Microstructure and bonding properties of diffusion–bonded composite comprising an Fe–Al alloy and carbon steel

This study discusses microstructure evolution, diffusion behavior and bonding strength of a couple comprising of an iron aluminium alloy (Fe–Al) and high carbon-steel (FeCMn) during diffusion bonding. A columnar microstructure evolves from the joint interface toward FeCMn and disappears in couples bonded for a long period. Aluminium diffusion from Fe–Al to FeCMn and columnar microstructure evolution are retarded as compared to a couple consisting of an Fe–Al and ferrite steel. The carbide in the FeCMn impedes the aluminium diffusion and retards the columnar grain evolution. When the carbide is dissolved in the ferrite during the aluminium diffsuion from Fe–Al, coarse grains evolve due to the coalescence of the columnar grains and a high-bonding strength is obtained. The hardness variation is minimum in the FeCMn of a couple bonded for a short period, which is explained by the microstructural changes in the columnar grain evolution and carbide dissociation.     

Cathodic performance of some sulfide electrodes in liquid ammonia

The cathodic performance of some metal sulfide electrodes has been investigated in a liquid ammonia solution of NH₄SCN. In dry liquid ammonia, the     

Direct measurement of energetic electron flow in Q-shu University experiment with steady-state spherical tokamak

In magnetized plasmas, the presence of a significant number of energetic electrons has been observed but quantitative characteristics of these electrons are proving difficult to investigate. A Langmuir probe offers a means to provide quantitative measurement of these energetic electrons that takes into account electron emissions (secondary electron emission and electron reflection) from the probe tips and sheath expansion around the probe tips caused by a considerable negative potential. In this paper, these effects are experimentally confirmed and an analytical means to measure energetic electron characteristics are proposed. An analysis of plasmas produced by a high frequency wave is then applied leading to the successful detection of an asymmetric flow of energetic electrons. The estimated electron temperature and current density were approximately 4-5 keV and 2-3 kA/m(2).     

First neutral beam injection experiments on KSTAR tokamak

The first neutral beam (NB) injection system of the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak was partially completed in 2010 with only 1∕3 of its full design capability, and NB heating experiments were carried out during the 2010 KSTAR operation campaign. The ion source is composed of a JAEA bucket plasma generator and a KAERI large multi-aperture accelerator assembly, which is designed to deliver a 1.5 MW, NB power of deuterium at 95 keV. Before the beam injection experiments, discharge, and beam extraction characteristics of the ion source were investigated. The ion source has good beam optics in a broad range of beam perveance. The optimum perveance is 1.1-1.3 μP, and the minimum beam divergence angle measured by the Doppler shift spectroscopy is 0.8°. The ion species ratio is D(+):D(2)(+):D(3)(+) = 75:20:5 at beam current density of 85 mA/cm(2). The arc efficiency is more than 1.0 A∕kW. In the 2010 KSTAR campaign, a deuterium NB power of 0.7-1.5 MW was successfully injected into the KSTAR plasma with a beam energy of 70-90 keV. L-H transitions were observed within a wide range of beam powers relative to a threshold value. The edge pedestal formation in the T(i) and T(e) profiles was verified through CES and electron cyclotron emission diagnostics. In every deuterium NB injection, a burst of D-D neutrons was recorded, and increases in the ion temperature and plasma stored energy were found.