Power flows from biased end electrodes in the C-2W advanced FRCs

M. Kaur, E. Trask, D. Gupta, R. Clary, P. Yushmanov, and the TAE team

In TAE Technologies’ experimental device, C-2W [1], record-breaking, advanced beam-driven field-reversed configuration (FRC) plasmas are produced. Long-lived, hot FRCs with excluded flux radius up to 50 cm are sustained in steady-state in the central confinement vessel by utilizing several advanced subsystems. These subsystems include variable energy neutral beams, advanced divertors, open field-line biased electrodes, variable axial magnetic fields with mirrors, a fueling setup, and an active plasma control system. In this presentation, we discuss dynamic biasing experiments used to infer power flows into FRC electron and ion channels from the biasing system. The probable mechanism for ion heating is likely due to ExB heating and is supported by correlations between temperature and impurity ion rotation rate, dominated by ExB rotation. The ionization of gas near electrode boundaries creates high-energy electrons in the midplane due to the large ambipolar potential between the electrodes and the confinement region. The presence of high-energy electrons is supported by the observation of high-energy x-rays in the confinement vessel that can couple to bulk electrons likely via beam-plasma/two-stream instability.

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