Study of empirical performance projections for fusion reactor designs using new tungsten-wall confinement scalings and implications

Recent advances in high-temperature-superconductor (HTS) technology have opened the door to an exciting new generation of compact, high-field reactor designs. These concepts exploit the large B_T enabled by HTS and rely on empirical confinement scalings to design for a target fusion gain. A recent update to the ITPA H-mode database introduced additional data from the JET ITER-like wall and ASDEX-Upgrade full tungsten wall operations, and utilized existing data from C-Mod, DIII-D, and other machines to produce an updated confinement scaling [1]. The updated scaling for ITER-like constraints states that global confinement has a vanishingly small dependence on B_T, considering its error bars, and scales modestly stronger than linearly with Iₚ [1]. One observation from the scaling is that the exponents of I_p, geometric axis radius, and power degradation remain the largest and clearest levers on confinement, consistent with earlier iterations of the scaling. This underscores the value of high I_p in achieving high confinement. Despite its heavy weighting in the scaling, some design studies largely ignore the importance of high I_p. This work examines how empirical performance projections for reactor designs are affected by the recent confinement database update.

[1] Verdoolaege, G. et al. Nucl. Fusion 61, 076006 (2021).