An analysis is made of the errors that arise in line-intensity measurements due to the experimental averaging of the time-varying intensities caused by electron-temperature fluctuations in continuous-plasma sources. These calculations are made both for periodic and for random electron-temperature fluctuations. The errors are dependent on the method of measurement. The possible errors in the monochromator method usually positive and significant for typical spectral lines and electron temperatures. An alternative method, which is shown to be subject to less error, is to use a polychromator and to measure the average of the instantaneous line-intensity ratio. In either method (but more applicable to the monochromator method) the additional measurement of the root-mean-square value of the intensity ratio gives another set of equations and allows the determination of both the mean electron temperature and the oscillation amplitude or standard deviation for gaussian-noise temperature fluctuations.
R. F. WEBER and A. GARSCADDEN, "Errors Due to Averaging Spectral-Line Intensities in the Presence of Electron-Temperature Variations," J. Opt. Soc. Am. 61, 1330-1334 (1971)