Electrode Geometry Effects on Plume Characteristics and Thruster Performance of ZaP-HD

Abstract

The addition of sheared-flow stabilization (SFS) to a Z-pinch configuration has allowed increased stability and plasma lifetime. This shows great promise for use as a compact, linear,fusion device and as a future deep space propulsion engine. Previous theses have examined the feasibility of this endeavor with promising results. For such a device, an understanding of how the physical geometry can change thruster and pinch performance would be required. To begin this investigation, the end wall electrode geometry was altered on the University of Washington’s Z-Pinch High Density (ZaP-HD) experiment. Thruster parameters were determined through plume characterization utilizing simultaneous measurements of electron temperature and density by way of a triple Langmuir probe. This method allowed for performance parameters to be resolved in time and space through a multitude of shots. The Langmuir probe revealed a radially uniform temperature plume with peak electron temperatures of 60 eV and number densities on the order of 1020 m−3 . These measurements were supplemented by ion Doppler spectroscopy to determine flow speeds of up to 103 km/s with an open configuration and 27 km/s on the more restrictive electrode geometry. Thruster performance metrics of thrust and specific impulse are extrapolated from these measurements: 123 mN with 16,000 s Isp, 824 µN with 7,000 s Isp, and 252 µN with 6,500 s Isp for the respective configurations of no, spoked and original end wall.