Open Access Conference Proceedings

We investigate how the geometry of nanovoids present during the (sub)nanosecond electrical breakdown in liquid water influences the electron multiplication. Our analysis uses a particle-tracing Monte Carlo simulation toolkit Geant4-DNA. The electron multiplication in nanovoids is one of the possible scenarios describing the charge generation in liquid water. In our simplified model, we assume a constant homogeneous electric field, an ellipsoidal shape of nanovoids, and isotropic distribution of the primary electron's velocity. The quantity of interest is the number of ionizations per number of launched primary electrons. We study this yield of electrons as we vary the ellipsoid eccentricity parameter while keeping the volume constant. The nanovoids with zero eccentricity (spherical case) produce smaller yield since the suppressed length does not favor electron multiplication. On the other hand, a very prolonged ellipsoid causes the loss of most electrons because of early collisions with the void-liquid interface. Therefore, for a particular value of eccentricity, the yield is maximal. The results of this study contribute to the elucidation of the initial phases of discharge evolution in polar liquids and is one of the first steps towards quantitative assessment of the importance of microscopic parameters involved. The understanding of this phenomenon promises the explanation of macroscopic parameters observed in the (sub)nanosecond electrical breakdown experiments

Keywords: Nanovoids, electrostriction, liquid water electric breakdown, nanosecond pulsed electric field

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