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The hot tail generation is expected to be the dominant mechanism for the runaway electron (RE) seed formation during disruptions, especially in large devices with high electron temperature such as international thermonuclear experimental reactor. This issue has been studied in the HL-2A tokamak by using the superthermal electrons produced by lower hybrid waves (LHWs), which can adjust the hot tail distribution. It was observed that RE generation was significantly enhanced during disruptions with LHWs. The measurements show that the multitudinous superthermal electrons with energy of 40–60 keV created by LHWs greatly transform the landscape of hot tail distribution. The tail electrons can be directly converted into REs under the acceleration of the high toroidal electric field during disruptions. Runaway current plateaus are more likely to be formed than in normal disruptions without LHWs. However, some abnormal phenomena have also been observed, that is, RE generation was not enhanced and no runaway current plateau was formed during some disruptions with LHWs. It is found that this is attributed to the complete loss of RE seeds caused by strong magnetic fluctuations, which prevents the generation of REs during disruptions. This may provide a way to avoid the generation of REs during disruptions by actively exciting magnetic fluctuations. [ABSTRACT FROM AUTHOR]

A hydrazone compound 2-bromo-N'-(2-hydroxy-3-methoxybenzylidene)benzohydrazide (H2L) was prepared and characterized by IR, UV-Vis and NMR spectra. Based on the hydrazone compound, a new oxidovanadium(V) and a new dioxidomolybdenum(VI) complexes, [VO(L)(OEt)(EtOH)] (I) and [MoO2(L)(OH2)] (II), were prepared and characterized by IR, UV-Vis, NMR spectra, and single crystal X-ray diffraction (CIF files nos. 1866755 (I) and 1866756 (II)). Complex I crystallizes as the monoclinic space group P21/c with unit cell dimensions a = 12.8733(12), b = 13.5088(13), c = 11.9262(11) Å, β = 91.765(2)°, V = 2073.0(3) Å3, Z = 4, R1 = 0.0524, wR2 = 0.1329, GOOF = 1.245. Complex II crystallizes as the monoclinic space group P21/c with unit cell dimensions a = 8.1140(9), b = 16.2975(19), c = 13.4318(15) Å, β = 106.456(2)°, V = 1703.4(3) Å3, Z = 4, R1 = 0.0296, wR2 = 0.0728, GOOF = 1.046. X-ray analysis indicates that the complexes are mononuclear species with the metal atoms in octahedral coordination. The complexes were studied for catalytic oxidation property on some olefins with tert-butyl hydrogen peroxide as oxidant. [ABSTRACT FROM AUTHOR]

It has been observed that the plasma velocity shear can be strongly affected by external source input, such as neutral beam injection, lower hybrid current drive, supersonic molecule beam injection, and impurity injection. Such a change in velocity shear can lead to turbulence suppression or enhancement by inducing a spectral shift in the turbulence radial wavenumber spectrum. A theoretical model, based on the nonlinear evolution of the turbulence amplitude with an externally driven velocity shear, combined with the thermal transport equation, has been used to describe the turbulence evolution. A critical growth rate γ0 for the turbulence regulation has been identified in this theoretical model, and the parametric dependency of γ0 is investigated. A threshold Uc of the reduction value of the velocity shear rate U, intimately related to γ0, has been found for the triggering radial wavenumber shift. This indicates that the turbulence could be regulated by external source input, when U > Uc. [ABSTRACT FROM AUTHOR]

The electrodeposition of nano-iron films from Fe2O3 precursor in an ionic liquid composed of 33·3 mol-% choline chloride (ChCl) and 66·7 mol-% ethylene glycol (EG) has been investigated. The electrodeposition process was carried out at 1·5-1·9 V and 60-120°C for 3 hours. The influences of experimental parameters on the electrodeposition process and the morphology of the deposited nano-iron films were studied. The results show that compact and uniform nano-iron (particle size is approximately 100-200 nm) films can be electrodeposited in the Fe2O3-saturated ChCl-EG ionic liquid at 1·8-1·9 V and 60-120°C. The electrodeposition temperature and applied potential have significant influences on the characteristics of the deposited nano-iron films and the electrodeposition process. It is suggested that the controllable electrodeposition process can be used to prepare nano-iron films with various particle sizes from Fe2O3 in CHCl-EG eutectic melt. [ABSTRACT FROM AUTHOR]

Particle transport has been studied in the Tore Supra tokamak by using modulated ion cyclotron resonance heating to generate perturbations of density and temperature. For the first time, a reversal of the particle convective velocity and a strong increase in the turbulent particle flux have been clearly observed. When the mixed critical gradient ζc=R/LT+4(R/Ln)=22 is exceeded, the particle flux increases sharply and the convective velocity reverses from inward to outward. These observations are in agreement with quasilinear, gyrokinetic calculations. The critical gradient corresponds to a transition from an instability driven by the ion temperature gradient to the onset of another instability caused by trapped electrons. [ABSTRACT FROM AUTHOR]

Experiments to study inward heat transport phenomena have been performed in the Tore Supra tokamak with off-axis electron cyclotron resonance heating (ECRH). Both power balance and perturbation transport analysis have been done for low-frequency (1 Hz) ECRH modulation experiments. Heat diffusivity and heat pinch have been separately determined by fitting the experimental data of the amplitude and phase of the Fourier transform of the modulated temperature with a linear transport model including convection term. Comparison with the critical gradient model has shown that the heat pinch previously obtained could include a pseudo-pinch due to the non-linearity of the diffusivity and an additional non-diffusive heat pinch. The pinch effect is reduced for higher densities. [ABSTRACT FROM AUTHOR]