Yasuhiko TAKEIRI

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The driving and damping mechanism of plasma flow is an important issue because flow shear has a significant impact on turbulence in a plasma, which determines the transport in the magnetized plasma. Here we report clear evidence of the flow damping due to stochastization of the magnetic field. Abrupt damping of the toroidal flow associated with a transition(More)
In the Large Helical Device (LHD), a reversed magnetic shear (RS) configuration having non-monotonic rotational transform profile was formed by intense counter neutral beam (NB) current drive. In the RS configuration helical plasma, the reversed shear Alfvén eigenmode (RSAE) with n=1 toroidal mode number was identified together with energetic-ion-driven(More)
The electron density was measured at various bias voltages to understand how the plasma grid bias affects the electron near the plasma grid in large-scaled negative ion sources. It was found that the response of the electron to the bias voltage changes depending on negative ion production processes. The electron density remarkably decreases with increasing(More)
The central ion temperature in the large helical device (LHD), as measured by charge-exchange recombination spectroscopy, has been improved to a record 5.6 keV by combining 21 MW of neutral beam heating with the injection of a carbon pellet. The intensity of the neutral beam emission of the hydrogen Balmer line (Hα : n = 3 → 2) was observed to weaken along(More)
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