Current Status of Research on Electromagnetically Produced Unsteady Shock Waves

Fast shock waves in light gases can be produced simply by electromagnetic acceleration. Unlike rail spark gaps or magnetic annular tubes, which produce quasistationary, shock-wavelike phenomena, T tubes and conical theta pinches or Z pinches generate nonstationary shock waves of the blast wave type if the plasma of the driving discharge does not advance right into the shock front and appreciably influence the plasma formed there. The investigations of free-running shock waves and the distributions of the parameters in the plasmas behind these shock fronts are discussed. Shadowgraphs, interferograms, microwave interferograms and probe measurements have afforded a fairly complete picture of such nonstationary waves revealing their uses and limitations.