Overview of the Flux-Coil-Generated Field-Reversed Configuration

A Flux-Coil-Generated Field-Reversed Configuration (FRC) device has been assembled with the goal of producing an FRC dominated by large-orbit ions. The inner (flux) coil is used to pre-ionize the working gas and then accelerate the plasma into an FRC while the outer (limiter) coil provides the axial bias field. Two chords of infrared interferometry at 12 and 20 cm radii measure the electron density. Spectroscopy monitors NII (λ = 568 nm) at an 18-cm radial chord to measure ion temperature and rotational energy. Three magnetic probe arrays are located outside of the chamber, through the midplane, and at the axial end of the FRC. During the more quiescent portion of the FRC, the magnetic field-null r₀∼ 20-24 cm, the separatrix r_s∼ 27-30 cm, the field-reversal δB ∼ 300-500 G, the electron density n_e∼ 2-9x10^13 cm^-3, the ion temperature T_i∼ 20-40 eV and the ion rotational energy E_iθ∼ 7-19 eV. Ongoing neutral particle analyzer studies suggest even higher rotational energy. The FRC plasma lifetime is τ∼ 60-100 μs.