Superconducting cooling system

In spite of the usually low cooling efficiencies (see the exercise above), recent experiments have demonstrated an anti-Stokes cooling from room temperature to 77 K within a certain internal volume of Yb + doped fluorochloride and fluoride glasses under high photon irradiances (Fernandez et ai, 2000). Future practical applications of optical cooling of solids include cooling systems for spacecraft electronics and detectors, as well as for superconductive circuits. 

Hehum is used for low-temperature research (—272.2°C or 34°F). It has become important as a coolant for superconducting electrical systems that, when cooled, oiler httle resistance to the electrons passing through a conductor (wire or magnet). When the electrons are stripped from the hehum atom, a positive He ion results. The positive hehum ions (nuclei) occur in both natural and man-made radioactive emissions and are referred to as alpha particles. Hehum ions (alpha particles) are used in high-energy physics to study the nature of matter. 

To minimize interference between the different plasma collection schemes used it was decided to use a spatially separated system. The antiproton collection, cooling, and compression is housed in the same superconducting magnet system as the recombination trap, but the positron accumulator is a stand-alone system connected to the main apparatus by a beam line incorporating differential pumping and a fast valve. Figure 1 shows a schematic lay-out of the apparatus and the following sub-sections describe the individual parts of the apparatus in more detail. 

Another major use of helium is in low-temperature cooling systems. This application is based on the fact that liquid helium—at —454°F (—270°C)—is cold enough to cool anything else. For example, it is used in superconducting devices. 

Superconductivity has been known since 1911, and superconducting systems based on various metal alloys (e.g., NbTi and Nb3Sn) are currently used as magnets and in electronics. These materials exhibit superconductivity only at temperatures below 23 K and require cooling by liquid helium. The discovery of ceramics that exhibit superconductivity at temperatures up to 120 K, the so-called high-temperature superconductors, has sparked a tremendous amount of scientific activity and commercial interest around the world. 

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