| 摘要 |
In a "permanent" magnet system based on high-temperature superconductors, a superconducting magnet is cooled to a temperature below its critical temperature with a cooler. The magnet is coupled to a cold body of solid nitrogen which is insulated to minimize heat input to the system. The superconducting magnet is energized to generate a magnetic field and the cooler is removed. Unlike conventional superconducting magnets in which the magnet operating temperature is maintained at a fixed point, in the system of the present invention the operating temperature is allowed to rise from an initial value of approximately 20 K to as high as 63 K (the melting point of nitrogen), enabling operation over an extended period without the aid of direct cooling. The superconducting magnet is recooled periodically to lower its temperature to approximately 20 K. The magnetic field is maintained and the system is fully operable during the recooling process. For large systems, the time period between recooling cycles can exceed one year. This cryocoolerless lightweight "permanent" magnet system is particularly effective in on-board or portable applications which would benefit from the absence of a cumbersome cryocooler.
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