Thermoluminescence Detectors

Thermoluminescence Detectors (TLDs) are based on the emission of Thermoluminscence (TL) on heating of previously exposed crystalline materials. The intensity of the emitted TL is a function of the dose deposited in the material, and can therefore be used for dosimetry. The production of TL in dosimetric materials is a complex, multistage process involving the transfer of charge and energy between different defect states within the crystal. The final measured TL intensity is the net result of the reaction between photons or nuclear particles of the irradiation field, the type, number and distribution of the defects present within the crystal at the time of irradiation and heating, the nature of the irradiated crystal and on other factors such as the irradiation rate, temperature, and energy of the absorbed particles.

The simplest model of the TL process involves a single state for holes and a single state for electrons. Electrons trapped at trap sites of the crystal are thermally elevated into the conduction band during the heating process. Once in the conduction band, the electrons are captured by holes trapped in luminescence centers, with emission of photons.

Several materials were found to be suitable for TLD dosimetry. The most common application of TLD dosimeters is in personnel dosimetry. Specifications (materials, geometry, shielding) of TLD dosimeters can be found in the paragraph on TLD Badges.

The most common application of TLDs is in gamma ray and X-ray dosimetry. However, they can also be used for neutron dosimetry and for the dosimetry of heavy ion beams (© Copyright, Dr. Oliver Geiß).

Irradiators (for calibration purposes) and readers are needed for the operation of TL dosimetry systems. The TLD Read Process follows strict guidelines.

---

www.nucleonics-online.com/657.html
Edited on 16 July 2002 - E-mail to the Webmaster