Probe-Shift Error in Remote Diagnostic of Volume Radiation Sources

Determination of the distribution of the emission coefficient in a volume radiation source sometimes entails mathematical analysis of an externally measured distribution of radiative flux. Through an analysis of a hypothetical source exhibiting cylindrical symmetry, it is shown that the finite aperture of the measuring device causes a probe-shift error in the results. The shift is a strong function of the size and magnitude of the second spatial derivative of the emission and increase with the aperture size. Nomenclature tw,h) = measured radiative power, W = calculated radiative flux, W/m2 — aperture height of analyzer, m = emission coefficient, W/m3 = ideal radiative flux, W/m2 = radial coordinate, m = radius of source, m — aperture width of analyzer, m = depth coordinate normal to source axis, m = lateral coordinate normal to source axis, m — effective value of lateral coordinate, m = nominal value of lateral coordinate, m = axial coordinate of source , m = standard deviation of Gauss distribution, m