Dual-anode in-situ repair method for mitigating conductive-film degradation in micro-cathode arc thrusters

Micro-cathode arc thruster (μCAT) is an electric propulsion device suitable for miniature spacecraft and has attracted extensive attention due to its low power requirements, simple, and compact structure. The conductive film is a critical component of the thruster's pulsed discharge circuit. However, during long-term operation, it is difficult to maintain a balance between ablation and deposition. Excessively thin or thick films often lead to open or short circuits, which significantly limits the thruster's operational lifespan. In discharge energy spectrum experiments with a ring-structured thruster, it was observed that plasma generated by the discharge deposits along the thruster's axial direction. This indicates that plasma from ring-shaped discharges can repair the coaxial conductive film perpendicular to the axis. Based on this, a dual-anode structure is proposed, which alternates between two discharge modes to achieve in-situ repair of the conductive film, thereby substantially extending the thruster's operational lifespan. This study experimentally investigated the effectiveness of dual-anode in situ repair. Initially, plasma deposition along the axial direction generated by the ring-structure discharge was analyzed through energy-dispersive spectroscopy (EDS), confirming the feasibility of utilizing ring discharge to repair the coaxial conductive film. Subsequently, full lifespan tests were compared between the conventional single-anode structure and the novel dual-anode structure. The evolution of discharge parameters was plotted in real-time using current and voltage probes. Simultaneously, a four-probe was employed to accurately measure conductive film resistance, resistivity, and thickness. High-resolution observations of film surface morphological changes were conducted using scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM). The experimental results demonstrate that the lifespan of the dual-anode thruster was significantly extended to 432,000 pulses (including 270,000 discharges from the coaxial structure) from the 120,000 pulses achieved by the single-anode mode, representing a 260% improvement in overall longevity. Furthermore, the film parameters in the dual-anode mode exhibited a slow, serrated decline, in contrast to the monotonic degradation observed in the single-anode mode, providing direct evidence of the restorative effect of the ring discharge. Through successive experimental data, this research comprehensively elucidates the effectiveness of the dual-anode in-situ repair mechanism, offering a new solution for extending the lifetime of μCAT thrusters.