Abstract
Helicon plasma sources play a central role in applications ranging from material treatment to space propulsion and fusion, yet the physical processes governing their ignition and transient ionization remain incompletely understood. Here we develop a self-consistent, fully coupled multiphysics framework implemented in COMSOL Multiphysics, that integrates Maxwell’s equations, electron energy transport, drift–diffusion kinetics, and heavy-species chemistry to capture the complete spatiotemporal evolution of helicon discharges. The model reproduces experimental measurements across pressure, magnetic field, and frequency ranges, and reveals a previously unresolved transient ionization stage characterized by a rapid density rise within ~ 10− 4 s, accompanied by a two-peak electron temperature structure that governs the formation of the dense plasma core. By tracking the RF power flow and field topology, we characterize the transient redistribution of RF energy during ignition. A short-lived phase of localized energy deposition accompanies the onset of ionization, followed by a gradual restructuring of the RF field distribution as the plasma density increases, together with rapid density growth and profile restructuring. Systematic parametric scans further reveal the sensitivity of this mode-coupling process to gas pressure, magnetic field strength, and driving frequency. These results provide a unified picture of the ignition in helicon plasmas and establish a predictive tool for the design and optimization of RF plasma sources across space propulsion, manufacturing, and fusion technologies.
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The datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request.
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Acknowledgements
Discussions with Rod Boswell are appreciated. This work is supported by the National Natural Science Foundation of China (Nos. 92271113, 12411540222, 12481540165), the Fundamental Research Funds for Central Universities (No. 2022CDJQY-003), the Chongqing Entrepreneurship and Innovation Support Program for Overseas Returnees (No. CX2022004), the Natural Science Foundation Project of Chongqing (No. CSTB2025NSCQ-GPX0725), and the ENN’s Hydrogen-Boron Fusion Research Fund (No. 2025ENNHB01-011).
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J.-J.M. conceived the study with L.C. and designed the methodology. J.-J.M. performed the multiphysics modelling and simulations, conducted the data analysis, and prepared all figures and visualizations. M.-Y.W. provided assistance with numerical verification and discussion. H.Z. and Y.-W.Z. contributed to discussions and supported validation of the results. I.Z. and E.K. contributed to physical interpretation and discussion of wave–plasma coupling. S.I. and S.-J.Y. provided technical advice and project coordination. L.C. supervised the project and acquired funding. J.-J.M. drafted the manuscript, and all authors reviewed and approved the final version.
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Ma, JJ., Chang, L., Wu, MY. et al. Revealing the transient ionization dynamics and mode-coupling mechanisms of helicon discharge through a self-consistent multiphysics model. Sci Rep (2026). https://doi.org/10.1038/s41598-026-47901-z
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DOI: https://doi.org/10.1038/s41598-026-47901-z
