Experimental identification of the energy flux lost to the wall of a cusp-type magnetic nozzle radiofrequency plasma thruster

Abstract Performance of electric propulsion devices utilizing ionized gases, i.e., plasmas, is strongly affected by particle and energy losses to physical boundaries. In the present study, the spatial profiles of the energy flux lost to the wall in a cusp-type magnetic nozzle radiofrequency plasma thruster are experimentally investigated. The results show the inhibition of the energy flux lost to the radial wall surface upstream of the cusp due to the geometrical isolation of the plasma from the wall, while the energy flux lost near the cusp increases. Although the total energy lost to the walls remains nearly unchanged in the presence of the cusp magnetic field, the thrust increases. The experimental measurements are qualitatively explained by a global source model taking a change in the discharge area along the magnetic field lines into account. The results suggest that the reduction in discharge volume under a nearly constant loss power yields an increase in plasma density, contributing to the thrust enhancement.