LHD captures plasma-burst ion heating: local energy rises 30% within 0.1 milliseconds
Using Japan's Large Helical Device, researchers directly observed changes in ion velocity during MHD bursts. Local ion kinetic energy along the magnetic field increased by around 30% in under 0.1 milliseconds.
Read the Japanese originalAnnouncement date：2026-11-10
Researchers working with Japan's Large Helical Device (LHD) have captured the instant when a sudden plasma disturbance transfers energy to ions. A study published in Communications Physics on 10 November reports that local ion kinetic energy along the magnetic field rose by around 30% within 0.1 milliseconds of an MHD burst. A phenomenon usually associated with instability also reveals how energy moves through a magnetically confined plasma.
A change faster than ion collisions
The team used fast charge-exchange spectroscopy at 10 kHz to measure how ion velocities are distributed along the magnetic field. The distribution changed much faster than the approximately 2–3 milliseconds needed for ion-ion collisions. Flattening at particular velocities provided evidence of wave-to-particle energy transfer through Landau damping and transit-time damping.
How an edge disturbance reaches the core
These MHD bursts occurred mainly near the plasma edge. Yet changes in ion energy extended inward and contributed to higher core-ion energy. The paper combines magnetic reconnection at the onset of a burst, subsequent wave-particle interactions and phase-space transport to explain the observations. A 2022 study had identified collisionless energy transfer from waves to ions; the new measurements resolve more of its rapid evolution and spatial reach.
For fusion reactor design, suppressing disturbances alone will not be enough. Researchers must also understand how those events redistribute particles and heat. The roughly 30% increase is local and specific to LHD experimental conditions, not an increase in the plasma's total energy or proof of a future power plant operating method.
- Ida et al., Communications Physics（2026年11月10日）
- Ida et al., Communications Physics（2022年9月28日）
- NIFS：LHD研究基盤
Information checked as of：2026-11-13
Research paper published 10 November 2026. The 30% rise concerns local ion kinetic energy parallel to the magnetic field during an LHD experiment, not total plasma energy.