Electrode with Controllable Electron Emission in C-2W FRC Experiments

In the TAE Technologies current experimental device, C-2W (also called ``Norman'') [1], record breaking, advanced beam-driven field reversed configuration (FRC) plasmas are produced and sustained in steady state utilizing variable energy neutral beams, advanced divertors, end bias electrodes, and an active plasma control system. The end bias electrode system provides stabilization and heating of the high-beta axisymmetric plasmas by inducing azimuthal plasma rotation via the application of radial electric fields [2]. The radial electric fields are produced by flat coaxial bias electrodes. The negative bias voltage of 3-4 kV on the central electrode was proven sufficient for stabilizing C-2W FRC plasmas.

Using an electrode with electron emission as an active electrode results in reduction of E field near the electrodes and in elimination of arcs on their surfaces. Electron emission also reduces electrode voltage drop (sheath), and stable FRC plasma is reproduced with significantly lower bias voltage (<1.7kV). The details of the electrode-biasing system with an active electrode as well as experimental results will be presented.

[1] H. Gota et al., Nucl. Fusion 59, 112009 (2019).

[2] A.D. Beklemishev et al., Fusion Sci.Technol. 57, N4, 351 (2010).