Preparation of a beam emission spectroscopy diagnostic based on a Lyman-alpha line to diagnose core and edge-plasma density fluctuation on the HL-2A tokamak

In this article,the design of a Lyman-alpha-based beam emission spectroscopy(LAB)diagnostic on the HL-2A tokamak has been proposed for the first time.The purpose of this novel diagnostic is to measure density fluctuations of tokamak plasma.The light-collection system of LAB,which consists of the first mirror and two groups of coaxial double-mirror telescopes,can realize a twosegmented viewing field ofρ=0–0.2 andρ=0.75–1,which is optimized to measure plasma density fluctuation,not only in the edge transport barrier region but also in the internal transport barrier region,to investigate the underlying physics of turbulence in tokamaks.Spectrometers are developed to separate out the Doppler-shifted target line(122.03 and 122.17 nm)from the background Lyman-alpha line(121.53 nm).Here,30 Core-LAB channels and 30 Edge-LAB channels are under development on the HL-2A tokamak.It has high radial spatial resolutions of about 2.7 mm and 3.3 mm for the core and edge channels,respectively.Taking the high light intensity of this Lyman-alpha line into account,temporal resolution of 200 k Hz can be ensured by broad bandwidth amplifiers.This high spatio-temporal resolution makes LAB a potential keen tool to experimentally investigate tokamak plasma physics.

Progress of Lyman-alpha-based beam emission spectroscopy(Ly BES)diagnostic on the HL-2A tokamak

An edge Lyman-alpha-based beam emission spectroscopy(LyBES)diagnostic,using a heating NBI(neutral beam injection)system,is currently under development on the HL-2A tokamak.The 20-channel edge LyBES,which is intended to measure the density fluctuation in plasma edge(from R=1960 mm to R=2026 mm)with an improved spatial resolution of 3.3 mm,is a complement to the existing conventional beam emission spectroscopy(BES)diagnostic.In this article,we introduce the progress of LyBES diagnostic,including the collection optics,the monochromator,and the detector system.The reflectance of the collection mirrors is measured to be~82%at 122 nm,and the aberration geometrical radius of the collection optics is tested to be~150μm in the aimed area.The linear dispersion of the LyBES monochromator is designed to be~0.09 nm mm^(-1).The bandwidth of the detector system with the 5×10^(7)V A^(-1)preamplifier gain is measured to be~280 kHz,and the peak-to-peak noise of the detector system is tested to be~16 mV.The finalized design,components development and testing of the LyBES diagnostic have been completed at present,and an overall performance of the LyBES diagnostic is to be confirmed in the next HL-2A campaign.

An improved TDE technique for derivation of 2D turbulence structures based on GPI data in toroidal plasma

This paper reports an improved time-delay estimation(TDE)technique for the derivation of turbulence structures based on gas-puff imaging data.The improved TDE technique,integrating an inverse timing search and hierarchical strategy,offers superior accuracy in calculating turbulent velocity field maps and analyzing blob dynamics,which has the power to obtain the radial profiles of equilibrium poloidal velocity,blob size and its radial velocity,even the fluctuation analysis,such as geodesic acoustic modes and quasi-coherent mode,etc.This improved technique could provide important 2D information for the study of edge turbulence and blob dynamics,advancing the understanding of edge turbulence physics in fusion plasmas.

Optical design of a novel near-infrared phase contrast imaging(NI-PCI)diagnostic on the HL-2A tokamak

The optical design of near-infrared phase contrast imaging(NI-PCI)diagnosis on HL-2A is introduced in this paper.This scheme benefits from the great progress of near-infrared laser technology and is a broadening of traditional phase contrast technology.This diagnostic can work as a keen tool to measure plasma wavenumber spectra by inferring string-integrated plasma density fluctuations.Design of both the front optical path which is the path before the laser transmitting into the tokamak plasma and the rear optics which is the path after the laser passing through the plasma is detailed.The 1550 nm laser is chosen as the probe beam and highprecision optical components are designed to fit the laser beam,in which a phase plate with a 194-nm-deep silver groove is the key.Compared with the conventional 10.6μm laser-based PCI system on HL-2A,NI-PCI significantly overcomes the unwanted phase scintillation effect and promotes the measurement capability of high-wavenumber turbulence with an increased maximal measurable wavenumber from 15 cm^(-1)to 32.6 cm^(-1).

A dual-route optical emission spectroscopy diagnostic with wide spectral range and high wavelength resolution on HL-2A tokamak

A dual-route optical emission spectroscopy(D-OES)diagnostic is newly developed to monitor the optical emission from the X-point plasma region on the HL-2 A tokamak.This diagnostic is composed of an imaging system,a beam-splitting system for dual-route measurements,fiber bundles,a spectrometer system,and a control and acquisition system.One route is used to obtain wide-spectral-range spectra,and the other route is used to acquire high-wavelengthresolution line shapes.The spectral resolution of the wide-range spectrometers is 0.8 nm with a coverage of 800 nm(@200-1000 nm).The spectral resolution of the high-resolution spectrometer is 0.01 nm with a coverage of 6 nm(@200-660 nm).The spatial resolution of each route of D-OES is about 4 cm with 11 channels.The temporal resolution is 16 ms at maximum in the single-channel mode.Wide-range spectra(containing Balmer series and a Fulcher band)and highly resolved Ha line shapes are obtained by D-OES in the hydrogen glow discharge in the lab.D-OES measurements are carried out in the high-density deuterium experiments of HL-2A.The electron density n_(e)and deuterium temperature T_(D) in the X-point multifaceted asymmetric radiation from the edge(MARFE)region are derived simultaneously by fitting the measured D_(a) shape.The density n_(e)is observed to increase from~8.7×10^(18)m^(-3)to~7.8×10^(19)m^(-3),and the temperature T_(D)drops from~14.4 eV to~2.3 eV after the onset of MARFE in the discharge#38260.

Atsttrin reduces lipopolysaccharide-induced neuroinflammation by inhibiting the nuclear factor kappa B signaling pathway

Progranulin is closely related to neuronal survival in a neuroinflammatory mouse model and attenuates inflammatory reactions. Atsttrin is an engineered protein composed of three progranulin fragments and has been shown to have an effect similar to that of progranulin. Atsttrin has anti-inflammatory actions in multiple arthritis mouse models, and it protects against further arthritis development. However, whether Atsttrin has a role in neuroinflammation remains to be elucidated. In this study, we produced a neuroinflammatory mouse model by intracerebroventricular injection of 1 μL lipopolysaccharide(10 μg/μL). Atsttrin(2.5 mg/kg) was administered via intraperitoneal injection every 3 days over a period of 7 days before intracerebroventricular injection of 1 μL lipopolysaccharide(10 μg/μL). In addition, astrocyte cultures were treated with 0, 100 or 300 ng/mL lipopolysaccharide, with 200 ng/mL Atsttrin simultaneously. Immunohistochemistry, enzyme-linked immunosorbent assay and real-time reverse transcription-polymerase chain reaction were performed to examine the protein and mRNA levels of inflammatory mediators and to assess activation of the nuclear factor kappa B signaling pathway. Progranulin expression in the brain of wild-type mice and in astrocyte cultures was increased after lipopolysaccharide administration. The protein and mRNA expression levels of tumor necrosis factor-α, interleukin-1β and inducible nitric oxide synthase were increased in the brain of progranulin knockout mice after lipopolysaccharide administration. Atsttrin treatment reduced the lipopolysaccharide-induced increase in the protein and mRNA levels of tumor necrosis factor-α, interleukin-1β, matrix metalloproteinase-3 and inducible nitric oxide synthase in the brain of progranulin knockout mice. Atsttrin also reduced the expression of cyclooxygenase-2, inducible nitric oxide synthase and matrix metalloproteinase 3 mRNA in lipopolysaccharide-treated astrocytes in vitro, and decreased the concentration of tumor necrosis factor α and interleukin-1β in the supernatant. Furthermore, Atsttrin significantly reduced the levels of phospho-nuclear factor kappa B inhibitor α in the brain of lipopolysaccharide-treated progranulin knockout mice and astrocytes, and it decreased the expression of nuclear factor kappa B2 in astrocytes. Collectively, our findings show that the anti-neuroinflammatory effect of Atsttrin involves inhibiton of the nuclear factor kappa B signaling pathway, and they suggest that Atsttrin may have clinical potential in neuroinflammatory therapy.

Scaling Laws of Heat Flux Width in the HL-2A Closed Divertor Tokamak

The scaling law of divertor heat flux width is one of the key topics of magnetic confinement fusion,which is almost inversely proportional to the poloidal magnetic field on some opened divertor tokamaks.This work focuses on the scaling laws of the closed divertor heat flux width in the HL-2 A tokamak under different discharge conditions,such as the Ohmic,L-and H-modes.The results indicate that there are basic similarities of the scaling laws of the heat flux width between the opened and closed divertors.However,a larger spreading width in the private flux region is found,which is relevant to a small expansion factor of the magnetic flux in the closed divertor.

Evolution of edge turbulent transport induced by L-mode detachment in the HL-2A tokamak

This paper presents the characteristics of L-mode detachment,together with the behavior of edge turbulent transport and plasma confinement on the HL-2A tokamak.Partially detached and pronounced detached states have been achieved in L-mode plasma.Stored energy was maintained before and after detachment.Edge turbulence and its transport have increased obviously in the partially detached state.In the pronounced detached state,redistribution of the density and temperature profiles due to detachment leads to low amplitude of electron temperature and pressure,as well as very weak edge turbulence and transport.Despite strong plasma radiation in the pronounced detached state,reduced edge turbulent transport contributes to maintaining stored energy in detached L-mode plasma in HL-2A.Different detachment states play an important role in the redistribution of density and temperature profiles,which requires further study.

Impact of resonant magnetic perturbation on blob motion and structure using a gas puff imaging diagnostic on the HL-2A tokamak

The impact of resonant magnetic perturbation(RMP)on blob motion and structure in the SOL of the HL-2A tokamak is studied using a gas puff imaging diagnostic.Ellipse fitting is applied to study the structure and motion of blobs quantitatively.The radial locations,amplitudes and scale sizes of blobs are obtained based on the fitted ellipse.Furthermore,based on the measurement of blob location,the radial and poloidal velocities of blobs are calculated.With the application of RMP,the edge poloidal shear flow is significantly weakened and the wave number spectrum changes from quasisymmetric to significantly up-down asymmetric.The application of RMP also causes the detected blob location to be much further into the far scrape-off layer(SOL)and increases the blob amplitude.Blob poloidal velocity in the SOL is slowed.Larger-size and longer-lifetime blobs are observed with RMP.With the application of RMP,stronger-amplitude and larger-size blobs are detected in the far SOL and they may cause a more serious erosion problem to the first wall.

高蛋白饮食通过调控肠道菌群影响肥胖相关研究进展

肠道菌群与肥胖症的发生、发展密切相关,饮食模式可通过影响宿主的肠道菌群参与机体能量代谢,进而发挥减重作用。高蛋白饮食不仅能改变肠道菌群的组成结构与肠道微生态的多样性,在肠道内还可被菌群进一步分解产生色氨酸、吲哚、5-羟色胺等一系列代谢产物,对人体的脑-肠轴及肠道黏膜免疫发挥调控作用,可有效降低肥胖患者体重,并改善机体的慢性低度炎症与代谢状态,为肥胖症的防治提供新的思路。

肠道菌群与肥胖发病机制的关系

肥胖作为威胁大众健康的全球性问题,不仅会导致包括2型糖尿病、冠心病、高血压、骨关节炎等在内的诸多疾病,也给社会造成了严重的经济负担。肠道菌群作为携带人体"第二基因"的"隐形器官",参与了人体的营养和能量的代谢过程,不仅可通过影响机体的能量代谢吸收、肠壁通透性介导肥胖的发生、发展,也可以通过参与机体碳水化合物、胆汁酸、胆碱等的代谢过程,产生小分子化学物质,与人体的组织器官相互作用,形成肠道菌群-肠-靶器官轴,介导肥胖症的发生发展。

Tomography of emissivity for Doppler coherence imaging spectroscopy diagnostic in HL-2A

A newly developed Doppler coherence imaging spectroscopy(CIS)technique has been implemented in the HL-2 A tokamak for carbon impurity emissivity and flow measurement.In CIS diagnostics,the emissivity and flow profiles inside the plasma are measured by a camera from the line-integrated emissivity and line-averaged flow,respectively.A standard inference method,called tomographic inversion,is necessary.Such an inversion is relatively challenging due to the ill-conditioned nature.In this article,we report the recent application and comparison of two different tomography algorithms,Gaussian process tomography and Tikhonov tomography,on light intensity measured by CIS,including feasibility and benchmark studies.Finally,the tomographic results for real measurement data in HL-2A are presented.

Observation of blobs using a gas puff imaging diagnostic on the HL-2A tokamak

A gas puff imaging(GPI) diagnostic has been developed and applied to measure edge plasma turbulence on the HL-2A tokamak.The principle and experimental setup of GPI are described.GPI is applied to investigate blobs in the edge and scrape-off layer.Statistical characterizations of GPI line emission intensity are calculated, including the probability density functions(PDFs),skewness, and kurtosis of the intensity, which are found to be consistent with measurements by Langmuir probes.Besides, the track of blob motions is recorded by time sequence of individual frames.The characteristics of the original images and the relatively high-frequency(>10 kHz)/low-frequency(1–10 kHz) component images are illustrated.The observation of the blob’s structures and high-speed motions proves the success and high performance of the GPI diagnostic.

Progress of plasma density fluctuation measurements with phase contrast imaging on HL-2A tokamak

A CO2 laser-based phase contrast imaging(PCI) diagnostic has been developed on HL-2A tokamak.It can detect line integrated plasma density fluctuations by measuring the phase shift of laser beam after being scattered by the bulk plasma.The diagnosed radial region ranges from ρ≡r/a =0.625 to 0.7.32-channel HgCdTe detectors with alternative-current biased amplifiers are arranged in line at the imaging plane of the optical path.This PCI is able to diagnose density fluctuations with wavenumbers ranging from 2 to 15 cm-1 and the time resolution is better than 2 μs.The first experimental data were achieved in 2018 spring campaign of HL-2A tokamak.High performance is confirmed in different discharging configurations and makes it a keen tool in broadband turbulence investigations.

Effect of edge turbulent transport on scrape-off layer width on HL-2A tokamak

Effect of edge turbulent transport on scrape-off layer(SOL)width has been investigated in Ohmically heated L-mode plasma under limiter configurations on HL-2A tokamak.It has been found that SOL width is doubled when plasma current decreases about 20%.With larger plasma current,E×B shear is stronger and has greater suppression effect on edge turbulent transport.SOL width is larger when power of relative density fluctuation level in the edge region is larger.It is concluded that edge turbulent transport plays a significant role on SOL width.These experimental findings may provide a better understanding and controlling of power exhaust for present and future fusion devices.

Effect of resonant magnetic perturbation on boundary plasma turbulence and transport on J-TEXT tokamak

The effect of resonant magnetic perturbation(RMP) on boundary turbulence and transport in J-TEXT plasma is experimentally investigated.Edge plasma fluctuations in discharges with and without the(m/n=3/1) RMP currents are diagnosed by using Langmuir probe arrays.It was found that fluctuations in the edge and scrape-off layer(SOL) regions decrease with the application of a 6 kA RMP.The broadband turbulence at the radial location of ρ~0.9 which has a characteristic frequency of 40-150 kHz was strongly suppressed when applying RMP,as was the radial turbulent particle flux and blob transport in the near-SOL region.These experimental findings make RMP a promising method of suppressing and controlling turbulence and particle transport in a plasma boundary.

Towards advanced divertor configurations on the J-TEXT tokamak

Developing advanced magnetic divertor configurations to address the coupling of heat and particle exhaust with impurity control is one of the major challenges currently constraining the further development of fusion research.It has therefore become the focus of extensive attention in recent years.In J-TEXT,several new divertor configurations,including the high-field-side single-null poloidal divertor and the island divertor,as well as their associated fundamental edge divertor plasma physics,have recently been investigated.The purpose of this paper is to briefly summarize the latest progress and achievements in this relevant research field on J-TEXT from the past few years.

Experimental study of sheath potential coefficient in the J-TEXT tokamak

Sheath potential coefficient α is a key parameter, which is used to estimate plasma potential(Vp)for edge plasma physics study. Recently, a series of experiments has been carried out under hydrogen plasmas in the J-TEXT tokamak with swept probe, which is employed for current–voltage(I–V) characteristic measurement. Electron temperature is evaluated from I–V curve by three-parameter fitting method, and the electron energy probability function shows that electron distribution is Maxwellian both outside and inside of last closed flux surface(LCFS). Plasma potential is obtained by crossing point between I–V exponential fitting curve and electron saturation current extrapolating line, which is in good agreement with first derivative probe technique. The α coefficient profile in the vicinity of the LCFS is obtained, which is in the range of 2.1–3, and decreases from outside to inside of LCFS.

Comparison between fluctuation of floating potential gradient and velocity of blob structure on HL-2A tokamak

Several results based on the Langmuir probes’data on the HL-2A tokamak are presented.The blob structures’radial and poloidal drift velocities,estimated by the gradient of floating potential and by time delay evaluation,are compared in different line-averaged density and electron cyclotron resonance heating conditions.A positive correlation is observed in the comparison between blobs’radial velocity estimated by the two methods mentioned above,regardless of the situation differences mentioned above.Correlation is also observed in the comparison between the blobs’poloidal velocity estimated by the two methods in different situations,while a shift due to the different line-averaged density is observed.These results imply that the radial gradient of floating potential may have some value as a reference during data analysis in low-parameter discharge.

Mitigation of ELMs by Electrostatic Field in Tokamaks

Mitigation of ELMs by electrostatic field is studied. The perpendicular heating in cyclotron waves tends to pile up the resonant particles toward the low magnetic field side in which a electrostatic field may result [J. Y. Hsu, V. S. Chan, R. W. Harvey, R. Prater, and S. K. Wong, Phys. Rev. Lett. 53, 564 (1984)]. The electrostatic field can make circulating particles trapped or make trapped particles circulating depending on the field direction. The trapped- particle population and bootstrap current change accordantly. Modulating bootstrap current, mitigation of type-1 ELM by the electrostatic field is possible. The electrostatic potential needed for the mitigation is quantitatively estimated. Experiments by either ECRH or biasing are being prepared to verify the theory.