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A new magnetohydrodynamics (MHD) code based on initial value approach, GMEC_I, has been developed for simulating various MHD physics in tokamak plasmas, as the MHD foundation of the gyrokinetic-MHD energetic particle simulation code (GMEC) family. GMEC_I solves multi-level reduced-MHD models that form a hierarchy of physics complexity, which provide conveniences for the cross-code verification and the identification of key physics effect in tokamak geometry. The field-aligned coordinates are used to represent mode structure efficiently. High-order finite difference methods are used for spatial discretization. The shifted metric methods are used for numerical stability. The discrete expansion forms of physics equations in the code are generated symbolically using the compile-time symbolic solver, which is specifically developed to reduce the complexity of the high-order finite difference form of the MHD equations. Advanced computational techniques have been implemented for optimizing memory access and code parallelization that show a good efficiency using both thread building block and message passing interface. Benchmarks between GMEC_I and the eigenvalue code MAS are presented for ballooning modes without and with diamagnetic drift effects, and tearing modes, which show excellent agreements. [ABSTRACT FROM AUTHOR]

We have developed a hybrid code GMEC: Gyro-kinetic Magnetohydrodynamics (MHD) Energetic-particle Code that can numerically simulate energetic particle-driven Alfvén eigenmodes and energetic particle transport in tokamak plasmas. In order to resolve the Alfvén eigenmodes with high toroidal numbers effectively, the field-aligned coordinates and meshes are adopted. The extended MHD equations are solved with the five-point finite difference method and the fourth-order Runge–Kutta method. The gyrokinetic equations are solved by particle-in-cell method for the perturbed energetic particle pressures that are coupled into the MHD equations. Up to now, a simplified version of the hybrid code has been completed with several successful verifications, including linear simulations of toroidal Alfvén eigenmodes and reversed shear Alfvén eigenmodes. [ABSTRACT FROM AUTHOR]

An efficient numerical code FP3D has been developed to calculate particle orbits and evaluate particle confinement in 3D magnetic fields including stellarators and tokamaks with 3D fields. The magnetic field is either calculated from coils directly or obtained from equilibrium codes. FP3D has been verified with the 3D equilibrium code Variational Moments Equilibrium Code [Hirshman and Whitson, Phys. Fluids 26, 3553–3568 (1983)] for magnetic field calculation and with the drift-kinetic code Stellarator Fokker–Planck Iterative Neoclassical Conservative Solver [Landreman et al., Phys. Plasmas 21(4), 042503 (2014)] for neoclassical transport. The code has been applied successfully to the National Compact Stellarator Experiment stellarator [Nelson et al., Fusion Eng. Des. 66, 169–174 (2003)] for the calculation of neoclassical transport coefficient with the 3D magnetic field obtained directly from coils. FP3D is also used to calculate ripple losses in the tokamak Experimental Advanced Superconducting Tokamak [Y. Wan, Plasma Sci. Technol. 8(3) (2006)]. [ABSTRACT FROM AUTHOR]

Chirping toroidicity-induced Alfvén eigenmodes (TAEs) are destabilized during neutral beam injection on the National Spherical Torus Experiment (NSTX (Ono M. et al 2000 Nucl. Fusion 40 557)) by super-Alfvénic ions with velocities up to five times larger than the Alfvén velocity. TAEs exhibit repeated bursts in amplitude and down-chirps in frequency. Larger bursts, so-called TAE avalanches, are eventually observed and correlate with a loss of fast ions up to 30% over ∼1ms. Frequency, amplitude and radial structure of TAEs are characterized via magnetic pickup coils and a multi-channel reflectometer system. The modes have a broad radial structure, which appears to be unaffected by the large frequency and amplitude variations. However, the large mode amplitude does impact the modes' dynamics by favouring the coupling among different modes. In addition, the coupling involves kink-like modes and can therefore degrade the thermal plasma confinement. In spite of the non-linear regime characterizing the TAE dynamics, the measured properties are found to be in reasonable agreement with solutions from the ideal MHD code NOVA. © 2012 IAEA, Vienna.

Kinetic theory and experimental observations of a special class of energetic particle driven instabilities called here beta-induced Alfv́n-acoustic eigenmodes (BAAEs) are reported confirming, previous results [N. N. Gorelenkov, Plasma Phys. Controlled Fusion 49, B371 (2007)]. The kinetic theory is based on the ballooning dispersion relation where the drift frequency effects are retained. BAAE gaps are recovered in kinetic theory. It is shown that the observed certain low-frequency instabilities on DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] and National Spherical Torus Experiment [M. Ono, S. M. Kaye, Y.-K. M. Peng, Nucl. Fusion 40, 557 (2000)] are consistent with their identification as BAAEs. BAAEs deteriorate the fast ion confinement in DIII-D and can have a similar effect in next-step fusion plasmas, especially if excited together with multiple global toroidicity-induced shear Alfv́n eigenmode instabilities. BAAEs can also be used to diagnose safety factor profiles, a technique known as magnetohydrodynamic spectroscopy. © 2009 American Institute of Physics.

The stability of α-particle driven shear Alfvén eigenmodes (AE) for nominal burning plasma (BP) parameters in the proposed international tokamak experimental reactor (ITER), fusion ignition research experiment (FIRE) and IGNITOR tokamaks is studied. JET plasma, where fusion as were generated in tritium experiments, is also studied to compare the numerical predictions with the existing experiments. An analytic assessment of toroidal AE (TAB) stability is first presented, where the α-particle β due to the fusion reaction rate and electron drag is simply and accurately estimated in plasmas with central temperature in the range of 7-20 keV. In this assessment the hot particle drive is balanced against ion-Landau damping of the background douterons, and electron collision effects and stability boundaries are determined. Then two numerical studies of AE instability are presented. In one, the HIgh-n STability (HINST) code is used to predict the instabilities of low and moderately high frequency Alfvén modes. HINST computes the non-perturbative solutions of the AE including effects of ion finite Larmor radius, orbit width, trapped electrons etc. The stability calculations are repeated using the global code NOVAK. We show that for these plasmas the spectrum of the least stable AE modes is at medium-/high-n numbers. In HINST, TAEs are locally unstable due to the α pressure gradient in all the devices under consideration except IGNITOR. However, NOVAK calculations show that the global mode structure enhances the damping mechanisms and produces stability for the nominal FIRE proposal and near-marginal stability for the nominal ITER proposal. NBI ions produce a strong stabilizing effect for JET. However, in ITER, the beam energies needed to penetrate to the core must be high (∼1 MeV) so that a diamagnetic drift frequency comparable to that of α-particles is produced by the beam ions which induces a destabilizing effect. A serious question remains whether the perturbation theory used in NOVAK overestimates the stability predictions, so that it is premature to conclude that the nominal operation of all three BP proposals without neutral beam injection are stable (or marginally stable) to AEs.

OBJECTIVE: The paper aimed at exploring the correlation between CT findings of diffuse axonal injury and the expression of neuronal aquaporin in patients with craniocerebral injury. PATIENTS AND METHODS: 150 patients with diffuse axonal injury diagnosed by CT and 50 healthy physical examinators were selected as the study objects. According to the craniocerebral CT and GCS scale scores, the patients were divided into DAI light group, medium group, and heavy group. The general conditions of patients were observed and recorded, and the brain pathological morphology, craniocerebral edema and CT imaging results of the patients in each group were compared. Changes in serum and brain AQP-4 levels were detected by RT-PCR and Western blot, and the correlation between CT manifestations of DAI and the expression of neuronal aquaporin was investigated. RESULTS: The results of DAI's pathological morphology, cerebral edema and CT imaging showed that the brain tissue of each group of DAI had a certain degree of injury. With the increase of the injury degree, the degree of edema and the number of axonal injuries sharply increased, and the difference was significant (p-value < 0.05). Therefore, CT could be used as an effective basis for the rapid and efficient diagnosis of DAI. RT-PCR, Western blot and Spearman correlation analysis showed that the levels of AQP-4 in the serum and brain tissue of DAI patients were significantly increased. With the increase of the degree of diffuse axonal injury, the expression level of AQP-4 was further increased, and the difference was significant (p-value < 0. 05). The CT manifestations of patients in each group were positively correlated with the expression level of AQP-4 protein. CONCLUSIONS: AQP-4 can be used as an important molecular index to judge the condition and prognosis of DAI, providing a new non-invasive detection method for the clinical diagnosis and treatment of DAI, which has high clinical application value. [ABSTRACT FROM AUTHOR]

It was shown that asymmetric vertical displacement event disruptions in JET and ITER do not produce a large asymmetric force on conducting structures surrounding the plasma, provided that the current quench (CQ) time is less than the resistive wall penetration time. This is verified with JET data. In ITER, the CQ is expected to be comparable to the resistive wall penetration time, which gives a small wall force. It is shown that runaway electrons (REs) in JET do not produce a large wall force, and this is verified with JET data. This occurs if the RE current is about half of the initial plasma current. In ITER, the RE current might be comparable to the initial current, and REs might lengthen the CQ time sufficiently to produce a large wall force. [ABSTRACT FROM AUTHOR]

A Boundary Element based Discontinuous Deformation Analysis (BE-DDA) method is developed by implementing the improved dual reciprocity boundary element method into the open close iterations based DDA. This newly developed BE-DDA is capable of simulating both the deformation and movement of blocks in a blocky system. Based on geometry updating, it adopts an incremental dynamic formulation taking into consideration initial stresses and dealing with external concentrated and contact forces conveniently. The boundaries of each block in the discrete blocky system are discretized with boundary elements while the domain of each block is divided into internal cells only for the integration of the domain integral of the initial stress term. The contact forces among blocks are treated as concentrated forces and the open-close iterations are applied to ensure the computational accuracy of block interactions. In the current method, an implicit time integration scheme is adopted for numerical stability. Three examples are used to show the effectiveness of the algorithm in simulating block movement, sliding, deformation and interaction of blocks. At last, block toppling and tunnel stability examples are conducted to demonstrate that the BE-DDA is applicable for simulation of blocky systems. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Linear and nonlinear simulations of high-order harmonics q = 1 energetic particle modes excited by trapped energetic particles in tokamaks are carried out using kinetic/magnetohydrodynamic hybrid code M3D-K. It is found that with a flat safety factor profile in the core region, the linear growth rate of high-order harmonics (m = n > 1) driven by energetic trapped particles can be higher than the m/n = 1/1 component. The high m = n > 1 modes become more unstable when the pressure of energetic particles becomes higher. Moreover, it is shown that there exist multiple resonant locations satisfying different resonant conditions in the phase space of energetic particles for the high-order harmonics modes, whereas there is only one precessional resonance for the m/n = 1/1 harmonics. The fluid nonlinearity reduces the saturation level of the n = 1 component, while it hardly affects those of the high n components, especially the modes with m = n = 3,4. The frequency of these modes does not chirp significantly, which is different with the typical fishbone driven by trapped particles. In addition, the flattening region of energetic particle distribution due to high-order harmonics excitation is wider than that due to m/n = 1/1 component, although the m/n = 1/1 component has a higher saturation amplitude. [ABSTRACT FROM AUTHOR]

Copper mine tailing should be reused for environmental and economical benefits. A copper mine tailing from Liaoning province was studied by AAS, XRD, and SEM-EDS. It was shown that chalcopyrite and pyrite were the main valuable minerals in the tailing. Chalcopyrite was embedded closely in the pyrite mineral as revealed in SEMEDS. By regrinding, the chalcopyrite was liberated from pyrite. Besides, ammonium humate is a good organic surfactant. With ammonium humate as the selective depressor, chalcopyrite can be separated from pyrite by flotation in a relative low pulp pH of 10.6. Comprehensive flotation tests conducted on the copper mine tailing indicated that Cu concentrate with Cu grade of 20.16% and S concentrate with S grade of 48.02% were obtained, achieving a good recovery result from the tailing. The mechanism of ammonium humate was proved by IR spectrum and XPS spectrum, showing that there was a chemical adsorption between ammonium humate and pyrite, thus depressing pyrite from flotation. The research can offer a way to treat similar copper tailing. [ABSTRACT FROM AUTHOR]