What material is contained in a TLD dosimeter?

A thermoluminescent dosimeter (TLD) utilizes lithium fluoride as its sensing material. When ionizing radiation interacts with lithium fluoride, it causes certain electrons in the crystal lattice to be excited to a higher energy state. Over time, these excited electrons are trapped in imperfections within the crystal structure.

When the TLD is heated, the trapped electrons return to their original state, releasing energy in the form of light. The intensity of this light is proportional to the amount of radiation exposure that the dosimeter has received. This property allows TLDs to be effective for monitoring radiation exposure over time, making lithium fluoride an ideal choice because of its favorable thermoluminescent properties and its close atomic number to tissue, which enhances its use for radiation measurement.

Other materials mentioned, such as silicon, calcium sulfate, and aluminum oxide, while they have applications in radiation detection, do not serve the same purpose as an active dosimeter material in thermoluminescence specifically. Therefore, lithium fluoride stands out as the correct answer to this question regarding the contents of a TLD dosimeter.