Inverse problem for non-thermal electron cyclotron emission during RF heating and current drive

It is shown that the inverse problem for the electron distribution function is exactly soluble, i.e., given a set of non-thermal radiation spectra it is possible to determine uniquely the structure of the distribution function whose emission generates them. The result makes it possible to avoid the use of phenomenological approaches, in which the fitting model artificially determines what is measured, (i.e., the adjustable parameters of the model), and allows to compare directly the experimental distribution function, with the predicted ones, obtained from theoretical models and Fokker-Planck calculations. (author) 4 refs., 8 figs