Journal: Aerospace Science and Technology, vol. 178, pp. 113168, 2026.
Title: Trade-offs between plump collimation and axial thrust in a cusped field thruster with modified exit magnetic topology
Authors: Yueh-Heng Li*, Tzu-Ting Lei, Ta-Yen Huang
Rank: 11.8% (7/59), SCIE, ENGINEERING: AEROSPACE, 2025.
Abstract: This study investigates how exit magnetic topology influences the discharge behavior, plume structure, and thrust performance of a cusped field thruster (CFT). A conventional three-layer magnetic configuration and a modified four-layer design were experimentally compared. The three-layer configuration provides effective electron confinement but forms an inclined exit separatrix, resulting in a double-peak plume with relatively large divergence. The four-layer configuration strengthens the cusp magnetic field near the outlet, producing a more vertically oriented separatrix and modifying downstream electron transport.
Three-dimensional COMSOL simulations agree well with magnetic-probe measurements. Plume characteristics were measured using a Faraday probe over an input power range of 160–220 W. The three-layer configuration produces a wide double-peak plume with a pronounced centerline ion-current deficit, whereas the four-layer design improves central plume filling and shifts the plume peaks inward. However, increased ion flux at large angles indicates redistribution of ion momentum rather than a uniform reduction in plume divergence.
The four-layer configuration produces a higher total ion beam current, increasing from 0.742 to 0.945 A between 160 and 220 W. Nevertheless, its measured axial thrust remains lower than that of the three-layer configuration because more ion momentum is directed off-axis. Scaling analysis shows a steeper increase in axial thrust with input power, suggesting improved performance at higher power levels. Overall, the results demonstrate that exit magnetic topology can effectively tailor plume structure and ion acceleration, highlighting important trade-offs among ion production, plume collimation, and axial momentum conversion.
