Which material is commonly used as the active sensor in a thermoluminescent dosimeter?

Which material is commonly used as the active sensor in a thermoluminescent dosimeter?

• A. Selenium
• B. Lithium fluoride
• C. Cesium iodide
• D. Sodium chloride

Answer: (B)

Lithium fluoride is used because it forms a stable, tissue-equivalent crystal that stores energy from ionizing radiation in trap sites and then emits light when heated. This luminescence, measured as a glow after irradiation, is proportional to the absorbed dose, making LiF (especially doped LiF:Mg,Ti) the reliable active sensor in thermoluminescent dosimeters. Its effective atomic number is close to that of human tissue, which gives more accurate dose readings across common energies, and it has favorable glow-curve characteristics and reusability after annealing. Other materials listed aren’t standard TLD sensors. Selenium, CsI, and NaCl are used in other radiation detectors or dosimetry contexts, but they don’t provide the same combination of tissue-equivalence, stable trap-based luminescence, and reusability that LiF offers in thermoluminescent dosimetry.

Lithium fluoride is used because it forms a stable, tissue-equivalent crystal that stores energy from ionizing radiation in trap sites and then emits light when heated. This luminescence, measured as a glow after irradiation, is proportional to the absorbed dose, making LiF (especially doped LiF:Mg,Ti) the reliable active sensor in thermoluminescent dosimeters. Its effective atomic number is close to that of human tissue, which gives more accurate dose readings across common energies, and it has favorable glow-curve characteristics and reusability after annealing.

Other materials listed aren’t standard TLD sensors. Selenium, CsI, and NaCl are used in other radiation detectors or dosimetry contexts, but they don’t provide the same combination of tissue-equivalence, stable trap-based luminescence, and reusability that LiF offers in thermoluminescent dosimetry.