Investigation of the flow of ions in plasma opening switch

Summary form only given. Recent studies of the interaction of pulsed, strong magnetic fields with multi-ion species plasmas of densities 10/sup 13/-10/sup 15/ cm/sup -3/ are described. The experiments are performed using a planar plasma opening switch (POS) configuration. Motivated by previous observations that demonstrated simultaneous rapid magnetic field penetration and plasma reflection, leading to ion-species separation both for short-and long-duration POS, we investigate in more detail the ion dynamics. The diagnostics are based on time-dependent, spatially-resolved spectroscopic observations. 3D-spatial resolution is obtained by impurity injection techniques. Measurements of the evolution of the ion axial velocity distributions (using line Doppler profiles) are presented and compared to time-dependent measurements of the magnetic field and electron density. It is found that a significant fraction of the protons acquire a velocity that is more than twice the velocity of the magnetic field. The spatially resolved measurements of the electron density evolution, combined with the data of the ion axial velocities, are used to extract information on the lateral ion motion (perpendicular to the direction of the magnetic field flux and propagation) that is otherwise difficult to measure directly. A simple method that allows for a limited control of the plasma composition, based on different times-of-flight of various ions, is developed and implemented. Measurements of the ion dynamics, performed for plasmas having effective different compositions during the magnetic pulse, are presented and discussed.