Fundamental theory of the direct magnetic energy recovery in a thermonuclear field reversed configuration system

Helion’s Trenta prototype compressed Field Reversed Configuration (FRC) plasmas to thermonuclear fusion conditions, reaching 9 keV plasma temperatures [1].  FRC plasmas are fundamentally high-beta and if heated through pulsed, adiabatic compression, they operate in a unique collisional regime that supports both thermonuclear fusion conditions as well as a non-equilibrium ion to electron temperature ratio during compression. Further,  high-Beta magnetized FRC plasma compression systems can directly recover particle energy through MHD expansion driving magnetic expansion.

In the presented work, past theoretical FRC analyses [2,3] will be expanded upon from fundamental theoretical and empirical scaling relationships. In this work, direct inductive magnetic energy recovery will be described, including system, electrical, and MHD fluid efficiencies. Prior estimates for the fundamental thermodynamic efficiencies of such systems are based on early theta-pinch machines of the 1960s; these estimates gave efficiencies on the order of 60% assuming a constant-pressure burn, low electrical system efficiencies, and adiabatic expansion [4].  We will describe potential custom fusion burn cycles [5], including generalized Diesel and Otto with axial and radial expansion, and their theoretical system efficiencies using realistic modern circuit components.

As will be shown, direct electricity recovery for a thermonuclear FRC system is projected to significantly exceed thermal energy recovery systems, with optimal burn cycles exceeding 90% recovery.

[1] Kirtley, D et al. “Thermonuclear Field Reversed Configuration plasmas in the Trenta prototype” IEEE Pulsed Power Conference and Symposium on Fusion Energy (2021).

[2] Intrator, T. P., et. al. Physics of Plasmas (2008). ​

[3] Kirtley, D., Milroy, R. Fundamental Scaling of Adiabatic Compression of Field Reversed Configuration Thermonuclear Fusion Plasmas. J Fusion Energy 42, 30 (2023).

[4]  T.A. Oliphant et al. “Direct conversion of thermonuclear plasma energy by high magnetic compression and expansion”, Nucl. Fusion 13 529 (1973)