Interpretation of Luminous Phenomena Observed in Electromagnetic Shock Tubes

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Abstract
A series of experiments with electromagnetically driven shock waves in various gases have shown that the luminous emission observed along the tube should often be interpreted as being due to direct ionization produced by the driver discharge and not to thermal ionization produced by the shock wave. The experiments also show that for high Mach numbers obtained at low initial pressures (of the order of 1 mm Hg), the shock front and the front of the discharge plasma jet (contact front) practically coincide. Thus, in contradiction with the conclusions reached by Kolb, Griem, and others, the state of the luminous gas following ths shock front cannot be calculated by the Rankine‐Hugoniot equations from the velocity of the front. The results presented have been obtained by spectrographic investigation of the light emitted along a special H‐shaped glass tube in which the gas between one of the electrode pairs is initially different from that filling the rest of the tube.