Runaway Electron Measurements in the EAST Tokamak

An experimental study of runaway electrons in the EAST tokamak has been performed by a recently developed multi‐channel hard x‐ray diagnostics based on NaI(TL) scintillator detectors. It is found that in the current quench phase, the inductive loop voltage plays an important role in the generation of runaway electrons. And the avalanche mechanism was the main mechanism for runaway electrons after the disruptions. The distribution and transportation of runaway electrons were also investigated by multi‐channel hard x‐ray diagnostics. It is also found that the intensity of runaway electrons emission in the core plasma was much higher than those in the downside of the cross‐section, while the emission intensity of runaway electrons in the core plasma was almost the same. Calculated shrinking coefficient of runaway electrons emission after the plasma disruption was about 26 m/s according to the experimental data (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Observation of Runaway Electron Behaviour During Disruptions in LHCD Discharges in the HT‐7 Tokamak

Production of runaway electrons during disruptions has been observed in the HT‐7 Tokamak. The runaway current plateaus, which can carry part of the pre‐disruptive current, are observed in lower‐hybrid current drive (LHCD) limiter discharges. It is found that the runaway current can mitigate the disruptions effectively. We can use gas puffing to increase the line‐averaged density to restrain the runaway electrons and rebuild the plasmas after the disruptions. Detailed observations are presented on the runaway electrons generated following disruptions in the HT‐7 tokamak discharges. The results indicate that the magnetic oscillations play a significant role in the loss of runaway electrons in disruptions. There are two important preconditions to rebuild plasmas by runaway electrons after the disruptions. One of them are weak magnetic oscillations; another one are LHWs (lower‐hybrid waves) (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dense two-dimensional silver single and double nanoparticle arrays with plasmonic response in wide spectral range

We report the properties of plasmons in dense planar arrays of silver single and double nanostructures with various geometries fabricated by electron beam lithography (EBL) as a function of their size and spacing. We demonstrate a strong plasmon coupling mechanism due to near-field dipolar interactions between adjacent nanostructures, which produces a major red shift of the localized surface plasmon resonance (LSPR) in silver nanoparticles and leads to strong maximum electric field enhancements in a broad spectral range. The extinction spectra and maximum electric field enhancements are theoretically modeled by using the finite element method. Our modeling revealed that strong averaged electric field enhancements of up to 60 in visible range and up to 40 in mid-infrared result from hybridization of multipolar resonances in such dense nanostructures; these are important for applications in surface enhanced spectroscopies.     

On the simulation of the pivot bearing inside HDD

The pivot bearing is an important mechanical component in HDD. Several quasi-rigid (QR) body motion modes of the HDD are related to the stiffness of the pivot bearing such as the axial translation mode, the lateral translation mode and the rocking mode. In the shock simulation of the HDD, the pivot bearing is often simplified to identical theoretical models wherein the bearing is simulated with springs or beams. The overall axial stiffness and the radial stiffness of these models are often carefully checked and match well with the experimental values. However, how well these theoretical models represent the rotational stiffness of the bearing is still not fully understood. This is partly due to the difficulties in obtaining the experimental rotational stiffness of the pivot bearing. In this paper, three different theoretical models are examined for the simulation of the bearing. The rotational stiffness of these three theoretical models is derived analytically. The theoretical formulations are verified with the finite element analysis results.     

Turbidimetric determination of some sulphur compounds in ethanol from fermentation

A simple method is described which can be used for the determination of certain sulphur compounds found in industrial ethanol obtained from fermentation of molasses. The method is based on the turbidimetric determination of sulphate after the sample has been treated with dilute hydrogen peroxide solution, by precipitation of the sulphate with barium chloride under appropriate conditions. Several samples of fermentation ethanol have been analysed by this method and the sulphur contents found compared with the total acidity.