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Impact of T_(i)/T_(e )ratio on ion transport based on east H-mode plasmas

Plasma Science and Technology 2024年第4期26卷 68-78页

作者：刘建文臧庆梁云峰陈佳乐邬潇河 Alexander KNIEPS 扈嘉辉金仡飞张斌储宇奇刘海庆吕波段艳敏李妙辉陈颖杰龚先祖 the east team Institute of Plasma Physics Chinese Academy of SciencesHefei 230031People’s Republic of China University of Science and Technology of China Hefei 230026People’s Republic of China Forschungszentrum Jülich GmbH Institut für Energie-und Klimaforschung-PlasmaphysikPartner of the Trilateral Euregio Cluster(TEC)Jülich 52425Germany

At the east tokamak, the ion temperature(T_(i)) is observed to be clamped around 1.25 keV in electron cyclotron resonance(ECR)-heated plasmas, even at core electron temperatures up to 10 keV(depending on the ECR heating power and the plasma density). This clamping results from the lack of direct ion heating and high levels of turbulence-driven transport. Turbulent transport analysis shows that trapped electron mode and electron temperature gradient-driven modes are the most unstable modes in the core of ECR-heated H-mode plasmas. Nevertheless, recently it was found that the T_(i)/T_(e)ratio can increase further with the fraction of the neutral beam injection(NBI) power, which leads to a higher core ion temperature(Ti0). In NBI heating-dominant H-mode plasmas, the ion temperature gradient-driven modes become the most unstable modes.Furthermore, a strong and broad internal transport barrier(ITB) can form at the plasma core in high-power NBI-heated H-mode plasmas when the T_(i)/T_(e)ratio approaches ~1, which results in steep core Teand Tiprofiles, as well as a peaked neprofile. Power balance analysis shows a weaker Teprofile stiffness after the formation of ITBs in the core plasma region, where Ticlamping is broken,and the core Tican increase further above 2 keV, which is 80% higher than the value of Ticlamping in ECR-heated plasmas. This finding proposes a possible solution to the problem of Ticlamping on east and demonstrates an advanced operational regime with the formation of a strong and broad ITB for future fusion plasmas dominated by electron heating.

关键词： ion temperature clamping transport neutral beam injection stiffness internal transport barrier

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Observation of Doppler shift f_(D) modulated by the internal kink mode using conventional reflectometry in the east tokamak

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Plasma Science and Technology 2024年第3期26卷 1-9页

作者：李恭顺张涛耿康宁文斐叶凯萱徐立清朱翔张学习钟富彬周振杨书琪周子强喻琳兰婷王守信提昂张寿彪刘海庆李国强高翔 the east team Institute of Plasma Physics Chinese Academy of SciencesHefei 230031People's Republic of China Advanced Energy Research Center Shenzhen UniversityShenzhen 518060People's Republic of China University of Science and Technology of China Hefei 230026People's Republic of China

In this paper we present a new experimental observation using a conventional reflectometry technique,poloidal correlation reflectometry(PCR),in the Experimental Advanced Superconducting Tokamak(east).The turbulence spectrum detected by the PCR system exhibits an asymmetry and induced Doppler shift f_(D)during the internal kink mode(IKM)rotation phase.This Doppler shift f_(D)is the target measurement of Doppler reflectometry,but captured by conventional reflectometry.Results show that the Doppler shift f_(D)is modulated by the periodic changes in the effective angle between the probing wave and cutoff layer normal,but not by plasma turbulence.The fishbone mode and saturated long-lived mode are typical IKMs,and this modulation phenomenon is observed in both cases.Moreover,the value of the Doppler shift f_(D)is positively correlated with the amplitude of the IKM,even when the latter is small.However,the positive and negative frequency components of the Doppler shift f_(D)can be asymmetric,which is related to the plasma configuration.A simulated analysis is performed by ray tracing to verify these observations.These results establish a clear link between f_(D)and IKM rotation,and are helpful for studying the characteristics of IKM and related physical phenomena.

关键词： microwave reflectometry Doppler shift internal kink mode

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Experimental study of core MHD behavior and a novel algorithm for rational surface detection based on profile reflectometry in east

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Plasma Science and Technology 2024年第3期26卷 66-75页

作者：叶凯萱周振张涛马九阳王嵎民李恭顺耿康宁吴茗甫文斐黄佳张洋邵林明杨书琪钟富彬高善露喻琳周子强向皓明韩翔张寿彪李国强高翔 the east team Institute of Plasma Physics Hefei Institutes of Physical ScienceChinese Academy of SciencesHefei 230031People's Republic of China University of Science and Technology of China Hefei 230026People's Republic of China Hebei Key Laboratory of Compact Fusion Langfang 065001Peoples Republic of China ENN Science and Technology Development Co. Ltd.Langfang 065001Peoples Republic of China Advanced Energy Research Center Shenzhen UniversityShenzhen 518060People's Republic of China

Microwave reflectometry is a powerful diagnostic that can measure the density profile and localized turbulence with high spatial and temporal resolution and will be used in ITER,so understanding the influence of plasma perturbations on the reflect signal is important.The characteristics of the reflect signal from profile reflectometry,the time-of-flight(TOF)signal associated with the MHD instabilities,are investigated in east.Using a 1D full-wave simulation code by the Finite-DifferenceTime-Domain(FDTD)method,it is well validated that the local density flattening could induce the discontinuity of the simulated TOF signal and an obvious change of reflect amplitude.Experimental TOF signals under different types of MHD instabilities(sawtooth,sawtooth precursors and tearing mode)are studied in detail and show agreement with the simulation.Two new improved algorithms for detecting and localizing the radial positions of the low-order rational surface,the cross-correlation and gradient threshold(CGT)method and the 2D convolutional neural network approach(CNN)are presented for the first time.It is concluded that TOF signal analysis from profile reflectometry can provide a straightforward and localized measurement of the plasma perturbation from the edge to the core simultaneously and may be a complement or correction to the q-profile control,which will be beneficial for the advanced tokamak operation.

关键词： MHD instabilities profile reflectometry rational surface detection convolutional neural network(CNN) east tokamak

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Comparison of transport coefficients before and after density pump-out induced by resonant magnetic perturbation using a BOUT++ six-field model on the east tokamak

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Plasma Science and Technology 2024年第6期26卷 111-119页

作者：邓成成刘子奚夏天阳刘彦君厉鹏程龙飞飞高翔王守信李国强刘海庆臧庆李玖瑛杨康宁吴茗甫尹晓宇李弘谢锦林兰涛毛文哲刘阿娣周楚丁卫星庄革刘万东 the east team Department of Plasma Physics and Fusion Engineering University of Science and Technology of ChinaHefei 230026People’s Republic of China Institute of Plasma Physics Chinese Academy of SciencesHefei 230031People’s Republic of China

Many experiments have demonstrated that resonant magnetic perturbation(RMP) can affect the turbulent transport at the edge of the tokamak. Through the Experimental Advanced Superconducting Tokamak(east) density modulation experiment, the particle transport coefficients were calculated using the experimental data, and the result shows that the particle transport coefficients increase with RMP. In this study, the six-field two-fluid model in BOUT++ is used to simulate the transport before and after density pump-out induced by RMP,respectively referred as the case without RMP and the case with RMP. In the linear simulations,the instabilities generally decreases for cases with RMP. In the nonlinear simulation, ELM only appears in the case without RMP. Additionally, the particle transport coefficient was analyzed,and the result shows that the particle transport coefficient becomes larger for the case with RMP,which is consistent with the experimental conclusion. Moreover, its magnitude is comparable to the results calculated from experimental data.

关键词： BOUT++ resonant magnetic perturbation(RMP) transport coefficients

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The Experimental Advanced Superconducting Tokamak

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Engineering 2021年第11期7卷 1523-1528页

作者： Jiangang Li Yuanxi Wan the east team Institute of Plasma Physics Chinese Academy of SciencesHefei 230031China

1.Introduction New sustainable energy is urgently needed to meet the fastgrowing requirement for clean energy in this century.Nearly 80%of the world’s energy is still generated by burning fossil fuels,resulting in pollution and climate change.To realize long-term sustainable development,it is necessary to explore large-scale new energy sources that do not produce carbon dioxide(CO_(2)),within the next few decades.

关键词： energy Tokamak sustainable

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Observation of Pedestal Plasma Turbulence on east Tokamak

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Plasma Science and Technology 2013年第8期15卷 732-737页

作者：高翔张涛韩翔张寿彪王嵎民刘子奚杨曜刘少承史楠凌必利李建刚 the east team Institute of Plasma Physics Chinese Academy of Sciences

Pedestal plasma turbulence was experimentally studied by microwave reflectometry on east tokamak. The characteristics of edge pedestal turbulence during dithering L-H transition, ELM-free H-mode phase and inter-ELM phase have recently been studied on east. An edge spatial structure of density fluctuation and its dithering temporal evolution is observed for the first time on the east tokamak during the L-H transition phase. A coherent mode usually appears during the ELM-free phase prior to the first ELM on east tokamak. The mode frequency gradually decreases as the pedestal evolves. Analysis shows that the coherent mode is in the pedestal region inside the separatrix. In plasma with type-III ELMs, a precursor mode before ELM is usually observed. The frequency of the precursor was initially about 150 kHz and gradually decreased till the next ELM. The mode amplitude increases or shows saturation before ELM. In the plasma with compound ELMs composed of high and low frequency ELMs, the precursor was also observed before the high frequency ELM while the harmonic oscillations with frequencies of 20 kHz, 40 kHz and 60 kHz appear before the low frequency ELM.

关键词： H-mode pedestal turbulence reflectometry

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Electron Cyclotron Emission Imaging Observations of m/n=1/1 and Higher Harmonic Modes during Sawtooth Oscillation in ICRF Heating Plasma on east

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Chinese Physics Letters 2015年第6期32卷 111-114页

作者： AZA MHussain 高炳西刘万东谢锦林 the east team Key Laboratory of Basic Plasma Physics Department of Modern PhysicsUniversity of Science and Technology of China

The m/n = 1/1 and its higher harmonic modes are observed in sawtooth oscillations by using the novel high- resolution 2D ECE imaging system on the experimental advanced superconducting Tokamak （east）. Higher harmonic modes are appearing for a short time during the crash phase of sawtooth oscillation in lower βp plasma, which is not the preferabie position in the poloidal cross section. These modes generate sharp pressure points on the inversion radius during the crash phase of sawtooth oscillation. Furthermore, reconnection events proceed in two distinctive phases. In the first phase, a small amount of heat is expelled through the weak reconnection while in the second phase the remaining large quantity of heat and particles emerged rapidly from the hot core to the peripheral region of the inversion radius. In addition, these harmonic modes are only found before and after the ICRF pulse, while in the ICRF pulse only the （1,1） mode exists in the sawtooth oscillation.

关键词： Electron Cyclotron Emission Imaging Observations of m/n

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Study on divertor heat flux under n=3 and n=4 resonant magnetic perturbations using infrared thermography diagnostic in east

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Plasma Science and Technology 2022年第10期24卷 30-36页

作者：梁瑞荣龚先祖张斌仰振东贾曼妮孙有文马群张家源胡云禅钱金平 the east team Institute of Plasma Physics Hefei Institutes of Physical ScienceChinese Academy of SciencesHefei 230031People's Republic of China University of Science and Technology of China Hefei 230026People's Republic of China Tongling University Tongling 244000People's Republic of China

Resonant magnetic perturbations(RMPs)with high toroidal mode number n are considered for controlling edge-localized modes(ELMs)and divertor heat flux in future ITER H-mode operations.In this paper,characteristics of divertor heat flux under high-nRMPs(n=3 and 4)in H-mode plasma are investigated using newly upgraded infrared thermography diagnostic in east.Additional splitting strike point(SSP)accompanying with ELM suppression is observed under both RMPs with n=3 and n=4,the SSP in heat flux profile agrees qualitatively with the modeled magnetic footprint.Although RMPs suppress ELMs,they increase the stationary heat flux during ELM suppression.The dependence of heat flux on q_(95)during ELM suppression is preliminarily investigated,and further splitting in the original strike point is observed at q 495=during ELM suppression.In terms of ELM pulses,the presence of RMPs shows little influence on transient heat flux distribution.

关键词： resonant magnetic perturbation(RMP) divertor heat flux strike point splitting infrared thermography diagnostic

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Q-Band X-Mode Reflectometry and Density Profile Reconstruction

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Plasma Science and Technology 2015年第12期17卷 985-990页

作者：屈浩张涛张寿彪文斐王嵎民孔德峰韩翔杨曜高宇黄灿斌蔡剑青高翔 the east team Institute of Plasma Physics Chinese Academy of Sciences

By installing an X-mode polarized Q-band（32-56 GHz） reflectometry at the low field side on east,the zero density cutoff layer was determined and the edge density profile was measured in normally operating plasmas.A Monte Carlo procedure has been developed to analyze the density profiles by considering the error of time delay measured by reflectometry.By combining this Q-band and previously developed V- and W-band reflectometries,the density profiles from edge to core can be measured in most east experiments.The line integrated densities deduced from density profiles measured by reflectometry are consistent with those directly measured by a horizontal interferometer.The density pedestal measured by reflectometry shows a clear crash during an ELM（edge localized mode） event,after which the pedestal gradually increases and recovers in 10 ms and then remains little changed up to the next ELM.

关键词： Reconstruction interferometer fitting normally east deduced considering normalized cutoff localized

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Physical design of a new set of high poloidal mode number coils in the east tokamak

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Plasma Science and Technology 2022年第3期24卷 106-113页

作者：廖亮梁云峰刘少承张华祥戢翔孙有文魏文崟王辉辉钱金平王亮贾曼妮曾龙高翔 the east team Institute of Plasma Physics Hefei Institutes of Physical ScienceChinese Academy of SciencesHefei 230031People's Republic of China University of Science and Technology of China Hefei 230026People's Republic of China Forschungszentrum Jülich GmbH Institut für Energie-und Klimaforschung-PlasmaphysikPartner of the Trilateral Euregio Cluster(TEC)Jülich D-52425Germany International Joint Research Laboratory of Magnetic Confinement Fusion and Plasma Physics State Key Laboratory of Advanced Electromagnetic Engineering and TechnologySchool of Electrical and Electronic EngineeringHuazhong University of Science and TechnologyWuhan 430074People's Republic of China

An external resonant magnetic perturbation(RMP)field,which is an effective method to mitigate or suppress the edge localized mode(ELM),has been planned to be applied on the ELM control issue in ITER.A new set of magnetic perturbation coils,named as high m coils,has been developed for the east tokamak.The magnetic perturbation field of the high m coils is localized in the midplane of the low field side,with the spectral characteristic of high m and wide n,where m and n are the poloidal and toroidal mode numbers,respectively.The high m coils generate a strong localized perturbation field.Edge magnetic topology under the application of high m coils should have either a small or no stochastic region.With the combination of the high m coils and the current RMP coils in the east,flexible working scenarios of the magnetic perturbation field are available,which is beneficial for ELM control exploration on east.Numerical simulations have been carried out to characterize the high m coil system,including the magnetic spectrum and magnetic topology,which shows a great flexibility of magnetic perturbation variation as a tool to investigate the interaction between ELM and external magnetic perturbation.

关键词： resonant magnetic perturbation ELM control tokamak

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