Computational Model for Photoionization in Pure SF6 Streamer at 1-15 atm

TL;DR

This paper develops and validates a detailed computational model for SF6 photoionization in streamer discharges across 1-15 atm, improving accuracy and convergence in simulations.

Contribution

The paper introduces a comprehensive SF6 photoionization model that captures non-local effects and compares it with simplified approaches, providing detailed parameters for 1-15 atm.

Findings

The model accurately predicts streamer structures and breakdown voltages.

Artificially increasing photoionization intensity affects positive and negative streamers differently.

Enhanced photoionization can lead to underestimation of breakdown voltage and morphological changes.

Abstract

Photoionization plays a crucial role in achieving accurate quantitative predictions in SF6 streamer simulations, but accurate models for SF6 photoionization remains limited, motivating this paper. First, we develop a computational model for SF6 photoionization and provide the detailed theoretical modeling process, as well as comparison between experiment and simulation. A concise summary of model parameters within the comprehensive pressure range of 1 - 15 atm is provided for direct reference. Then, we perform comparative studies against simplified approaches. The results demonstrate that the proposed model effectively captures the non-local effects of SF6 photoionization, enhancing both the spatial numerical convergence and the accuracy of the streamer structure. Finally, we perform comparative studies by artificially increasing the photoionization intensity through multiplying the photoionization source term Sph by a factor of 50 (50*Sph) relative to the baseline intensity. Regarding breakdown voltage prediction, 50*Sph leads to a significant underestimation of the breakdown voltage for positive streamers, introducing errors greater than 0.5 kV, while exerting a small impact on negative streamers. Regarding streamer propagation dynamics, the radius of the positive streamer head exhibits pronounced shrinking, and 50*Sph reduces this shrinking and significantly lowers the head field by more than 700 Td. In contrast, 50*Sph has little impact on the morphology of the negative streamers and slightly enhances the head field by less than 30 Td.