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.

[A case of sclerocornea combined with open-angle glaucoma].

A patient complained of progressive visual acuity decline in the left eye for 3 years was admitted. The appearance of the patient was bilateral microcornea. After ocular ultrasonography, ultrasound biomicroscopy, etc, the patient was diagnosed as sclerocornea of the left eye with open-angle glaucoma. Trabeculectomy of the left eye was performed after drug treatment failed, and there were no surgical complications. The intraocular pressure of the left eye was normal and the anterior chamber was well formed 6 months after surgery.

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.

[Evaluation of CT-guided iodine-125 seeds brachytherapy for intracranial malignant tumors under control of target and dose].

Objective: To assess the efficacy and safety of CT-guided iodine-125 seeds in the treatment of intracranial malignancies under control of target and dose. Methods: From November 2003 to May 2016, with the clinical data of 412 operations on 310 patients in 12 hospitals in the past 14 years, this study analyzed the method of CT guided iodine-125 particles brachytherapy in the treatment of intracranial malignant tumors and evaluated the efficacy and complications. Stratification analysis of intracranial malignant tumors was performed. Results: Overall survival (OS) of patients with single brain metastases, low-grade glioma, high-grade gliomas, recurrence after surgery, recurrence after radiotherapy and others were 19, 67, 41, 26, 23, 46 months respectively.And the progression free time (PFS) of patients with single brain metastases, low-grade glioma, high-grade gliomas, recurrence after surgery, recurrence after radiotherapy and others were 19, 42, 6, 9, 11, 12 months respectively.Various complications were observed with a relatively low incidence of 10.4%.Three cases deceased at an interval of 7-45 days after treatment. Conclusions: For patients with intracranial malignancies, iodine-125 seeds brachytherapy could achieve a satisfactory treatment efficacy with tolerated complications.Iodine-125 seeds brachytherapy may act as a first-line regimen.

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.

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.

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.

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.

Electromagnetic interference reduction design of alternating integrator for EAST.

An alternating integrator has been designed for the Experimental Advanced Superconducting Tokamak that is intended for long pulse operation of up to 1000 s. The electromagnetic operating environment for the device is so complex that it could affect the performance of the integrator. The new integrator system is carefully designed and actualized based on specific reduced electromagnetic interference requirements, which were formulated based on consideration of processing of the input signals, the isolation properties, and the circuit board layout and grounding. The developed integrator shows excellent electromagnetic compatibility and low-drift properties.

[Determination of protocatechuic acid in Blumea riparia (Bl.) DC. by RP-HPLC].

OBJECTIVE: To determine the content of protocatechuic acid in Blumea riparia by RP-HPLC. METHOD: mu-Bondapak C18 column was used, mobile phase consisted of methanol-water-glacial acetic acid(19:80:1) and detection was performed at UV 260 nm. RESULT: The standard curve was linear in the range of 3.31-41.8 micrograms.ml-1. The correlation coefficient was 0.9999. The average recovery rate and RSD were 98.05% and 1.94% (n = 6) respectively. CONCLUSION: The method provides scientific indexes for quality control of riparia.

New dual gas puff imaging system with up-down symmetry on experimental advanced superconducting tokamak.

Gas puff imaging (GPI) offers a direct and effective diagnostic to measure the edge turbulence structure and velocity in the edge plasma, which closely relates to edge transport and instability in tokamaks. A dual GPI diagnostic system has been installed on the low field side on experimental advanced superconducting tokamak (EAST). The two views are up-down symmetric about the midplane and separated by a toroidal angle of 66.6°. A linear manifold with 16 holes apart by 10 mm is used to form helium gas cloud at the 130×130 mm (radial versus poloidal) objective plane. A fast camera is used to capture the light emission from the image plane with a speed up to 390,804 frames/s with 64×64 pixels and an exposure time of 2.156 µs. The spatial resolution of the system is 2 mm at the objective plane. A total amount of 200 Pa.L helium gas is puffed into the plasma edge for each GPI viewing region for about 250 ms. The new GPI diagnostic has been applied on EAST for the first time during the recent experimental campaign under various plasma conditions, including ohmic, L-mode, and type-I, and type-III ELMy H-modes. Some of these initial experimental results are also presented.