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.

Wide Operational Windows of Edge-Localized Mode Suppression by Resonant Magnetic Perturbations in the DIII-D Tokamak.

Edge-localized mode (ELM) suppression by resonant magnetic perturbations (RMPs) generally occurs over very narrow ranges of the plasma current (or magnetic safety factor q_{95}) in the DIII-D tokamak. However, wide q_{95} ranges of ELM suppression are needed for the safety and operational flexibility of ITER and future reactors. In DIII-D ITER similar shape plasmas with n=3 RMPs, the range of q_{95} for ELM suppression is found to increase with decreasing electron density. Nonlinear two-fluid MHD simulations reproduce the observed q_{95} windows of ELM suppression and the dependence on plasma density, based on the conditions for resonant field penetration at the top of the pedestal. When the RMP amplitude is close to the threshold for resonant field penetration, only narrow isolated magnetic islands form near the top of the pedestal, leading to narrow q_{95} windows of ELM suppression. However, as the threshold for field penetration decreases with decreasing density, resonant field penetration can take place over a wider range of q_{95}. For sufficiently low density (penetration threshold) multiple magnetic islands form near the top of the pedestal giving rise to continuous q_{95} windows of ELM suppression. The model predicts that wide q_{95} windows of ELM suppression can be achieved at substantially higher pedestal pressure in DIII-D by shifting to higher toroidal mode number (n=4) RMPs.

Fast island phase identification for tearing mode feedback control on J-TEXT tokamak.

A new method to control the tearing mode (TM) in tokamaks has been proposed [Q. Hu and Q. Yu, Nucl. Fusion 56, 034001 (5pp.) (2016)], according to which, the external resonant magnetic perturbation needs to be applied in certain magnetic island phase regions. Therefore, it is very important to identify the helical phase of magnetic islands in real time. The TM in tokamak plasmas is normally rotating and carries magnetic oscillations, which are known as Mirnov oscillations and can be detected by Mirnov probes. When the O-point or X-point of the magnetic island passes through the probe, the signal will experience a zero-crossing. A poloidal Mirnov probe array and a corresponding island phase identification method are presented. A field-programmable gate array is used to provide the magnetic island helical phase in real time by using multichannel zero crossing detection. This system has been developed on the J-TEXT tokamak and works well. This paper introduces the establishment of the fast magnetic island phase identifying system.

Structure of Bergman-type W-TiZrNi approximants to quasicrystal, analyzed by lattice inversion method.

The combined interatomic pair potentials of TiZrNi, including Morse and Inversion Gaussian, are successfully built by the lattice inversion method. Some experimental controversies on atomic occupancies of sites 6-8 in W-TiZrNi are analyzed and settled with these inverted potentials. According to the characteristics of composition and site preference occupancy of W-TiZrNi, two stable structural models of W-TiZrNi are proposed and the possibilities are partly confirmed by experimental data. The stabilities of W-TiZrNi mostly result from the contribution of Zr atoms to the phonon densities of states in lower frequencies.

Analytical compensation of axisymmetric equilibrium fluxes picked up by locked mode detectors in tokamaks.

In the detection of locked modes using saddle loops, the problem of how to remove the axisymmetric equilibrium flux picked up by the loops has still to be solved. The problem becomes more difficult when there are conductive structures located near the saddle loops. In this paper, we present an analytical model based on lumped eddy current circuits and use it to interpret the measured equilibrium flux and the corresponding eddy current fluxes. Using this model, precise compensation for fluxes induced by the horizontal field coils and the toroidal field coils, with relative errors of less than 1%, has been realized for the saddle loops in the Joint Texas Experimental Tokamak. This paper also presents a new method to compensate for the detection of equilibrium flux by the locked mode detector.

Measurement of 2∕1 intrinsic error field of Joint TEXT tokamak.

The amplitude and spatial phase of the intrinsic error field of Joint TEXT (J-TEXT) tokamak were measured by scanning the spatial phase of an externally exerted resonant magnetic perturbation and fitting the mode locking thresholds. For a typical plasma with current of 180 kA, the amplitude of the 2∕1 component of the error field at the plasma edge is measured to be 0.31 G, which is about 1.8 × 10(-5) relative to the base toroidal field. The measured spatial phase is about 317° in the specified coordinate system (r, θ, ϕ) of J-TEXT tokamak. An analytical model based on the dynamics of rotating island is developed to verify the measured phase.

Clear lens phacoemulsification with continuous curvilinear capsulorhexis and foldable intraocular lens implantation for the treatment of a patient with bilateral anterior lenticonus due to Alport syndrome.

The case of a 29-year-old man is reported who presented with a gradually progressive, painless decrease in vision over 10 years. Anterior segment examination with a slit lamp revealed anterior lenticonus in both eyes. The patient had previously been diagnosed with bilateral sensorineural deafness, however investigations revealed microscopic haematuria and renal insufficiency that subsequently led to a diagnosis of classical Alport syndrome. Since the patient's quality of vision was severely affected by the bulging anterior lens capsule, surgical treatment was required. Clear lens phacoemulsification with continuous curvilinear capsulorhexis and foldable intraocular lens implantation were performed in each eye 2 days apart. One week after surgery, visual acuity was excellent in both eyes. Clear lens phacoemulsification with continuous curvilinear capsulorhexis and foldable intraocular lens implantation was a safe and effective therapeutic choice in this patient for the management of anterior lenticonus due to Alport syndrome.

Concentrated point defects in and order-disorder transition temperature of intermetallic compounds.

In this Letter, a scheme that combines first-principles methods, statistical mechanics, and a self-consistent procedure is presented to evaluate the point defect concentrations in intermetallic compounds. The obtained point defect concentrations can be further used to predict the order-disorder transformation temperature.

[Study on the variation and mechanism of diameter of nailfold capillary and its blood flow speed in patient with chronic pain syndrome].

Diameter of nailfold capillaries and their blood flow speed in 90 patients with pain syndrome were measured accurately by using YJD clinical microcirculatory image analyser, and the data obtained were compared with that of 31 normal subjects. The results showed (1) Shortening of capillary loop and slow down of blood flow were revealed in patients no matter where the location of pain was; (2) The disturbance of microcirculation was more prominent in case of chronic pain patient, manifested chiefly as slow down of blood flow speed (0.19 +/- 0.09 mm/s in afferent branch) and increase of loop diameter (15.86 +/- 6.50 microns), as compared with those in normal subjects (0.35 +/- 0.13 mm/s and 14.01 +/- 3.31 microns respectively), the difference were significant, P < 0.01; (3) Typing according to Syndrome Differentiation of TCM, the afferent loop diameter of the Blood Stasis type were 9.23 +/- 1.65 microns, it was significantly different from that of other types; and the blood flow speed of this group was markedly slowing down (0.18 +/- 0.08 mm/s in afferent branch), the change was of significant difference in comparing with normal group, P < 0.01. Authors considered that the mechanism of changes in microcirculation was related to increase of blood viscosity and spasm or diastole of capillaries induced by neurohumoral regulation, and many humoral factors, as histamine, may take part in this procedure.