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The new tokamak generation will be characterized by the necessity of full remote maintenance for most of the critical components. Because no human intervention can be envisaged, the remote systems will have to prove high reliability and rescue capabilities. The availability of the fusion facility will have to be maximized, as a consequence, the efficiency of the maintenance equipment will become a key factor. To fulfill these constraints, the remote maintenance principles will need to be simplified as much as possible and be taken into account at the early stages of the tokamak design. This is an iterative process between Tokamak and Maintenance designs in order to reach the best possible tradeoff. Such an exercise of this iterative work was done on the China Fusion Engineering Test Reactor (CFETR) preliminary design. Main targets were established in the view of optimization of the remote maintenance, then an assessment of the first maintenance scenario, envisaged for the in-vessel components, was done and alternative solutions were proposed. This process was repeated during meetings with the tokamak subsystem owners. This paper will present the results of a first phase of optimization that can represent the current state of the remote maintenance design for CFETR. The work has provided guidelines for main tokamak subsystems such as the magnet configuration, the blanket and divertor modularity, the neutron shielding and cryostat arrangement, and the transfer and hot cell configuration. It also produced some innovative solutions for the overall maintenance scheme like the implementation of a hot cell at the top of the tokamak hall avoiding cask transfers. On this basis a CFETR maintenance scenario is proposed. [ABSTRACT FROM AUTHOR]

The authors have summarized and analyzed the research and application of biological treatment on the oil production wastewater of Shengli oilfield. The results indicated that the biological wastewater treatment technology had special advantages in removing dissolved oil, emulsified oil, and other organic pollutants. By biological treatment or combining it with other process, oil production wastewater can be discharged, reinjected, or recycled effectively. Biological technology plays an important part in solving the problem of wastewater in the petroleum industry. [ABSTRACT FROM PUBLISHER]

Recent analysis of ocean bottom pressure (OBP) data from the Gravity Recovery and Climate Experiment (GRACE) satellites reveals strong El Nino/Southern Oscillation (ENSO)-like oscillating phenomena in the subpolar gyre of the North Pacific. The oscillation is further enhanced by subtracting the OBP values in the subtropical gyre, indicating a mass imbalance between these two northern gyres in these time-scales. Such OBP oscillating features have not been reported before. Motivated by the satellite observations, a non-Boussinesq ocean model that conserves mass rather than volume was used to diagnose the long-term prospect of the oscillating features. Model simulations from the years 1948 to 2006 demonstrate that the subpolar OBP oscillation correlates closely with the tropical ENSO events. Further analysis of the wind stress curl (WSC) from National Center for Environmental Protection/National Center for Atmospheric Research (NCEP/NCAR) products and sea surface height (SSH) data from altimeters suggests that the tropical ENSO can affect the OBP anomaly of the subpolar gyre through an atmospheric bridge by altering and deepening the Aleutian Low and/or through oceanic waves by enhancing the water mass anomaly in the semi-closed northern Pacific basin. [ABSTRACT FROM AUTHOR]

In order to meet the heating requirement of EAST tokamak, ion cyclotron range of frequency (ICRF) heating is utilized as one of the main auxiliary heating methods, which plays an important role in coupling radio frequency (RF) power into the plasma. As a member of plasma facing components, ICRF antenna suffers the plasma radiation as well which is one of the causes of the thermal load on the antenna. Plasma radiation and RF thermal load during the operation of ICRF and thermal load caused by HALO current during vertical displacement event will contribute together to a huge thermal load on the surface of the antenna and consequently the structural stability and reliability of ICRF antenna will be affected. Therefore, cooling channels is needed to remove heat on the ICRF antenna. In this paper, cooling channels for straps of ICRF antenna are designed based on the thermal load on the antenna, and thermal-structural analysis of straps with cooling channels is also carried out by the finite-element method. [ABSTRACT FROM AUTHOR]

We investigate the pressure and temperature dependence of the lattice dynamics of the underdoped, stoichiometric, high-temperature superconductor YBa2Cu4O8 by means of Raman spectroscopy and ab initio calculations. This system undergoes a reversible pressure-induced structural phase transition around 10 GPa to a collapsed orthorhombic structure that is well reproduced by the calculation. The coupling of the B1g-like buckling phonon mode to the electronic continuum is used to probe superconductivity. In the low pressure phase, self-energy effects through the superconducting transition renormalize this phonon, and the amplitude of this renormalization strongly increases with pressure. Whereas our calculation indicates that this mode's coupling to the electronic system is only marginally affected by the structural phase transition, the aforementioned renormalization is completely suppressed in the high pressure phase, demonstrating that under hydrostatic pressures higher than 10 GPa, superconductivity in YBa2Cu4O8 is greatly weakened or obliterated. [ABSTRACT FROM AUTHOR]

The concentrations and stoichiometry of soil carbon (C), nitrogen (N), and phosphorus (P) have critical implications for nutrient cycling and ecosystem function. While their high sensitivity to atmospheric N deposition is well known, it remains unclear for the soil depth-dependence of such responses to N deposition. Here, we examined the responses of soil C : N : P stoichiometry at three soil depths in the upper humus horizon (0–5, 5–10, and 10–20 cm) of Haplic Chernozem (Loamic) across a gradient of urea addition rates (0, 2, 10, 20, and 50 g N m–2 year–1) after five years treatments in a hay-harvest meadow steppe of northern China. We found that the effects of increasing N addition rates on the concentrations and stoichiometry of soil C, N and P did not depend on soil depth, though those parameters varied greatly across different soil layers. Across all soil depths, the concentrations of soil C and N increased with increasing N addition rates, but soil P concentration was not affected by N addition. The higher sensitivity of soil N than soil C to N enrichment resulted in decreasing soil C : N ratio across the N addition gradient, especially for the surface soil layer. Soil N : P ratio showed a positive response to the increases of N addition rates. The unbalanced responses of soil C, N, and P concentrations to N enrichment, as indicated by the decreases of soil C : N ratio and the increases of soil N : P ratio across the N addition gradient, highlighted the role of N enrichment in decoupling soil nutrient cycling in the temperate steppe. [ABSTRACT FROM AUTHOR]

A China Fusion Engineering Testing Reactor (CFETR) will be built to test and verify the feasibility of engineering and technology in practice for the future fusion reactor. Long pulse and steady-state operation will be demonstrated with duty cycle time more than 30%–50%. Because of the beta and gamma activation of the component bulk and surface dust (beryllium, carbon, and tungsten), special remote handling (RH) techniques will be required during machine maintenance periods. The divertor cassettes’ remote replacement is one of the key maintenance operations for the CFETR to meet the requirements of duty cycle time. RH maintenance strategies will have a significant impact on the layout of the machine and design of components. In this article, an overview of the CFETR divertor components’ remote maintenance strategy and the description of the maintenance process of the divertor cassettes were introduced. The engineering design features of the divertor RH systems (DHRSs) were described to meet the requirements such as high efficiency and reliability. Preliminary assessment of the divertor RH system is done in order to successfully and efficiently carry out RH maintenance tasks. [ABSTRACT FROM AUTHOR]

For the last 20 years Shengli oilfield has done research into the application of microbial enhanced oil recovery (MEOR). The authors summarize and analyze MEOR progress in mechanism research and field application in Shengli oilfield. The results indicate MEOR could improve oil recovery after water flooding and polymer flooding with multiple mechanisms. Cumulative oil increment of MEOR application on seven blocks was 212,366 t. The research and application of MEOR should concentrate on air assisted microbial flooding and indigenous microbial flooding in the future. [ABSTRACT FROM AUTHOR]

Deuterium high-confinement (H-mode) plasmas, lasting up to 3.45 s, have been generated in the EAST by ion cyclotron range of frequency (ICRF) heating. H-mode access was achieved by coating the molybdenum-tiled first wall with lithium to reduce the hydrogen recycling from the wall. H-mode plasmas with plasma currents between 0.4 and 0.6MA and axial toroidal magnetic fields between 1.85 and 1.95 T were generated by 27MHz ICRF heating of deuterium plasma with hydrogen minority. The ICRF input power required to access the H-mode was 1.6-1.8MW. The line-averaged density was in the range (1.83-2.3)×1019 m-3. 200-500 Hz type-III edge localized mode activity was observed during the H-mode phase. The H-mode confinement factor, H98IPB(y, 2), was ~0.7. [ABSTRACT FROM AUTHOR]

The latest superconducting magnets (SM) for fusion are mostly force-cooled, mainly because it allows reliable electrical insulation of the coils using vacuum pressure impregnation (VPI). SM of this type have many leads, feeders and coolant tubes, located in cryostat vacuum, which must sustain high voltages, induced on them by fast current changes. However vacuum loss can spoil their insulation. A few such cases occurred during the T-15 tokamak coils testing, initially having bare leads relying upon vacuum. But its loss generated a coil quench, a protecting current dump at high voltage, followed by breakdown and arc. Even leads insulation by Teflon and fiberglass tape wrap proved to be insufficient. Nevertheless, similar tape wrap insulation of leads and feeders (ILF) was used in EAST, KSTAR, SST-1 and W-7X. So far, seven breakdowns occurred during their coil tests at operating voltage \sim<3 kV. Breakdowns never initiated in the coils, but always on their leads, feeders and sensor lines, indicating that their insulation made by tape wrap were too weak. Instead of ILF improvement some projects undertake Paschen tests. These are planned as the baseline for ITER too. But these tests are valid for the coil with open insulated surface, but are not appropriate for the final tests, when insulation should not be exposed to vacuum. Up to now ILF final tests have been done in all devices at 10–21 kV, but only in good vacuum in spite of the fact that such tests could not guarantee safe operation in case of vacuum loss. We propose to increase ILF strength to the same level, as in the coils, using vacuum-tight grounded stainless steel casings filled up by VPI over magnet leads. This will provide reliable and easily testable solid insulation. Besides, casings would exclude He leaks, providing the second vacuum tight barrier over the ILF. Thus it would increase the magnet reliability and would make it possible to avoid the needs of all single coils test. [ABSTRACT FROM PUBLISHER]

Plasma heating using fast waves was successfully performed on the Experimental Advanced Superconducting Tokamak (EAST) in the H minority regime in deuterium plasmas at 27MHz and Bo = 2.0 T. With 1.0MW of ion cyclotron range of frequency (ICRF) power injected at a line-averaged electron density of 4.0 × 1019 m-3, the electron temperature increased from 1.0 keV to above 2.0 keV and the loop voltage dropped. An increase in the stored energy by 30 kJ was obtained. The first H-mode plasma of 6.4 s was achieved with a combination of lower hybrid wave and ICRF heating. Density pump-out was observed during L-mode discharges at a high electron density of 4.0 × 1019 m-3. In these discharges, re-attachment of the plasma was observed when ICRF power was applied. [ABSTRACT FROM AUTHOR]

In the search for the mechanism of high-temperature superconductivity, intense research has been focused on the evolution of the spin excitation spectrum on doping from the antiferromagnetic insulating to the superconducting state of the cuprates. Because of technical limitations, the experimental investigation of doped cuprates has been largely focused on low-energy excitations in a small range of momentum space. Here we use resonant inelastic X-ray scattering to show that a large family of superconductors, encompassing underdoped YBa2Cu4O8 and overdoped YBa2Cu3O7, exhibits damped spin excitations (paramagnons) with dispersions and spectral weights closely similar to those of magnons in undoped cuprates. The comprehensive experimental description of this surprisingly simple spectrum enables quantitative tests of magnetic Cooper pairing models. A numerical solution of the Eliashberg equations for the magnetic spectrum of YBa2Cu3O7 reproduces its superconducting transition temperature within a factor of two, a level of agreement comparable to that of Eliashberg theories of conventional superconductors. [ABSTRACT FROM AUTHOR]

The GaN growth mechanism using Li3N flux was reinvestigated by designing a new experiment that allowed us to grow GaN simultaneously under varying Ga/Li3N molar ratios. The results confirm the two-step reactions involved in the Ga–Li3N system: Li3N+Ga→Li3GaN2+Li (1) and Li3GaN2+Ga→GaN+Li (2). It is found that reaction (2) is the main cause leading to small GaN crystals in the products. Larger GaN crystals, however, can grow by a different pathway. The growing process is concerned with the formation of Li–Ga–N melt by dissolving Li3GaN2 in Li–Ga melt after reaction (1). GaN crystals up to 3 mm grow from the Li–Ga–N melt upon cooling on the GaN particles by reaction (2). Our results suggest that it is necessary to restrain reaction (2) by choosing proper Ga/Li3N molar ratios so as to obtain GaN crystals in larger size. [ABSTRACT FROM AUTHOR]

We report Raman analysis of A1(LO) (longitudinal optical) and E2(high) phonon lifetimes in a bulk GaN single crystal and their temperature dependence from 77 K to 770 K. Both the A1(LO) and E2(high) phonons in GaN were observed decaying primarily into two phonons of equal energy [Klemens model, P. G. Klemens, Phys. Rev. 148, 845 (1966)]. This is a rare example of a high-quality free-standing GaN bulk single crystal displaying abnormal A1(LO) phonon decay. These results will have significant impact on designing and understanding of GaN-based high-speed, high-power electric devices. [ABSTRACT FROM AUTHOR]