X-ray radiography of underwater electrical wire explosion and its use in hydrodynamic instability research
File(s)
Author(s)
Strucka, Jergus
Type
Thesis
Abstract
This thesis describes an investigation of underwater electrical wire explosion and its utility in hydrodynamic instability research. The experiments described here were performed at the European Synchrotron. The primary diagnostics consisted of multi-frame X-ray radiography and electrical diagnostics such as current and high voltage probes. The synchrotron X-ray source allowed us to perform multi-MHz radiography, obtaining up to 256 consecutive radiographs, with exposure time ∼ 60 ps, temporal resolution Δt ∼ 176−704 ns, and spatial resolution Δx ∼ 3.2−32 μm spanning multi-mm field-ofview. These diagnostics were used to investigate electrical explosion of a single wire and its interaction with a cylindrically convergent shockwave. Measured quantities included commonly published parameters of the explosion, such as the shock and the plasma expansion speed, and parameters that were not previously published, such as the water mass density or the internal structure of the exploding wire at a spatial resolution Δx ∼ 3.2 μm.
Importantly, these experiments are some of first direct observations of the development of electrothermal instability, with perturbation spectrum spanning at least 20−200 μm. The magnitude of the instability was observed to be a strong function of the material, and even ∼ 10 μs after explosion, the instability remnant could seed other hydrodynamic instabilities, such as the Richtmyer-Meshkov instability. Additionally, these measurements were used to validate a 2D MHD simulation, which showed that the electrothermal instability does not change the average resistivity of the wire, as compared to a completely uniform explosion. As such, the underwater electrical wire explosion remains a valid method to estimate electrical conductivity of metals.
Finally, we also demonstrated the utility of the underwater electrical wire explosion, used in combination with multi-MHz synchrotron radiography, to obtain high-quality measurements of hydrodynamic instabilities...
Importantly, these experiments are some of first direct observations of the development of electrothermal instability, with perturbation spectrum spanning at least 20−200 μm. The magnitude of the instability was observed to be a strong function of the material, and even ∼ 10 μs after explosion, the instability remnant could seed other hydrodynamic instabilities, such as the Richtmyer-Meshkov instability. Additionally, these measurements were used to validate a 2D MHD simulation, which showed that the electrothermal instability does not change the average resistivity of the wire, as compared to a completely uniform explosion. As such, the underwater electrical wire explosion remains a valid method to estimate electrical conductivity of metals.
Finally, we also demonstrated the utility of the underwater electrical wire explosion, used in combination with multi-MHz synchrotron radiography, to obtain high-quality measurements of hydrodynamic instabilities...
Version
Open Access
Date Issued
2023-08-21
Date Awarded
01/12/2023
Advisor
Bland, Simon
Sponsor
First Light Fusion Limited (Firm)
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)