Experimental observations of the structure of strong shock-waves in argon

Variations in shock-wave structure in argon were investigated at initial shock-tube pressures of 3 and 25 torr, corresponding to velocities of 6-8.5 km/s and 3.5-6.2 km/s, respectively. Results show the existence of two types of shock-wave structure. At the lower velocities (3.5-6.2 km/s), it was found that the shock wave experienced two-stage compression at the translation front and at the relaxation zone, with subsequent monotonic variations in density and electron concentration. At higher velocities (6-8.5 km/s), the shock wave was characterized by one- or two-stage compression, nonmonotonic variations in density and electron concentration along the shock-heated areas. Shock waves in the intermediate velocity range are shown to be unstable, with non-one-dimensional disturbances before and behind the front.