Streamer discharges in oxygen-enriched gas mixtures are widely used

yet the modeling of oxygen-induced photoionization and its influence on primary and secondary streamers still require further investigation. In this work

a computational method is developed to evaluate the photoionization rate induced by oxygen photons in streamer discharges

and a fluid discharge model incorporating oxygen-induced photoionization is constructed by coupling the drift-diffusion equations with Poisson’s equation. The variations in the electric field at the streamer head and the electron density inside the channel in a needle-to-plate gap are examined

and the results are compared with experimental data to analyze the effects of oxygen concentration on the development characteristics of primary and secondary streamers. The results show that

when the oxygen concentration increases from 20% to 90%

the electric field at the head of the primary streamer in N₂-O₂ mixtures decreases by 17%

and the electron density inside the channel decreases by 10%~50%; for secondary streamers

the electric field changes by less than 10%

while the electron density decreases by about 50%. At 90% oxygen concentration

oxygen-photon-induced photoionization can account for up to 40% of the total photoionization rate. The calculated streamer channel diameter

propagation velocity

normalized optical emission intensity

and current waveforms exhibit an average deviation of less than 10% from the experimental measurements. This study contributes to a deeper understanding of oxygen-induced photoionization mechanisms in streamer discharges.