Effects of different biasing and fueling configurations on FRC and mirror plasmas in the C-2W fueling region using triple Langmuir probes

TAE Technologies’ current experimental device, C-2W (also known as “Norman”), produces and sustains a steady-state field-reversed configuration (FRC) plasma through neutral beam injection, edge biasing, and a robust real-time plasma control system [1]. Understanding how different biasing and fueling configurations affect the plasma edge is important for optimizing confinement and performance. This helps us grasp the physics C-2W's fueling region and its effects on FRC vs. mirror plasma. This study investigates the C-2W fueling region and its influence on FRC and mirror plasmas using two insertable triple Langmuir probes to measure electron density, temperature, and floating potential. One probe was mounted in the fueling regions, near the mirror plug magnets, and was actuated to scan its insertion depth across different radial positions along the plasma edge. It was initially biased with a positive voltage and then allowed to float in order to suppress high-frequency noise. A second fixed probe was installed in the divertor region. By comparing measurements taken at similar magnetic flux potentials, the data reveal how edge biasing and fueling configurations shape plasma profiles and transport dynamics. These insights support experimental efforts to refine edge control strategies critical for achieving high-performance FRC plasmas.

[1] H. Gota et al., Nucl. Fusion 64, 112014 (2024).