Potential accuracies of some new approaches for determination by Thomson scattering lidar of the electron temperature profiles in thermonuclear plasmas

Abstract

Two new approaches are proposed for determination by Thomson scattering lidar of the electron temperature in thermonuclear fusion plasmas. They are based on an analysis of the relativistic Thomson scattering spectrum. One of them is based on the unambiguous temperature dependence of the ratio of the return-signal powers of two spectral regions. The second approach is based on the unambiguous temperature dependence of the "center-of-mass wavelength" of the lidar-return spectrum. Analytical expressions are derived of the corresponding errors in the determination of the electron temperature. Their validity is confirmed by computer simulations. On the basis of the theoretical expressions a comparison is performed between the potential accuracies of the new methods and the routine fitting approach. As a result it is shown that the new approaches would have comparable efficiency with the fitting approach. Thus the three (the fitting and the novel) approaches may be used for mutually validating the results obtained for the electron temperature. They may be used as well for distinguishing the real inhomogeneities in the recovered temperature profiles from apparent ones due to statistical fluctuations. The novel approaches may also have some practical advantages consisting of the simple, clear and stable measurement procedure without any hypotheses or other considerations about the weight or the variance of the experimental data or the goodness of the fit.