UC Irvine

The ion phase space development and anomalous configuration-space and velocity-space transport in the near wake of a plasma-obstacle system have been investigated. The experiments were performed on the UCI Q-machine, using laser-induced fluorescence to measure the spatial evolution of the perpendicular ion velocity distribution. Ion and electron configuration-space transport and ion velocity-space transport were consistent with turbulent wave-particle interactions and agreed with observations in edge plasma-limiter regions of tokamaks. Near-wake ion acceleration resulted in local twofold increases in ion perpendicular kinetic energy densities over ambient plasma values. Large-amplitude, low-frequency noise (f ≤ 20 kHz), probably drift wave turbulence, was observed. Large density fluctuations (δn/n ~ 0.25) were inferred at the obstacle edge. The obstacle prewake exhibited density enhancements many Debye lengths upstream of the obstacle, indicating a collisionless shock front. The obstacle midwake displayed an ion flux peak. Numerical simulations were carried out to differentiate particle ballistic effects from other plasma effects. Results scale to several space-plasma-obstacle systems.