Analysis of Visible Light Images

Precise nonperturbative measurements of plasma evolution and magnetic flux inflow are vital for the study and characterization of magnetic reconnection in laboratory plasmas. In the reconnection scaling experiment (RSX),1 parallel current-carrying plasma columns, or flux ropes, are generated to experimentally model naturally occurring rope driven reconnection dynamics much like those observed in solar arcades and prominences. Filamentary-shaped plasmas2 are free to evolve through mutual or self-interaction and can exhibit complex three-dimensional (3D) behavior. During reconnection in RSX, the flux ropes can pinch, merge, and twist on microsecond time scales, stipulating the need for fast time-resolved imaging techniques.

To externally view the hydrogen plasma, a Cooke Di-Cam intensified charge coupled device (CCD) camera3 with ultraviolet to near-infrared spectral sensitivity is positioned with a lateral view into the chamber (Fig. 1) to collect high resolution 12-bit images of unfiltered plasma emission. Digitally stored images are used to establish shot-to-shot repeatability and resolve pinch velocities during reconnection. Images are processed with peak intensity fitting routines to locate each flux rope center. Combined with external measurements of current and guide field, we extract information on reconnection flux inflow. Results from this method are presented and compared with velocity data from in situ measurements.