Feasibility study of direct spectra measurements for Thomson scattered signals for KSTAR fusion-grade plasmas

Abstract

Feasibility study of direct spectra measurements of Thomson scattered photons for fusion-grade plasmas is performed based on a forward model of the KSTAR Thomson scattering system. Expected spectra in the forward model are calculated based on Selden function including the relativistic polarization correction. Noise in the signal is modeled with photon noise and Gaussian electrical noise. Electron temperature and density are inferred using Bayesian probability theory. Based on bias error, full width at half maximum and entropy of posterior distributions, spectral measurements are found to be feasible. Comparisons between spectrometer-based and polychromator-based Thomson scattering systems are performed with varying quantum efficiency and electrical noise levels. K: Analysis and statistical methods; Data processing methods; Plasma diagnosticscharged-particle spectroscopy; Spectrometers 1Corresponding author.

Bayesian modelling of Thomson scattering and multichannel interferometer diagnostics using Gaussian processes

“…The FIR interferometer diagnostic system provides line integrated electron densities, i.e., no spatial resolution, without such calibration factors [23,24,25,26]. Bayesian analysis for Thomson scattering [9,27,28], interferometer [5,29] systems and joint , the parameters we wish to determine, and observations are shown as red and blue circles, respectively. Note that the observations can be taken from previous inference, e.g., an observed Thomson scattered amplitude D TS is taken from the inference results described in Section 3.1.…”

“…no spatial resolution, without such calibration factors [23][24][25][26]. Bayesian analysis for Thomson scattering [9,27,28], interferometer [5,29] systems and joint analysis [30] have been previously reported. They made impressive progress, especially evaluating uncertainties of electron temperature and density.…”