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The study of local overheating and plasma formation on stainless steel z-pinch targets

Hatch, Maren W.; Awe, Thomas J.; Hutsel, Brian T.; Yu, Edmund Y.; Jauregui, Luis J.; Barrick, Erin J.; Gilmore, Mark A.

Plasma formation from intensely ohmically heated conductors is known to be highly non-uniform, as local overheating can be driven by micron-scale imperfections. Detailed understanding of plasma formation is required to predict the performance of magnetically driven physics targets and magnetically-insulated transmission lines (MITLs). Previous LDRD-supported work (projects 178661 and 200269) developed the electrothermal instability (ETI) platform, on the Mykonos facility, to gather high-resolution images of the self-emission from the non-uniform ohmic heating of z-pinch rods. Experiments studying highly inhomogeneous alloyed aluminum captured complex heating topography. To enable detailed comparison with magnetohydrodynamic (MHD) simulation, 99.999% pure aluminum rods in a z-pinch configuration were diamond-turned to ~10nm surface roughness and then further machined to include well-characterized micron-scale "engineered" defects (ED) on the rod's surface (T.J. Awe, et al., Phys. Plasmas 28, 072104 (2021)). In this project, the engineered defect hardware and diagnostic platform were used to study ETI evolution and non-uniform plasma formation from stainless steel targets. The experimental objective was to clearly determine what, if any, role manufacturing, preparation, or alloy differences have in encouraging nonuniform heating and plasma formation from high-current density stainless steel. Data may identify improvements that may be implemented in the fabrication/preparation of electrodes used on the Z machine. Preliminary data shows that difference in manufacturer has no observed effect on ETI evolution, stainless alloy 304L heated more uniformly than alloy 310 at similar current densities, and that stainless steel undergoes the same evolutionary ETI stages as ultra-pure aluminum, with increased emission tied to areas of elevated surface roughness.

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TYPE SAND Report YEAR 2022
DOIOSTI

Use of hydrodynamic theory to estimate electrical current redistribution in metals

Physics of Plasmas

Yu, Edmund Y.; Awe, Thomas J.; Cochrane, Kyle C.; Yates, K.C.; Hutchinson, T.M.; Peterson, Kyle J.; Bauer, Bruno S.

Using the analogy between hydrodynamic and electrical current flow, we study how electrical current density j redistributes and amplifies due to two commonly encountered inhomogeneities in metals. First, we consider flow around a spherical resistive inclusion and find significant j amplification, independent of inclusion size. Hence, even μm-scale inclusions can affect performance in applications by creating localized regions of enhanced Joule heating. Next, we investigate j redistribution due to surface roughness, idealized as a sinusoidal perturbation with amplitude A and wavelength λ. Theory predicts that j amplification is determined by the ratio A/λ, so that even "smooth"surface finishes (i.e., small A) can generate significant amplification, if λ is correspondingly small. We compare theory with magnetohydrodynamic simulation to illustrate both the utility and limitations of the steady-state theory.

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TYPE Journal Article YEAR 2020
DOIOSTIScopus

Experimental observation of the stratified electrothermal instability on aluminum with thickness greater than a skin depth

Physical Review E

Hutchinson, T.M.; Awe, Thomas J.; Bauer, B.S.; Yates, K.C.; Yu, Edmund Y.; Yelton, William G.; Fuelling, S.

A direct observation of the stratified electrothermal instability on the surface of thick metal is reported. Aluminum rods coated with 70μm Parylene-N were driven to 1 MA in 100ns, with the metal thicker than the skin depth. The dielectric coating suppressed plasma formation, enabling persistent observation of discrete azimuthally correlated stratified thermal perturbations perpendicular to the current whose wave numbers, k, grew exponentially with rate γ(k)=0.06ns-1-(0.4ns-1μm2rad-2)k2 in ∼1g/cm3, ∼7000K aluminum.

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TYPE Journal Article YEAR 2018
DOIOSTIScopus

Stagnation Morphology in Magnetized Liner Inertial Fusion Experiments

Gomez, Matthew R.; Harding, Eric H.; Ampleford, David A.; Jennings, Christopher A.; Awe, Thomas J.; Chandler, Gordon A.; Glinsky, Michael E.; Hahn, Kelly D.; Hansen, Stephanie B.; Jones, Brent M.; Knapp, Patrick K.; Martin, Matthew; Peterson, Kyle J.; Rochau, G.A.; Ruiz, Carlos L.; Schmit, Paul S.; Sinars, Daniel S.; Slutz, Stephen A.; Weis, Matthew R.; Yu, Edmund Y.

Abstract not provided.

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TYPE Conference Poster YEAR 2017
OSTIOSTI

A Path to Increased Performance in Magnetized Liner Inertial Fusion

Gomez, Matthew R.; Slutz, Stephen A.; Jennings, Christopher A.; Harvey-Thompson, Adam J.; Weis, Matthew R.; Lamppa, Derek C.; Hutsel, Brian T.; Ampleford, David A.; Awe, Thomas J.; Bliss, David E.; Chandler, Gordon A.; Geissel, Matthias G.; Hahn, Kelly D.; Hansen, Stephanie B.; Harding, Eric H.; Hess, Mark H.; Knapp, Patrick K.; Laity, George R.; Martin, Matthew; Nagayama, Taisuke N.; Rovang, Dean C.; Ruiz, Carlos L.; Savage, Mark E.; Schmit, Paul S.; Schwarz, Jens S.; Smith, Ian C.; Vesey, Roger A.; Yu, Edmund Y.; Cuneo, M.E.; Jones, Brent M.; Peterson, Kyle J.; Porter, John L.; Rochau, G.A.; Sinars, Daniel S.; Stygar, William A.

Abstract not provided.

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TYPE Conference Poster YEAR 2017
OSTI
Results 1–25 of 85
Results 1–25 of 85