Data analysis tools and coding activity in support of the FTU Collective Thomson Scattering diagnostic

The recent implementation of data processing tools and the code activity, aimed at the interpretation of spectra measured in the tokamak FTU with the renewed Collective Thomson Scattering (CTS) system, are presented in this paper. Such instrumental renovation allowed investigating anomalous emissions originating from parametric decay instability (PDI) of an electron cyclotron (EC) pump wave in presence of magnetohydrodynamics (MHD) rotating islands, as foreseen by recent theoretical models. Aim of these experiments is to study the possible effects of these anomalous phenomena on the EC power absorption and on the CTS used as standard thermal diagnostic. The codes here presented have been implemented for the calibration of the CTS spectra and for the proper visualization of signals, for direct comparison with the MHD spectrograms and with the plasma parameters. The software also allows analysing data acquired simultaneously with two radiometric systems as is possible in FTU since the beginning of 2016. The calibration of the spectra is necessary for comparing the actual power of the signals, that can span orders of magnitude, from the lowest compatible with thermal (CTS) radiation and providing information on the ions dynamic, to the strong anomalous emission theoretically expected from PDIs. The Thermal Collective Scattering (TCS) code, able either to predict or to interpret thermal ion spectra, has been optimized and integrated in the overall data analysis tools. The analysis of the data and the interpretation of the scenarios achieved in the experiments are presently underway using the tools here presented. © 2018 Istituto di Fisica del Plasma - CNR. Published by IOP Publishing Ltd on behalf of Sissa Medialab.