A possible alternative to the active debris removal (ADR) by laser is the ablative propulsion by a remotely transmitted electron beam (e-beam). The e-beam ablation has been widely used in industries, and it might provide higher overall energy efficiency of an ADR system and a higher momentum-coupling coefficient than the laser ablation. However, transmitting an e-beam efficiently through the ionosphere plasma over a long distance (10 m–100 km) and focusing it to enhance its intensity above the ablation threshold of debris materials are new technical challenges that require novel methods of external actions to support the beam transmission.
Therefore, Osaka Metropolitan University researchers conducted a preliminary study of the relevant challenges, divergence, and instabilities of an e-beam in an ionospheric atmosphere, and identified them quantitatively through numerical simulations. Particle-in-cell simulations were performed systematically to clarify the divergence and the instability of an e-beam in an ionospheric plasma. The major phenomena, divergence and instability, depended on the densities of the e-beam and the atmosphere. The e-beam density was set slightly different from the density of ionospheric plasma in the range from 10 10 to 10 12 m −3 . The e-beam velocity was changed from 10 6 to 10 8 m∕s, in a nonrelativistic range.
Results revealed that nonrelativistic e-beams of density from 10 10 to 10 12 m −3 emitted in ionospheric plasmas of density from 10 10 to 10 12 m −3 experience the laminar-to-turbulent transition. The turbulence should originate from the beam electron/ion two-stream instability because the transition length can be approximated by the theoretical formula of the two-stream instability. In the laminar region, the lateral expansion of the electron beam was suppressed in the plasma. The beam compression factor was quantified for the first time. These results indicate that for the use of e-beams for ADR applications, the laminar region with suppressed divergence can be beneficial for efficient focusing and ablation, but the turbulence due to plasma instabilities needs to be considered in ADR system design.
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Journal of Thermophysics and Heat Transfer
Particle-In-Cell Study of Electron Beam Propagation Through Ionospheric Plasma
4-Dec-2025