(Color online) Schematic of the C-2 facility.
(Color online) Evolution of the excluded flux radius in C-2 obtained from a series of external diamagnetic loops at the two θ-pinch formation sections and magnetic probes embedded inside the central metal confinement chamber. Time is measured from the instant of synchronized field reversal in the θ pinch sources, and distance z is given relative to the center of the confinement chamber.
(Color online) Contours of electron density n e (r, t) for the single-source (translating) and dual source (collision-merging) FRCs, obtained from a six-channel two-color CO2/HeNe interferometry located at the midplane of the central confinement chamber using the Abel inversion technique.
(Color online) Simulation of FRC formation, translation, and merging dynamics for the same shot as shown in Fig. 2 , i.e., #5512, showing time histories of both magnetic flux and temperature predicted by the 2-D resistive MHD code, LamyRidge. The magnetic reconnection induced by collision is clearly demonstrated by the evolution of the flux contours.
(Color online) Comparison of the initial translated CTs and the resultant merged FRC, showing time traces of the external poloidal field, B e , the excluded flux radius, , the poloidal flux, , and the total temperature, T t = T i + T e , derived from radial pressure balance, for individual CTs produced by θ-pinches on the north side and the south side, respectively, and the result from merging individual CTs formed under identical conditions. Note that the two single CTs were not captured by the end mirrors due to their high translation speeds. Merging occurs around 30 μs, as indicated.
(Color online) Comparison of radial electron temperature profiles, T e (r), obtained from a nine-chord Thomson scattering system for individual plasmoids and merged FRCs.
(Color online) Ion temperature, T i , from Doppler spectroscopy and electron temperature, T e , from Thomson scattering vs total temperature, T t , derived from radial pressure balance, in merged FRCs.
(Color online) Effect of dynamic translation speed. The data are obtained right after merging (∼ 40 μs) of the FRCs from a series of reproducible and well-controlled discharges with the same magnetic configurations and gas fuelling rates. The translation speed is varied by energizing the θ-pinch coils at various different times during the initial formation process.
(Color online) Tomographic reconstruction of bremsstrahlung radiation in the FRC with n = 2 mode, obtained from a 60-chords visible tomography system. Frame (a) was obtained at the onset of the n = 2 mode, and frames (b)–(d) during half cycle of the n = 2 mode, rotating in the ion diamagnetic direction.
(Color online) (a) Line-integrated density measurements, , from separate channels at different impact parameters of the CO2/HeNe interferometer, located at the center of the confinement chamber (z = 0) and fitted results for shot #4047; (b) density profiles during the n = 2 rotation at ∼ 0.5 ms, obtained from the modified RR model.
(Color online) (a) Fluctuation spectra at the edge, obtained from the reflectometer; (b) line-integrated density, , obtained from the interferometer with a line of sight near the center of the FRC.
(Color online) Effect of quadrupole stabilization against the n = 2 mode, which can be clearly seen from the amplitude oscillations on the line-integrated density, . Onset of the n = 2 modes also indicated.
(Color online) Time evolution of plasma rotation frequency, Ω, with and without quadrupole stabilization.
(Color online) (a) Magnetic flux confinement time of merged FRCs in C-2, τ ϕ , vs the LSX scaling for conventional θ-pinch-formed FRCs, , along with the results from recent FRC translation experiments, FIX 3 , TCS 6 , as well as those obtained on C-2 during the initial start-up phase with only one single θ-pinch formation source attached to the central confinement chamber and a strong magnetic mirror plug at the downstream end to capture the translated FRCs; (b) diffusivities, D ⊥, derived from τ ϕ , vs classical diffusivities, , for the well-centered merged FRCs in C-2.
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