Inhomogeneity scale lengths in a collisionless, Q-machine plasma column

Radial inhomogeneity scale lengths for radial electric field, ion density, and magnetic-field-aligned electron drift velocity have been measured and interpreted in magnetized, low temperature, collisionless, Q-machine plasma. When the ion Larmor radius \textit{$\rho $}$_{i}$ is on the order of [much smaller than] the half-width-at-half-maximum $\ell _r \{E(r)\}$ of the radially-localized radial electric field profile $E(r)$, the radial profile of the azimuthal ion drift velocity, measured using laser-induced-fluorescence (LIF), has a peak $V_{\theta }$ that, because of finite [negligible]-Larmor-radius effects, is significantly lower than [comparable to] the peak $V_{sum}$ of the combined radial profile of the \textbf{\textit{E}}x\textbf{\textit{B}} and diamagnetic drift velocities. For example, when \textit{$\rho $}$_{i}$/$\ell _r \{E(r)\}$=1 [2] we find that $V_{\theta }$/$V_{sum}$=0.58 [0.25]. Results of an experimentally benchmarked test-particle simulation are presented and applied using experimentally relevant electric field profiles. Work supported by U.S.-NSF and the US-Japan Exchange Program.