K. Gao

Investigating the momentum balance of a plasma pinch: An air-side stereoscopic imaging system for locating probes

The momentum balance of a plasma pinch in the Reconnection Scaling Experiment (RSX) is examined in three dimensions using several repositionable, insertable probes. A new camera-based system described here triangulates the locations of the probe tips so that their measurements are spatially registered. The optical system locates probes to within ±1.5 mm of their absolute 3D position in the vessel and to within ±0.7 mm relative to other probes, on the order of the electron inertial length (1-2 mm).

Experimental measurements of magnetic field generation from sheared flows

Summary form only given. The generation and destruction of magnetic field is an important feature of solar, magnetosphere and cosmic plasmas, for example during reconnection, dynamo, and turbulent processes. We have experimentally measured spatially resolved profiles of magnetic flux ropes. These data include ion flow, magnetic field, current density, and plasma pressure, which allow us to verify a screw pinch equilibrium and also infer the electron fluid flow in three dimensions. Parallel currents along each flux rope result in a mutual attraction, which compresses and distorts the cylindrically symmetric equilibrium profiles. The electron and ion fluid flows turn out to be different, and we show that sheared axial electron fluid flow v_e generates magnetic field B(t) via the induction term curl X̅v_e X B = -curl X E = dB/dt. Data show a quadrupole out of plane magnetic field signature with four fold symmetry that is driven by flux rope flows with two fold symmetry. This mechanism provides a natural and general mechanism for large scale sheared flows to acquire smaller scale magnetic features, disordered structure, and possibly turbulence.

Application of Stereo Vision to the Reconnection Scaling Experiment

The measurement and simulation of the three-dimensional structure of magnetic reconnection in astrophysical and lab plasmas is a challenging problem. At Los Alamos National Laboratory we use the Reconnection Scaling Experiment (RSX) to model 3D magnetohydrodynamic (MHD) relaxation of plasma filled tubes. These magnetic flux tubes are called flux ropes. In RSX, the 3D structure of the flux ropes is explored with insertable probes. Stereo triangulation can be used to compute the 3D position of a probe from point correspondences in images from two calibrated cameras. While common applications of stereo triangulation include 3D scene reconstruction and robotics navigation, we will investigate the novel application of stereo triangulation in plasma physics to aid reconstruction of 3D data for RSX plasmas. Several challenges will be explored and addressed, such as minimizing 3D reconstruction errors in stereo camera systems and dealing with point correspondence problems.