We report the results of an experimental and theoretical project dedicated to the study of Quasi Single Helicity Reversed Field Pinch plasmas. The project has involved several RFP devices and numerical codes. It appears that QSH spectra are a feature common to all the experiments.

A compact 1.5 microm all-fiber pulsed coherent Doppler lidar system for wind sensing, which includes the functions of variable pulse width and automatic polarization control has been developed. The system configuration is introduced and key components used in the system are explained. Theoretical performances of the system in wind sensing are estimated and compared with experimental results. The measurable range corresponding to the detection probability of >80% is approximately 1 km or more in the case of 150 m range resolution under the normal atmospheric conditions.

Discharges with improved plasma confinement in a high pinch parameter region (0 -2) have been discovered in the TPE-1RM2O reversed field pinch experiment. These discharges become possible with careful control of the waveforms of the plasma current and the toroidal magnetic field after intensive discharge cleaning and are called the 'Improved High Theta Mode' (IHTM). In these discharges the increase of electron density is distinct when compared with low 0 cases (-1.55). The electron temperature increases slightly with 0 but the ion temperature remains almost constant. Consequently, the poloidal beta increases, from 8% at 0 N 1.55 to 18% at 0 N 2.0, and the energy confinement time increases from 0.2 to 0.4 ms. The fluctuation level of the magnetic field corresponding to the dynamo activities is reduced by about a factor of 3 in IHTM, which may explain this improvement. Possible causes of IHTM are discussed. It is found that the m = 1 mode rotates continuously during IHTM, while it always stops rotating just before a large soft X ray emission crash occurs.

A series of detailed experiments has been conducted in three laboratory plasma devices to measure the dynamo electric field along the equilibrium field line ͑the ␣ effect͒ arising from the correlation between the fluctuating flow velocity and magnetic field. The fluctuating flow velocity is obtained from probe measurement of the fluctuating E؋B drift and electron diamagnetic drift. The three major findings are the following: ͑1͒ The ␣ effect accounts for the dynamo current generation, even in the time dependence through a ''sawtooth'' cycle; ͑2͒ at low collisionality the dynamo is explained primarily by the widely studied pressureless magnetohydrodynamic ͑MHD͒ model, i.e., the fluctuating velocity is dominated by the E؋B drift; ͑3͒ at high collisionality, a new ''diamagnetic dynamo'' is observed, in which the fluctuating velocity is dominated by the electron diamagnetic drift. In addition, direct measurements of the helicity flux indicate that the dynamo activity transports magnetic helicity from one part of the plasma to another, but the total helicity is roughly conserved, verifying Taylor's ͓Phys. Rev. Lett. 33, 1139 ͑1974͒; Rev. Mod. Phys. 58, 741 ͑1986͔͒ conjecture.

Edge plasma fluctuations are studied with inserted triple Langmuir probes and magnetic coils in the TPE-1RM20 reversed-field pinch [Yo Yagi et al.]. l\vo-point measurements show that density and potential fluctuations have relatively low mode numbers (m <3, n <40). High coherence (y=0.5) with magnetic field fluctuations and similar mode spectra suggest that density and potential fluctuations are mainly caused by electromagnetic turbulence. Broadband magnetic fluctuations are dominated by m =0, low-n modes and internally resonant m = 1 and m =2 modes. A coherent (j=20-30 kHz) m =0, low-n mode is also observed. Particle flux driven by electrostatic electric field fluctuations is 50%-100% of total flux obtained from D a line intensity measurement. Low-frequency fluctuations (j<100 kHz) give the main contribution to the total flux. Electrostatic fluctuation driven electron energy flux is only of the order of 10% of total nonradiative power loss.