Plasma spectroscopy using the shock tube as a light source

Measurement of optical properties of plasmas is de scribed as an important application of the gas-driven shock tube. The electrical engineering context is the study and application of plasmas having temperatures of order 1eV (11 600°K) for which both atomic and collective properties need to be known. The gas driven shock tube heats samples of gas to temperatures of 9000-13 000°K at total pressures of 10-20 atm. Steady state conditions during which the gas is in collisional thermal equilibrium persist for 100-200 µs. Spectral line emission (e.g., H, C, C⁺, P, P⁺, Fe, Fe⁺, O, U, U⁺, U⁺⁺) and continuum radiation are correlated with the measured thermodynamic state of the gas to obtain either absolute transition probabilities, Stark broadening, and Stark shift parameters for the particular lines, or complete tabulations of optical depth versus wavelength for complex and incompletely classified spectra. The atomic data, as well as some newly developed spectroscopic techniques, facilitate the measurement of composition, temperature, pressure, and electron density in high temperature plasma devices. Measured optical depths of uranium plasmas already directly test predictions vital to the design of proposed, gas-core fission reactors.