We investigate three-dimensional (3-D) bow shocks in a highly collisional magnetized aluminium plasma, generated during the ablation phase of an exploding wire array on the MAGPIE facility (1.4 MA, 240 ns). Ablation of plasma from the wire array generates radially diverging, supersonic ( $$M_S \sim 7$$ ), super-Alfvénic ( $$M_A > 1$$ ) magnetized flows with frozen-in magnetic flux ( $$R_M \gg 1$$ ). These flows collide with an inductive probe placed in the flow, which serves both as the obstacle that generates the magnetized bow shock, and as a diagnostic of the advected magnetic field. Laser interferometry along two orthogonal lines of sight is used to measure the line-integrated electron density. A detached bow shock forms ahead of the probe, with a larger opening angle in the plane parallel to the magnetic field than in the plane normal to it. Since the resistive diffusion length of the plasma is comparable to the probe size, the magnetic field decouples from the ion fluid at the shock front and generates a hydrodynamic shock, whose structure is determined by the sonic Mach number, rather than the magnetosonic Mach number of the flow. The 3-D simulations performed using the resistive magnetohydrodynamic (MHD) code Gorgon confirm this picture, but under-predict the anisotropy observed in the shape of the experimental bow shock, suggesting that non-MHD mechanisms may be important for modifying the shock structure.
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Design of a Multiple Exploding Wire Setup to Study Shock Wave Dynamics
Shock wave dynamics is a topic with a wide variety of applications ranging from removal of kidney stones to inertial confinement fusion. In reality, the shock front is most often followed by a decay in flow properties, and therefore it is of interest to better understand shock dynamic events for these situations. Thus, an experimental facility that can provide results that are accurate, highly controlled, affordable and with a quick turn-around time are needed. Here, we present the design of an exploding wire system that can be coupled to either a two-dimensional or a three-dimensional test section to provide the user with a multitude of settings to study shock dynamics emanating from shock waves with decaying flow properties behind the shock front. Schlieren photographs taken with an ultra-high speed camera are also presented to show that the exploding wire system functions as intended in both two- and three-dimensional setups.
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- Award ID(s):
- 1803592
- PAR ID:
- 10159376
- Date Published:
- Journal Name:
- Experimental techniques
- Volume:
- 44
- ISSN:
- 1747-1567
- Page Range / eLocation ID:
- 241-248
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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