Experimental characterization of a transition from collisionless to collisional interaction between head-on-merging supersonic plasma jets

Abstract

We present results from experiments on the head-on merging of two supersonic plasma jets in an initially collisionless regime for the counter-streaming ions. The plasma jets are of either an argon/impurity or hydrogen/impurity mixture and are produced by pulsed-power-driven railguns. Based on time- and space-resolved fast-imaging, multi-chord interferometry, and survey-spectroscopy measurements of the overlapping region between the merging jets, we observe that the jets initially interpenetrate, consistent with calculated inter-jet ion collision lengths, which are long. As the jets interpenetrate, a rising mean-charge state causes a rapid decrease in the inter-jet ion collision length. Finally, the interaction becomes collisional and the jets stagnate, eventually producing structures consistent with collisional shocks. These experimental observations can aid in the validation of plasma collisionality and ionization models for plasmas with complex equations of state.

arXiv comment10 pages, 9 figures, 5 tables (accepted, to appear in the May 2015 APS-DPP special issue of Physics of Plasmas)

References in corpus (8)

• Filamentation instability of counter-streaming laser-driven plasmas
• Experimental characterization of railgun-driven supersonic plasma jets motivated by high energy density physics applications
• Experimental characterization of the stagnation layer between two obliquely merging supersonic plasma jets
• Experimental evidence for collisional shock formation via two obliquely merging supersonic plasma jets
• Laboratory plasma physics experiments using merging supersonic plasma jets
• Particle-in-cell simulations of collisionless shock formation via head-on merging of two laboratory supersonic plasma jets
• Multi-chord fiber-coupled interferometer with a long coherence length laser
• Multi-chord fiber-coupled interferometry of supersonic plasma jets and comparisons with synthetic data

Cited by in corpus (8)

• Laboratory Space Physics: Investigating the Physics of Space Plasmas in the Laboratory
• Experiment to Form and Characterize a Section of a Spherically Imploding Plasma Liner
• Experimental Measurements of Ion Heating in Collisional Plasma Shocks and Interpenetrating Supersonic Plasma Flows
• Experimental characterization of a section of a spherically imploding plasma liner formed by merging hypersonic plasma jets
• Observation of Rayleigh-Taylor-Instability Evolution in a Plasma with Magnetic and Viscous Effects
• Observation of Shock-Front Separation in Multi-Ion-Species Collisional Plasma Shocks
• Experimental Study of Ion Heating in Obliquely Merging Hypersonic Plasma Jets
• Formation of Transient High-$\beta$ Plasmas in a Magnetized, Weakly Collisional Regime