Particle fueling via Pellet Injection in C-2W

In TAE Technologies’ current experimental device, C-2W, advanced beam-driven field-reversed configuration (FRC) plasmas are produced and sustained utilizing high energy neutral beams, edge-biasing electrodes, and an active plasma control system [1]. A common method of fueling in plasma devices is gas puffing from the edge of the vessel, which is not optimal for the closed field lines characteristic of an FRC. In that case, most ionization takes place in the scrape-off-layer (SOL) instead of the FRC core.  Another method that promises more efficient core fueling is cryogenic pellet injection. This method employs the controlled propulsion of cryogenically frozen deuterium or hydrogen pellets of varying particle inventories. A critical parameter for efficient pellet fueling is the injection location since fast ion properties dominate pellet ablation rates. Here, we present promising experimental and simulation data of effective plasma fueling via pellets in the confinement vessel aiming directly at the FRC or indirectly via the mirror region. Utilizing 3D pellet tracking capabilities using diagnostic cameras to accurately position the pellet, we show we can successfully fuel FRC plasmas during plasma start-up conditions and quasi steady state. These results pave the way for designing advanced fueling systems for Copernicus, TAE’s next experimental device. 

[1] H. Gota et al., Nucl. Fusion 61, 106039 (2021).