Edge plasma measurement in open-field line region on C-2W FRC

In 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.

Edge biasing improves FRC performance by applying a high electric field in the scrape-off layer (SOL) as was known from past experiments on C-2W. Hence, understanding edge plasma condition is important in order to study biasing power propagation into FRC. To observe the electron density and temperature in the open-field line region, an insertable triple Langmuir probe has been installed near the mid-plane in the confinement vessel (CV). The radial profiles between SOL and the CV wall have been scanned. In addition to this probe, C-2W has multipoint measurements of floating potential along the machine axis and b-dot probes to measure the FRC’s global mode numbers and the magnetic field fluctuation from CV through the mirror region. By combining multi-diagnostics systems, we can understand the transportation of biasing into the FRC. Detailed results will be presented.

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