We report the measurement of total molybdenum ion density for L-mode and H-mode plasmas on EAST using spectral lines observation and calculation based on an impurity transport code.A flat-filed extreme ultraviolet spe...We report the measurement of total molybdenum ion density for L-mode and H-mode plasmas on EAST using spectral lines observation and calculation based on an impurity transport code.A flat-filed extreme ultraviolet spectrometer with some spatial resolution is used to obtain the radial profiles of molybdenum spectral line emissions.The absolute calibration for the extreme ultraviolet spectrometer is finished by comparing the calculated bremsstrahlung intensity with the readings of CCD detector.Molybdenum ion transport study is performed using the radial ion density profiles and one-dimensional impurity transport code STRAHL.The total molybdenum density profiles are determined from the transport analysis.The molybdenum density during L-mode and H-mode phases are obtained,which are about 3 and 4 orders of magnitude smaller than the electron density,respectively.An inward pinch is found during the H-mode phase that leads to the peaked profile of molybdenum density.展开更多
The hybrid scenario is a projection for CFETR operation with high plasma current and density.Therefore, the energetic particles(EPs) generated by fusion reactions can destabilize Alfvén eigenmodes(AEs), which cou...The hybrid scenario is a projection for CFETR operation with high plasma current and density.Therefore, the energetic particles(EPs) generated by fusion reactions can destabilize Alfvén eigenmodes(AEs), which could result in significant EPs loss and redistribution. Both the eigenvalue code NOVA-K and the wrapped local stability code TGLFEP are used to analyze AE stability. The simulation indicates the beta-induced Alfvén eigenmodes with n?>?5 in the core region are the most unstable. The NOVA-K code is used to benchmark the critical density gradient calculated by TGLFEP. In addition, the EPtran code is employed to predict EP transport induced by unstable AEs and turbulence, which reduce EP density in the core and drive approximately 30% EP transport from the core to the edge, thus the EP density profile flattens and EPs with lower energy deposit near the edge.展开更多
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 b...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.展开更多
The change in the toroidal rotation of plasma caused by electron cyclotron wave（ECW） injection has been observed in EAST. It is found that the response of the rotation is similar for all possible ECW toroidal inject...The change in the toroidal rotation of plasma caused by electron cyclotron wave（ECW） injection has been observed in EAST. It is found that the response of the rotation is similar for all possible ECW toroidal injection angles. The core toroidal rotation velocity increases in the co-current direction along with a rise in the plasma temperature and stored energy. The profile of the electron temperature, ion temperature and toroidal rotation velocity gradually become peaked.The change in toroidal rotation in the core increases with the ECW injection power. Different behavior is observed when the ECWs are injected into low hybrid current drive（LHCD） target plasmas, where the electron temperature and rotation profile become peaked, while the ion temperature profile flattens after ECW injection, suggesting different transport characteristics in energy and momentum.展开更多
Nonlinear couplings of various Alfvén modes driven by energetic particles in HL-2 A are addressed by employing the Fourier bicoherence and Lissajous-curve technique. Long-lived modes and high-frequency coherent m...Nonlinear couplings of various Alfvén modes driven by energetic particles in HL-2 A are addressed by employing the Fourier bicoherence and Lissajous-curve technique. Long-lived modes and high-frequency coherent modes are presented. Then the squared bicoherence of three waves establishes the existence of three-wave coupling. Lissajous-curves of those waves manifest that their phases are locked, which again confirms that they are nonlinearly coupled to each other. Moreover, coupled modes triggered by supersonic molecular beam injection are investigated. The phase evolution of them is given by the Lissajous-curve. Further details of phase-flip and phase-slip are presented and discussed.展开更多
Ion temperature, as one of the most critical plasma parameters, can be diagnosed by charge exchange recombination spectroscopy (CXRS). Iterative least-squares fitting is conventionally used to analyze CXRS spectra to ...Ion temperature, as one of the most critical plasma parameters, can be diagnosed by charge exchange recombination spectroscopy (CXRS). Iterative least-squares fitting is conventionally used to analyze CXRS spectra to identify the active charge exchange component, which is the result of local interaction between impurity ions with a neutral beam. Due to the limit of the time consumption of the conventional approach (~100 ms per frame), the Experimental Advanced Superconducting Tokamak CXRS data is now analyzed in-between shots. To explore the feasibility of real-time measurement, neural networks are introduced to perform fast estimation of ion temperature. Based on the same four-layer neural network architecture, two neural networks are trained for two central chords according to the ion temperature data acquired from the conventional method. Using the TensorFlow framework, the training procedures are performed by an error back-propagation algorithm with the regularization via the weight decay method. Good agreement in the deduced ion temperature is shown for the neural networks and the conventional approach, while the data processing time is reduced by 3 orders of magnitude (~0.1 ms per frame) by using the neural networks.展开更多
A linear simulation study of energetic passing particle-driven low-frequency fishbone instability in tokamak plasmas has been carried out using the global kinetic-MHD(magnetohydrodynamics)hybrid code M3D-K.This work i...A linear simulation study of energetic passing particle-driven low-frequency fishbone instability in tokamak plasmas has been carried out using the global kinetic-MHD(magnetohydrodynamics)hybrid code M3D-K.This work is focused on the interaction of energetic passing beam ions and n=1 mode with a monotonic safety factor q profile and q_(0)<1.Specifically,the stability and mode frequency as well as mode structure of the n=1mode are calculated for scans of parameter values of beam ion beta,beam ion injection energy,beam ion orbit width,beam ion beta profile,as well as background plasma beta.The excited modes are identified as a low-frequency fishbone with the corresponding resonance of w_(φ)+w_(θ)=w,where w_(φ)is the beam ion toroidal transit frequency and w_(θ)is the beam ion poloidal transit frequency.The simulated mode frequency is approximately proportional to the beam ion injection energy and beam ion orbit width.The mode structure is similar to that of internal kink mode.These simulation results are similar to the analytic theory of Yu et al.展开更多
In this article,we present the optical design of a novel diagnostic on the HL-2A tokamak,i.e.the 20-channel edge Lyman-alpha beam emission spectroscopy,which is a promising solution for edge density turbulence researc...In this article,we present the optical design of a novel diagnostic on the HL-2A tokamak,i.e.the 20-channel edge Lyman-alpha beam emission spectroscopy,which is a promising solution for edge density turbulence research on tokamaks,as it offers the possibility of density fluctuation measurement with a 3.3 mm spatial resolution while maintains a high temporal resolution of 1μs.The optical path,including the reflective collection optics,the high-dispersion spectrometer,and the linear detector array,is carefully optimized to obtain a good image quality and a high throughput.The maximum root mean square radius of the collection optics is 64μm.The detected photon flux is estimated to be about 1011 photons/s/channel.展开更多
Direct measurements of the intrinsic torque profile in L-mode plasmas on the EAST tokamak have been performed using the balanced neutral beam injection.Co-and counter-current neutral beams are modulated to balance the...Direct measurements of the intrinsic torque profile in L-mode plasmas on the EAST tokamak have been performed using the balanced neutral beam injection.Co-and counter-current neutral beams are modulated to balance the intrinsic and externally injected torques, which result in the rotation profile close to zero and flat.The experimental results show that the intrinsic torque derived from momentum balance equations is found to be in the co-current direction, peaked in the plasma edge and negligibly small in the core.展开更多
The control of large edge localized modes(ELMs) is a critical issue for the successful operation of future burning plasma devices,such as the international thermonuclear experimental reactor(ITER) and China fusion eng...The control of large edge localized modes(ELMs) is a critical issue for the successful operation of future burning plasma devices,such as the international thermonuclear experimental reactor(ITER) and China fusion engineering test reactor(CFETR). In this paper, we present a new active and effective means of ELM suppression using ion cyclotron resonant heating(ICRH) on the experimental advanced superconducting tokamak(EAST). We obtained the key role of the external E × B velocity shear near the pedestal top and the scrape-off-layer(SOL) induced by the RF sheath potential of ICRH in ELM suppression. The experimental results showed a positive correlation between the RF sheath and the E × B shear rate in SOL. BOUT++ simulations indicate that increased E × B velocity shear rates in the pedestal and SOL regions promote ELM suppression;thereby, supporting the experimental observations on EAST. These findings suggest a new simple approach to access the ELM suppressed regimes in plasma with low torque input as ITER baseline discharges.展开更多
System validation and density fluctuation calibration of phase contrast imaging(PCI) on an HL-2 A tokamak are presented. Signals from different channels show not only a pronounced modulation of an incident laser beam ...System validation and density fluctuation calibration of phase contrast imaging(PCI) on an HL-2 A tokamak are presented. Signals from different channels show not only a pronounced modulation of an incident laser beam induced by a sound wave, but also an excellent magnification and low image distortion of optics. The frequencywavenumber spectrum is achieved by using two-dimensional Fourier transform of time series signals. The conversion coefficient between detected signal amplitude and chord integral plasma density fluctuation is 2.35 × 1013m-2/mV, which promises a suitable signal level at the order of volts of the PCI in typical HL-2 A discharges.展开更多
基金National Key Research and Development Program of China(Grant No.2017YFE031300)the Key Program of Research and Development of Hefei Science Center of China(Grant No.2017HSC-KPRD002)+4 种基金the National Natural Science Foundation of China(Grant No.11805231)the Natural Science Foundation of Anhui Province of China(Grant Nos.1908085J01,1808085QA14,and 1908085QF274)the ASIPP Science and Research Fund of China(Grant No.DSJJ-17-03)Collaborative Innovation Program of Hefei Science Center,CAS(Grant No.2019HSC-CIP005)Anqing Normal University Research Project,China(Grant Nos.043-180079 and 044-140001000024).
文摘We report the measurement of total molybdenum ion density for L-mode and H-mode plasmas on EAST using spectral lines observation and calculation based on an impurity transport code.A flat-filed extreme ultraviolet spectrometer with some spatial resolution is used to obtain the radial profiles of molybdenum spectral line emissions.The absolute calibration for the extreme ultraviolet spectrometer is finished by comparing the calculated bremsstrahlung intensity with the readings of CCD detector.Molybdenum ion transport study is performed using the radial ion density profiles and one-dimensional impurity transport code STRAHL.The total molybdenum density profiles are determined from the transport analysis.The molybdenum density during L-mode and H-mode phases are obtained,which are about 3 and 4 orders of magnitude smaller than the electron density,respectively.An inward pinch is found during the H-mode phase that leads to the peaked profile of molybdenum density.
基金supported by National Natural Science Foundation of China (Grant No. 11535013)the National Key Research and Development Program of China (Grant Nos. 2017YFA0402500 and 2018YFE0302101)
文摘The hybrid scenario is a projection for CFETR operation with high plasma current and density.Therefore, the energetic particles(EPs) generated by fusion reactions can destabilize Alfvén eigenmodes(AEs), which could result in significant EPs loss and redistribution. Both the eigenvalue code NOVA-K and the wrapped local stability code TGLFEP are used to analyze AE stability. The simulation indicates the beta-induced Alfvén eigenmodes with n?>?5 in the core region are the most unstable. The NOVA-K code is used to benchmark the critical density gradient calculated by TGLFEP. In addition, the EPtran code is employed to predict EP transport induced by unstable AEs and turbulence, which reduce EP density in the core and drive approximately 30% EP transport from the core to the edge, thus the EP density profile flattens and EPs with lower energy deposit near the edge.
基金supported by the National Key Research and Development Program of China (No.2017YFE0300405)National Natural Science Foundation of China (Nos.11875124, 11705052, 11575055 and 11611130164)the National Magnetic Confinement Fusion Science Program of China (No.2015GB120002)
文摘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.
基金supported by the National Magnetic Confinement Fusion Science Program of China (2013GB112004, 2015GB103002)National Natural Science Foundation of China (11305212, 11405212)+1 种基金the MajorProgram of Development Foundation of Hefei Center for Physical Science and Technology (2016FXZY008)the Natural Science Research Key Project of the Education Department of Anhui Province under grant No. KJ2016A434
文摘The change in the toroidal rotation of plasma caused by electron cyclotron wave（ECW） injection has been observed in EAST. It is found that the response of the rotation is similar for all possible ECW toroidal injection angles. The core toroidal rotation velocity increases in the co-current direction along with a rise in the plasma temperature and stored energy. The profile of the electron temperature, ion temperature and toroidal rotation velocity gradually become peaked.The change in toroidal rotation in the core increases with the ECW injection power. Different behavior is observed when the ECWs are injected into low hybrid current drive（LHCD） target plasmas, where the electron temperature and rotation profile become peaked, while the ion temperature profile flattens after ECW injection, suggesting different transport characteristics in energy and momentum.
基金supported in part by National Natural Science Foundation of China (Nos. 11875021, 11835010, 11875024, 11775072, 11505053, 11475058)by the ITER-CN (Nos. 2017YFE0300501, 2017YFE0300405, 2017YFE0301202 and 2017YFE030168)
文摘Nonlinear couplings of various Alfvén modes driven by energetic particles in HL-2 A are addressed by employing the Fourier bicoherence and Lissajous-curve technique. Long-lived modes and high-frequency coherent modes are presented. Then the squared bicoherence of three waves establishes the existence of three-wave coupling. Lissajous-curves of those waves manifest that their phases are locked, which again confirms that they are nonlinearly coupled to each other. Moreover, coupled modes triggered by supersonic molecular beam injection are investigated. The phase evolution of them is given by the Lissajous-curve. Further details of phase-flip and phase-slip are presented and discussed.
基金supported by National Natural Science Foundation of China(No.11535013)the National Key Research and Development Program of China(Nos.2017YFA0402500,2018YFE0302100)the Users with Excellence Project of Hefei Science Center CAS(No.2018HSC-UE010)
文摘Ion temperature, as one of the most critical plasma parameters, can be diagnosed by charge exchange recombination spectroscopy (CXRS). Iterative least-squares fitting is conventionally used to analyze CXRS spectra to identify the active charge exchange component, which is the result of local interaction between impurity ions with a neutral beam. Due to the limit of the time consumption of the conventional approach (~100 ms per frame), the Experimental Advanced Superconducting Tokamak CXRS data is now analyzed in-between shots. To explore the feasibility of real-time measurement, neural networks are introduced to perform fast estimation of ion temperature. Based on the same four-layer neural network architecture, two neural networks are trained for two central chords according to the ion temperature data acquired from the conventional method. Using the TensorFlow framework, the training procedures are performed by an error back-propagation algorithm with the regularization via the weight decay method. Good agreement in the deduced ion temperature is shown for the neural networks and the conventional approach, while the data processing time is reduced by 3 orders of magnitude (~0.1 ms per frame) by using the neural networks.
基金the National MCF Energy R&D Program of China(Nos.2019YFE03030004 and 2019YFE03050001)National Natural Science Foundation of China(Nos.11975232 and 11975270)。
文摘A linear simulation study of energetic passing particle-driven low-frequency fishbone instability in tokamak plasmas has been carried out using the global kinetic-MHD(magnetohydrodynamics)hybrid code M3D-K.This work is focused on the interaction of energetic passing beam ions and n=1 mode with a monotonic safety factor q profile and q_(0)<1.Specifically,the stability and mode frequency as well as mode structure of the n=1mode are calculated for scans of parameter values of beam ion beta,beam ion injection energy,beam ion orbit width,beam ion beta profile,as well as background plasma beta.The excited modes are identified as a low-frequency fishbone with the corresponding resonance of w_(φ)+w_(θ)=w,where w_(φ)is the beam ion toroidal transit frequency and w_(θ)is the beam ion poloidal transit frequency.The simulated mode frequency is approximately proportional to the beam ion injection energy and beam ion orbit width.The mode structure is similar to that of internal kink mode.These simulation results are similar to the analytic theory of Yu et al.
基金supported by the National Key R&D Program of China(Nos.2017YFE0301201 and 2018YFE0303102)National Natural Science Foundation of China(Nos.11875124 and 12075241).
文摘In this article,we present the optical design of a novel diagnostic on the HL-2A tokamak,i.e.the 20-channel edge Lyman-alpha beam emission spectroscopy,which is a promising solution for edge density turbulence research on tokamaks,as it offers the possibility of density fluctuation measurement with a 3.3 mm spatial resolution while maintains a high temporal resolution of 1μs.The optical path,including the reflective collection optics,the high-dispersion spectrometer,and the linear detector array,is carefully optimized to obtain a good image quality and a high throughput.The maximum root mean square radius of the collection optics is 64μm.The detected photon flux is estimated to be about 1011 photons/s/channel.
基金supported by the National Key Research and Development Program of China(Nos.2017YFE0301300 and 2017YFE0302000)Key Program of Research and Development of Hefei Science Center,CAS(No.2017HSCKPRD002)+2 种基金Distinguished Young Scholar of Anhui Provincial Natural Science Foundation(1908085J01)the Key Projects of Hunan Provincial Department of Education(18A238)the Key Laboratory of Magnetic Confinement Nuclear Fusion Research in Hengyang(2018KJ108)。
文摘Direct measurements of the intrinsic torque profile in L-mode plasmas on the EAST tokamak have been performed using the balanced neutral beam injection.Co-and counter-current neutral beams are modulated to balance the intrinsic and externally injected torques, which result in the rotation profile close to zero and flat.The experimental results show that the intrinsic torque derived from momentum balance equations is found to be in the co-current direction, peaked in the plasma edge and negligibly small in the core.
基金supported by the National Key Research and Development Program(Grant Nos.2016YFA0400600,and 2016YFA0400601)the National MCF Energy R&D Program(Grant No.2018YFE0311200)+1 种基金the National Natural Science Foundation of China(Grant Nos.11975265,and U1967206)the Comprehensive Research Facility for Fusion Technology Program of China(Grant No.2018-000052-73-01-001228)。
文摘The control of large edge localized modes(ELMs) is a critical issue for the successful operation of future burning plasma devices,such as the international thermonuclear experimental reactor(ITER) and China fusion engineering test reactor(CFETR). In this paper, we present a new active and effective means of ELM suppression using ion cyclotron resonant heating(ICRH) on the experimental advanced superconducting tokamak(EAST). We obtained the key role of the external E × B velocity shear near the pedestal top and the scrape-off-layer(SOL) induced by the RF sheath potential of ICRH in ELM suppression. The experimental results showed a positive correlation between the RF sheath and the E × B shear rate in SOL. BOUT++ simulations indicate that increased E × B velocity shear rates in the pedestal and SOL regions promote ELM suppression;thereby, supporting the experimental observations on EAST. These findings suggest a new simple approach to access the ELM suppressed regimes in plasma with low torque input as ITER baseline discharges.
基金supported by the National Magnetic Confinement Fusion Energy Research Project(No.2015GB120002)the National Key Research and Development Program of China(No.2017YFE0300405)the National Natural Science Foundation of China(Nos.11705052,11575055,and 11611130164)
文摘System validation and density fluctuation calibration of phase contrast imaging(PCI) on an HL-2 A tokamak are presented. Signals from different channels show not only a pronounced modulation of an incident laser beam induced by a sound wave, but also an excellent magnification and low image distortion of optics. The frequencywavenumber spectrum is achieved by using two-dimensional Fourier transform of time series signals. The conversion coefficient between detected signal amplitude and chord integral plasma density fluctuation is 2.35 × 1013m-2/mV, which promises a suitable signal level at the order of volts of the PCI in typical HL-2 A discharges.
