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Intermittent helicity injection for field-reversed configurations control: shear-driven tilt suppression and ion heating.

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Title: Intermittent helicity injection for field-reversed configurations control: shear-driven tilt suppression and ion heating.
Authors: Ahmadi, T.1 (AUTHOR) tara@ts.t.u-tokyo.ac.jp, Ono, Y.1 (AUTHOR), Tanabe, H.1 (AUTHOR)
Source: Nuclear Fusion. 2026, Vol. 66 Issue 1, p1-8. 8p.
Subjects: Spheromaks, Plasma heating, Magnetohydrodynamics, Magnetic control, Magnetic reconnection, Magnetohydrodynamic instabilities
Abstract: The sustainment of field-reversed configurations through controlled magnetic merging is investigated using three-dimensional Hall magnetohydrodynamic simulations. Motivated by experimental demonstrations of tilt-stable field-reversed configuration (FRC) formation via counter-helicity merging, this study explores the impact of intermittent injection of spheromak and FRC-type plasmas into a pre-formed FRC core. Two merging strategies are considered: (i) the injection of compact spheromaks and (ii) the merging of externally generated FRCs. The results indicate that spheromak-FRC merging produces localized reconnection and strong bi-directional toroidal shear flows, which effectively suppress the n = 1 tilt mode and generate significant ion heating. In contrast, FRC–FRC merging yields weaker reconnection-driven flows and reduced thermalization, resulting in lower ion temperature increments and incomplete suppression of global MHD instabilities. A parametric study of the injection (compression) speed reveals a trade-off between energy deposition and stability, with optimal performance observed at intermediate velocities. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:The sustainment of field-reversed configurations through controlled magnetic merging is investigated using three-dimensional Hall magnetohydrodynamic simulations. Motivated by experimental demonstrations of tilt-stable field-reversed configuration (FRC) formation via counter-helicity merging, this study explores the impact of intermittent injection of spheromak and FRC-type plasmas into a pre-formed FRC core. Two merging strategies are considered: (i) the injection of compact spheromaks and (ii) the merging of externally generated FRCs. The results indicate that spheromak-FRC merging produces localized reconnection and strong bi-directional toroidal shear flows, which effectively suppress the n = 1 tilt mode and generate significant ion heating. In contrast, FRC–FRC merging yields weaker reconnection-driven flows and reduced thermalization, resulting in lower ion temperature increments and incomplete suppression of global MHD instabilities. A parametric study of the injection (compression) speed reveals a trade-off between energy deposition and stability, with optimal performance observed at intermediate velocities. [ABSTRACT FROM AUTHOR]
ISSN:00295515
DOI:10.1088/1741-4326/ae11c7