Observation of Discharge Instability Induced by Shockwave in Self-Sustained High-Pressure Pulsed Glow Discharge

Abstract

Self-sustained high-pressure pulsed glow discharge is applied to excitation discharge on transversely excited atmospheric (TEA) gas lasers. Influence of shockwaves with Mach number M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> of 1.1 and 1.35 on the discharge has been investigated. The normal Shockwave, which is normal to gas flow direction in TEA gas lasers, is produced by a shock tube with gas mixture of helium and argon to simulate reflected shockwave in discharge cavity. Discharge instability depends on both the shock Mach number and the position of shockwave in the cavity. The discharge does not collapse by gas density disturbance caused by the shockwave with M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> = 1.1, where the gas densities in front of and behind the shockwave are rho <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> = 0.52 kg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and rho <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> = 0.60 kg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , respectively. In the two shockwaves with identical M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> = 1.35 having rho <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /rho <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> = 0.83/0.55 or 0.67 kg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /0.45 kg/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , the recovery of discharge depends on rho <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , and the gas density disturbance caused by oblique shockwave destroys the discharge even if the cavity is occupied by the gas having suitable density in still gas. The discharge may not be disturbed with spatial distribution of preionization electron density due to the shockwave.