What chemical is found in dosimeter badges?

• A. Sodium fluoride
• B. Calcium fluoride
• C. Lithium fluoride
• D. Lithium chloride

Answer: (C)

Lithium fluoride is used in dosimeter badges because it serves as a thermoluminescent material that stores energy when exposed to ionizing radiation and releases light when heated, with the light output proportional to the absorbed dose. Its composition gives a tissue-equivalent response, meaning its energy absorption mirrors that of human tissue, which helps produce more accurate dose readings for the wearer. In practical badges, lithium fluoride is used in forms like LiF:Mg,Ti (and other doped variants) that are stable, can be read out reliably, and are reusable after annealing. While other fluorides exist, they don’t offer the same combination of tissue equivalence, light yield, and stability for badges, and lithium chloride is avoided due to hygroscopicity and instability in practical badge use.