This study addresses critical challenges for the Thomson Scattering (TS) diagnostics in the high radiation environment of the EAST tokamak by focusing on optical performance enhancement and radiation-induced degradation mitigation. First, we developed and characterized a novel reverse-telephoto, off-axis optical collection assembly that incorporates an aspheric surface and a deliberate lens tilt. This design successfully expands the usable field of view and maintains high imaging quality while satisfying the stringent mechanical constraints of the diagnostic port. Secondly, analysis of lens elements recovered after two years of operation revealed severe Radiation-Induced Absorption (RIA), predominantly in the 400–600 nm range, with overall transmission at 532 nm decreasing by 55. 43%. Spectroscopic investigations, including Raman scattering and Electron Paramagnetic Resonance (EPR), identified structural modifications and the formation of point defects, specifically the F + center (indicative of displacement damage) and the E^’ center (indicative of ionization damage), with defect concentration correlating to the lens’s position and thickness. Finally, we validated the efficacy of a lead-boron polyethylene (Pb-BPE) shielding strategy through FLUKA Monte Carlo simulations and a 30-day experimental irradiation test. Simulations predicted an up to 80% reduction in neutron fluence, which was experimentally confirmed by the substantially higher post-irradiation transmittance observed in shielded samples, especially for the radiation sensitive ZF6 glass. This research provides a robust solution combining advanced optical engineering and targeted radiation shielding to ensure the long-term reliability and enhanced spatial coverage of TS diagnostics in next-generation fusion devices. Experimental data confirm that the transmittance (specific value) of shielded samples after irradiation is significantly higher, especially for radiation-sensitive ZF6 glass, the improvement is particularly obvious.
Zhou et al. (Sun,) studied this question.