Design and Performance of a Low Attenuation Electromagnetic Shock Tube

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Abstract
Various aspects of the design of a low attenuation electromagnetic shock tube are discussed. The driver gas is nitrogen at atmospheric pressure and is separated from the driven gas by a thin Mylar diaphragm. Particular attention is paid to matching electromechanically the shock tube driver to the energizing capacitor bank. These considerations may increase the uniformity of flow behind the shock wave as well as improve the efficiency of the shock tube. A simple criterion is evolved in terms of the various shock tube parameters, which states that the driver gas should be ejected as a single body during the first discharge of the capacitor bank. The construction of the shock tube is described. Measured shock velocities in air and argon for different capacitor voltages and downstream gas pressures are given and are compared with the velocities predicted by the simple theory. It is concluded that the shock driving mechanism is predominantly electromagnetic in nature but that at low downstream gas pressures (≤ 1 mm Hg) this mechanism is augmented by the wave action which accompanies Joule heating of the driver gas.