The estimate of coefficients of the convection–diffusion equation (CDE) from experimental measurements belongs to the category of inverse problems, which are known to come with issues of ill-conditioning or singularity. Here we concentrate on a particular class that can be reduced to a linear algebraic problem, with explicit solution. Ill-conditioning of the problem corresponds to the vanishing of one eigenvalue of the matrix to be inverted. The comparison with algorithms based on matching experimental data against numerical integration of the CDE sheds light on the accuracy of the parameter estimation procedures, and suggests a path for a more precise assessment of the profiles and of the related uncertainty. Several instances of the implementation of the algorithm to real data are presented.
JET-EFDA collaborators (2012). Estimate of convection-diffusion coefficients from modulated perturbative experiments as an inverse problem. Plasma Physics and Controlled Fusion, 54(12), . https://doi.org/10.1088/0741-3335/54/12/124025