REDUCED ABSORPTION-COEFFICIENT OF THE 1ST RESONANCE LINE OF CS IN HIGH-TEMPERATURE HELIUM

For application to seed-fraction measurements in a closed cycle MHD power-generation system, the relation between the number density of cesium and the profile of the first resonance line of cesium (7(2) P3/2-6(2)S1/2, 852.1 nm) has been investigated experimentally in high-temperature helium heated in a shock tube. The column density of cesium was measured by using a modified hook method. The emissivity of the blue wing of the Cs 852.1 nm line was obtained from the emission spectrum. Combining these results, the reduced absorption coefficient of the line was determined for the conditions of closed-cycle MHD working gases. Using this reduced absorption coefficient, the number density of Cs can be measured by monitoring the change of absorption at a fixed wavelength in the wing of the line.