Validate the performance and deployment value of spin-polarized fuel

Determine whether spin-polarized fuel remains sufficiently polarized and manufacturable at the required polarization fractions and production rates, and whether its predicted benefits address the principal challenges limiting fusion-power deployment.

Background

The paper identifies two unresolved uncertainties concerning the practical value of spin-polarized fuel (SPF). First, SPF may not perform as assumed: it could depolarize too rapidly or prove difficult to produce with sufficiently high polarization fraction and production rate. Second, even if SPF behaves as predicted, its benefits—including improved tritium burn efficiency, higher power density, anisotropic neutron emission, and relaxed confinement requirements—may not alleviate the limitations that ultimately govern fusion-power deployment. These issues require experimental and systems-level validation beyond the paper’s zero-dimensional modeling and projections.

References

There are, of course, significant uncertainties. First is that SPF does not work as expected. This could include it depolarizing too quickly or being hard to make at high polarization fraction and/or rate. Second is that all of the predicted benefits conferred by SPF are simply not useful for fusion deployment, and that the most challenging aspects of deployment are limited by things not helped by SPF.

— Reaching high fusion gain with grams of spin-polarized fuel  (2610.11080 - Parisi, 8 Oct 2026) in Section Discussion, final paragraph