Core profile prediction and transport analysis of the Helios stellarator fusion power plant

Details on the transport properties and profile prediction analysis of the preconceptual design of the “Helios” stellarator fusion power plant (Swanson et al., 2025) are discussed in the present work. A multi-scale framework is used that incorporates turbulent timescales in the evolution of macroscopic profiles on transport timescales. High-fidelity electrostatic gyrokinetic and drift-kinetic calculations are performed to simulate transport fluxes. Scenarios are considered that include alpha heating power, auxiliary electron heating, radiation losses, and collisional energy exchange in the presence of turbulent/neoclassical losses to predict the steady-state temperature profiles, using a prescribed density profile. Targeting an ignited plasma, the results of this analysis show that a near-ignited scenario can be found with a fusion power output of P fus = 945 MW , fusion gain of Q f u s = 47 , a confinement scaling factor of H ISS04 = 1.34 , and a Sudo density fraction of f Sudo = 〈 n e 〉 / n Sudo = 1.25 . Results indicate a slightly lower fusion power and confinement enhancement factor, and a higher but reasonable Sudo density fraction compared with the reference values of P fus ref = 958 MW , H ISS04 ref = 1.4 and f Sudo ref = 1.1 , respectively. Additional transport calculations with impurities were performed on the final profiles. Inclusion of fully kinetic impurities produced a strong reduction in gyrokinetic heat and particle fluxes for the bulk ions.