Addressing Current Challenges in OSL Dosimetry Using MgB4O7:Ce,Li: State of the Art, Limitations and Avenues of Research.

The objective of this work is to review and assess the potential of MgB4O7:Ce,Li to fill in the gaps where the need for a new material for optically stimulated luminescence (OSL) dosimetry has been identified. We offer a critical assessment of the operational properties of MgB4O7:Ce,Li for OSL dosimetry, as reviewed in the literature and complemented by measurements of thermoluminescence spectroscopy, sensitivity, thermal stability, lifetime of the luminescence emission, dose response at high doses (>1000 Gy), fading and bleachability. Overall, compared with Al2O3:C, for example, MgB4O7:Ce,Li shows a comparable OSL signal intensity following exposure to ionizing radiation, a higher saturation limit (ca 7000 Gy) and a shorter luminescence lifetime (31.5 ns). MgB4O7:Ce,Li is, however, not yet an optimum material for OSL dosimetry, as it exhibits anomalous fading and shallow traps. Further optimization is therefore needed, and possible avenues of investigation encompass gaining a better understanding of the roles of the synthesis route and dopants and of the nature of defects.

Synthesis and thermoluminescent response to γ-rays and neutrons of MgB4O7:Dy and MgB4O7:Dy,Na.

MgB4O7 doped with rare earths and alkaline elements has been reported as a good TLD because of its high sensitivity, effective atomic number close to that of biological tissue and low fading. In this work, thermoluminescent matrices were synthesized of MgB4O7:Dy and MgB4O7:Dy, Na to evaluate their thermoluminescent response (TL) when exposed to γ-rays and neutrons. The amount of Dy was studied in a concentration range of 0.01-1.5 mol% of total doping, while for Na the concentration of 0.5 mol% was established to determine the TL response as a function of doping. The synthesis of the powders was carried out by the method of wet reaction assisted by heat treatment and the samples were characterized by techniques of scanning electron microscopy and X-ray diffraction to determine the size of grain and crystallographic phase. For the dosimetric study, thermoluminescent phosphors were irradiated with a source of 137Cs at an estimated dose 6.8 ±â€¯0.4 mGy to evaluate their response to γ-rays exposure, while for neutrons a source of 241AmBe was used (estimated dose of 3.1 ±â€¯0.1 mGy). The thermoluminescent responses are similar for all materials exposed to γ-rays as for neutrons, the differences are shown to 280 °C, where a peak of high temperature is observed in materials exposed to neutrons.

Neutron+Gamma response of undoped and Dy doped MgB4O7 thermoluminescence dosimeter.

Thermoluminescence properties of undoped and Dy doped MgB4O7 compounds were studied with the irradiation of 252Cf source. The TL kinetic parameters of MgB4O7: Dy were studied by computer glow curve deconvolution (CGCD) method. The glow curve structures of 1% Dy doped magnesium tetraborate compound consists of at least five glow peaks with a main dosimetric peak at about 220 °C. The highest sensitivity which is approximately 1.90 and 1.47 times higher than that of TLD-600 and TLD-700 was found for MgB4O7: Dy (1 mol%). The results clearly showed that Dysprosium doped magnesium borate has a potential to be considered as the thermoluminescence neutron + gamma dosimeter.

Characterisation and luminescence studies of Tm and Na doped magnesium borate phosphors.

In this study, structural and luminescence properties of magnesium borate of the form MgB4O7 doped with Tm and Na were investigated by X-ray diffraction (XRD), Raman spectroscopy and cathodoluminescence (CL). The morphologies of the synthetised compounds exhibit clustered granules and road-like materials. As doping trivalent ions into a host with divalent cations requires charge compensation, this effect is discussed. The CL spectra of undoped MgB4O7 shows a broad band emission centred around 350 nm which is postulated to be produced by self-trapped excitons and some other defects. From the CL emission spectrum, main emission bands centred at 360, 455, 475 nm due to the respective transitions of (1)D2→(3)H6,(1)D2→(3)F4 and (1)G4→(3)H6 suggest the presence of Tm(3+) ion in MgB4O7 lattice site. CL mechanism was proposed to explain the observed phenomena which are valuable in possibility of the developing new luminescent materials for different applications. In addition, the experimental Raman spectrum of doped and undoped MgB4O7 were reported and discussed.