Magnetic confinement in a ring-cusp ion thruster discharge plasma

Abstract

An experimental investigation, in conjunction with a volume averaged analytical model, has been developed to improve the confinement and production of the discharge plasma for plasma thrusters and ion sources. The research conducted explores the discharge performance of a ring-cusp ion source based on the magnetic field configuration, geometry, and power level. Analytical formulations for electron and ion confinement are developed to predict the ionization efficiency for a given discharge chamber design. Explicit determination of discharge loss and volume averaged plasma parameters are obtained via a series of experimental measurements on a ring-cusp NASA Solar Technology Application Readiness (NSTAR) ion thruster to assess the validity of the analytical model. Measurements of the discharge loss with multiple magnetic field configurations compare well with plasma parameter predictions for propellant utilizations between 80% and 95%. The results indicate that increasing the magnetic strength of the first closed magnetic contour line reduces Maxwellian electron diffusion and electrostatically confines the ion population and subsequent loss to the anode wall. The results also indicate that increasing the strength and minimizing the area of the magnetic cusps improves primary electron confinement, increasing the probability of an ionization collision prior to loss at the cusp.

The Wisconsin Plasma Astrophysics Laboratory

“…Additionally, owing to the insulating boundary condition, in situ probes at the ceramic tile can directly measure the loss width. Understanding the loss width scalings in a magnetic cusp is important not only for predicting plasma confinement in WiPAL but also to a number of other applications such as plasma processing (Malik et al 1994), Hall-thrusters (Sengupta 2009), and neutral beam injectors (Stirling et al 1979).…”

Magnetic cusp confinement in low-β plasmas revisited

“…In practical applications, multicusp plasma sources are used in plasma processing or in ion sources, e.g. for satellite propulsion [7][8][9] or negative ion sources for accelerators 10 (including neutral beam injectors for fusion). In these sources the plasma can be generated by filaments or by radiofrequency or microwave coupling.…”

Effect of Orifice Diameter on the Performance of a Miniature Microwave Neutralizer

“…[1][2][3] Ion and Hall thrusters have emerged as two of the most used electric propulsion schemes. 2,[4][5][6] The operation of such propulsion systems require the use of an electron source, referred to as the "neutralizer." [7][8][9][10][11][12] The various limitations imposed upon the geometry, power, and material requirements of the neutralizers for space propulsion make their development challenging.…”