Model-Based Control of the Dimensionless Gain in KSTAR by Leveraging Real-time Estimation of the Confinement Time

H. Al Khawaldeh, S.T. Paruchuri, T. Rafiq, E. Schuster

65th Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)

Denver, CO, USA, October 30 – November 3, 2023

Controlling Q, which is defined as the ratio of the fusion power to the auxiliary power, will be critical in ITER and future nuclear-fusion power reactors. By writing the global energy confinement time as τ = Hsτs, where τs is a particular confinement scaling (e.g. ITER89P) and Hs is a ratio defining the confinement quality, it is indeed possible to show [1] that Q ∝ G (= βN*Hs/q95) where βN is the normalized beta and q95 is the safety factor at ρ = 0.95. Thus, Q is maximized by requiring high pressure (βN) , high confinement quality (Hs), and high current-carrying capacity (inverse of q95). Therefore, the dimensionless gain G plays a key role in defining a stable plasma scenario with a specific target fusion gain. As part of the effort by the KSTAR program on developing Q = 10 scenarios for ITER, a model-based control algorithm is proposed for the regulation of G by leveraging real-time estimation of the global energy confinement time and the associated confinement-quality factor [2]. The controller is designed by embedding the 1D magnetic diffusion equation and a 0D energy balance equation in the synthesis process. The performance and robustness of the proposed controller are tested in higher-fidelity nonlinear simulations for KSTAR based on COTSIM.

[1] T. Luce, Fusion Science and Technology 48:2 (2005) 1212-1225.
[2] K. E. J. Olofsson et al., IEEE CCTA, Montreal, Canada, 2020.

*Supported by the US DOE under DE-SC0010537.