Evaluation of TL and OSL responses of CaF2:Tm for electron beam processing dosimetry

Synthesis, photo- and thermo-luminescent properties of Mg2P2O7:Tm3+ phosphors

In this work, both undoped and Thulium (Tm3+) doped (0.3-10 mol%) magnesium pyrophosphate (Mg2P2O7) powders were synthesized by the solvent evaporation method to study their photo-and thermoluminescent properties. Two crystalline phases were observed in the powders by X-Ray diffraction (XRD), the main phase being Mg2P2O7 and the second one thulium phosphate (TmPO4). The superficial morphology was analyzed by scanning electron microscopy (SEM), which revealed that the powders are agglomerates with an undefined form and grains with non-uniform size distribution. The photoluminescence (PL) emission spectra of Tm3+ doped powders show the 1D2 → 3F4 transition, associated with Tm3+ ions, at 452 and 458 nm. The thermoluminescence (TL) properties were analyzed in the undoped and Tm3+ doped powders exposed to 90Sr beta source. The TL glow curve of Tm3+ doped powders exhibits three maxima at about ⁓64-66 °C, ⁓198-202 °C, and ⁓301 °C. The TL dose-response is sub-linear from 0.11 to 0.54 Gy, linear between 0.79 and 24.95 Gy, and supra-linear from 34.99 to 599.95 Gy. Acceptable repeatability with a coefficient of variation of ∼1% was obtained after ten cycles of irradiation and readout. At 63 d of storage, the powders show fading of 30%, and at 1.6 years (585 d), the integrated TL intensity decays by 47%. The kinetic parameters of activation energy and frequency factor were evaluated using the Initial Rise, Booth, Bohun, and Porfianovitch (BBP) and Hoogenstraaten methods and Glow Curve Deconvolution with a general order kinetic model.

An investigation of luminescence properties of CaF2: Dy nanophosphor irradiated with gamma rays and low energy proton beams

This paper reports the luminescence properties of nanocrystalline calcium fluoride doped with dysprosium (CaF₂: Dy). The nanophosphor has been synthesized by the chemical co-precipitation technique and the dopant concentration has been optimized at 0.3 mol% using thermoluminescence (TL) intensity emitted post 50Gy gamma dose irradiation of samples doped with different dopant concentrations. X-ray diffraction shows the formation of crystalline particles with an average size of 49.233 nm. Photoluminescence (PL) emission spectrum shows the characteristic peaks at 455 nm, 482 nm, 573 nm corresponding to ⁴I_15/2 to ⁶H_15/2, ⁴F_9/2 to ⁶H_15/2 and ⁴F_9/2 to ⁶H_13/2 Dy³⁺ transitions respectively. PL excitation spectrum shows a peak at 327 nm which corresponds to the Dy³⁺ transition of ⁶H_15/2 to ⁴L_19/2. Gamma (of 1.25 MeV) and low energy proton beam (of 30 keV) irradiated nanophosphor shows a variation in TL glow curve structure and peak position with an increase in radiation dose/fluence. However, the nanophosphor shows a wide linear dose response for ⁶⁰Co gamma radiation in the range 10 Gy - 1.5 kGy and for low energy proton beam in the fluence range of 10¹²-10¹⁴ ions/cm². Srim 2013 has been used to calculate the ion beam parameters including the range of protons in CaF₂: Dy 0.3 mol%. The nanophosphor CaF₂: Dy could be further investigated as a potential dosimeter for gamma rays and proton beam by studying its TL properties for different energies of these radiations.