Thermal bubble breakdown in cryogenic liquids under non-uniform fields

The electrical forces acting on thermally induced bubbles in nonuniform field gaps with/without fins, and the correlation between bubble behavior and dielectric characteristics in liquid nitrogen are studied. It is shown that the gradient force and Maxwell stress greatly affect the bubble dynamics and bubble shape in the gap. In particular, the pronounced gradient force near the fin tip reduces the growth of bubbles there. This results in a reduced effect of thermal bubbles on the breakdown voltage.