A high-density and high-confinement tokamak plasma regime for fusion energy.

The tokamak approach, utilizing a toroidal magnetic field configuration to confine a hot plasma, is one of the most promising designs for developing reactors that can exploit nuclear fusion to generate electrical energy1,2. To reach the goal of an economical reactor, most tokamak reactor designs3-10 simultaneously require reaching a plasma line-averaged density above an empirical limit-the so-called Greenwald density11-and attaining an energy confinement quality better than the standard high-confinement mode12,13. However, such an operating regime has never been verified in experiments. In addition, a long-standing challenge in the high-confinement mode has been the compatibility between a high-performance core and avoiding large, transient edge perturbations that can cause very high heat loads on the plasma-facing-components in tokamaks. Here we report the demonstration of stable tokamak plasmas with a line-averaged density approximately 20% above the Greenwald density and an energy confinement quality of approximately 50% better than the standard high-confinement mode, which was realized by taking advantage of the enhanced suppression of turbulent transport granted by high density-gradients in the high-poloidal-beta scenario14,15. Furthermore, our experimental results show an integration of very low edge transient perturbations with the high normalized density and confinement core. The operating regime we report supports some critical requirements in many fusion reactor designs all over the world and opens a potential avenue to an operating point for producing economically attractive fusion energy.

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.

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.

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.

Non-inductive vertical position measurements by Faraday-effect polarimetry on EAST tokamak.

Vertical instability control in an elongated plasma is highly desirable for a tokamak reactor. A multi-channel 694 GHz far-infrared laser-based polarimeter-interferometer system has been used to provide a non-inductive vertical position measurement in the long-pulse EAST tokamak. A detailed comparison of vertical position measurements by polarimetry and external inductive flux loops has been used to validate Faraday-effect polarimetry as an accurate high-time response vertical position sensor.

[Application of purse string suture with Harmonious Clips and Olympus endoloop in single channel endoscopy for large gastric antrum mucosa defect].

Objective: To evaluate the feasibility and safety of purse string suture with Harmonious Clips and Olympus endoloop in single channel endoscopy for large gastric antrum mucosa defect. Methods: A total of 33 patients who underwent ESD of gastric antrum in single channel endoscopy at the First people's Hospital of Wujiang District from January 2015 to April 2018 were retrospectively analyzed. Everyone had one lesion, and the diameters were all more than 3 cm. After the resection and hemostasis, purse string suture with Harmonious Clips and Olympus endoloop or no suture in study group (n=16) and the control group (n=17). The degree of abdominal pain, postoperative gastrointestinal decompression time, incidence of delayed hemorrhage, postoperative hospital stay and the healing rate were observed and compared. Results: All patients successfully completed resection, no perforation occurred, and all the lesions were resected completely in one time. All patients in the study group were sutured successfully. The abdominal pain score on the first day after operation was (2.7±0.7) in the study group, and (3.6±0.8) in the control group(t=3.686, P=0.001). The mean time of postoperative gastrointestinal decompression was (1.6±0.5) days in the study group, while (2.4±0.7) days in the control group(t=3.675, P=0.001). No delayed bleeding occurred in the study group, while 5 cases in the control group had delayed bleeding. The rate of delayed hemorrhage was 29.4% in control group, 4 cases successfully achieved hemostasis through endoscopy therapy, 1 case was given surgical intervention after ineffective endoscopic hemostasis(P=0.044). The average postoperative hospital stay were (6.2±1.1) days and (5.9±2.0) days respectively (t=0.423, P=0.675). Two months after the operation, the two groups of patients reviewed the gastroscopy, the results showed that, all wounds in the study group were healed completely, the healing rate was 100%. There were 6 cases of incomplete wound healing in the control group, the healing rate was 64.7%(P=0.018). No recurrence was found after 6 months of operation through reviewing gastroscopy. Conclution: It indicates good feasibility and efficacy about the purse string suture with Harmonious Clip and Olympus endoloop in single channel endoscopy for large gastric antrum mucosa defect. It is safe and reliable, worth of being generalized.

Metformin regulates tight junction of intestinal epithelial cells via MLCK-MLC signaling pathway.

OBJECTIVE: To observe the effect of metformin on the tight junction of intestinal epithelial cells and its relevant mechanism. MATERIALS AND METHODS: Caco-2 cell monolayers were incubated with or without tumor necrosis factor-α (TNF-α) (10 ng/mL) in the absence or presence of indicated concentrations of metformin. Transepithelial electrical resistance (TEER) was measured at various time points. Caco-2 cell permeability was assessed using fluorescein permeability test. Immunofluorescence was used to detect the distribution of tight junction protein. Western blotting and Real-Time PCR were used to detect the expression of tight junction protein and Myosin light chain kinase (MLCK)-Myosin light chain (MLC) signaling pathway. RESULTS: Metformin attenuates the effects of TNF-α on Caco-2 cell TEER and paracellular permeability, prevents TNF-α-induced morphological disruption of tight junctions, ameliorates the inhibiting effect of TNF-α on epithelial tight junction-related protein expression and suppresses the TNF-α-induced increase in MLCK production. CONCLUSIONS: Metformin can stabilize and up-regulate tight junction protein by inhibiting MLCK-MLC signaling pathway, thus ameliorating the tight junction of intestinal epithelial cells.

[Textual research on the origin and producing area of Baitouweng (Radix Pulsatillae)].

Baitouweng (Pulsatilla Root), a commonly used traditional Chinese medicine, was first recorded in Shen nong ben cao jing (Shennong's Classic of Materia Medica) . Pulsatilla chinensis (Bunge) Regel from Ranunculaceae had become the authentic source for the Baitouweng since the Song Dynasty, which was consistent with the Radix Pulsatillae collected in the Chinese Pharmacopoeia. Chuzhou, Anhui province, being regarded as the main producing area in ancient times, had been its genuine producing area since the period of Republic of China. From the Tang Dynasty to Ming Dynasty, the origin of Baitouweng recorded in the works of Chinese materia medica could also include P. cernua, P. dahurica and P. ambigua. Therefore, P. chinensis in Chuzhou, with large quantity and high quality, is a superior resource that need to increase its protection and further studies, whereas P. cernua, P. dahurica and P. ambigua have better to be used as local drugs.

Initial measurements of plasma current and electron density profiles using a polarimeter/interferometer (POINT) for long pulse operation in EAST (invited).

A double-pass, radially viewing, far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique has been implemented for diagnosing the plasma current and electron density profiles in the Experimental Advanced Superconducting Tokamak (EAST). POINT has been operated routinely during the most recent experimental campaign and provides continuous 11 chord line-integrated Faraday effect and density measurement throughout the entire plasma discharge for all heating schemes and all plasma conditions (including ITER relevant scenario development). Reliability of both the polarimetric and interferometric measurements is demonstrated in 25 s plasmas with H-mode and 102 s long-pulse discharges. Current density, safety factor (q), and electron density profiles are reconstructed using equilibrium fitting code (EFIT) with POINT constraints for the plasma core.

Halo current diagnostic system of experimental advanced superconducting tokamak.

The design, calibration, and installation of disruption halo current sensors for the Experimental Advanced Superconducting Tokamak are described in this article. All the sensors are Rogowski coils that surround conducting structures, and all the signals are analog integrated. Coils with two different cross-section sizes have been fabricated, and their mutual inductances are calibrated. Sensors have been installed to measure halo currents in several different parts of both the upper divertor (tungsten) and lower divertor (graphite) at several toroidal locations. Initial measurements from disruptions show that the halo current diagnostics are working well.

Faraday-effect polarimeter-interferometer system for current density measurement on EAST.

A multichannel far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique is under development for current density and electron density profile measurements in the EAST tokamak. Novel molybdenum retro-reflectors are mounted in the inside wall for the double-pass optical arrangement. A Digital Phase Detector with 250 kHz bandwidth, which will provide real-time Faraday rotation angle and density phase shift output, have been developed for use on the POINT system. Initial calibration indicates the electron line-integrated density resolution is less than 5 × 10(16) m(-2) (∼2°), and the Faraday rotation angle rms phase noise is <0.1°.

Analysis of uncertainty in equilibrium reconstruction in the EAST superconducting tokamak.

The analysis of uncertainties of magnetic measurements in equilibrium reconstruction is carried out on the EAST (Experimental Advanced Superconducting Tokamak) tokamak. It is shown that uncertainties of magnetic diagnostics are about 0.2% and 10 mWb for flux loops and 0.6% and 20 G for magnetic probes. Analyzing the sensitivity of the magnetic data uncertainty in the plasma shape reconstruction is presented, based on EFIT fixed boundary and fitting mode and applying overall uncertainty as fitting weight in EFIT. It is found that reconstruction uncertainties are ranged in 0.5-1.4 cm for 6 control segments, less than 0.8 cm for X-points, and 1.0-1.6 cm for strike points with 95% confidence, in the last experimental campaign on the EAST tokamak.

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.

Poloidal beta and internal inductance measurement on HT-7 superconducting tokamak.

Poloidal beta beta(theta) and internal inductance l(i) measurements are very important for tokamak operation. Much more plasma parameters can be inferred from the two parameters, such as the plasma energy confinement time, the plasma toroidal current profile, and magnetohydrodynamics instability. Using diamagnetic and compensation loop, combining with poloidal magnetic probe array signals, poloidal beta beta(theta) and internal inductance l(i) are measured. In this article, the measurement system and arithmetic are introduced. Different experimental results are given in different plasma discharges on HT-7 superconducting tokamak.

[Detection of serum hepatitis B virus large envelope protein and its relationship with viral replication.].

BACKGROUND: To explore the significance of HBV large envelope protein (LHBs) in diagnosing HBV replication in chronic hepatitis B patients. METHODS: Serum HBV DNA was quantitively detected by using real-time polymerase chain reaction (RT-PCR), the LHBs and Pre-S1 were detected by using enzyme linked immunosorbent assay (ELISA) and HBV markers were detected by time differentiate immunofluorescence assay in 340 serum samples collected from chronic hepatitis B patients. RESULTS: Serum LHBs level was closely correlated with number of HBV DNA copies (r=0.899, P=0.0380). There was no significant difference between positive rate of LHBs and that of HBV DNA in different HBeAg pattern (P>0.05); the positive rate of LHBs was 83.15%, which was higher than that of Pre-S1 and HBeAg which were 50.54% and 54.48%, respectively. There was significant difference (P less than 0.05). CONCLUSION: The level of serum LHBs can be used to estimate the state of HBV replication and the sensitivity was superior to both Pre-S1 and HBeAg. So it may be used as a new serological marker to detect HBV replication.