Research Directions for Solenoid-Free Plasma Initiation on Pegasus-III

Pegasus-III (A ~ 1.2, I_p ≤ 0.3 MA, B_T ≤ 0.6 T) research is developing the physics and technology basis of solenoid-free plasma initiation, which is critical to next-step STs and may simplify the cost and complexity of magnetic fusion energy systems. The 2025 local helicity injection (LHI) campaign tested 2 injector systems at B_T < 0.3 T. Circular injectors with new limiter geometry have improved T_e at fixed n_e and reduced impurity generation. A prototype non-circular injector designed to optimize Taylor and helicity balance constraints achieved plasmas with I_p < 0.1 MA. EBW measurements via the SAMI diagnostic have been made and are determined to be mysterious and important. Experiments extending to B_T= 0.6 T are planned as TF joint reinforcements are completed. A dual-electrode CHI system and ~100 kW 28 GHz microwave heating system are in fabrication. A proposed thrust aims to enhance predictive modeling of HI via improved experimental and interpretive modeling coupled with time-dependent NIMROD and M3D-C1 simulations. Privately-funded efforts to accelerate LHI injector technology development and fusion materials are beginning with a dedicated injector conditioning and test stand.