Model-based Burn Control with Neon Gas Injection for Divertor Protection in ITER

V. Graber, E. Schuster, C. C. Klepper, E. Lerche, T. M. Biewer, J. D. Lore

68th Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)

Chicago, IL, USA, November 2-6, 2026

In a tokamak reactor, the plasma must be driven towards certain operational limits (e.g., density and beta limits) to maximize fusion power. Divertor constraints are particularly consequential since excessive thermal loading can destroy the plasma-facing components (PFCs). Simultaneously regulating fusion power while ensuring divertor integrity is challenging due to the strong interdependence between the plasma’s core and edge dynamics. As a burn controller increases fusion power, heat flux through the scrape-off-layer onto the PFCs increases, threatening divertor survivability. In response, neon gas can be injected to radiatively cool the exhaust, but the leak of these impurities into the plasma’s core presents a performance trade-off. Motivated by this challenge, a divertor-safe burn controller for ITER is presented in this work. Based on a coupled core-edge plasma model, the proposed controller regulates core density and temperature while employing a neon gas injection strategy for divertor protection. The control architecture takes advantage of the Diagnostic Residual Gas Analyzer (DRGA). By measuring sub-divertor neutral concentrations in ITER, including hydrogen isotopes, helium isotopes, and seeded impurities, the DRGA enables real-time regulation of sub-divertor neon concentration for the purpose of radiative cooling.

*Supported by the US DOE under DE-SC0010661 and by Oak Ridge National Laboratory under Contract DE-AC05-00OR22725.