Analytical Ion Thruster Discharge Performance Model

Abstract

A particle and energy balance model of the plasma discharge in magnetic ring-cusp ion thrusters has been developed. The model follows the original work of Brophy in the development of global 0-D discharge models that utilize conservation of particles into and out of the thruster and conservation of energy into the discharge and out of the plasma in the form of charged particles to the walls and beam and plasma radiation. The present model is significantly expanded over Brophy's original work by including self-consistent calculations of the internal neutral pressure, electron temperature, primary electron density, electrostatic ion confinement (due to the ring-cusp fields), plasma potential, discharge stability, and time dependent behavior during recycling. The model only requires information on the thruster geometry, ion optics performance and electrical inputs such as discharge voltage and currents, etc. to produce accurate performance curves of discharge loss versus mass utilization efficiency. The model has been benchmarked against the NEXIS Laboratory Model (LM) and Development Model (DM) thrusters, and successfully predicts the thruster discharge loss as a function of mass utilization efficiency for a variety of thrusters. The discharge performance model will be presented and results showing ion thruster performance and stability given.

Miniature ion thruster ring-cusp discharge performance and behavior

“…Placed in alternating polarity, these magnets provide strong cusp boundaries near the walls to confine the plasma while the bulk plasma remains effectively unmagnetized and thus, well suited for uniform plasma generation and beam flatness. Since the cusp magnetic fields can be approximated as boundary-only effects, most design efforts of conventional scale ring-cusp ion thrusters have relied on analytical models 6,7 and semi-empirical treatment of cusp confinement physics. 8,9 For example, plasma losses to the cusp are estimated using the semi-empirical hybrid leak width and concepts such as the highest closed magnetic field contour are used as a design figure-of-merit and for discharge models.…”

“…8,9 For example, plasma losses to the cusp are estimated using the semi-empirical hybrid leak width and concepts such as the highest closed magnetic field contour are used as a design figure-of-merit and for discharge models. 7,10 This approach has worked well for larger ion thrusters, however, these design principles become difficult to implement at the miniature scale as the cusp fields are no longer localized to the discharge boundary. In fact, the ring cusps produce complex and strong B-field structures that dominate most of the chamber volume.…”

Investigation on Operating Parameters of the Homemade Penning-Type Ion Source for Cyclotron

“…A result of simulation study using Fluent 6 showed that gas flow rate linearly affects gas pressure in the anode cavity [10], and gas pressure linearly affects the intensity of the Measurement data Calculation data using the least square fit method by I ~ const. V 3/2 ionization [11]. The linear relation was not observed in the experiment.…”

Magnetic confinement in a ring-cusp ion thruster discharge plasma

“…19,5,20 Existing volume averaged approaches provide a qualitative assessment of discharge plasma production and confinement. 21,22 Existing two and 3D approaches are also promising. Stueber 23 and Wirz and Goebel 24 indicated qualitative agreement with the NASA Solar Technology Application Readiness ͑NSTAR͒ and NASA's Evolutionary Xenon Thruster ͑NEXT͒ engines.…”