A continuous electromagnetic characterization system for high-resolution quality assurance of long superconducting tapes

Background

High-temperature superconducting (HTS) tapes, particularly those based on rare-earth barium copper oxide (REBCO) coated conductors, have become essential components in the development of ultra-high-field superconducting magnets for applications such as particle accelerators and fusion reactors. These magnets are critical for advancing scientific research and enabling new energy technologies, as they allow for the generation of extremely strong magnetic fields in compact volumes. However, the performance and reliability of these magnets are directly tied to the quality and uniformity of the HTS tapes used in their construction. As the demand for longer and higher-performing HTS conductors grows, there is an increasing need for advanced quality control methods that can ensure the tapes are free from defects that could compromise magnet performance or safety.

Current approaches to HTS tape characterization face significant limitations. Traditional methods often rely on short-sample testing, which does not capture the full length of the tape and may miss localized defects that can cause catastrophic failures, such as hot spots or quenches, in operational magnets. Other techniques, such as reel-to-reel scanning Hall probe microscopy or commercial systems like TAPESTAR™, may lack the ability to perform continuous, high-resolution, two-dimensional imaging of current density under the extreme conditions—namely, low temperatures and high magnetic fields—that these conductors experience in service. Additionally, many existing systems cannot operate at the high speeds required for inline production environments, nor do they provide the spatial resolution necessary to detect sub-millimeter scale defects across the tape width. These shortcomings hinder the ability of manufacturers and end-users to fully assess conductor quality, optimize production processes, and ensure the long-term reliability of HTS-based magnet systems.

Technology

This technology is a continuous reel-to-reel electromagnetic characterization system designed for long high-temperature superconducting (HTS) tapes, such as rare-earth barium copper oxide (REBCO) coated conductors. It integrates a 7.5-T superconducting magnet and a cryogenic system capable of cooling the tape from 20 K to 77 K, enabling in-field measurements at low temperatures that closely mimic real-world operating conditions. The system employs two complementary measurement methods: a magnetic-circuit-based sensor for assessing trapped magnetic fields and a high-resolution, 21-chip Hall sensor array (each with a 100 × 100 μm² active area) for two-dimensional imaging of screening current density. This configuration allows for the detection of sub-millimeter scale defects and critical current variations with spatial resolutions of approximately 1 mm along the tape and less than 0.65 mm across, at scanning speeds exceeding 100 mm/s. Data acquisition is performed with a 28-bit resolution system using oversampling and averaging to minimize noise, supporting high-throughput, contactless, and damage-free quality control suitable for production environments.

What differentiates this solution is its unique combination of high spatial resolution, high-speed continuous scanning, operation under high magnetic fields, and low-temperature measurement—all within a single integrated system. Unlike existing technologies, which may offer only some of these capabilities, this system enables comprehensive, real-time quality assurance for long HTS tapes by detecting minute defects and critical current variations that are often missed by conventional methods. Its ability to characterize conductors under extreme conditions provides valuable insights into their true performance limits, supporting better material selection, design optimization, and manufacturing improvements. This makes it an essential tool for advancing the reliability and performance of HTS conductors in demanding applications such as fusion reactors and high-energy physics magnets, while also establishing a new standard for quality control in the superconducting materials industry.

Benefits

• Enables continuous, high-speed, and contactless electromagnetic characterization of long high-temperature superconducting tapes, suitable for inline production environments.
• Detects sub-millimeter scale defects and critical current variations with high spatial resolution (~1 mm along tape length and <0.65 mm across tape width), improving quality assurance and reliability.
• Operates under high magnetic fields (up to 7.5 T, with potential extension to 20 T) and low temperatures (20 K to 77 K), revealing performance characteristics not detectable by conventional methods.
• Combines two complementary measurement methods—a magnetic-circuit-based sensor and a high-resolution 21-chip Hall sensor array—for comprehensive 2D imaging of screening current density and trapped magnetic fields.
• Employs advanced data acquisition with 28-bit resolution and noise reduction techniques (oversampling and averaging) for precise and reliable measurements.
• Supports development and optimization of HTS conductors by providing valuable data for manufacturers and aiding fusion energy and high-energy physics applications.
• Offers a unique integration of high spatial resolution, high-speed scanning, in-field measurement, and cryogenic cooling in a single system, surpassing existing technologies.

Applications

• Inline HTS tape quality assurance
• Defect detection in superconducting magnets
• Performance mapping for fusion reactors
• High-field HTS conductor certification
• Manufacturing process optimization for HTS

Additional info

This reel-to-reel system continuously characterizes long high-temperature superconducting tapes. It employs magnetic-circuit sensors for trapped fields and a 21-chip Hall array for 2D screening current density imaging. Integrating a 7.5-T magnet and 20-77 K cryocooling, it detects sub-millimeter defects and critical current variations with high spatial resolution (~1 mm along, <0.65 mm across) at speeds exceeding 100 mm/s, utilizing 28-bit data acquisition.