Electron cyclotron emission imaging(ECEI)is a critical diagnostic tool for measuring two-dimensional electron temperature fluctuations.The optical system,a key component of the ECEI diagnostic,determines the spatial r...Electron cyclotron emission imaging(ECEI)is a critical diagnostic tool for measuring two-dimensional electron temperature fluctuations.The optical system,a key component of the ECEI diagnostic,determines the spatial resolution,field of view,and imaging performance of electron temperature fluctuations.In this study,comprehensive laboratory tests and characterizations of the optical system,including the local oscillator(LO)coupling optics and the radio frequency(RF)receiving optics,were conducted to ensure optimal performance during plasma discharge experiments.Laboratory testing of the LO optics revealed that the light intensity at the edge channels reaches 36%of that at the central channels;however,both are sufficient to effectively drive the down-converted mixers.The RF optics focus covers the entire non-harmonic overlap region,corresponding to a normalized plasma minor radius range of ρ=−0.2 to 0.9,and offers three zoom modes:narrow,medium,and wide,with poloidal resolutions of 1.5 cm,1.8 cm,and 2.1 cm,respectively.The characterizations for these zoom modes align well with the optical design specifications.It was observed that the imaging surfaces of all zoom modes are exceptionally flat,indicating high-quality ECEI measurements with excellent spatial resolution.The LO lens,focusing lens,and zoom adjustment lens are capable of remote independent control,which enhances the operational flexibility of the system.Preliminary analyses conducted with the ECEI system successfully captured the two-dimensional structure and spatiotemporal evolution of phenomena such as sawtooth crashes,demonstrating the robust capability of the system to provide valuable insights into plasma dynamics.展开更多
The Doppler backscattering(DBS)diagnostic is widely used to measure the localized density fluctuations and the propagation velocity of turbulent structures.Microwave is launched at a frequency that approaches a cutoff...The Doppler backscattering(DBS)diagnostic is widely used to measure the localized density fluctuations and the propagation velocity of turbulent structures.Microwave is launched at a frequency that approaches a cutoff layer in the plasma at an angle oblique to the cutoff layer.A new Q-band multichannel DBS system based on a comb generator has been designed and tested for application on the HL-3 tokamak.With the comb generator and heterodyne scheme,the stability and flexibility of the new DBS system are improved.The new DBS diagnostic has a high output power(~10 dBm),good power flatness(<5 dB in Q-band),and frequency stability,and the inter-frequency separation is tunable remotely.This article introduces the system design,laboratory test results,and initial experimental results from the HL-3 tokamak.With the help of the newly developed multichannel DBS,the turbulence information can be studied with high temporal and spatial resolution.展开更多
The influence of m/n=2/1(m and n are poloidal and toroidal mode numbers)tearing modes on plasma perpendicular flows and micro-fluctuations has been investigated in HL-2A neutral beam injection heated L-mode plasmas.It...The influence of m/n=2/1(m and n are poloidal and toroidal mode numbers)tearing modes on plasma perpendicular flows and micro-fluctuations has been investigated in HL-2A neutral beam injection heated L-mode plasmas.It is found that the local perpendicular rotation velocity and turbulence energy are modulated by the alternation between the island X-point and O-point of the naturally rotating tearing modes.Cross-correlation analysis indicates that the modulation of density fluctuations by the tearing mode is not only limited to the island region,but also occurs in the edge region near the last closed flux surface.The turbulence exhibits distinct spectral characteristics inside and outside the island region.In addition,it is observed that the particle flux near the strike point is also significantly impacted by the tearing modes.The experimental evidence reveals that there are strong core-edge interactions between the core tearing modes and the edge transport.展开更多
The dynamics of long-wavelength(kθ<1.4 cm^(-1)),broadband(20 kHz–200 kHz)electron temperature fluctuations(Te/Te)of plasmas in gas-puff experiments are observed for the first time in HL-2A tokamak.In a relatively...The dynamics of long-wavelength(kθ<1.4 cm^(-1)),broadband(20 kHz–200 kHz)electron temperature fluctuations(Te/Te)of plasmas in gas-puff experiments are observed for the first time in HL-2A tokamak.In a relatively low density(ne(0)■0.91×10^(19)m^(-3)–1.20×10^(19)m^(-3))scenario,after gas-puffing the core temperature increases and the edge temperature drops.On the contrary,temperature fluctuation drops at the core and increases at the edge.Analyses show the non-local emergence is accompanied with a long radial coherent length of turbulent fluctuations.While in a higher density(ne(0)?1.83×10^(19)m^(-3)–2.02×10^(19)m^(-3))scenario,the phenomena are not observed.Furthermore,compelling evidence indicates that E×B shear serves as a substantial contributor to this extensive radial interaction.This finding offers a direct explanatory link to the intriguing core-heating phenomenon witnessed within the realm of non-local transport.展开更多
This paper discusses edge oscillatory plasma flows, geodesic acoustic mode （GAM） and limit cycle oscillations （LCOs）, which have been measured by Doppler reflectometry prior to the high confinement mode （H-mode）...This paper discusses edge oscillatory plasma flows, geodesic acoustic mode （GAM） and limit cycle oscillations （LCOs）, which have been measured by Doppler reflectometry prior to the high confinement mode （H-mode） in the HL-2A tokamak. The complex relations between the flows and background turbulence have been analyzed. It was observed that the GAM and LCO coexist, and these two flows and turbulence have strong nonlinear interactions during the intermediate confinement phase （I-phase）. Dynamics of the shear flows and turbulence prior to the H-mode shows that the oscillatory flows quench the turbulence along with the increase of the mean E x B flow at the early stage of the I-phase, then the oscillatory flows are damped and the further increased mean flow takes over the role in turbulence suppression. The reduced turbulent transport results in the formation of a steep edge transport barrier. It suggests that the oscillatory flows can initiate the L-H transition through providing a positive feedback for the increase of the mean E × B flow strength.展开更多
Data analysis on tokamak plasmas is mainly based on various diagnostic systems,which are usually modularized and independent of each other.This leads to a large amount of data not being fully and effectively exploited...Data analysis on tokamak plasmas is mainly based on various diagnostic systems,which are usually modularized and independent of each other.This leads to a large amount of data not being fully and effectively exploited so that it is not conducive to revealing the deep physical mechanism.In this work,Bayesian probability inference with machine learning methods have been applied to the electron cyclotron emission and Thomson scattering diagnostic systems on HL-2A/2M,and the effects of integrated data analysis(IDA)on the electron temperature of HL-2A with Bayesian probability inference are demonstrated.A program is developed to infer the whole electron temperature profile with a confidence interval,and the program can be applied in online analysis.The IDA results show that the full profile of the electron temperature can be obtained and the diagnostic information is more comprehensive and abundant with IDA.The inference models for electron temperature analysis are established and the developed programs will serve as an experimental data analysis tool for HL-2A/2M in the near future.展开更多
Over the past several years,high-β_(N) experiments have been carried out on HL-2A.The high-β_(N) is realized using double transport barriers(DTBs)with hybrid scenarios.A stationary high-β_(N) (>2)scenario was ob...Over the past several years,high-β_(N) experiments have been carried out on HL-2A.The high-β_(N) is realized using double transport barriers(DTBs)with hybrid scenarios.A stationary high-β_(N) (>2)scenario was obtained by pure neutral-beam injection(NBI)heating.Transient high performance was also achieved,corresponding to β_(N)≥3,ne/ne_(G)∼0.6,H_(98)∼1.5,f_(bs)∼30%,q_(95)∼4.0,and𝐺∼0.4.The high-β_(N) scenario was successfully modeled using integrated simulation codes,that is,the one modeling framework for integrated tasks(OMFIT).In high-𝛽𝑁plasmas,magnetohydrodynamic(MHD)instabilities are abundant,including low-frequency global MHD oscilla-tion with n=1,high-frequency coherent mode(HCM)at the edge,and neoclassical tearing mode(NTM)and Alfvénic modes in the core.In some high-β_(N) discharges,it is observed that the NTMs with m/n=3/2 limit the growth of the plasma energy and decrease β_(N).The low-n global MHD oscillation is consistent with the coupling of destabilized internal(m/n=1/1)and external(m/n=3/1 or 4/1)modes,and plays a crucial role in triggering the onset of ELMs.Achieving high-β_(N) on HL-2A suggests that core-edge interplay is key to the plasma confinement enhancement mechanism.Experiments to enhance β_(N) will contribute to future plasma operation,such as international thermonuclear experimental reactor.展开更多
基金partly supported by the National MCF Energy R&D Program of China(No.2022YFE03060003)partly by the Chinese National Fusion Project for ITER(No.2024YFE03190000)+2 种基金partly by National Natural Science Foundation of China(No.12405254)partly by the Innovation Program of Southwestern Institute of Physics(No.202301XWCX001-02)partly by Sichuan Science and Technology Program(No.2023ZYD0014).
文摘Electron cyclotron emission imaging(ECEI)is a critical diagnostic tool for measuring two-dimensional electron temperature fluctuations.The optical system,a key component of the ECEI diagnostic,determines the spatial resolution,field of view,and imaging performance of electron temperature fluctuations.In this study,comprehensive laboratory tests and characterizations of the optical system,including the local oscillator(LO)coupling optics and the radio frequency(RF)receiving optics,were conducted to ensure optimal performance during plasma discharge experiments.Laboratory testing of the LO optics revealed that the light intensity at the edge channels reaches 36%of that at the central channels;however,both are sufficient to effectively drive the down-converted mixers.The RF optics focus covers the entire non-harmonic overlap region,corresponding to a normalized plasma minor radius range of ρ=−0.2 to 0.9,and offers three zoom modes:narrow,medium,and wide,with poloidal resolutions of 1.5 cm,1.8 cm,and 2.1 cm,respectively.The characterizations for these zoom modes align well with the optical design specifications.It was observed that the imaging surfaces of all zoom modes are exceptionally flat,indicating high-quality ECEI measurements with excellent spatial resolution.The LO lens,focusing lens,and zoom adjustment lens are capable of remote independent control,which enhances the operational flexibility of the system.Preliminary analyses conducted with the ECEI system successfully captured the two-dimensional structure and spatiotemporal evolution of phenomena such as sawtooth crashes,demonstrating the robust capability of the system to provide valuable insights into plasma dynamics.
基金supported by National Natural Science Foundation of China(Nos.12105087,12275096,and 11922503)the Joint Funds of the National Natural Science Foundation of China(No.U21A20440)the Science and Technology Planning Project of Sichuan Province(No.2023YFG0139)。
文摘The Doppler backscattering(DBS)diagnostic is widely used to measure the localized density fluctuations and the propagation velocity of turbulent structures.Microwave is launched at a frequency that approaches a cutoff layer in the plasma at an angle oblique to the cutoff layer.A new Q-band multichannel DBS system based on a comb generator has been designed and tested for application on the HL-3 tokamak.With the comb generator and heterodyne scheme,the stability and flexibility of the new DBS system are improved.The new DBS diagnostic has a high output power(~10 dBm),good power flatness(<5 dB in Q-band),and frequency stability,and the inter-frequency separation is tunable remotely.This article introduces the system design,laboratory test results,and initial experimental results from the HL-3 tokamak.With the help of the newly developed multichannel DBS,the turbulence information can be studied with high temporal and spatial resolution.
基金the National Key R&D Program of China(Nos.2017YFE0301201 and 2017YFE0301106)National Natural Science Foundation of China(Nos.11705051,11820101004,11875021 and 11775069)the Young Elite Scientists Sponsorship Program by CAST(No.2018QNRC001).
文摘The influence of m/n=2/1(m and n are poloidal and toroidal mode numbers)tearing modes on plasma perpendicular flows and micro-fluctuations has been investigated in HL-2A neutral beam injection heated L-mode plasmas.It is found that the local perpendicular rotation velocity and turbulence energy are modulated by the alternation between the island X-point and O-point of the naturally rotating tearing modes.Cross-correlation analysis indicates that the modulation of density fluctuations by the tearing mode is not only limited to the island region,but also occurs in the edge region near the last closed flux surface.The turbulence exhibits distinct spectral characteristics inside and outside the island region.In addition,it is observed that the particle flux near the strike point is also significantly impacted by the tearing modes.The experimental evidence reveals that there are strong core-edge interactions between the core tearing modes and the edge transport.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFE0301203)the Innovation Program of Southwestern Institute of Physics(Grant No.202301XWCX001)+2 种基金the Sichuan Science and Technology Program(Grant Nos.2023ZYD0014 and 2021YFSY0044)the National Natural Science Foundation of China(Grant No.12175055)the Shenzhen Municipal Collaborative Innovation Technology Program-International Science and Technology Cooperation Project(Grant No.GJHZ20220913142609017)。
文摘The dynamics of long-wavelength(kθ<1.4 cm^(-1)),broadband(20 kHz–200 kHz)electron temperature fluctuations(Te/Te)of plasmas in gas-puff experiments are observed for the first time in HL-2A tokamak.In a relatively low density(ne(0)■0.91×10^(19)m^(-3)–1.20×10^(19)m^(-3))scenario,after gas-puffing the core temperature increases and the edge temperature drops.On the contrary,temperature fluctuation drops at the core and increases at the edge.Analyses show the non-local emergence is accompanied with a long radial coherent length of turbulent fluctuations.While in a higher density(ne(0)?1.83×10^(19)m^(-3)–2.02×10^(19)m^(-3))scenario,the phenomena are not observed.Furthermore,compelling evidence indicates that E×B shear serves as a substantial contributor to this extensive radial interaction.This finding offers a direct explanatory link to the intriguing core-heating phenomenon witnessed within the realm of non-local transport.
基金partially supported within the framework of the cooperation between the French Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA) and the China National Nuclear Corporation (CNNC)partially supported by National Natural Science Foundation of China under Grant Nos. 11305053, 10990213, 10975049, 11475057, 11275062, 11375057 and 11575055partially supported by Chinese National Fusion Project for ITER under Grant Nos. 2013GB107000 and 2014GB108000
文摘This paper discusses edge oscillatory plasma flows, geodesic acoustic mode （GAM） and limit cycle oscillations （LCOs）, which have been measured by Doppler reflectometry prior to the high confinement mode （H-mode） in the HL-2A tokamak. The complex relations between the flows and background turbulence have been analyzed. It was observed that the GAM and LCO coexist, and these two flows and turbulence have strong nonlinear interactions during the intermediate confinement phase （I-phase）. Dynamics of the shear flows and turbulence prior to the H-mode shows that the oscillatory flows quench the turbulence along with the increase of the mean E x B flow at the early stage of the I-phase, then the oscillatory flows are damped and the further increased mean flow takes over the role in turbulence suppression. The reduced turbulent transport results in the formation of a steep edge transport barrier. It suggests that the oscillatory flows can initiate the L-H transition through providing a positive feedback for the increase of the mean E × B flow strength.
基金supported by the National Magnetic Confinement Fusion Energy Research and Development Program of China(Nos.2019YFE03090100,2019YFE03040004)the National Science Foundation for Young Scientists of China(No.12005052)。
文摘Data analysis on tokamak plasmas is mainly based on various diagnostic systems,which are usually modularized and independent of each other.This leads to a large amount of data not being fully and effectively exploited so that it is not conducive to revealing the deep physical mechanism.In this work,Bayesian probability inference with machine learning methods have been applied to the electron cyclotron emission and Thomson scattering diagnostic systems on HL-2A/2M,and the effects of integrated data analysis(IDA)on the electron temperature of HL-2A with Bayesian probability inference are demonstrated.A program is developed to infer the whole electron temperature profile with a confidence interval,and the program can be applied in online analysis.The IDA results show that the full profile of the electron temperature can be obtained and the diagnostic information is more comprehensive and abundant with IDA.The inference models for electron temperature analysis are established and the developed programs will serve as an experimental data analysis tool for HL-2A/2M in the near future.
基金supported in part by the ITER-CN(Grants No.2017YFE0301202 and 2019YFE03020000)by National Natural Science Foundation of China(Grants No.12125502,11875021 and 11835010)by Sichuan Foundation(Grant No.2020JDJQ0070).
文摘Over the past several years,high-β_(N) experiments have been carried out on HL-2A.The high-β_(N) is realized using double transport barriers(DTBs)with hybrid scenarios.A stationary high-β_(N) (>2)scenario was obtained by pure neutral-beam injection(NBI)heating.Transient high performance was also achieved,corresponding to β_(N)≥3,ne/ne_(G)∼0.6,H_(98)∼1.5,f_(bs)∼30%,q_(95)∼4.0,and𝐺∼0.4.The high-β_(N) scenario was successfully modeled using integrated simulation codes,that is,the one modeling framework for integrated tasks(OMFIT).In high-𝛽𝑁plasmas,magnetohydrodynamic(MHD)instabilities are abundant,including low-frequency global MHD oscilla-tion with n=1,high-frequency coherent mode(HCM)at the edge,and neoclassical tearing mode(NTM)and Alfvénic modes in the core.In some high-β_(N) discharges,it is observed that the NTMs with m/n=3/2 limit the growth of the plasma energy and decrease β_(N).The low-n global MHD oscillation is consistent with the coupling of destabilized internal(m/n=1/1)and external(m/n=3/1 or 4/1)modes,and plays a crucial role in triggering the onset of ELMs.Achieving high-β_(N) on HL-2A suggests that core-edge interplay is key to the plasma confinement enhancement mechanism.Experiments to enhance β_(N) will contribute to future plasma operation,such as international thermonuclear experimental reactor.
