The dynamics of discontinuities in a cylindrical energy deposition based on a nanosecond discharge
The focusing of a secondary shock wave was experimentally recorded during the implementation of an extended nanosecond high-current discharge of a cylindrical configuration in air. Using high-speed shadowgraph recording (up to 300 000 frames/s) of the emerging unsteady flow, cylindrically symmetric gas-dynamic discontinuities were visualized: a diverging shock wave moving from the discharge plasma boundary, a diverging contact discontinuity separating the shock-heated gas from the nonequilibrium region excited by the discharge plasma, and also a converging compression wave (secondary shock wave) moving from the contact surface to the axis of symmetry and focusing on it 50-60 microseconds after discharge with the formation of a heated long-lived cord.