As was written, previously absorbed energy from electromagnetic radiation or other ionizing radiation in these materials is re-emitted as light upon heating of the material. The intensity of light emitted is measure by TLD reader and it is dependent upon the radiation exposure. A typical basic TLD reader contains the following components:
- Heater. Heater raises the temperature of the TL material
- Photomultiplier tube. PMT amplifies and measures the light output.
- Meter/Recorder. Recorder is able to display and record data.
In order to obtain the dose received, the TLD chip must be heated in this TLD reader. The trapped electrons return to the ground state and emit photons of visible light. The amount of light emitted relative to the temperature is called the glow curve. This curve is analyzed to determine the dose. After the readout is complete, the TLD is annealed at a high temperature. This process essentially zeroes the TL material by releasing all trapped electrons. The TLD is then ready for reuse. There are two types of readers. Automatic, and manual readers. The automatic TLD reader is a lot more complicated than it might expected.