Characterization and spectroscopic study of positive streamers in water

This paper first presents a characterization of positive streamers in pure water (conductivity ∼ 0.05 μS/cm), initiated by a fast rectangular impulse voltage in a point-plane electrode geometry. According to the conditions, two main streamers types can be observed, with average propagation velocities from 0.5 to 30 km/s. Then, a spectroscopic investigation of positive streamer propagation is carried out. According to the conditions, spectra of the light emitted close to the point, show the OH band, atomic lines (OI, H_α) and a strong continuum from 350 to 500 nm. From an analysis of the OH band and from the broadening of the atomic lines (H_α and OI at 777 nm), the kinetic temperature and the electron density within filaments of both streamer types can be evaluated.