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The viscosity coefficient of the electron perpendicular stress tensor in Braginskii's theory is corrected by the addition of a term of the same order of magnitude, through the inclusion of a term beyond pitch angle scattering in the mass-ratio expansion of the electron-ion collision operator. [ABSTRACT FROM AUTHOR]

© 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The study of edge localized mode (ELM) behavior, stationary heat flux and transient heat flux during the ELM crash phase is performed for a China Fusion Engineering Test Reactor (CFETR) 1 GW hybrid mode operation scenario (= 7.2 m, = 6.5 T, = 13.78 MA). Modeling and simulation start with a scenario obtained by multi-code integrated modeling on the one modeling framework for integrated tasks framework. Linear stability and nonlinear simulations of ELM dynamics are carried out using the BOUT++ six-field reduced magnetohydrodynamic module, which show a much smaller ELM energy loss (ΔELM ~ 0.13%) compared to that of a Type-I ELM. Parametric analysis of the weak linear growth rate and small ELM energy loss characteristics shed light on physics corresponding to a grassy ELM regime for CFETR 1 GW hybrid scenario. The transient heat flux on the divertor target during this small ELM phase is investigated using BOUT++. We found that upstream radial transport in the scrape-off-layer (SOL) induced by small ELMs is weak, which keeps it in the drift-dominated region. However, the heat flux width is still broadened to = 4.64 mm by the increase of separatrix temperature during ELM nonlinear evolution. The impact of transient peak heat load and ELM energy fluence on tungsten melting and net erosion rate of divertor target is evaluated for the first-time using physics-based transport that connects the pedestal with the SOL. Energy fluence caused by a single ELM pulse is below the tungsten melting limit, while tungsten erosion would exceed the material requirements. We conclude that external mitigation methods, such as divertor detachment and advanced divertor geometry are likely needed for the steady state operation of CFETR. [ABSTRACT FROM AUTHOR]

A conventional single null divertor geometry has been proposed for Chinese fusion engineering testing reactor (CFETR) with fusion power up to gigawatt level. Modeling using the SOLPS5.0 code package shows promising results for divertor power exhaust by seeding with neon (Ne) and deuterium (D2). Partial detachment for both inner and outer divertor targets can be achieved with a peak heat load lower than 3 MW/m2. The effective ion charge number, Zeff, at the core boundary is below three, which can be further reduced by increasing the upstream D2 puffing rate. A higher D2 puffing rate helps to increase electron density (ne) in scrape-off layer (SOL) and the impurity screening ability. Based on the SOLPS modeling results, the lifetime of tungsten (W) divertor targets has been estimated by using the DIVIMP code, which indicates that W sputtering is mainly contributed by Ne ions at a far SOL region due to high electron and ion temperature (Te and Ti) there. Upstream D2 puffing can reduce the W erosion rate and W impurity concentration inside the separatrix due to decreasing Te and Ti at the far SOL region. The modeling results show a viable operation regime for the CFETR divertor. [ABSTRACT FROM AUTHOR]

A coupling model for the waves in ion cyclotron resonance frequency (ICRF) in tokamak plasmas is described. The simulation is performed based on the finite element method. A cold plasma dielectric tensor is used. A perfectly matched layer (PML) is applied to describe the ICRF wave single-pass absorption in the core plasma. The selection of PML characteristic parameters is optimized in a wide wave frequency range and validated for plane waves and ICRF waves. The dependencies of the coupling resistance on the plasma-antenna gap, average plasma density, and plasma profiles are given. The simulation results are in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

China fusion engineering test reactor (CFETR) is now in the conceptual design phase. The main objective of CFETR is demonstration of fusion energy with 50 ~ 200 MW fusion power, fuel cycle of T self-sustained and steady-state operation with duty cycle of 0.3 ~ 0.5. The design of CFETR involves complex system structure, and there are complex constrains between physics and engineering. Between optimization of performance parameters and design of main structure and key components, numerous data exchange and iterative optimization are necessary for optimal design of subsystems. To do the optimization design, the CFETR integration design platform is under development. The main technical schemes for it include: a physical design platform and various engineering design modules are developed, then a global framework integrates them by standard interfaces and communication technologies; and a standard material and design criterion database unifies the reference data for the integration platform. The detailed study will be presented in this paper. [ABSTRACT FROM PUBLISHER]

This paper reports a field study on the downdrag and dragload of two pairs of bored piles installed in consolidating ground in the Zhejiang coastal area, China. During and after the construction of a 2.5-m-high embankment, the dragload and downdrag induced on the four piles, surface and subsurface soil settlement, pore water pressure, and lateral earth pressure were monitored. The field measurements show that the maximum dragloads in piles founded on relatively stiffer (end-bearing pile) and relatively softer layers (floating pile) ranged from 1,198 to 1,238 kN and from 798 to 870 kN, respectively. This suggests that the dragload in a floating pile can be one-third less than that in an end-bearing pile with similar geometries and embedded in the same consolidating ground. Deduced β values above the neutral plane (NP) in the clay strata ranged from 0.28 to 0.3, respectively. A much smaller β (0.04-0.06) was found below the NP. The existing analytical solutions overestimated the depth of the NP, leaving the structural design of the piles on the safe side. [ABSTRACT FROM AUTHOR]

A reproducible stationary high-confinement regime with small "edge-localized modes" (ELMs) has been achieved recently in the Experimental Advanced Superconducting Tokamak, which has a metal wall and low plasma rotation as projected for a fusion reactor. We have uncovered that this small ELM regime is enabled by a wide edge transport barrier (pedestal) with a low density gradient and a high density ratio between the pedestal foot and top. Nonlinear simulations reveal, for the first time, that the underlying mechanism for the observed small ELM crashes is the upper movement of the peeling boundary induced by an initial radially localized collapse in the pedestal, which stops the growth of instabilities and further collapse of the pedestal, thus providing a physics basis for mitigating ELMs in future steady-state fusion reactors. [ABSTRACT FROM AUTHOR]

We report the observation of a set of coherent high frequency electromagnetic fluctuations that leads to a turbulence induced self-regulating phenomenon in the DIII-D high bootstrap current fraction plasma. The fluctuations have frequency of 130-220  kHz, the poloidal wavelength and phase velocity are 16-30  m^{-1} and ∼30  km/s, respectively, in the outboard midplane with the estimated toroidal mode number n∼5-9. The fluctuations are located in the internal transport barrier (ITB) region at large radius and are experimentally validated to be kinetic ballooning modes (KBM). Quasilinear estimation predicts the KBM to be able to drive experimental particle flux and non-negligible thermal flux, suggesting its significant role in regulating the ITB saturation.

Rationale and Objectives: The purpose of the study was to investigate interobserver and intersequence variability in measuring hepatocellular carcinoma on magnetic resonance imaging (MRI)., Methods and Materials: Twenty treatment-naïve lesions on Gadoxetic Acid enhanced MRI scans from 20 patients were retrospectively measured by six reviewers with different levels of experience, twice, six weeks apart, on eight different MRI sequences, in randomized order. The sequences include arterial, hepatobiliary, transitional, portal venous, T2, and diffusion weighted images. The single longest diameter (SLD) and longest diameter perpendicular to the longest overall diameter were measured on axial images and products of diameters calculated in accordance to response evaluation criteria in solid tumors v1.1 and World Health Organization response criteria respectively. Lesion-wise intraclass correlation coefficients were used to estimate measurement agreement., Results: All intraclass correlation coefficients were greater than 0.95. No substantive differences between SLD and products of diameters metrics. Means (∼2.8 mm, SLD) and standard deviations (∼2 mm, SLD) were similar across sequences and observers. Similarly, pairwise comparison between observers grouped by experience showed statistically significant differences, but the effect size was minor (∼2 mm). Arterial and HPB-weighted images had similar mean dimensions (2.76 cm) while the smallest mean was in the transitional phase (2.62 cm). A lesion was not measured on 140 occasions (7%), mostly in ADC., Conclusion: There is high interobserver and intersequence reliability despite small differences between observers based on experience level. Our results suggest that accurate measurements can be made on arterial phase despite the possibility of indistinct margins. Lesions, however, are more likely to be missed on diffusion-related sequences., (Copyright © 2019 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.)

Competing Interests: The authors have no conflicts of interest to disclose.

Competing Interests: The authors have no conflicts of interest to disclose.