Miniature ion thruster ring-cusp discharge performance and behavior

Abstract

Miniature ion thrusters are an attractive option for a wide range of space missions due to their low power levels and high specific impulse. Thrusters using ring-cusp plasma discharges promise the highest performance, but are still limited by the challenges of efficiently maintaining a plasma discharge at such small scales (typically 1-3 cm diameter). This effort significantly advances the understanding of miniature-scale plasma discharges by comparing the performance and xenon plasma confinement behavior for 3-ring, 4-ring, and 5-ring cusp by using the 3 cm Miniature Xenon Ion thruster as a modifiable platform. By measuring and comparing the plasma and electron energy distribution maps throughout the discharge, we find that miniature ring-cusp plasma behavior is dominated by the high magnetic fields from the cusps; this can lead to high loss rates of high-energy primary electrons to the anode walls. However, the primary electron confinement was shown to considerably improve by imposing an axial magnetic field or by using cathode terminating cusps, which led to increases in the discharge efficiency of up to 50%. Even though these design modifications still present some challenges, they show promise to bypassing what were previously seen as inherent limitations to ring-cusp discharge efficiency at miniature scales. Published by AIP Publishing. https://doi

Numerical investigation of plasma behavior in a micro DC ion thruster using the particle-in-cell/Monte Carlo collision (PIC/MCC) method

“…In this work, we did not consider the design of ion optical system in order to keep the consistency of the operational conditions adopted in the simulation and experiment. For the latter, instead of using the real ion optical system, Wirz group used a metal plate with a cross slit in their experiments [18]. This treatment is reasonable to obtain the fundamental plasma characteristics in the ionization chamber.…”

“…The tungsten cathode heater supply generates linearly scaled voltage from 0 to 6 V across the filament during the operation. The screen grid bias to 5 V below the cathode potential [18].…”

“…Spatially resolved measurements with a Langmuir probe were performed showing that plasma structure is independent of the discharge power and weaker magnet fields can improve overall performance of ion thruster operation. Dankongkakul and Wirz [18] measured the plasma structure inside the micro ion thruster with multiple magnet configurations, which provides critical insights into the discharge plasma behavior and obtains the energy distribution function of the electrons. These experimental results recognize the critical role played by the magnet field and provide experimental data support for the follow-up numerical simulation research.…”

Microplasma thruster powered by X-band microwaves

“…A variety of micropropulsion systems or microthrusters have been proposed and developed, including micro electric propulsion systems or micro plasma/ion thrusters; 4-13 they can be electrostatic, electromagnetic, and electrothermal as with conventional-scale electric thrusters, 14 each with its own advantages and disadvantages depending on the application and mission. The electrostatic thrusters rely on the ion acceleration by electrostatic fields to achieve the thrust: micro ion thrusters (employing various dc, rf, and microwave plasma/ ion sources), [15][16][17][18][19] Hall thrusters (in which the electrostatic fields are produced largely by the actions of plasma electrons interacting with magnetic fields), 20,21 field emission electron propulsion thrusters, 22,23 colloid thrusters, 24,25 and electrodeless thrusters making use of magnetic nozzles; [26][27][28][29][30] these thrusters require not only grids/electrodes but also a separate system of neutralizers, except that the last ones in which the ambipolar electric fields formed lead to equal currents of ions and electrons leaving the thruster. The electromagnetic thrusters rely on the plasma acceleration via interaction of the current and magnetic fields: micro pulsed plasma thrusters.…”

Investigation of very low Earth orbits (VLEOs) for global spaceborne lidar

“…2. MiXI-ARCH [29][30][31] -The Miniature Xenon Ion (MiXI) thruster with Axial Ring Cusp Hybrid (ARCH) discharge is an experimental thruster offering high specific impulse and moderate thrust in a compact, low mass package. While this system has no flight heritage, laboratory experiments show great promise in terms of thrust and specific impulse relative to power demand and size.…”