The magnetic mirror fusion concept dates to the early 1950s, but decades ago it was sidelined by technical difficulties and researchers turned to tokamak fusion in their quest for confinement. Now it’s getting another look—with significantly more powerful technology—through WHAM, the Wisconsin HTS Axisymmetric Mirror, an experiment in partnership between startup Realta Fusion and the University of Wisconsin–Madison.

A new type of cold spray coating, made from the metal tantalum and applied to the plasma-facing steel walls of fusion reactors, could lead to efficient, compact fusion reactors that are easy to repair and maintain, according to a study recently published in the journal Physica Scripta. The study was led by scientists and engineers at the University of Wisconsin–Madison and involved researchers from South Korea, France, and Germany.

Realta Fusion of Madison, Wis., and Zap Energy of Everett, Wash., are just two of the eight fusion developers selected by the Department of Energy for funding last week under the public-private Milestone-Based Fusion Development Program. They are the two companies with power plant concepts that don’t fit neatly into established fusion confinement categories. As energy secretary Jennifer Granholm said when she announced the awardees, “Some are working on more technically mature approaches like tokamaks and stellarators and laser inertial fusion, and others are working on innovative concepts with lower technical maturity like mirror and Z-pinch, which could lead to more compact and lower cost systems.”