Current polarity effects on laboratory plasma jets

• Published in: Physics of plasmas 2021-08, Vol.28 (8)
• Main Authors: Banasek, J. T., Rocco, S. V. R., Potter, W. M., Lavine, E. S., Seyler, C. E., Kusse, B. R., Hammer, D. A.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Bremsstrahlung; Computational fluid dynamics; Density; Electron energy; Experiments; Fluid flow; Hall effect; Laser beam heating; Magnetohydrodynamics; Metal foils; Plasma; Plasma jets; Plasma physics; Signal to noise ratio; Thomson scattering
• ISSN: 1070-664X; 1089-7674
• DOI: 10.1063/5.0048400

Plasma jets produced by a pulsed power machine were investigated using Thomson scattering and other diagnostics in order to make detailed comparisons to simulations. These jets were produced from a 15 μm thick disk of Al foil on a 1.2 MA, 100 ns rise time, pulsed power machine. Experiments were performed with both a radially inward and a radially outward current flow in the Al foil to investigate the effects of voltage polarity in the experiments and determine how extended magnetohydrodynamic (XMHD) effects, such as the Hall effect, change the formation of the jet. We recorded Thomson scattering spectra with a low enough laser energy to not perturb the plasma while providing a high enough signal to noise ratio to resolve the scattered features. This enabled the measurement of the electron temperature in the jet region of the plasma, 15.5 ± 4 eV for both current polarities. Jets with a radially outward current flow were heated more from inverse bremsstrahlung when 10 J of laser energy was used, implying that these jets are denser than the ones with a radially inward current. This higher density was confirmed by interferometry measurements. Experimental results were compared with XMHD computer simulations, which predicted electron temperatures 1.5–3 σ above those measured, and significantly higher density than experiments in both polarities. Possible sources of this discrepancy are discussed.