Feasibility of using carbon doped aluminium oxide co-doped with magnesium as a thermoluminescence dosimeter

Abstract

Nano-polycrystalline samples of aluminum oxide doped carbon (Al2O3:C) and aluminum oxide doped carbon co-doped with magnesium (Al2O3:C, Mg) were investigated in search for the most efficient thermoluminescence (TL) dosimeter with low sensitivity to light and applicable for various radiation energy. Six samples were prepared and the samples were found to be nano-polycrystalline powder with particle size in the range of 30 to 250 nm through X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM) analysis. Those samples were exposed to Cobalt-60 gamma rays to determine the optimum concentration of dopant. The optimum concentration of dopant in atomic weight percentage (at%) is 0.2 at% of carbon dopant for doped sample (C2) and 0.2 at% of magnesium dopant of co-doped sample (C2MG2). Samples with optimum dopant were irradiated by 10 and 12 MeV electrons, 6 and 10 MV high energy x-rays over a lower dose range 0.5 to 4.0 Gy from linear accelerator (LINAC) and by Cobalt-60 gamma rays over the dose ranges of 0.5 to 4.0 Gy, and a higher dose range 10 to 100 Gy. Sample C2 and C2MG2 exhibit two TL peaks at higher dose while single peak at lower dose. Sample C2MG2 shows a linear dose response over a dose range of 0.5 to 4.0 Gy subjected to 10 and 12 MeV electrons and 6 and 10 MV high energy x-rays. Sample C2MG2 also shows a linear dose response over a dose range of 0.5 to 4.0 Gy and 10 to 100 Gy when exposed to Cobalt-60 gamma rays. TL sensitivity of sample C2MG2 is 14.22 higher than that of sample C2 when exposed to Cobalt-60 gamma rays. TL sensitivity of sample C2MG2 subjected to electron and high energy x-rays irradiation is still higher than that of sample C2 but lower in value compared to TL sensitivity of sample C2MG2 subjected to Cobalt-60 gamma rays. Addition of Mg has also minimized thermal fading of sample C2MG2 and improved reproducibility significantly for all delivered energy. However, sample C2MG2 is more sensitive to sunlight compared to sample C2, and both samples were not sensitive to fluorescence light even after 24 h of exposure. The minimum detectable dose of sample C2MG2 subjected to Cobalt-60 gamma rays, electron and high energy x-rays are 2.76, 12.49 and 13.83 mGy, respectively. TL properties of sample C2MG2 are influenced by the energy of electrons and photons. Sample C2MG2 also shows good TL properties as TL dosimeter. The measured effective atomic number, Zeff of sample C2MG2 is 11.14 and can be considered as bone-equivalence material. Kinetic analysis revealed that the glow curve of sample C2MG2 followed general kinetic order. Using four different methods, the activation energies were calculated to be in the range of 1.08 to 1.70 eV and frequency factor is between 1012 to 1019 s-1. The findings of the study show that nano-polycrystalline Al2O3:C, Mg is less affected by the light and has a capability to be used in radiation dose monitoring