Interactions of magnetized plasma flows in pulsed-power driven experiments

Abstract

A supersonic flow of magnetized plasma is produced by the application of a 1 MA-peak, 500 ns current pulse to a cylindrical arrangement of parallel wires, known as an inverse wire array. The plasma flow is produced by the × acceleration of the ablated wire material, and a magnetic field of several Tesla is embedded at source by the driving current. This setup has been used for a variety of experiments investigating the interactions of magnetized plasma flows. In experiments designed to investigate magnetic reconnection, the collision of counter-streaming flows, carrying oppositely directed magnetic fields, leads to the formation of a reconnection layer in which we observe ions reaching temperatures much greater than predicted by classical heating mechanisms. The breakup of this layer under the plasmoid instability is dependent on the properties of the inflowing plasma, which can be controlled by the choice of the wire array material. In other experiments, magnetized shocks were formed by placing obstacles in the path of the magnetized plasma flow. The pile-up of magnetic flux in front of a conducting obstacle produces a magnetic precursor acting on upstream electrons at the distance of the ion inertial length. This precursor subsequently develops into a steep density transition via ion-electron fluid decoupling. Obstacles which possess a strong private magnetic field affect the upstream flow over a much greater distance, providing an extended bow shock structure.In the region surrounding the obstacle the magnetic pressure holds off the flow, forming a void of plasma material, analogous to the magnetopause around planetary bodies with self-generated magnetic fields.

Characterization of Plasma Formation and Mass Ejection in Exploding Foil Initiators

“…Here the traversal of electrons through the bridge between high-voltage and ground sides generates a magnetic field as indicated in figure 3c [20]. This field draws the plasma regions forming closer together, creating the pinched effect and shapes the regions of plasma formation observed in Figure 1 and overlaid above in Figure 3b-d.…”

“…The movement of plasma regions PB1 and PB2 towards the centre axis of the figure generates two opposing magnetic fields. Upon contact of the two plasma regions, the magnetic reconnection results in the magnetic energy being transferred to kinetic energy and the plasma being propelled in directions normal to its previous direction of propagation (into and out of the plane of the page in the case of Figure 3) [20]. The non-symmetric laminar structure of the EFI, with its tamper layer beneath the bridge, directs the ejection primarily in the one direction, i.e.…”

Persistent mysteries of jet engines, formation, propagation, and particle acceleration: have they been addressed experimentally?

“…New laboratory studies are also being performed with laser driven [180,181,182,183,184,185,186] and pulsed power driven [187,188,189,190,191,192] experimental platforms. In both types of platforms the plasma flows are supersonic (sonic Mach number M > 5), for laser experiments so far they are also super-Alfvenic, while pulsed power experiments operate at Alfvén Mach number 0.7 ≤ M A ≤ 2.…”

Experimental observations of detached bow shock formation in the interaction of a laser-produced plasma with a magnetized obstacle

“…Ours are not the only experiments pursuing laboratory-scale magnetized shocks, recent z-pinch experiments at the MAGPIE facility [21][22][23] have demonstrated shock formation in the interaction of a magnetized plasma with initially unmagnetized, conducting obstacles, as well as in the interaction of a magnetized plasma with an external, magnetized obstacle at laboratory scales. And, more similar to our experiments, Rigby et al 24 provide evidence of magnetized shock formation in the interaction of a laser-produced plasma with a magnetized sphere.…”