Thermo-mechanical analysis and optimization of a water-cooled racetrack-type Faraday shield for a large-area RF ion source

The Faraday shield (FS) is a critical component of radio-frequency (RF) ion sources, serving to protect the dielectric chamber from plasma bombardment and suppress capacitive coupling between the RF coil and plasma. With the increasing demand for high-power and long-pulse operation in neutral beam injection (NBI) systems, the thermal and structural reliability of the FS has become a key design concern. In this work, a water-cooled racetrack FS for a large-area RF ion source was designed and investigated. A coupled fluid–thermal–structural finite-element model was established to evaluate its thermal and mechanical performance under various operating conditions. Three sidewall thicknesses (4.2 mm, 4.5 mm, and 4.8 mm) were analyzed under cooling-water inlet pressures ranging from 0.4 MPa to 1.5 MPa. Temperature distribution, equivalent stress, and structural deformation were obtained through steady-state simulations. After determining the optimal wall thickness, a more realistic stepped distribution of heat load was applied, and transient simulations were performed under long-pulse operation. Numerical predictions were subsequently validated through experiments.The results indicate that the maximum temperatures of the three configurations are approximately 36 °C under uniformly distributed heat loading. Increasing the wall thickness reduces structural deformation while slightly increasing equivalent stress. Considering thermal performance, structural reliability, and manufacturability, a wall thickness of 4.5 mm was selected as the optimal design. Under the stepped distribution of heat load condition corresponding to 100 kW RF, the maximum temperature, equivalent stress, and deformation reach 45.89 °C, 86.6 MPa, and 0.235 mm, respectively, all remaining well below the allowable limits of TU1 oxygen-free copper. Good agreement is achieved between transient simulation and experimental measurements. The proposed FS demonstrates excellent cooling capability and structural reliability, providing a useful reference for the design and optimization of RF ion source components in NBI systems.