Figure 2
From: Long-lived laser-induced arc discharges for energy channeling applications
Two-color interferometry results on long-lived discharges. (a) Example of interferograms recorded at delay 2 μs (left) and 120 μs (right) in the single shot regime, showing the formation of a shock wave and the expansion of the subsequent channel. (b) Radial profiles of electron density (blue) and of neutral density (red) at delay 280 μs, showing the formation of a large channel with a strongly depleted neutral density while the plasma remains confined at the center in the form of a much narrower cylinder. Negative densities come from measurement uncertainties estimated at 4 × 1022 m−3 for electrons and 1024 m−3 for neutrals37. (c) Time evolution of on-axis electron density (blue circles) and of the discharge current (red solid curve). The electron detection threshold (green solid line) is estimated to be around 4 × 1022 m−3 37. Electron density initially quickly decays, but starts oscillating with the low-frequency current at longer times. Blue arrows indicate times at which measurements could not detect free electrons. (d) Time evolution of the neutral channel radius (blue circles) and of the total quantity of lacking neutral molecules with respect to air in standard pressure and temperature conditions (red squares), showing the channel is still expanding and remains at a low density even after a delay 900 μs.
