) techniques. The TL readout of Li2B4O7:Cu crystals showed two well-defined glow peaks at 402K (peak-1) and 513K (peak-2) for a 4K/s heating rate. While the low temperature TL peak-1 fades completely within 24h at room temperatures, the main dosimetric peak-2 remains the same. The TL sensitivity of the grown single crystal is found to be 3.3 times that of a conventional TL phosphor, TLD-100. The Li2B4O7:Cu crystals showed a linear TL dose–response in the range from 1mGy to 1kGy. The TL analysis using a variable dose method revealed first order kinetics for both the peaks. Trap depth and frequency factor for peak-1 were found to be 0.81eV and 5.2×109 s−1, whereas for peak-2 the values were 1.7eV and 1.7×1016 s−1, respectively. [ABSTRACT FROM AUTHOR]