Synthesis and characterization of europium doped lithium tetraborate single crystals for thermoluminescent dosimetry applications
摘要
The search for efficient, tissue-equivalent, and reusable thermoluminescent dosimeters (TLDs) for personal and clinical dosimetry is a persistent endeavor in radiation physics. This work presents a comprehensive investigation of Europium (Eu)-doped Lithium Tetraborate (Li₂B₄O₇:Eu, 3 mol%) single crystals grown by the Czochralski pulling technique for applications in gamma, X-ray, and proton dosimetry. Optically transparent single crystals were successfully synthesized. The thermoluminescence (TL) glow curve of the developed phosphor, irradiated with a Co-60 gamma source, exhibited a single, well-defined peak at approximately 210 °C, indicative of good thermal stability and minimal fading at room temperature. The dose–response was linear from 0.1 Gy to 10 Gy for gamma rays and from 0.5 to 20 Gy for protons. A supralinear response was observed for gamma doses above 10 Gy up to 100 Gy. Energy dependence studies with X-rays (50 kVp to 300 kVp) revealed minimal variation, attributable to the near tissue-equivalent effective atomic number (Zeff ≈ 7.42 for the doped material) of the Li₂B₄O₇ host matrix. Repeatability tests over 10 cycles of irradiation and readout showed excellent repeatability with a standard deviation of less than 2.5%. Fading analysis indicated a signal loss of only about 4% over 30 days of storage in dark conditions. A comparative study with the commercial standard TLD-100 (LiF:Mg,Ti) demonstrated that the Li₂B₄O₇:Eu crystal possesses a superior linear dose response, lower energy dependence, and comparable fading characteristics. Notably, the proton response showed a high TL efficiency relative to gamma rays, confirming its suitability for proton therapy dosimetry. The developed Li₂B₄O₇:Eu single crystal emerges as a versatile and promising TLD for diverse radiotherapy and diagnostic applications.