What crystal is used in a thermoluminescent dosimeter (TLD)?

• A. Lithium Fluoride
• B. Cesium Iodide
• C. Barium Sulfate
• D. Amorphous Silicon

Answer: (A)

Thermoluminescent dosimeters rely on a crystal that traps energy deposited by ionizing radiation and then releases that energy as light when heated. Lithium fluoride fits this role well because its crystal lattice forms stable electron traps that store dose information and release it as luminescence in a predictable, measurable way. This material also has a good match to human tissue in terms of radiation interaction (a useful plus for dosimetry), allowing for accurate dose assessment over a wide range of exposures. Doped forms like LiF:Mg,Ti enhance trap depth and light yield, improving sensitivity and linearity of response.

Other options aren’t used as the primary TLD crystal. Cesium iodide is a scintillator that emits light immediately under radiation rather than storing energy for later release. Barium sulfate is typically a phosphor or filler and not used for thermoluminescent storage. Amorphous silicon is used in electronic dosimeters, not in thermoluminescent crystals.