passive dosimeter thermoluminescent dosimeter https://www.landauer.com/blog/unveiling-science-thermoluminescent-dosimeters-key-radiation-safety-and-measurement TLD A device which measures ionizing radiation dose by storing and then releasing the energy produced by the radiation. Energy is stored in the form of excited electrons. When the dosimeter is heated the electrons return to the ground state, resulting in the emission of light. The intensity of the emitted light directly corresponds to the radiation dose received, allowing for quantifiable measurements.