Thermoluminescent material

A dosimeter is used to collect cumulative evidence of exposure to radiation and is worn as a badge. Dosimeters contain a thermoluminescent material such as lithium fluoride. Any incident radiation knocks electrons out of the flu-... 

Thermoluminescent materials absorb and store radiation that is subsequently released as light when the material is heated. The amount of light released is directly proportional to the amount of radiation absorbed. 

When radiation energy is absorbed by crystals of certain materials (e.g. lithium fluoride, lithium borate and calcium fluoride), the absorbed energy is trapped (stored) as displaced electrons within the crystal structure. If the material is heated later after the exposure, the trapped electrons are released and the stored absorbed energy is released in the form of visible light. This process is called thermoluminescence. Materials having this characteristic are called thermoluminescent. 

The size of the electric pulse is measured, and is proportional to the light output from the TLD material, which in turn is proportional to the total radiation energy absorbed, i.e. to the total radiation dose accumulated over the time that the TLD material was exposed. The TLD material can be used again after read-out. Thermoluminescent materials are commonly used in personal dose meters, in so-called TLD badges. 

There are many thermoluminescent materials, but those useful for dosimetry should have the following characteristics. 

In principle, different types of passive detectors can be used such as thermoluminescent materials, electret devices, and solid-state nuclear track detectors. 

A second type of badge detector is a thermoluminescence dosimeter that traps energy from radiation in a thermoluminescent material that releases this energy when it is heated. These detectors have largely replaced film badges because they are very sensitive and have a linear response over a wide range of doses as well as dose rates. 

Artificial sources of radiation are commonly used in industry, research, medicine, nuclear power plants (NPP), etc. Some workers are exposed to natural sources, for example, in mines and other conditions where the radon concentration in air might be higher than in normal cases. Relatively high dose rates are measured during air travel due to the elevated levels of cosmic rays at high altitudes. This means that many people are exposed in their work. Some of them are monitored individually, for example, by a small photographic film, thermoluminescent material, or portable electronic devices. These types of detectors on the body register the dose due to the external sources and yield an estimate of the dose received by the wearer. 

Kovalev D, Heckler H, Averboukh B, Ben-Chorin M, Schwartzkopff M, Koch F (1998) Hole burning spectroscopy of porous silicon. Phys Rev B 57(7) 3741-3744 McKeever SWS (1984) Thermoluminescence in quartz and silica. Radiat Prot Dosim 8(l/2) 81-98 Moscovitch M, Horowitz YS (2007) Thermoluminescent materials for medical applications LiF Mg, Ti and LiFiMg, Cu, P. Radiat Meas 41 S71-S77 Pincik E, Bartos P, Jergel M, Falcony C, Bartos J, Kucera M, Kakos J (1999) The metastability of porous silicon/crystalline silicon structure. Thin Solid Films 343-344 277-280 Rivera T (2011) Synthesis and thermoluminescent characterization of ceramics materials. In Sikalidis C (ed) Advances in ceramics - synthesis and characterization, processing and specific applications. InTech, Rijeka, Croatia pp 127-164 Skryshevskii YA, Skryshevskii VA (2001) Thermally stimulated luminescence in porous silicon. J Appl Phys 89(5) 2711-2714... 

In thermoluminescence dating, a sample of the material is heated, and the light emitted by the sample as a result of the de-excitations of the electrons or holes that are freed from the traps at luminescence centers is measured providing a measure of the trap population density. This signal is compared with one obtained from the same sample after a laboratory irradiation of known dose. The annual dose rate for the clay is calculated from determined concentrations of radioisotopes in the material and assumed or measured environmental radiation intensities. 

Trace-element analysis of metals can give indications of the geographic provenance of the material. Both emission spectroscopy (84) and activation analysis (85) have been used for this purpose. Another tool in provenance studies is the measurement of relative abundances of the lead isotopes (86,87). This technique is not restricted to metals, but can be used on any material that contains lead. Finally, for an object cast around a ceramic core, a sample of the core material can be used for thermoluminescence dating. 

Thermoluminescence measurements on a few milligrams of material scraped from fired-clay objects, such as pottery and figurines, can readily establish whether objects made of these materials are genuine antiquities, recent copies, or fakes. Chemical tests on what appeared to be a broken and restored terracotta statuette, purporting to be of Etruscan origin (from... 

Zimmerman, D. W., M. P. Yuhas, and P. Meyers (1974), Thermoluminescence authenticity measurements on core material from the bronze horse of the New York Metropolitan Museum of Art, Archaeometry 16, 19-30. 

Mechanoluminescence or triboluminescence arises from the mechanical action on solids lyoluminescence is where the emission of light occurs when a material goes into solution. Thermoluminescence is observed during the heating of a solid that has previously absorbed energy from radiation, as ions trapped in the solid recombine. (See also Glossary for an explanation of the terms.)... 

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