Near-Field Ion Energy and Species Measurements of a 5-kW Hall Thruster

A molecular beam mass spectrometer has been used to determine the ion composition and energy distribution of the P5 5-kW class laboratory Hall thruster. A skimmer was used to obtain a sample of the plasma 10 cm downstream of the thruster exit plane. The thruster was operated at several discharge conditions and rotated with respect to the sampling skimmer in order to determine ion-energy profiles at various plume angles. These measurements were compared to data taken 75 cm from the discharge plane to examine the evolution of the ion energy profile and facility effects. Both ion-energy measurements and time-of-flight mass spectroscopy revealed evidence of singly, doubly, triply, and quadruply charged xenon ions within the plume. Ion-energy distributions were used to determine that the P5's magnetic field is oriented such that the plume has an overall inward focus. The ion-energy distributions taken 10 cm from the thruster had smaller full width at half maxima and less evidence of elastic collisions than those taken at 75 cm. Comparisons made with laser-induced fluorescence data showed good agreement. (Author)