Probe-shift error in remote diagnostics of volume-radiation sources

The effect of finite width of the exit-slit on the spatial accuracy of the spectrometric determination of the distribution of the radial emission coefficient of a radiating column with axial symmetry for which the emission coefficient varies from a minimum at the outer radius to a maximum at or near the axis is discussed. Models are used which are often employed in analyzing radiation from plasma streams, electric arc columns, and flames. It is shown that there is a positioning error involved in the determination of emission coefficients by analyzing radiative power distributions obtained by observing an axisymmetric source from the side with a spatial scanning analyzer of finite width and then using the Abel integral equation for subsequent determination of the emission coefficient. The error depends on the geometry of the source and measuring system as well as the shape of the emission coefficient distribution and analyzer width.