Generation of episodic magnetically driven plasma jets in a radial foil Z-pinch

Abstract

We present experimental results of the formation of magnetically driven plasma jets, showing for the first time a way of producing episodic jet/ouflows in the laboratory. The jets are produced using a 6.5 µm thick aluminum disc (a radial foil), which is subjected to the 1 MA, 250 ns current pulse from the MAGPIE generator [I. H. Mitchell et al., Rev. Sci. Instrum. 67, 1533(1996]. The early time motion of the foil is characterized by the bulk motion of the mass due to the magnetic pressure, together with the formation of a surface plasma following the direction of the J × B force. A low density plasma fills the region above the foil preceding the formation of subsequent magnetically driven jets on the axis of expanding magnetic bubbles. The outflows emerge in timescales of ∼30-40 ns and their episodic nature is the result of current reconnection in the foil, aided by the formation of current-driven instabilities in the jet and the distribution of mass available from the foil. The additional inductance due to the new current path inside the cavities was measured using an inductive probe, allowing to estimate the energy balance associated with the episodes. The measured temperature of the compressed jet resulted in Te∼300 eV and a magnetic Reynolds number of ReM ∼200-1000, allowing the experiments to be in the regime relevant for scaled representations of astrophysical outflows.

Interaction of a supersonic, radiatively cooled plasma jet with an ambient medium

“…11,26 In this paper we also present results from numerical simulations, which accurately reproduce the dynamics observed in the experiments and provide important insights on the interaction dynamics.…”

“…Magnetically driven jets are typically produced using high currents from pulsed-power facilities. [11][12][13][14] This experimental approach, together with high-power lasers, is the main tool used to generate hydrodynamic jets. Some of the first proof-of-principle experiments relevant to the dynamics of jet propagation from young stars comprised supersonic (Mach number & 1), adiabatic (i.e., without radiative cooling) flows propagating in vacuum.…”

Diagnosing collisions of magnetized, high energy density plasma flows using a combination of collective Thomson scattering, Faraday rotation, and interferometry (invited)

“…This technique has a number of advantages over other commonly used methods of measuring the magnetic field (B) in a plasma, such as placing "B-dot" magnetic pickup coils [21][22][23][24] in the path of the plasma flow. These probes can cause significant disruption to the flow and the signals they produce are subject to noise associated both with coupling of the drive voltage to the straycapacitance of the coil and with shorting/shielding of the coil by the plasma.…”

The hydrodynamics of astrophysical jets: scaled experiments and numerical simulations

“…Different techniques have been employed, to study laboratory simulations of astrophysical jets, i.e. high-power lasers (Hartigan et al 2009;Gregory et al 2009;Falize et al 2011), radial wires, and foil Z-pinch (Lebedev et al 2005;Suzuki-Vidal et al 2010). These experiments reproduce some features of the actual YSO jets such as jet velocities, temperatures, and cooling effects.…”