The present application relates generally to the field of ionizing radiation dosimeters and more specifically to radiation dosimeters that comprise a chalcogenide glass layer configured to interact with metal atoms.
A radiation dosimeter is an instrument for measuring the dose of radiation absorbed by a matter or the intensity of a source of radiation, usually measured over a period of time. Dosimeters are used in proximity to nuclear power sources, such as sea- or land-based nuclear reactors, in proximity to reactive elements in labs or in proximity to nuclear waste, and used by astronauts, among other things.
One of the more prevalent types of radiation dosimeters are film badge dosimeters. Film badge dosimeters are usually made of two parts: a reactive or photographic film and a film holder. The film is removable and may be developed in order to measure exposure. The film is sensitive to radiation and once developed, the areas of the film that have been exposed to radiation exhibit an increased optical density. Additionally, a badge may contain several films of different sensitivities or a single film with multiple coatings, in order to measure a wider range of exposure levels than in the single film/single coating implementation. However, film badge dosimeters have several disadvantages. Perhaps the most significant disadvantage is that they are not useful as a clear real-time indicator of radiation exposure.
Another form of dosimeter is the quartz fiber dosimeter. The quartz fiber dosimeter operates by measuring the decrease in electrostatic charge on a metal conductor in an ionization chamber due to ionization of air in the chamber caused by exposure to ionizing radiation. As opposed to the film badge dosimeters, the radiation doses can be read almost immediately. However, quartz fiber dosimeters are characterized by low accuracy and a small dynamic range.
Thermoluminescent dosimeters sense ionizing radiation as a function of the amount of visible light emitted by a crystal in the detector. The amount of light emitted is related to the amount of radiation exposure. Common thermoluminescent materials include calcium fluoride and lithium fluoride, among others. In operation, ionizing radiation causes electrons to jump to higher energy states where they are trapped due to intentional impurities in the crystal. When heated, the electrons drop back down to their ground state, and they release a photon of energy that equals the difference between the higher trapped energy state and the ground state. While thermoluminescent dosimeters are quite accurate and have the ability to detect a reasonably large dose of absorbed radiation (approximately 5 Gy), they also require relatively high temperature exposures, which can vary from 800-1000K, to return the crystals to their initial state. Therefore, supporting structures, circuitry, and systems usually should be rather robust. Additionally, thermoluminescent dosimeters consume comparatively large amounts of energy.
Solid state dosimeters, such as the GaTe sensor disclosed in U.S. Pat. No. 7,550,735 to Payne et al., measure exposure to ionizing radiation as a change in the electrical properties of an element. Solid state dosimeters are reasonably accurate, but they require a relatively constant power source in order to measure changes in the electrical properties of the exposed material.