Thermoluminescence is a form of luminescence that is exhibited by certain crystalline materials, such as some minerals, when previously absorbed energy from electromagnetic radiation or other ionizing radiation is re-emitted as light upon heating of the material. The phenomenon is distinct from that of black-body radiation.
High energy radiation creates electronic excited states in crystalline materials. In some materials, these states are trapped, or arrested, for extended periods of time by localized defects, or imperfections, in the lattice interrupting the normal intermolecular or inter-atomic interactions in the crystal lattice. Quantum-mechanically, these states are stationary states which have no formal time dependence; however, they are not stable energetically, as vacuum fluctuations are always "prodding" these states. Heating the material enables the trapped states to interact with phonons, i.e. lattice vibrations, to rapidly decay into lower-energy states, causing the emission of photons in the process.
The amount of luminescence is proportional to the original dose of radiation received. In thermoluminescence dating, this can be used to date buried objects that have been heated in the past, since the ionizing dose received from radioactive elements in the soil or from cosmic rays is proportional to age. This phenomenon has been applied in the thermoluminescent dosimeter, a device to measure the radiation dose received by a chip of suitable material that is carried by a person or placed with an object.
Thermoluminescence is a common geochronology tool for dating pottery or other fired archeological materials, as heat empties or resets the thermoluminescent signature of the material (Figure 1). Subsequent recharging of this material from ambient radiation can then be empirically dated by the equation:
Age = (subsequently accumulated dose of ambient radiation) / (dose accumulated per year)
This technique was modified for use as a passive sand migration analysis tool (Figure 2). [1] The research shows direct consequences resulting from the improper replenishment of starving beaches using fine sands. Beach nourishment is a problem worldwide and receives large amounts of attention due to the millions of dollars spent yearly in order to keep beaches beautified for tourists, [2] e.g. in Waikiki, Hawaii. Sands with sizes 90–150 μm (very fine sand) were found to migrate from the swash zone 67% faster than sand grains of 150-212 μm (fine sand; Figure 3). Furthermore, the technique was shown to provide a passive method of policing sand replenishment and a passive method of observing riverine or other sand inputs along shorelines (Figure 4). [1]
A radiation dosimeter is a device that measures dose uptake of external ionizing radiation. It is worn by the person being monitored when used as a personal dosimeter, and is a record of the radiation dose received. Modern electronic personal dosimeters can give a continuous readout of cumulative dose and current dose rate, and can warn the wearer with an audible alarm when a specified dose rate or a cumulative dose is exceeded. Other dosimeters, such as thermoluminescent or film types, require processing after use to reveal the cumulative dose received, and cannot give a current indication of dose while being worn.
Luminescence is the "spontaneous emission of radiation from an electronically excited species not in thermal equilibrium with its environment", according to the IUPAC definition. A luminescent object is emitting "cold light", in contrast to "incandescence", where an object only emits light after heating. Generally, the emission of light is due to the movement of electrons between different energy levels within an atom after excitation by external factors. However, the exact mechanism of light emission in "vibrationally excited species" is unknown, as seen in sonoluminescence.
X-ray fluorescence (XRF) is the emission of characteristic "secondary" X-rays from a material that has been excited by being bombarded with high-energy X-rays or gamma rays. The phenomenon is widely used for elemental analysis and chemical analysis, particularly in the investigation of metals, glass, ceramics and building materials, and for research in geochemistry, forensic science, archaeology and art objects such as paintings.
Thermoluminescence dating (TL) is the determination, by means of measuring the accumulated radiation dose, of the time elapsed since material containing crystalline minerals was either heated or exposed to sunlight (sediments). As a crystalline material is heated during measurements, the process of thermoluminescence starts. Thermoluminescence emits a weak light signal that is proportional to the radiation dose absorbed by the material. It is a type of luminescence dating.
A scintillation counter is an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a scintillating material, and detecting the resultant light pulses.
Radiation dosimetry in the fields of health physics and radiation protection is the measurement, calculation and assessment of the ionizing radiation dose absorbed by an object, usually the human body. This applies both internally, due to ingested or inhaled radioactive substances, or externally due to irradiation by sources of radiation.
Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as "The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this". Exposure can be from a source of radiation external to the human body or due to internal irradiation caused by the ingestion of radioactive contamination.
In physics, optically stimulated luminescence (OSL) is a method for measuring doses from ionizing radiation. It is used in at least two applications:
Health physics, also referred to as the science of radiation protection, is the profession devoted to protecting people and their environment from potential radiation hazards, while making it possible to enjoy the beneficial uses of radiation. Health physicists normally require a four-year bachelor’s degree and qualifying experience that demonstrates a professional knowledge of the theory and application of radiation protection principles and closely related sciences. Health physicists principally work at facilities where radionuclides or other sources of ionizing radiation are used or produced; these include research, industry, education, medical facilities, nuclear power, military, environmental protection, enforcement of government regulations, and decontamination and decommissioning—the combination of education and experience for health physicists depends on the specific field in which the health physicist is engaged.
An F center or Farbe center is a type of crystallographic defect in which an anionic vacancy in a crystal lattice is occupied by one or more unpaired electrons. Electrons in such a vacancy in a crystal lattice tend to absorb light in the visible spectrum such that a material that is usually transparent becomes colored. The greater the number of F centers, the more intense the color of the compound. F centers are a type of color center.
Radiation hardening is the process of making electronic components and circuits resistant to damage or malfunction caused by high levels of ionizing radiation, especially for environments in outer space, around nuclear reactors and particle accelerators, or during nuclear accidents or nuclear warfare.
The ionization chamber is the simplest type of gaseous ionisation detector, and is widely used for the detection and measurement of many types of ionizing radiation, including X-rays, gamma rays, alpha particles and beta particles. Conventionally, the term "ionization chamber" refers exclusively to those detectors which collect all the charges created by direct ionization within the gas through the application of an electric field. It uses the discrete charges created by each interaction between the incident radiation and the gas to produce an output in the form of a small direct current. This means individual ionising events cannot be measured, so the energy of different types of radiation cannot be differentiated, but it gives a very good measurement of overall ionising effect.
A film badge dosimeter or film badge is a personal dosimeter used for monitoring cumulative radiation dose due to ionizing radiation.
Radioluminescence is the phenomenon by which light is produced in a material by bombardment with ionizing radiation such as alpha particles, beta particles, or gamma rays. Radioluminescence is used as a low level light source for night illumination of instruments or signage. Radioluminescent paint is occasionally used for clock hands and instrument dials, enabling them to be read in the dark. Radioluminescence is also sometimes seen around high-power radiation sources, such as nuclear reactors and radioisotopes.
Absolute dating is the process of determining an age on a specified chronology in archaeology and geology. Some scientists prefer the terms chronometric or calendar dating, as use of the word "absolute" implies an unwarranted certainty of accuracy. Absolute dating provides a numerical age or range, in contrast with relative dating, which places events in order without any measure of the age between events.
Luminescence dating refers to a group of chronological dating methods of determining how long ago mineral grains were last exposed to sunlight or sufficient heating. It is useful to geologists and archaeologists who want to know when such an event occurred. It uses various methods to stimulate and measure luminescence.
A thermoluminescent dosimeter, or TLD, is a type of radiation dosimeter, consisting of a piece of a thermoluminescent crystalline material inside a radiolucent package.
X-ray detectors are devices used to measure the flux, spatial distribution, spectrum, and/or other properties of X-rays.
Optically stimulated luminescence (OSL) thermochronometry is a dating method used to determine the time since quartz and/or feldspar began to store charge as it cools through the effective closure temperature. The closure temperature for quartz and Na-rich K-feldspar is 30-35 °C and 25 °C respectively. When quartz and feldspar are beneath the earth, they are hot. They cool when any geological process e.g. focused erosion causes their exhumation to the earth surface. As they cool, they trap electron charges originating from within the crystal lattice. These charges are accommodated within crystallographic defects or vacancies in their crystal lattices as the mineral cools below the closure temperature.
Passive daytime radiative cooling (PDRC) is a zero-energy building cooling method proposed as a solution to reduce air conditioning, lower urban heat island effect, cool human body temperatures in extreme heat, move toward carbon neutrality and control global warming by enhancing terrestrial heat flow to outer space through the installation of thermally-emissive surfaces on Earth that require zero energy consumption or pollution. Application of PDRCs may also increase the efficiency of systems benefiting of a better cooling, such like photovoltaic systems, dew collection techniques, and thermoelectric generators.
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