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Recent large helical device experiments revealed that the transition from ion root to electron root occurred for the first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of the radial electric field were found to be in qualitative agreement with those estimated by neoclassical theory. A clear reduction of ion thermal diffusivity was observed after the mode transition from ion root to electron root as predicted by neoclassical theory when the neoclassical ion loss is more dominant than the anomalous ion loss.

When Ohmically heated low-density plasmas are additionally heated by higher-harmonics ion-cyclotron-range-of frequency heating, heated by neutral beam injection, or strongly gas puffed, the intensity of zonal flows in the geodesic acoustic mode frequency range in the tokamak core plasma decreases sharply and that of low-frequency zonal flow grows drastically. This is accompanied by a damping of the drift wave propagating in the electron diamagnetic drift direction, turbulence by trapped electron mode (TEM), and the increase of the mode propagating to ion diamagnetic drift direction (ITG). In the half-radius region, TEM and high-frequency zonal flows remain intense in both OH and heated phases. ITG and low-frequency zonal flows grow in heated plasmas, suggesting a strong coupling between ITG and low-frequency zonal flow.

It is shown that the low-density Ohmically heated tokamak plasmas have streamerlike eddies at the outer region at normalized minor radius of about 0.7 and high-frequency zonal flows of large amplitudes in the core. The amplitudes of the eddies e{phi}-tilde/kT{sub e} and n-tilde{sub e}/n{sub e} are of order of 0.5, similar to that of blobs in the tokamak plasma boundary. The waveforms are featured by pulses of complex shape with sharp fronts, similar to the results of streamer simulations by Garbet et al.. The time constant of the fronts is also in agreement with the simulation. The radial span of the eddies is estimated to be much larger than the poloidal span.

The helicity-induced Alfv\'en eigenmodes (HAEs) with the toroidal mode number $n=2$ and 3 are observed for the first time in the Large Helical Device plasmas heated by neutral beam injection. The observed mode frequency is about 8 times higher than that of the observed toroidicity-induced Alfv\'en eigenmodes, and is proportional to the Alfv\'en velocity. The modes are excited when the ratio of the beam velocity to the Alfv\'en velocity exceeds about unity. The frequency lies just above the lower bound of the HAE gap in the plasma edge region of $\ensuremath{\rho}g0.7$ ($\ensuremath{\rho}$: normalized minor radius).

Sawtooth oscillations have been observed in current-carrying helical plasmas by using electron-cyclotron-emission diagnostics in the Large Helical Device. The plasma current, which is driven by neutral beam injection, reduces the beta threshold of the sawtooth oscillation. When the central q value is increased due to the plasma current, the core region crashes, and, when it is decreased, the edge region crashes annularly. Observed rapid mixture of the plasma in the limited region suggests that these sawtooth crashes are reconnection phenomena. Unlike previous experiments, no precursor oscillation has been observed.

It was observed that the vacuum magnetic island produced by an external error magnetic field in the large helical device shrank in the presence of plasma. This was evidenced by the disappearance of flat regions in the electron temperature profile obtained by Thomson scattering. This island behavior depended on the magnetic configuration in which the plasmas were produced.

Ion-cyclotron heating was applied to the Large Helical Device. When the proton-cyclotron resonance was near the saddle point of the magnetic field-strength plane, strong ion-cyclotron damping occurred. Under these conditions efficient plasma heating was achieved for more than one minute. A high-energy ion tail was observed, and the effective tail temperature was determined by a balance between the wave acceleration and the electron-drag relaxation. There was no apparent sign of particle orbit loss effect in the investigated density range of 0.8-1.3x10(19) m(-3).

In a circular cross-section plasma bounded by a limiter, the {ital H}-mode transition is triggered by a rapid rampdown in plasma current during auxiliary heating, even in the case when the edge electron temperature gradually decreases prior to the transition. This result suggests that the transition is governed by the enhancement of the magnetic shear near the plasma edge, associated with the radial modification of the edge current-density profile.

We present the results of gravitational radiation experiments with two 1400-kg antennas at ${\ensuremath{\nu}}_{0}=145$ Hz. The square antennas, 1.65\ifmmode\times\else\texttimes\fi{}1.65\ifmmode\times\else\texttimes\fi{}0.19 ${\mathrm{m}}^{3}$, ${Q}_{M}\ensuremath{\simeq}2.0\ifmmode\times\else\texttimes\fi{}{10}^{5}$, with electrostatic transducers of $\ensuremath{\beta}\ensuremath{\simeq}1.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, have mean effective noise energy $\overline{D}\ensuremath{\simeq}0.034k{T}_{r}$. The observed cross correlation of the outputs of the two detectors gives an upper limit for the relation between the mean energy spectrum density $F({\ensuremath{\nu}}_{0})$ and the daily occurrence rate ${\stackrel{\ifmmode \dot{}\else \.{}\fi{}}{N}}_{G}$ of gravitational radiation pulses: $F({\ensuremath{\nu}}_{0}){{\stackrel{\ifmmode \dot{}\else \.{}\fi{}}{N}}_{G}}^{\frac{1}{2}}l~({3.6}_{\ensuremath{-}1.4}^{+1.0})\ifmmode\times\else\texttimes\fi{}{10}^{6}$ J ${\mathrm{m}}^{\ensuremath{-}2}$ ${\mathrm{Hz}}^{\ensuremath{-}1}$ ${\mathrm{day}}^{\ensuremath{-}\mathrm{\textonehalf{}}}$.