Events at Physics |
For driving reconnection, TREX applies a strong reconnection drive which includes the sudden energization of a system of coils encircling the plasma. Before the formation of the reconnection current layer, this reconnection drive produces a strong magnetosonic wave including a wave-front moving radially inward towards the center of the device. The propagation speed of this front is governed by the dispersion relation of the magnetosonic wave, directly related to the plasma density. We will discuss and show how the analysis of the wave propagation provides reliable density profiles which are consistent with measurements by Langmuir probes. These profiles characterize the initial plasma produced by an array of plasma guns, which is valuable for analyzing and understanding the plasma dynamics at later times during the plasma discharges.
Langmuir probes are commonly used for measuring plasma temperature, density, and potential. We have developed a number of techniques that optimize the functionality of multi-tip Langmuir probes used for measuring the full current-voltage characteristic at a 10 MHz sampling rate. These upgrades gives the probe increased signal-to-noise ratio, ability to measure lower plasma densities, and more accurate resulting measurements.
We have developed a pressure anisotropy probe that can measure plasma flows and temperature anisotropies during reconnection. TREX is in the collisionless kinetic regime in which we expect electron anisotropy effects to dominate the physics of the ion diffusion regime near the x-point of reconnection. Embedded jets, seen in laboratory data, are driven into the outflow as expected from spacecraft observation of the magnetosphere, theory, and simulations. This probe has successfully measured electron pressure anisotropy in the laboratory, validating the expected influence of kinetic effects during reconnection.