Flux-Coil Generated, Field-Reversed Configuration

We study two methods of forming a FRC: 1) pre-ionizing a static-gas fill, and 2) using a pre-injected plasma. A 0.6-m dia $\times$ 2-m pyrex vessel is configured with an external coil, to provide the bias-B$_z$ field, and a central, flux-coil to form the FRC diamagnetically. Diagnostics include: tomography, spectroscopy, interferometry, magnetic-probe arrays, particle time-of-flight, triple probe. The measured plasma parameters are: $n = 0.1-1 \times 10^{14}$ cm$^{-3}$, $T_i = 10-50$ eV, $B_{z0} \leq$ 20 mT and indicate that the FRC radial profile is a rigid-rotor,\footnote{N. Rostoker and A. Qerushi, Phys. Plasmas, 9(7):3057(2002)} $n(r) = n_0/ \cosh^2[(r^2-r_0^2)/r_0\Delta r]$, $B(r) = -B_0[1+\sqrt{\beta}\tanh[(r^2-r_0^2)/r_0\Delta r)]$, where $r_0$ is the magnetic-null radius, and $\Delta r$ is the FRC half-width. Data suggest that the sign of $E_r$ and the dominant-current carrying species are opposite to previous reports\footnote{W. S. Harris, E. Trask, T. Roche, et.al., PRL, 70(12):1818(2009)} and derive from different collisionality and magnetization regimes, resulting from the methods of formation. When $E_r$ points toward the magnetic field null, tomography indicates that the (ion) radial-diffusion coefficient is sub-classical and confining for ions.