Hall-effect thrusters work by ionizing atoms of a gas like Xenon, accelerating them to high speeds and expelling them to generate a gentle steady thrust.
Electrons emitted by the cathode circulate around an annular ceramic channel guided by a magnetic field. Xenon atoms, injected along the anode, get ionized by the high energy electrons.The ionized Xenon plasma is accelerated axially by an electric field, to exit velocities of up to 100,000 km/h to produce thrust.
https://psyche.asu.edu/2018/01/19/electric-thrusters-psyche-spacecraft-work/
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Psyche MissionPsyche Mission | A Mission to a Metal WorldThe Psyche mission will explore, for the first time ever, an asteroid made not of rock or ice, but of metal. The mission will investigate planet formation.