Determination of Electron Concentration Behind the Front of a Shock Wave in a Gas-Discharge Plasma in a Magnetohydrodynamic Shock Tube

摘要

Determination of the electron density behind a shock wave was made using the Stark broadening of the H (subscript beta) line. The method of measurement is discussed, and instrumental, Doppler and pressure broadening effects analyzed. The exposed films were tagged by a 9-step wedge filter for accurate photometry of the H (subscript alpha) and H (subscript beta) lines. Using the characteristic curves, film exposure was related to the incident intensity. The intensity was in turn related to the density of charged particles by use of the Holtsmark relations. The time-history of the density was obtained by using streak photography to observe the behavior of the H (subscript beta) line behind the shock front. For known shock velocities, the change in electron temperature was related by Saha's equation to the equilibrium temperature. The electron density and temperature so obtained are seen to agree with theoretical computations. The measurements of the electron density shows the existence of a smooth transition from the undisturbed gas to the discharge plasma. This is explained by the diffusion of electrons from the discharge region into the cold gas. (Author)