Experimental Evidence of Intrinsic Current Generation by Turbulence in Stationary Tokamak Plasmas.

High-ß_{θe} (a ratio of the electron thermal pressure to the poloidal magnetic pressure) steady-state long-pulse plasmas with steep central electron temperature gradient are achieved in the Experimental Advanced Superconducting Tokamak. An intrinsic current is observed to be modulated by turbulence driven by the electron temperature gradient. This turbulent current is generated in the countercurrent direction and can reach a maximum ratio of 25% of the bootstrap current. Gyrokinetic simulations and experimental observations indicate that the turbulence is the electron temperature gradient mode (ETG). The dominant mechanism for the turbulent current generation is due to the divergence of ETG-driven residual flux of current. Good agreement has been found between experiments and theory for the critical value of the electron temperature gradient triggering ETG and for the level of the turbulent current. The maximum values of turbulent current and electron temperature gradient lead to the destabilization of an m/n=1/1 kink mode, which by counteraction reduces the turbulence level (m and n are the poloidal and toroidal mode number, respectively). These observations suggest that the self-regulation system including turbulence, turbulent current, and kink mode is a contributing mechanism for sustaining the steady-state long-pulse high-ß_{θe} regime.

First Evidence of Local E×B Drift in the Divertor Influencing the Structure and Stability of Confined Plasma near the Edge of Fusion Devices.

The structure of the edge plasma in a magnetic confinement system has a strong impact on the overall plasma performance. We uncover for the first time a magnetic-field-direction dependent density shelf, i.e., local flattening of the density radial profile near the magnetic separatrix, in high confinement plasmas with low edge collisionality in the DIII-D tokamak. The density shelf is correlated with a doubly peaked density profile near the divertor target plate, which tends to occur for operation with the ion B×∇B drift direction away from the X-point, as currently employed for DIII-D advanced tokamak scenarios. This double-peaked divertor plasma profile is connected via the E×B drifts, arising from a strong radial electric field induced by the radial electron temperature gradient near the divertor target. The drifts lead to the reversal of the poloidal flow above the divertor target, resulting in the formation of the density shelf. The edge density shelf can be further enhanced at higher heating power, preventing large, periodic bursts of the plasma, i.e., edge-localized modes, in the edge region, consistent with ideal magnetohydrodynamics calculations.

Promising High-Confinement Regime for Steady-State Fusion.

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.

Low-to-High Confinement Transition Mediated by Turbulence Radial Wave Number Spectral Shift in a Fusion Plasma.

A new model for the low-to-high (L-H) confinement transition has been developed based on a new paradigm for turbulence suppression by velocity shear [G. M. Staebler et al., Phys. Rev. Lett. 110, 055003 (2013)]. The model indicates that the L-H transition can be mediated by a shift in the radial wave number spectrum of turbulence, as evidenced here, for the first time, by the direct observation of a turbulence radial wave number spectral shift and turbulence structure tilting prior to the L-H transition at tokamak edge by direct probing. This new mechanism does not require a pretransition overshoot in the turbulent Reynolds stress, shunting turbulence energy to zonal flows for turbulence suppression as demonstrated in the experiment.

Energy requirements of early-weaned Dorper cross-bred female lambs.

The net and metabolizable energy (NE and ME) requirements of Dorper cross-bred female lambs with BWs of 20-35 kg were assessed in a comparative slaughter trial. Thirty-five Dorper × thin-tailed Han cross-bred female lambs weaned at ~50 days of age (20.3 ± 2.15 kg BW) were used. Seven randomly selected lambs were slaughtered at the start of the trial (baseline group). An intermediate group consisting of seven randomly selected lambs fed ad libitum was slaughtered when the lambs reached an average BW of 28.5 kg. The remaining 21 lambs were allotted randomly to three levels of dry matter intake: ad libitum or restricted to 70% or 40% of the ad libitum intake. All the lambs were slaughtered when the sheep fed ad libitum reached a BW of 35 kg. Total body energy, nitrogen, fat, ash and moisture content were determined. In a digestibility trial, an additional 15 Dorper × thin-tailed Han cross-bred female lambs (28.7 ± 1.75 kg BW) were housed in metabolism cages and used in a completely randomized design experiment to evaluate the ME value of the diet at the three feed intake levels. The maintenance requirements for NE and ME were 245.5 and 380.3 kJ/kg metabolic shrunk body weight (SBW0.75 ) respectively. The partial efficiency of energy use for maintenance was 0.645. The NE requirements for growth ranged from 1.18 to 5.18 MJ/d for the lambs gaining 100-350 g/d from 20 to 35 kg BW. Partial efficiency of ME for growth was 0.44. In conclusion, the current study suggests that the NE requirement for maintenance and growth of Dorper early-weaned cross-bred female lambs is lower than the current AFRC and NRC recommendations.

New steady-state quiescent high-confinement plasma in an experimental advanced superconducting tokamak.

A critical challenge facing the basic long-pulse high-confinement operation scenario (H mode) for ITER is to control a magnetohydrodynamic (MHD) instability, known as the edge localized mode (ELM), which leads to cyclical high peak heat and particle fluxes at the plasma facing components. A breakthrough is made in the Experimental Advanced Superconducting Tokamak in achieving a new steady-state H mode without the presence of ELMs for a duration exceeding hundreds of energy confinement times, by using a novel technique of continuous real-time injection of a lithium (Li) aerosol into the edge plasma. The steady-state ELM-free H mode is accompanied by a strong edge coherent MHD mode (ECM) at a frequency of 35-40 kHz with a poloidal wavelength of 10.2 cm in the ion diamagnetic drift direction, providing continuous heat and particle exhaust, thus preventing the transient heat deposition on plasma facing components and impurity accumulation in the confined plasma. It is truly remarkable that Li injection appears to promote the growth of the ECM, owing to the increase in Li concentration and hence collisionality at the edge, as predicted by GYRO simulations. This new steady-state ELM-free H-mode regime, enabled by real-time Li injection, may open a new avenue for next-step fusion development.

Photoluminescence study on polar nanoregions and structural variations in Pb(Mg1/3Nb2/3)O3 ₋ PbTiO3 single crystals.

We report polar nanostructure and electronic transitions in relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 ₋ PbTiO (PMN-PT) single crystals around morphotropic phase boundary (MPB) region by variable-temperature (80-800 K) photoluminescence (PL) spectra and low-wavenumber Raman scattering (LWRS). The discontinuous evolution from peak positions and intensity of luminescence emissions can be corresponding to formation of polar nanoclusters and phase transitions. Six emissions have been derived from PL spectra and show obvious characteristics near phase transition temperatures, which indicates that PL spectral measurement is promising in understanding the microcosmic mechanism. The Raman mode at 1145 cm(-1) indicates that temperature dependent luminescence phenomena can be modulated by thermal quenching.

New edge coherent mode providing continuous transport in long-pulse H-mode plasmas.

An electrostatic coherent mode near the electron diamagnetic frequency (20-90 kHz) is observed in the steep-gradient pedestal region of long pulse H-mode plasmas in the Experimental Advanced Superconducting Tokamak, using a newly developed dual gas-puff-imaging system and diamond-coated reciprocating probes. The mode propagates in the electron diamagnetic direction in the plasma frame with poloidal wavelength of ∼8 cm. The mode drives a significant outflow of particles and heat as measured directly with the probes, thus greatly facilitating long pulse H-mode sustainment. This mode shows the nature of dissipative trapped electron mode, as evidenced by gyrokinetic turbulence simulations.

Clinical, imaging, and pathological characteristics of congenital infiltrating lipomatosis of the face.

Congenital infiltrating lipomatosis of the face (CILF) is a rare congenital disease of the head and neck region. In this study, the cases of 20 patients diagnosed with CILF were reviewed retrospectively to analyse the characteristics of the disease. The symptoms, signs, and clinical progression were investigated. Radiological changes were analysed according to the distribution of the trigeminal nerve. The pathological features of the fatty facial lesions, jaw hyperplasia, and lingual lesions were further identified. All 20 patients demonstrated hemifacial hypertrophy at birth. None had a family history of the disease. Significant radiological features of CILF (prevalence ≥90%) included thickened buccal subcutaneous fat, palatal submucosal fat, and temporal subcutaneous fat, maxillary tuberosity heteroplasia, and fatty infiltration of the masseteric intermuscular space. With regard to the trigeminal nerve, the frontal branch region (CNV1) was rarely affected, while the maxillary (CNV2) and mandibular (CNV3) branch regions showed considerable changes. Pathologically, CILF was observed to be characterized by the infiltration of mature adipose tissue into the adjacent buccal soft tissue, osteal remodelling surrounded by sheets of mature lipocytes and supporting fibrovascular stroma, and lingual hamartoma. In summary, CILF exhibits distinct characteristics that are related to the regions controlled by the maxillary and mandibular branches of the trigeminal nerve, suggesting that CILF may be associated with early neural development.

Magnetic topology changes induced by lower hybrid waves and their profound effect on edge-localized modes in the EAST tokamak.

Strong mitigation of edge-localized modes has been observed on Experimental Advanced Superconducting Tokamak, when lower hybrid waves (LHWs) are applied to H-mode plasmas with ion cyclotron resonant heating. This has been demonstrated to be due to the formation of helical current filaments flowing along field lines in the scrape-off layer induced by LHW. This leads to the splitting of the outer divertor strike points during LHWs similar to previous observations with resonant magnetic perturbations. The change in the magnetic topology has been qualitatively modeled by considering helical current filaments in a field-line-tracing code.

First evidence of the role of zonal flows for the L-H transition at marginal input power in the EAST tokamak.

A quasiperiodic Er oscillation at a frequency of <4 kHz, much lower than the geodesic-acoustic-mode frequency, with a modulation in edge turbulence preceding and following the low-to-high (L-H) confinement mode transition, has been observed for the first time in the EAST tokamak, using two toroidally separated reciprocating probes. Just prior to the L-H transition, the Er oscillation often evolves into intermittent negative Er spikes. The low-frequency Er oscillation, as well as the Er spikes, is strongly correlated with the turbulence-driven Reynolds stress, thus providing first evidence of the role of the zonal flows in the L-H transition at marginal input power. These new findings not only shed light on the underlying physics mechanism for the L-H transition, but also have significant implications for ITER operations close to the L-H transition threshold power.

Integration of full divertor detachment with improved core confinement for tokamak fusion plasmas.

Divertor detachment offers a promising solution to the challenge of plasma-wall interactions for steady-state operation of fusion reactors. Here, we demonstrate the excellent compatibility of actively controlled full divertor detachment with a high-performance (ßN ~ 3, H98 ~ 1.5) core plasma, using high-ßp (poloidal beta, ßp > 2) scenario characterized by a sustained core internal transport barrier (ITB) and a modest edge transport barrier (ETB) in DIII-D tokamak. The high-ßp high-confinement scenario facilitates divertor detachment which, in turn, promotes the development of an even stronger ITB at large radius with a weaker ETB. This self-organized synergy between ITB and ETB, leads to a net gain in energy confinement, in contrast to the net confinement loss caused by divertor detachment in standard H-modes. These results show the potential of integrating excellent core plasma performance with an efficient divertor solution, an essential step towards steady-state operation of reactor-grade plasmas.

Observation of confined current ribbon in JET plasmas.

We report the identification of a localized current structure inside the JET plasma. It is a field-aligned closed helical ribbon, carrying current in the same direction as the background current profile (cocurrent), rotating toroidally with the ion velocity (corotating). It appears to be located at a flat spot in the plasma pressure profile, at the top of the pedestal. The structure appears spontaneously in low density, high rotation plasmas, and can last up to 1.4 s, a time comparable to a local resistive time. It considerably delays the appearance of the first edge localized mode.

Comparison of the therapeutic effects of leflunomide and mycophenolate mofetil in the treatment of immunoglobulin A nephropathy manifesting with nephrotic syndrome.

OBJECTIVE: To evaluate the therapeutic effects and safety of a combination therapy of leflunomide (LEF) and prednisone for the treatment of immunoglobulin A (IgA) nephropathy manifesting with nephrotic syndrome. METHODS: 40 patients with IgA nephropathy manifesting with nephrotic syndrome were randomly divided into two groups. The treatment group was administered with a combination therapy of prednisone and LEF, and the control group with a combination therapy of prednisone and MMF. For the following comparison 24-h urinary protein excretion and the serum levels of albumin, cholesterol, and creatinine before and after the therapy were assessed. RESULTS: In the treatment group, the medication was markedly effective in 5 cases and effective in 7 cases; the total efficacy rate was 60.0%. In the control group, the treatment was markedly effective in 5 cases and effective in 8 cases; the total efficacy rate was 65.0%. The IgA levels in both groups decreased after therapy. There were no significant differences between the results for the two groups (p > 0.05). The treatments were well tolerated in both groups. CONCLUSION: LEF is a safe and effective drug for the treatment of IgA nephropathy manifesting with nephrotic syndrome.

Design of Langmuir probe diagnostic system for the upgraded lower tungsten divertor in EAST tokamak.

In order to achieve long-pulse H-mode plasma scenario over 400 s with high heating power in the Experimental Advanced Superconducting Tokamak (EAST) device, the lower graphite divertor will be upgraded into a tungsten (W) divertor with active water cooling, which consists of the W/Cu monoblock units and the W flat-tile units as the divertor plasma facing components. As a fundamental diagnostic tool, the divertor Langmuir probe (Div-LP) diagnostic system will be upgraded accordingly. This paper presents the design of two kinds of new Div-LP systems, which are planned to be utilized on the W/Cu monoblock units and the W flat-tile units for the upgraded lower tungsten divertor, respectively, including their structures and preliminary poloidal and toroidal layouts. The Div-LP diagnostic system can measure the plasma parameters with the schemes of triple-probe, double-probe, and single-probe, to obtain the spatial and temporal distribution of plasma behavior on the divertor targets, which is useful for the discharge control and operation in EAST. In addition, the thermal analysis of the two kinds of probe assemblies is also carried out by using the three-dimensional finite element code ANSYS, which is aimed to get the optimal designs to withstand the long-pulse and high-power operation in EAST future experiments.

Edge toroidal charge exchange spectra analysis in the EAST.

An edge toroidal charge exchange recombination spectroscopy (eCXRS) diagnostic has been deployed successfully on the Experimental Advanced Superconducting Tokamak (EAST) recently, providing edge plasma ion temperature and toroidal rotation. Edge CXRS on EAST typically monitors the carbon vi (529.059 nm, n = 8 → 7) spectral line. Spectral lines emitted from other different impurities that appeared in the wavelength ranges of 528 nm-530 nm illustrate the need to revise the edge change exchange spectra analysis in this region. Since the eCXRS sightlines end on the ion cyclotron range of frequencies (ICRF) stainless steel antenna, the passive Fe lines coming from the antenna could be recorded by eCXRS diagnostic when ICRF is used. A revised edge toroidal charge exchange spectra analysis including Fe spectral lines is presented. The accuracy of eCXRS measurement has been improved by the revised spectra analysis.

Changes in the expression of Fas on T lymphocytes after allogeneic fetal thymus transplantation in systemic lupus erytematosus mice.

BACKGROUND: Systemic lupus erythematosus (SLE) is an autoimmune disorder that can produce inflammation in many organ systems. The rate of spontaneous apoptosis in lymphocytes from human SLE patients has been reported to be increased both in vivo and in vitro. Studies of fetal thymus transplantation in an autoimmune syndrome indicate that cellular immunity can be reconstituted and regulatory T cell functions can be normalized. OBJECTIVES: The aim of this study was to assess changes in Fas expression on T lymphocytes following fetal thymus transplant. METHODS: (B/CxB6) F1 (H-2d/h) female F1 mice were assigned to groups designated transplantation, normal, and control. Mice in the transplantation and control groups received parental BALB/c lymphocytes intravenously. Thirty days after injection of the lymphocytes, each F1 mouse in the transplantation group received a fetal thymus graft under the right renal capsule. Mice in the control group did not receive thymus transplant and mice in the normal group received neither parental lymphocytes nor a fetal thymus graft. All mice received cyclosporin A at 2 mg/kg daily for the first 12 days after transplantation or starting on the corresponding day. Thirty days after thymus transplantation, F1 mice were sacrificed and expression of Fas in peripheral blood lymphocytes was analyzed by flow cytometry. RESULTS: The percentage of CD4Fas+ T lymphocytes was significantly increased in the control group and the transplantation group compared with the normal group. Corresponding significant differences were observed for CD8Fas+, CD4CD25Fas', and CD45RB(low)Fas+ T lymphocytes. CONCLUSIONS: In this study, we found that fetal thymus transplantation had a significant effect on the expression of Fas by T cell subtypes in SLE mice.

Retarding field analyzer for the EAST plasma boundary.

A novel bi-directional Retarding Field Analyzer (RFA) probe has been installed on a fast reciprocating drive system on the Experimental Advanced Superconducting Tokamak (EAST) to measure the ion temperature and fast electron fluxes. A Langmuir probe assembly was added on the top of the RFA head to control the RFA position relative to the last closed flux surface and to have a possibility to measure the electron density and temperature as well. Except the ion temperature, the fast electron fluxes from both ion and electron drift sides have been measured during lower hybrid current drive. The RFA probe has been also used to measure the fast electrons associated with edge localized modes (ELMs), indicating their substantial presence in the scrape-off-layer plasma of EAST.

Status of neutron diagnostics on the experimental advanced superconducting tokamak.

Neutron diagnostics have become a significant means to study energetic particles in high power auxiliary heating plasmas on the Experimental Advanced Superconducting Tokamak (EAST). Several kinds of neutron diagnostic systems have been implemented for time-resolved measurements of D-D neutron flux, fluctuation, emission profile, and spectrum. All detectors have been calibrated in laboratory, and in situ calibration using 252Cf neutron source in EAST is in preparation. A new technology of digitized pulse signal processing is adopted in a wide dynamic range neutron flux monitor, compact recoil proton spectrometer, and time of flight spectrometer. Improvements will be made continuously to the system to achieve better adaptation to the EAST's harsh γ-ray and electro-magnetic radiation environment.