Phase transition thermometer

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As a phase transition thermometer special high-precision are thermometer or calorimeter called. The electrical resistance of a substance that has cooled down to the limit of superconductivity is used as a measured variable , which is why they are also known as calorimetric low-temperature detectors . In the vicinity of this jump or phase transition temperature (hence the name of the process) the resistance of the substance changes very strongly even with the smallest changes in temperature , which is expressed in a very steep resistance-temperature characteristic .

With the help of such thermometers, temperature changes in the range of millionths of a degree Celsius can be measured, which is used in particle physics to detect individual particles (the impact causes a tiny increase in temperature in the material), such as photons or dark matter . A vapor-deposited tungsten , iridium or gold layer is often used as the resistance material.

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