Upgrade of the high-field side divertor Langmuir probe diagnostic system in J-TEXT tokamak

Langmuir probes on divertor target plates play a crucial role in investigating boundary plasma parameters and phenomena, such as divertor detachment. Former experimental results on the J-TEXT tokamak indicate that, due to the steep heat flux gradient in the near scrape-off layer region, the previously sparse Langmuir probes on the high-field-side (HFS) divertor target plate failed to accurately capture poloidal variations. A newly designed Langmuir probe diagnostic system with high poloidal resolution has been constructed on the HFS divertor target plate, comprising 96 probe tips, achieving a poloidal resolution of 4 mm. The novel integrated probe module is compact and easy to mount, making it well suited to the confined installation envelope within the divertor target. It simultaneously delivers high poloidal resolution and operational reliability, while effectively reducing the uncertainty introduced by installation tolerances. Preliminary experimental findings indicate that, benefiting from the enhanced poloidal spatial resolution, the new system can measure the spatial distributions of boundary physical parameters, including strike point positions and heat flux decay length ( \lambda _q ) on the target plate.