Performance Studies with an Electrically Driven Shock Tube

Studies of an electrically driven shock tube employing a coaxial electrode configuration have been made to determine the nature of the shock-heated plasma and the suitability of such a shock tube as a source for quantitative spectroscopic measurements. Good agreement has been found between the flow velocity measured experimentally and the velocity predicted from a mathematical treatment of the acceleration process. Image converter camera photographs have shown that the flow is highly turbulent and irregular, in contrast to expected shock-wave behavior. A graphical procedure has been employed to calculate the conditions behind fast shock waves in a 75% He-25% Ne gas mixture at an initial pressure of 1 Torr. Time-resolved spectroscopic measurements of plasma conditions demonstrate that the temperature and density are about half those values calculated for the observed shock speed of 5.5 cm/μsec. The measured plasma conditions and the internal consistency of the data indicate that the gas can be described as being in quasithermodynamic equilibrium to within 30%. The irregular nature of the flow, however, restricts the usefulness of the device as a spectroscopic source.