Simulation-based parametric correlation analysis of O and N radical production in atmospheric-pressure streamer discharges

Pulse-controlled atmospheric-pressure streamer discharges are attracting attention as an effective source of plasma for applications such as selective oxidation, sterilisation and nitrogen fixation. However, our understanding of how voltage waveform parameters consistently and quantitatively influence the production of reactive radicals remains limited. In this study, we performed 70 two-dimensional fluid simulations of streamer discharges in a needle-to-plane geometry, systematically varying the peak voltage (15-40 kV), the voltage rise time (1.9-45.9 ns) and the pulse width (8.5-193.9 ns).For each case, we quantified the discharge energy, streamer diameter, and total production of atomic oxygen and nitrogen radicals. Statistical analyses, including correlation analysis, segmented regression and principal component analysis, were employed to examine the relationships between these variables. The results demonstrate that O-radical production increases approximately linearly with total discharge energy (r = 0.995, p < 0.001), suggesting that energy deposition is the dominant control factor. N-radical production also correlates strongly with discharge energy (r = 0.966, p < 0.001), but shows an even stronger dependence on the fourth power of peak voltage (r = 0.988, p < 0.001), indicating that N-radical yield is sensitive to electric field strength as well as energy deposition. Rise time and pulse width were found to span an almost orthogonal parameter axis, having limited direct influence on total radical output under the tested conditions. These results suggest that O-and N-radical yields respond differently to pulse parameters, emphasising the importance of energy deposition and electric field strength as controlling factors. Such insights could inform the development of predictive frameworks and the design of waveform-driven plasma processes.