Korea Electrotechnology Research Institute (KERI) has developed an inspection system that can continuously measure the thickness and width of high-temperature superconducting wire by a noncontact method.
Korea Electrotechnology Research Institute (KERI) said on the 6th that the research team led by doctors Ha Hong-su and Park In-seong at the Cryogenic Instrument Research Center developed a technology that inspects high-temperature superconducting wire hundreds of meters long in real time without cutting it. The results were published as three papers from 2024 to this year in the international journal Transactions on Applied Superconductivity of the Institute of Electrical and Electronics Engineers (IEEE).
High-temperature superconducting wire is a thin tape-type material with a thickness of tens of μm (micrometers, one-millionth of a meter) and a width of 4–12 mm. It is used to manufacture superconducting magnets employed in fusion devices, magnetic resonance imaging (MRI), and power equipment.
Because a superconducting magnet is made by winding the wire hundreds of layers or more, even a slight difference in thickness can accumulate and cause errors in the magnet's shape. This can lead to concentrated stress in certain areas or instability in the magnetic field.
However, conventional contact inspection methods risked scratching or contaminating the wire surface, and even noncontact methods suffered reduced measurement accuracy if the wire shook while moving. In some cases, a section of the wire had to be cut and checked under a microscope for precise inspection.
The researchers applied two chromatic confocal laser sensors, one above and one below, to a reel-to-reel device that transfers the wire from one reel to another. The sensors simultaneously measure the distance to both surfaces of the wire to determine thickness, width, and surface profile.
They also applied technology that automatically adjusts tension and feed speed to reduce wire vibration, and developed a data analysis program that removes noise generated during measurement. The team said this allows real-time confirmation of three-dimensional shapes such as thickness deviations and curvature while moving the wire without cutting it.
The researchers added, "The developed technology can be applied not only to high-temperature superconducting wire but also to continuous production lines for thin materials such as copper foil and aluminum foil for secondary batteries, metal rolled products, and thin-film solar cells."