Effects of a magnetic discontinuity in a modified Advanced Cusp Field Thruster

Abstract Deviations from the ideal magnetic configuration in a modified Advanced Cusp Field Thruster (ACFT) without cylindrical symmetry are examined to understand their effect on electron behavior and thruster performance. Spatially resolved measurements of the magnetic field (B-field) and temperature at the central magnetic cusp during operation are compared with full-sized 3D particle-tracing simulations of electrons. The simulations reveal that, in addition to the well-known $$E \times B$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>E</mml:mi> <mml:mo>×</mml:mo> <mml:mi>B</mml:mi> </mml:mrow> </mml:math> drift, electrons also undergo circumferential motion due to magnetic field gradients and curvature, effects not previously associated with Cusp Field Thrusters (CFTs). Even small imperfections in the magnet configuration are found to measurably affect both the B-field and local heating at the thruster’s pole shoes. These results demonstrate that local deviations from ideal magnetic symmetry reduce electron confinement, increase wall losses, and ultimately affect thruster efficiency.