Demonstration of FRC core fueling via pellet injection on open field lines

TAE Technologies’ current experimental device C-2W (also known as “Norm”) produces and sustains a steady state field reversed configuration (FRC) plasma. [1] Norm plasmas are primarily fueled by gas ionized at the edge of the Scrape Off Layer (SOL), limiting changes in the FRC core inventory to diffusive processes. [2] Pellet injection is an alternative fueling scheme that promises non-disruptive and efficient matter injection deeper into the SOL and plasma core.

In this talk, we will present experimental data of FRC fueling from cryogenic pellets injected in an open magnetic mirror region between the CV and the divertor, supported by pellet ablation simulations. This setup is different than standard pellet fueling in tokamak devices where fast pellets penetrate the separatrix and deposit fuel onto closed field fields. In our case, pellet ablation takes place in a tandem cell, meters away from the closed magnetic flux surfaces of the plasma core. The characteristics of pellet ablation in that region allow for neutral particles to ionize closer to the magnetic axis than gas puffing. Using a combination of camera, interferometry and spectroscopic data from diagnostics distributed across the vessel, we independently study the pellet ablation process, particle transport dynamics and effects of pellet fueling on plasma performance. This work contributes to a better understanding of fueling and particle transport in FRC devices.

[1] T. Roche et al. Generation of field-reversed configurations via neutral beam injection. Nat. Commun. 16, 3487 (2025).

[2] H. Gota et al. Overview of C-2W: high temperature, steady-state beam-driven field-reversed configuration plasmas. Nucl. Fusion 61, 106039 (2021).