Speaker
Description
In this work we present our efforts to simulate the effect of Ohmic heating due to field emission on the morphology (shape) of a surface region. A popular model of field emission leading to material supply and eventual vacuum arc breakdown relies on the existence of protrusions with high electric field enhancement factors (β). β can sometimes be initialized to values as high as 100. However, finding such protrusions on surfaces has been quite difficult. While they have been found in a very few number of places (e.g., tin whiskers), their lack of presence in a general way leads to a criticism of these popular models because their basic assumption appears to not be met. This work endeavors to track the evolution of a moderately flat surface region exposed to high electric fields, and thus high temperatures, ideally transforming into a protrusion. The simulation methodology employed here is a parallel coupled finite element method, including a level set representation of the surface and adaptive mesh refinement, in the Sandia code Aria. Aria’s model will couple current density, temperature, mass transport, surface tension, and electric fields. It can track phase change, resulting in a transition from solid bulk material to liquid to vapor or microdroplets (via level set representation).
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