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Description
A dual diagnostic system that combines traditional Thomson scattering (TS) system with Television Thomson Scattering (TVTS) system based on laser beam combining technique is developed and experimentally demonstrated on EAST. The vertical dual TS system constructed in this study primarily consists of five components: the laser light source system, optical transmission system, optical collection system, spectrometer and detection system, and synchronous trigger timing control system. The system schematic is shown in Figure 1. In tokamak plasma, Thomson scattering electron temperature measurements are affected when the electron velocity distribution function deviates from the Maxwellian distribution. To investigate and evaluate this phenomenon, a dual Thomson scattering diagnostic system is required to overcome the limitations of a single system. The TVTS system in the dual system primarily covers a 32 mm region along the Z-axis with a spatial resolution of approximately 10 mm.
The study analyzed the theoretical basis for collaborative measurements in dual TS system and conducted subsystem optimization designs to meet the requirements for synchronous operation of dual systems. Based on the design of the two systems, the dual system can perform a comparative analysis of the Thomson scattering signals across Te from 50 to 4000 eV and ne from 0.1 to 1×1019m-3. Experiments on EAST H-mode discharges demonstrate the feasibility of the laser beam combining technique and the reliability of the dual diagnostic system. Subsequent simulation analysis and collaborative diagnostic methods for the dual systems are further discussed, offering new insights into electron temperature measurement in non-Maxwellian plasma. This work is significant for optimizing EAST plasma confinement performance, investigating core transport barriers, and advancing research on plasma dynamics.