Publications by authors named "Tokihiko Tokuzawa"

Article Synopsis
  • The Large Helical Device experiments revealed that heat pulses travel quickly and non-diffusively, with speed increasing as the pulse duration decreases.
  • There is a simultaneous movement of temperature gradients and turbulence, occurring over milliseconds, which fits the avalanche model's predictions.
  • These findings suggest that tighter, localized pulses lead to more instability in plasma, highlighting important considerations for maintaining steady-state conditions in future fusion reactors.
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A symmetry-breaking in rotational spatial pattern of quasi-periodic solitary oscillations is revealed with tomography measurement of plasma emission, simultaneously with background asymmetry in stationary plasma structure. Although the oscillatory pattern deformation is a natural course in the presence of asymmetry, elaborate analyses identify existence unfeatured nonlinear effects of the background asymmetry, i.e.

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Reflectometry has been expected to be one of the key diagnostics to measure density profiles. We have applied an ultrashort-pulse reflectometry (USPR) system to Large Helical Device in the National Institute for Fusion Science. Wide frequency band system is required to obtain wide density profile since an incident wave is reflected at the density layer corresponding to its cutoff frequency.

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An experimental technique to investigate fast ion confinement based on charge exchange spectroscopy of H(alpha)-light was applied to evaluate the confinement property of perpendicular fast ions in large helical device (LHD). Sensitivities of the H(alpha) spectra to the pitch angles of injected neutral beams (NBs) and these to the angle between the sight line of the measurement and NB injection path are examined. The energy dependence of the charge exchange cross section significantly affects the observed spectra since the driving NB is injected perpendicular to the magnetic field lines in the geometry of LHD.

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