Scientific Achievement
Researchers from Berkeley Lab’s Accelerator Technology & Applied Physics Division are developing a new technique that could safeguard magnets made from high-temperature superconductors (HTS) from the risks of quenching—sudden and unpredictable losses in superconductivity—that can cause catastrophic “hot spots” to develop in the magnet. The technique employs metal-oxide-semiconductor field effect transistors (MOSFETs) current controls to reduce power dissipation in these hot spots by orders of magnitude. It was tested on a two-component HTS conductor and demonstrated that it could improve quench protection and, potentially, field quality in various HTS conductor and magnet applications, such as particle and high-energy physics and future fusion reactors.
Significance and Impact
Quench protection is one of the critical problems in using HTS magnets for fusion and high-energy physics applications. While various novel quench detection techniques for HTS are now being explored, protection schemes are limited to a traditional configuration involving a single power supply and current switch. The approach developed here can control current distribution in individual HTS cable components, opening up a new dimension in magnet protection and expanding its safe operational margins. It also couples with a recently proposed no-quench strategy for HTS magnets (refer to “Thermal runaway criterion as a basis for the protection of high-temperature superconductor magnets”) where a real-time active current re-distribution may be used to keep the conductor from reaching a point of thermal runaway for a broad range of magnet operational conditions.
Research Details
Aims
To demonstrate the advantages of implementing current distribution control in multi-component HTS cable conductors to improve quench protection and mitigate developing hot spots.
Methodology
(a) The test setup. (b) A MOSFET control board (protective covers removed). (c) Electrical schematics of the setup. Each MOSFET symbol in the schematic represents two IAUC120N04S6L005 devices connected in parallel. (Credit: Berkeley Lab)
Network model numerical simulations were conducted for the current, voltage, and power dissipation along a partially current-shared HTS conductor stack and a two-component HTS tape conductor. The simulations confirmed the benefits of re-distributing current flow at the terminations to reduce heat dissipation in a local tape defect. An experimental setup was built to demonstrate a practical MOSFET-based control of the current distribution between the two HTS tape conductor components.
Results
The work validated the use of MOSFETs for cryogenic current distribution control in multi-component HTS conductors. We demonstrated “on-the-fly” control capability, achieving a factor of two reduction in heat dissipation in the conductor component having a local defect.
Next steps
The researchers are developing arrays of MOSFETs connected in parallel to control kA-level currents in practical HTS cables and magnets. The next big goal is to realize an advanced closed-loop quench protection scheme that feeds the thermal runaway sensor readings to the active current controls. The team will also explore the benefits of using current distribution controls beyond protection, such as reducing the conductor remnant magnetization and improving magnet field quality.
Contact: Maxim Marchevsky
Researchers: Maxim Marchevsky and Soren Prestemon.
Funding: The U.S. Department of Energy, Office of Science, Offices of Fusion Energy Sciences, and High Energy Physics supported the research.
Publication: M. Marchevsky and S. Prestemon. “Quench protection for high-temperature superconductor cables using active control of current distribution,” Supercond. Sci. Technol. 37 085026, 2024, https://doi.org/10.1088/1361-6668/ad6216.
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