Expected Performance of the JT-60SA Edge Thomson Scattering Diagnostic in OP2

Abstract

The edge Thomson scattering (ETS) diagnostic system for JT-60SA is designed to provide precise measurements of electron temperature (T_e) and density (n_e) profiles in the external region of the plasma, especially at the pedestal, extending also in the outer edge, which are critical for understanding confinement and stability in fusion plasmas. The system is optimized to achieve a spatial resolution of 5 mm in steep gradient regions and measure T_e and n_e with precisions better than 10% and 5%, respectively, for T_e ranging from 10 eV to 10 keV and n_e of $10^{19}$ m⁻³. As ETS will be installed before JT-60SA will enter its operational phase 2 (OP2), predicting the ETS system’s performance under realistic plasma conditions is crucial for optimizing its diagnostic capabilities. This work presents a synthetic diagnostic developed to evaluate and predict the performance of the ETS system during OP2. The approach models the entire system, including optical and detection elements, while accounting for plasma light background and noise. Key performance metrics, such as signal-to-noise ratio and measurement errors in Te and ne, are analyzed through these simulations. The results provide a detailed understanding of the expected performance of the ETS system under various operational scenarios. The insights gained support the system’s readiness for OP2. Additionally, they offer valuable feedback for commissioning, calibration, and efficient exploitation of the ETS diagnostic.