Qualification of the space-bound flux pump for the Hēki mission

There have been repeated proposals to utilize superconducting magnets in space since at least the 1970s for a range of applications, yet examples of their use remain scant. Using a flux pump (FP) to energize the superconducting magnet address a significant issue for their adoption in space, as it reduces the system-level power requirement for operating a superconducting magnet. This paper describes the ground tests to qualify a full conduction-cooled FP system for the Hēkimission, including its integration with the Hēkipayload for the International Space Station. We show the temperature dependence of the performance of the self-rectifier style FP. A control methodology is presented that allows the magnetic field to be set and that actively compensates for temperature variation of the FP. The data presented show the FP meets the performance requirements of the mission, and that the power it dissipates as heat into the cryogenic environment with the magnet at 0.5 T is approximately 10% of what could be achieved without the use of a FP. As part of Hēki, the FP operated on the ISS between October 2025 and March 2026, with the magnet energized to 0.5 T multiple times. Preliminary assessment of the on-orbit data shows the FP performance is consistent with the ground-based testing present here. Such a demonstration signals a maturing of this emerging superconducting technology for both in-space and terrestrial applications. Together with the maturing of REBCO-based coated conductor and miniaturized cryocooler technology, the results reported here represent an advancement towards space applications of superconducting magnets.