A parametric study of annular spark gaps, pressures, and spark discharges in flowing oxygen gas was performed with a Champion spark exciter. Measurements of breakdown voltage vs. pressure-distance product over a range of 50 torr-cm to 2500 torr-cm qualitatively trend with Paschen's curve. The spark duration remained constant at ～40 µs until the pressure-distance product exceeded 200 torr-cm and then steadily increased to ～80 µs. The mean spark energy increases quasi-linearly with the pressure-distance on a log-log plot indicating that a power relationship exists. The distribution of sparks at low energies and low pressures is not Gaussian and has no dominant peaks. Moderate and high spark energy distributions are bimodal, with the dominant mode near 80 mJ. As pressure increases, dominant and secondary modes approach the same probability.
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