Radiative interaction between driver and driven gases in an arc-driven shock tube

An electric-arc driven shock tube was operated with hydrogen as the driven gas and either hydrogen or helium as the driver gas. The electron density was measured behind the primary shock wave spectroscopically from the width of the hydrogen beta line. The intensity of the radiation produced by the driver and driven gases and directed along the axis of the shock tube was measured with a photomultiplier tube. The temperatures behind the primary shock wave were 3 to 4 times those calculated from the Rankine-Hugoniot relations. A proposed explanation for this difference is developed, involving strong heating of the driven gas at early times due to higher shock velocities and radiative energy transfer from the driver arc. The electron density ahead of the shock wave agreed roughly with the calculation based on the precursor phenomenon due to radiative transfer.