The large scale use of superconductivity continues to be dominated by applications for which there is generally no conventional option. In these cases, superconductivity has enabled new science and technology that could not exist without it. Thanks to persistent ongoing research, new ancillary technology and the development of new materials, the field is far from exhausted. The fields of fusion energy and high energy physics (HEP) have particularly benefited from the application of superconductivity. High magnetic fields are absolutely necessary to achieve the required performance parameters. Even though superconductivity is an enabling technology for these fields, it comes with a number of challenges. The progress in development of applications is driven from one side by the available materials and on the other, by the evolution, or sometimes revolution, in ancillary technologies. Technology for use in both fusion and accelerator magnets begins with the same materials and inherent constraints, yet results in substantially different configurations and unique challenges due to the operational requirements for the respective applications. This paper presents a comparison of the technology developed by the fusion and high energy physics programs, both the similarities and the differences, and prospects for future development.
When the quenching occurs in a superconducting coil, excessive jule heating in normal area may damage the coil. It is necessary to detect quenching in the coil as soon as possible and discharge the magnetic energy stored in the coil. Therefore, we propose a superconducting coil protection system based on an active power method. The system is highly resistant to the noise and does not require cancel voltage taps, so it is useful for both AC and DC coils. We have presented the effectiveness of the system using some test coils cooled in LN2 or LHe. However, we have not discussed the effectiveness of the proposed system for helium-free cryocooled magnets, in which a larger temperature rise occurs after quenching than in liquid-cooled magnets. In this paper, we verify the effectiveness and practicality of the proposed system through coil protection tests for a cryocooled Nb3Al LTS coil.
Slush hydrogen is a mixture of solid hydrogen particles and liquid hydrogen. The flow characteristics of slush hydrogen in two types of cryogenic valves (i.e., vertical- and horizontal-moving piston valves) were investigated by visualization of its flow and measurement of pressure loss. In a preliminary ice/water flow test, circulation flow was observed in a vertical-moving piston valve, and this caused the accumulation of ice particles in the flow path. Based on the preliminary test results about particle behavior in the valve, a horizontal-moving piston valve was improved, and it was observed that slush hydrogen flows smoothly and the pressure loss of slush hydrogen is only slightly larger compared to liquid hydrogen flow. These test results show that a horizontal-moving piston valve is more suitable for slush hydrogen compared to the vertical-moving piston valve, and that an appropriate flow path design leads a smooth flow of slush hydrogen at the same level as liquid hydrogen.
Electromagnetic stirring is an effective method in material processing. We have studied the application of superconducting technology to electromagnetic stirring. In the present paper, an electromagnetic stirring system using Nb-Ti AC superconducting cables was developed and its performance was investigated. Stirring experiments of molten gallium were carried out. It was confirmed that the stirring system worked completely without quenching of the superconducting magnets. The stirring system was able to apply so much rotational electromagnetic force that all of the molten gallium moved to the crucible wall due to centrifugal force and the bottom of the crucible appeared. The superconducting stirring system was compared with a conventional copper magnet coil of the same scale. The electromagnetic force applied to the liquid metal by the superconducting stirring system was about 100 times larger than that created by the copper magnet.