Schematic of the MRX device, illustrating the spheromak-forming flux-cores, compensation coils, solenoids, and major diagnostics utilized in this research. The measured poloidal flux (contours) and toroidal field (colors) of typical FRC and spheromak discharges are superimposed on the top figure.
Evolution of neon spheromaks under inductive sustainment. The grey area corresponds to time before merging is complete.
Two-dimensional measurements of the poloidal flux (contours separated by ) and toroidal field (colors, in millitesla) for argon spheromaks with (upper row) and without (lower row) inductive sustainment. The upper plasma transition from a spheromak to a FRC. The grey area at the bottom of each figure is the location of the solenoid coil.
Evolution of the midplane profiles, for argon spheromaks that are allowed to decay (open symbols), and which transition to a FRC via inductive current drive (closed symbols). The toroidal field (top row), poloidal field (middle row), and electron pressure (bottom row) are illustrated.
Time evolution of argon spheromaks with different solenoid firing voltages. The scan and quantities plotted are identical to those in Fig. 2, but with argon instead of neon.
Time evolution of argon spheromaks with different starting times for the solenoid current ramp.
Comparison of the profiles in sustained and decaying discharges, for argon (top row) and neon (bottom row) discharges.
Analysis of magnetic helicity balance. (a) The toroidal , trapped poloidal , and solenoid fluxes; (b) the magnetic helicity; and (c) the resistivity inferred from helicity balance and the parallel Spitzer resistivity . The arrows in (a) indicate which vertical axis is associated with each curve.
Comparison of the growth rate from HYM and measurements in neon plasmas, and the toroidal flux decay rate , as a function of the Lundquist number.
Schematic illustration of FRC formation utilizing only a single flux-core and a solenoid.
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