Concentration Measurements in a Transient Helium-Air Mixture Utilizing an Electron Beam

In order to determine the available test time in a helium-driven shock tunnel, an interface detection system has been developed to indicate the arrival of helium driver gas at the test section. This is done by exciting the gas at the test section with a high-energy electron beam and spectroscopically analyzing the resulting fluorescence to determine ine the helium concentration. Relative values of helium and air emission intensities are calculated and compared with experimental data from both static and transient gas mixtures.