Diagnostic of tokamak fusion plasma via correlation analysis of soft X-ray signals

Measurements of internally generated soft X-radiation have long been used for fusion plasma diagnostics at the JET Joint Undertaking tokamak fusion device. Such measurements have been used to monitor a variety of magnetohydrodynamic (MHD) phenomena. The main tool of analysis is a tomographic inversion to convert the line integrated data into local values of X-ray emissivity, which is the main physical parameter of interest. Due to the high intensity of X-ray emission and the high sampling frequency applied as well as the large number of collimated detectors, these measurements make it also possible to determine plasma dynamics through noise analysis methods. This paper reports on preliminary investigations of how correlation and spectral analysis of soft X-ray data can be used to determine various aspects of plasma behaviour. The objective is to determine both periodic (global) MHD modes as well as local turbulence and transport properties. (authors)