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Unmasking of Novel Conic Modes in Electrically Stressed Perfectly Conducting Liquids

Zhou, Chengzhe and Troian, Sandra M. (2020) Unmasking of Novel Conic Modes in Electrically Stressed Perfectly Conducting Liquids. . (Unpublished)

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Liquid metal ion sources (LMIS) are widely used in applications ranging from local ion implantation in semiconductors, to focused ion beam systems for milling and nanolithography, to space micropropulsion devices being developed by NASA. Above a critically large field strength, an electrically stressed liquid metal develops one or more cuspidal protrusions which undergo accelerated conic tip sharpening with runaway field self-enhancement. Zubarev (2001) first predicted from an inviscid model that the electric stresses at the liquid apex undergo self-similar divergent growth in finite time. The inviscid assumption is appropriate to liquid metals since the viscous boundary layer extends only a few tens of nanometers from the moving interface. In this work, we examine in more depth a two-parameter family of far-field self-similar solutions incorporating inertial, electrical and capillary effects, which to leading order describe electric and velocity potential fields corresponding to a rapidly accelerating dynamic Taylor cone. These far field solutions are incorporated self-consistently into boundary integral simulations which reveal the entire liquid shape in the near field. By invoking time reversal symmetry inherent to inviscid flow, we unmask an entire family of novel self-similar conic modes exhibiting features such as inertial recoil, tip bulging from accelerated advance and tip counter-current flow as well as multiple interface stagnation points. These dynamic configurations help explain for the first time the origin of decades old experimental observations that have reported phenomena such as tip oscillation, pulsation and breakup during operation. The various liquid tip shapes accessible to such systems should help correct persistent misconceptions of pre- and post-emission behavior in LMIS systems and related technologies.

Item Type:Report or Paper (Discussion Paper)
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Troian, Sandra M.0000-0003-1224-6377
Additional Information:The authors gratefully acknowledge Dr. Peter Thompson for designing and maintaining the computing cluster used in this work. SMT also acknowledges valuable discussions with Dr. Colleen Marrese-Reading and Dr. James E. Polk at the NASA Jet Propulsion Laboratory involving their ongoing experiments with liquid metal ion sources.
Record Number:CaltechAUTHORS:20210105-133434370
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107329
Deposited By: George Porter
Deposited On:06 Jan 2021 17:55
Last Modified:06 Jan 2021 17:55

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