A millimeter wave solid state source—far infrared laser combined interferometer system(MFCI)consisting of a three-channel 890 GHz hydrogen cyanide(HCN)laser interferometer and a threechannel 340 GHz solid state sourc...A millimeter wave solid state source—far infrared laser combined interferometer system(MFCI)consisting of a three-channel 890 GHz hydrogen cyanide(HCN)laser interferometer and a threechannel 340 GHz solid state source interferometer(SSI)is developed for real-time line-integrated electron density feedback and electron density profile of the EXL-50 spherical tokamak device.The interferometer system is a Mach–Zehnder type,with all probe-channels measured vertically,covering the plasma magnetic axis to the outermost closed magnetic plane.The HCN laser interferometer uses an HCN laser with a frequency of 890 GHz as a light source and modulates a100 k Hz beat signal by a rotating grating,giving a temporal resolution of 10μs.The SSI uses two independent 340 GHz solid-state diode sources as the light source,the frequency of the two sources is adjustable,and the temporal resolution of SSI can reach 1μs by setting the frequency difference of the two lasers at 1 MHz.The main optical path of the two interferometers is compactly installed on a set of double-layer optical platform directly below EXL-50.Dual optical path design using corner cube reflectors avoids the large support structures.Collinear the probebeams of two wavelengths,then the phase error caused by vibration can be compensated.At present,the phase noise of the HCN Interferometer is 0.08 rad,corresponding to a line-integrated electron density of 0.88×10^(17)m^(-2),one channel of measuring result was obtained by the MFCI system,and the highest density measured is about 0.7×10^(19)m^(-2).展开更多
EHL-2 spherical torus(ST)is one of the key steps of p-^(11)B(proton-boron or hydrogen-boron)fusion energy research in ENN.The fusion produced energy is carried mainly by alpha particles of average energy 3 MeV,which i...EHL-2 spherical torus(ST)is one of the key steps of p-^(11)B(proton-boron or hydrogen-boron)fusion energy research in ENN.The fusion produced energy is carried mainly by alpha particles of average energy 3 MeV,which ideally can be converted to electricity with high efficiency(>80%).However,there exist serious difficulties to realize such conversion in a fusion device,due to the high energy density and high voltage required.To comprehensively describe the progress of the EHL-2 physics design,this work presents preliminary considerations of approaches for achieving energy conversion,highlighting critical issues for further investigation.Specifically,we provide an initial simulation of alpha particle extraction in the EHL-2 ST configuration as a starting point for p-^(11)B fusion energy conversion.展开更多
The EHL-2(ENN He-Long 2)spherical torus(ST)project focuses on advancing spherical torus technology to address the unique challenges of p-^(11)B fusion,which demands significantly higher ion temperature and heat flux t...The EHL-2(ENN He-Long 2)spherical torus(ST)project focuses on advancing spherical torus technology to address the unique challenges of p-^(11)B fusion,which demands significantly higher ion temperature and heat flux to the divertor plate compared to traditional deuterium-tritium fusion.With a major radius of 1.05 m and a plasma current of 3 MA,the project aims to evaluate and optimize advanced divertor configurations,specifically the Super-X and X-point target(XPT)divertors.The design incorporates an up-down double-null configuration featuring a conventional inner divertor and an XPT outer divertor to effectively reduce the heat flux.The poloidal field(PF)coil system is meticulously optimized to balance engineering constraints with the flexibility in equilibrium configurations.This design is expected to provide a reference equilibrium configuration for other physics design issues and offer critical insight into heat load management.展开更多
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 plasm...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.展开更多
A three-fluid equilibrium plasma with bulk plasma and energetic electrons has been observed on the Xuanlong-50(EXL-50) spherical torus, where the energetic electrons play a crucial role in sustaining the plasma curren...A three-fluid equilibrium plasma with bulk plasma and energetic electrons has been observed on the Xuanlong-50(EXL-50) spherical torus, where the energetic electrons play a crucial role in sustaining the plasma current and pressure. In this study, the equilibrium of a multi-fluid plasma was investigated by analyzing the relationship between the external vertical magnetic field(B_(V)),plasma current(I_(p)), the poloidal ratio(β_(p)) and the Shafranov formula. Remarkably, our research demonstrates some validity of the Shafranov formula in the presence of multi-fluid plasma in EXL-50 spherical torus. This finding holds significant importance for future reactors as it allows for differentiation between alpha particles and background plasma. The study of multi-fluid plasma provides a significant reference value for the equilibrium reconstruction of burning plasma involving alpha particles.展开更多
This paper presents the first comprehensive simulation study of p-11B fusion reactions in a spherical torus.We developed relevant program modules for fusion reactions based on energetic particle simulation frameworks ...This paper presents the first comprehensive simulation study of p-11B fusion reactions in a spherical torus.We developed relevant program modules for fusion reactions based on energetic particle simulation frameworks and analyzed the two main fusion channels:thermal and beam-thermal.Using EHL-2 design parameters with n_(boron)=007n_(ion)and a hydrogen beam at 200 keV and 1 MW,our simulation indicates that p-11B reactions produce approximately 1.5×10^(15)αparticles per second(~0.7 kW)from the thermal channel,and5.3×10^(14)(~0.25 kW)from the beam-thermal channel.We conducted parameter scans to establish a solid physics foundation for the high ion temperature conditions(T_(i)>26ke V)designed for EHL-2.This work also laid the groundwork for studying various operation modes to explore different reaction channels.The simulation results suggest that the conditions in EHL-2 could be sufficient for investigating p-11B thermonuclear reactions.In addition,we found that EHL-2 offered good confinement for energetic particles,allowing us to research the interactions between these ions and plasmas.This research enhances our understanding of burning plasma physics.展开更多
EHL-2 is a compact,high-field spherical tokamak designed to explore the potential of an advanced p-11B nuclear fusion reactor.Due to its high plasma current and thermal energy,it is crucial to mitigate the impact asso...EHL-2 is a compact,high-field spherical tokamak designed to explore the potential of an advanced p-11B nuclear fusion reactor.Due to its high plasma current and thermal energy,it is crucial to mitigate the impact associated with disruptions to ensure the safe operation of EHL-2.This paper evaluates the performance requirements of the disruption prediction system on EHL-2,with a particular focus on applying generalizable knowledge transfer from existing devices to future ones.Furthermore,the key characteristics of disruption mitigation strategies are analyzed,and their overall mitigation performance on EHL-2 is assessed.This insight provides valuable guidance for optimizing the engineering design of EHL-2 and identifying its optimal operational regime.展开更多
The EXL-50U is China’s first large spherical torus device with a toroidal field reaching 1 T.The major radius of the EXL-50U ranges from 0.6 m to 0.8 m,with an aspect ratio of 1.4−1.8.The goal of plasma current in th...The EXL-50U is China’s first large spherical torus device with a toroidal field reaching 1 T.The major radius of the EXL-50U ranges from 0.6 m to 0.8 m,with an aspect ratio of 1.4−1.8.The goal of plasma current in the first experimental phase is 500 kA,and in the future second phase,the goal of plasma current is 1 MA.On the EXL-50U project,the ENN fusion team expeditiously accomplished a series of comprehensive tasks including physical and engineering design,main component construction installation,and system commissioning,all within a mere eighteen-month timeframe.In the experiments of 2024,the EXL-50U achieved a 500 kA limiter configuration discharge using ECRH(Electron Cyclotron Resonance Heating)for non-inductive current start-up and a current ramp-up with the synergetic effect of ECRH and central solenoid(CS).Preliminary divertor configuration plasmas were also obtained under 200 kA plasma current.The core ion temperature of 1 keV was achieved with low-power NBI heating,and the energy confinement time of 30 ms was reached with Ohmic heating in the flat-top phase.The current and future experiments of EXL-50U will strongly support the physical design and operational scenarios of EHL-2 in the areas of current drive,high ion temperature exploration,energy transport and confinement,and hydrogen-boron physical characteristics.At the same time,the experience in the design,construction,and commissioning of the engineering,heating,and diagnostics systems on EXL-50U is also very beneficial for enhancing the feasibility of the engineering design for EHL-2.展开更多
The EHL-2 spherical torus is designed to demonstrate proton-boron(p-11B)fusion within a compact spherical tokamak.Its planned heating system includes a negative ion-based neutral beam injection(N-NBI),two positive ion...The EHL-2 spherical torus is designed to demonstrate proton-boron(p-11B)fusion within a compact spherical tokamak.Its planned heating system includes a negative ion-based neutral beam injection(N-NBI),two positive ion-based NBI systems(P-NBI),electron cyclotron resonance heating(ECRH),ion cyclotron resonance heating(ICRH),and high harmonic fast wave(HHFW),with a total power output of 31 MW.According to scaling law estimates,the device is capable of achieving H-mode operation.The plasma density,,n_(e,min)at the minimum L-H power threshold,P_(lh),is estimated to be 4.4×10^(19)m^(-3).The pedestal parameters were calculated using the REPED model.Assuming B as the primary impurity ion,the predicted pedestal width and height are lower compared to the typical case with carbon impurities.The pedestal collisionality for EHL-2 is estimated to range between 0.06 and 0.17,indicating the potential for significant energy loss due to edge localized modes(ELMs).The heat flux on the divertor plate has been calculated using the JOREK code.The peak heat fluxes during ELM bursts are approximately 31.0 MW/m^(2)at the lower inboard target and 39.5 MW/m^(2)at the lower outboard target.A preliminary design of the resonant magnetic perturbation(RMP)coils has been completed to both control type-I ELMs and correct error fields.The system comprises 16 coils arranged into 24 pairs.In ELM control mode,a 14/2 component is generated at 1.7 G/kAt,with a current of 4.9 kA required to achieveσChirikow=1 at the resonant surface,where the normalized poloidal magnetic flux is 0.85.In error field(EF)modulation mode,2/1 and 3/1 components are generated at 3.5 G/kAt and 2.8 G/kAt,respectively.展开更多
The divertor design is critical to heat load handling and thus to achievements of highperformance plasma operations in the EHL-2(ENN He-Long 2)tokamak.This paper presents the design of an X-point target(XPT)divertor,f...The divertor design is critical to heat load handling and thus to achievements of highperformance plasma operations in the EHL-2(ENN He-Long 2)tokamak.This paper presents the design of an X-point target(XPT)divertor,featuring a conventional inner divertor and an XPT outer divertor,aimed at the effective control of heat loads,which may be extremely high during high ion temperature scenarios.The divertor target plates are made from carbon-based materials,which can handle heat loads of up to 5 MW/m².Divertor performances,including the heat load controllability,the onset of detachment and the in-out/up-down asymmetry,etc.,are evaluated using both the simple particle-tracking strategy and the complicated SOLPS-ITER code.Special attention is paid to the drift effects on particle/heat transport in the divertor/scrape-off layer region and on the divertor heat loads,focusing on the semi-detached/detached operation regimes.Results from SOLPS-ITER simulations demonstrated that the currently designed magnetic equilibrium and divertor configuration can effectively handle the power heat load in EHL-2.展开更多
The next generation fusion device listed on ENN’s fusion roadmap,named as(ENN He-Long)EHL-2,is under both physics and engineering designs.The instabilities of ideal magnetohydrodynamics(MHD)mode and neoclassical tear...The next generation fusion device listed on ENN’s fusion roadmap,named as(ENN He-Long)EHL-2,is under both physics and engineering designs.The instabilities of ideal magnetohydrodynamics(MHD)mode and neoclassical tearing mode(NTM)stabilized by electron cyclotron current drive(ECCD)for EHL-2’s two typical operation scenarios are analyzed.For high-ion-temperature operating(HITO)scenario,the vertical displacement event(VDE)could be a big challenge to the device safety.For the steady-state operating(SSO)scenario,the limitation may rise from the ideal MHD mode,NTM,etc.This suggests that the MHD analysis of both operation scenarios should be done with different focusing.Preliminary analysis based on the current physics and engineering design of both two scenarios is given in this paper.Based on the analysis result of above,the future assessments might target at active control method and the effect of boron on MHD activities.展开更多
ENN He Long-2(EHL-2)is the next-generation large mega-Ampere(MA)spherical torus(ST)proposed and funded by the ENN company.The design parameters are:Ti0>30 keV,n_(e0)~1×10^(20)m^(-3),Ip~3 MA,Bt~3 T.One of the b...ENN He Long-2(EHL-2)is the next-generation large mega-Ampere(MA)spherical torus(ST)proposed and funded by the ENN company.The design parameters are:Ti0>30 keV,n_(e0)~1×10^(20)m^(-3),Ip~3 MA,Bt~3 T.One of the biggest challenges of EHL-2 is how to achieve several MA current flat-tops with limited voltage-seconds(Vs)of the center solenoid(CS)coils.In order to minimize the consumption of Vs,a fully non-inductive start-up by electron cyclotron resonance heating(ECRH)will be applied in EHL-2.The ramp-up phase will be accomplished with the synergetic mode between the CS and non-inductive methods.The strategy of non-inductive start-up and ramp-up with synergetic mode has been verified on EXL-50U’s experiments.Based on this strategy,numerical simulations indicate the feasibility of EHL-2 achieving 3 MA plasma current.A high-performance steady-state scenario with Ip~1.5 MA is also designed.In this scenario,the bootstrap current fraction fBS>70%,the safety factor q at the magnetic axis q0>2,the minimum safety factor qmin>1,the poloidal betaβp>3 and normalized betaβN>2.3.Each design iteration integrates the validation of physical models with the constraints of engineering implementation,gradually optimizing the performance of the heating and current drive(H&CD)systems.Numerical simulation results for general auxiliary H&CD systems such as neutral beam injection(NBI),electron cyclotron(EC)wave,ion cyclotron wave(ICW),and lower hybrid wave(LHW)are presented.These simulation results ensure that the 31 MW H&CD systems comprehensively cover all scenarios while maintaining engineering feasibility.展开更多
Preionization has been widely employed to create initial plasma and help the toroidal plasma current formation.This research focuses on implementing a simple,economical and practical electron cyclotron resonance(ECR)p...Preionization has been widely employed to create initial plasma and help the toroidal plasma current formation.This research focuses on implementing a simple,economical and practical electron cyclotron resonance(ECR)preionization technique on the newly constructed EXL-50 spherical tokamak,and evaluating the effectiveness on improving the plasma current startup.Two types ECR microwave preionization experiments for the plasma initialization without the central solenoid are reported:(1)2.45 GHz microwave preionization and current startup with2.45 GHz ECR source;(2)2.45 GHz microwave preionization and current startup with 28 GHz ECR source.Application of the 2.45 GHz ECR microwave preionization to the experiments has contributed to(1)getting rid of the plasma breakdown delay;(2)the significant improvement of the discharge quality:the discharge is much longer and more stable while the driven plasma current is larger,compared to the discharge without preionization.展开更多
The toroidal component of the velocity for geodesic acoustic modes(GAMs)is first demonstrated.Multiple Langmuir probe arrays set up near the top tokamak of the J-TEXT were utilized for this study.A significant peak at...The toroidal component of the velocity for geodesic acoustic modes(GAMs)is first demonstrated.Multiple Langmuir probe arrays set up near the top tokamak of the J-TEXT were utilized for this study.A significant peak at the GAM frequency is observed in Mach number fluctuations.The toroidal velocity for the GAMs is estimated as 10–100 ms-1 and increases with the poloidal velocity.The ratio of toroidal component to the poloidal one of the velocity is mainly located in the interval between 0.3 and 1.0.With higher safety factors q,the ratio almost does not change with decreasing the safety factor,whereas it goes up sharply at low q.The coherencies between poloidal electric fields and Mach number fluctuations in turbulence frequency bands are also evaluated,and are higher than those between radial electric fields and Mach number fluctuations.展开更多
A neural network model with a classical annotation method has been used on the EXL-50tokamak to predict impending disruption.However,the results revealed issues of overfitting and overconfidence in predictions caused ...A neural network model with a classical annotation method has been used on the EXL-50tokamak to predict impending disruption.However,the results revealed issues of overfitting and overconfidence in predictions caused by inaccurate labeling.To mitigate these issues,an improved training framework has been proposed.In this approach,soft labels from previous training serve as teachers to supervise the further learning process;this has lead to a significant improvement in predictive model performance.Notably,this enhancement is primarily attributed to the coupling effect of the soft labels and correction mechanism.This improved training framework introduces an instance-specific label smoothing method,which reflects a more nuanced model assessment on the likelihood of a disruption.It presents a possible solution to effectively address the challenges associated with accurate labeling across different machines.展开更多
The influence of a molybdenum dust buildup on plasma edge turbulence has been studied in the EAST tokamak.The motion of the dust from the upper divertor region is detected by a fast visible CCD camera,the XUV spectrom...The influence of a molybdenum dust buildup on plasma edge turbulence has been studied in the EAST tokamak.The motion of the dust from the upper divertor region is detected by a fast visible CCD camera,the XUV spectrometer arrays,and the EUV spectrometer.The MoXV emission intensity sharply increases compared with the spectral lines of various ionization states of other elements,which implies that the dust particles are the molybdenum impurities.The radial distribution of Mo^(14+)ion simulated by a simplified 1 D transport model indicates that the molybdenum dust mainly deposits in the pedestal bottom region.Moreover,it is observed that the coherent mode(CM)appears atρ=0.94 after the molybdenum impurities enter the main plasma region.The influx of molybdenum impurities results in increasing pedestal electron density and decreasing pedestal electron temperature in contrast to that before the event of impurities dropping.It is also found that the electron density gradient in the pedestal increases when the ablation of the molybdenum impurities is observed in the pedestal region.The qualitative experimental results indicate that the onset of CM is likely related to the increase of the density gradient and edge collisionality in the pedestal.In comparison to the density gradient,the enhancement of CM amplitude largely depends on the increase of the edge collisionality.展开更多
The poloidal magnetic field( B_(p)) plays a critical role in plasma equilibrium, confinement and transport of magnetic confinement devices. Multiple diagnostic methods are needed to complement each other to obtain a m...The poloidal magnetic field( B_(p)) plays a critical role in plasma equilibrium, confinement and transport of magnetic confinement devices. Multiple diagnostic methods are needed to complement each other to obtain a more accurate B_(p) profile. Recently, the laser-driven ion-beam trace probe(LITP) has been proposed as a promising tool for diagnosing B_(p) and radial electric field( E_(r)) profiles in tokamaks [Yang X Y et al 2014 Rev. Sci. Instrum. 85 11E429]. The spherical tokamak(ST) is a promising compact device with high plasma beta and naturally large elongation. However, when applying LITP to diagnosing B_(p) in STs, the larger B_(p) invalidates the linear reconstruction relationship for conventional tokamaks, necessitating the development of a nonlinear reconstruction principle tailored to STs. This novel approach employs an iterative reconstruction method based on Newton's method to solve the nonlinear equation. Subsequently,a simulation model to reconstruct the B_(p) profile of STs is developed and the experimental setup of LITP is designed for EXL-50, a middle-sized ST. Simulation results of the reconstruction show that the relative errors of B_(p) reconstruction are mostly below 5%. Moreover, even with 5 mm measurement error on beam traces or 1 cm flux surface shape error, the average relative error of reconstruction remains below 15%, initially demonstrating the robustness of LITP in diagnosing B_(p) profiles in STs.展开更多
Ultrafast charge exchange recombination spectroscopy(UF-CXRS)has been developed on the EAST tokamak(Yingying Li et al 2019 Fusion Eng.Des.146522)to measure fast evolutions of ion temperature and toroidal velocity.Here...Ultrafast charge exchange recombination spectroscopy(UF-CXRS)has been developed on the EAST tokamak(Yingying Li et al 2019 Fusion Eng.Des.146522)to measure fast evolutions of ion temperature and toroidal velocity.Here,we report the preliminary diagnostic measurements after relative sensitivity calibration.The measurement results show a much higher temporal resolution compared with conventional CXRS,benefiting from the usage of a prismcoupled,high-dispersion volume-phase holographic transmission grating and a high quantum efficiency,high-gain detector array.Utilizing the UF-CXRS diagnostic,the fast evolutions of the ion temperature and rotation velocity during a set of high-frequency small-amplitude edgelocalized modes(ELMs)are obtained on the EAST tokamak,which are then compared with the case of large-amplitude ELMs.展开更多
To interpret the common symmetric peaks caused by the large-scale structure in the complex S(f)spectrum from the heterodyne Doppler reflectometry(DR)measurement in EAST,a 2D circular-shaped O-mode full-wave model base...To interpret the common symmetric peaks caused by the large-scale structure in the complex S(f)spectrum from the heterodyne Doppler reflectometry(DR)measurement in EAST,a 2D circular-shaped O-mode full-wave model based on the finite-difference time-domain method is built.The scattering characteristics and the influences on the DR signal from various scales are investigated.When the structure is located around the cutoff layer,a moving radial or poloidal large-scale structure k_(θ)k_(θ),match(k_(θ),match is the theoretic wavenumber of Bragg scattering)could both generate an oscillation phase term called‘phase modulation’,and symmetrical peaks in the complex S(f)spectrum.It was found that the image-rejection ratio A_(−1)/A_(+1)(A_(±1)represents the amplitudes of±1 order modulation peaks)could be a feasible indicator for experiment comparison.In the case when the structure is near the cutoff layer with the same arrangement as the experiment for the edge DR channel,the curve of A_(−1)/A_(+1)versus kθcan be divided into three regions,weak asymmetrical range with k_(θ)/k_(0)0.15(k_(0)is the vacuum wavenumber),harmonics range with 0.15k_(θ)/k_(0)0.4,and Bragg scattering range of 0.4k_(θ)/k_(0)0.7.In the case when the structure is located away from the cutoff layer,the final complex S(f)spectrum is the simple superimposing of modulation and Bragg scattering,and the modulation peaks have an amplitude response nearly proportional to the local density fluctuation,called the‘propagationroute effect’.Under the H-mode experiment arrangement for the core DR,a critical fluctuation amplitude Amp(n_(e,Mod.@route))/Amp(n_(e,Tur.@MSA)∼1.3–4.1(Amp(n_(e,Mod.@route))refers to the pedestal large-scale structure amplitude and Amp(ne,Tur.@MSA)refers to turbulence amplitude at the main scattering area)is needed for the structure in the pedestal to be observed by the core DR measurement.The simulations are well consistent with the experimental results.These effects need to be carefully considered during the DR signal analyses as the injecting beam passes through the plasma region with large-scale structures.展开更多
Following the reconstruction of the TEXT tokamak at Huazhong University of Science and Technology in China, renamed as J-TEXT, a plethora of experimental and theoretical investigations has been conducted to elucidate ...Following the reconstruction of the TEXT tokamak at Huazhong University of Science and Technology in China, renamed as J-TEXT, a plethora of experimental and theoretical investigations has been conducted to elucidate the intricacies of turbulent transport within the tokamak configuration. These endeavors encompass not only the J-TEXT device's experimental advancements but also delve into critical issues pertinent to the optimization of future fusion devices and reactors. The research includes topics on the suppression of turbulence, flow drive and damping, density limit, non-local transport, intrinsic toroidal flow, turbulence and flow with magnetic islands, turbulent transport in the stochastic layer, and turbulence and zonal flow with energetic particles or helium ash. Several important achievements have been made in the last few years, which will be further elaborated upon in this comprehensive review.展开更多
基金supported by the National MCF Energy R&D Program(Nos.2019YFE03040003 and 2017YFE0301205)supported in part by Key Program of Research and Development of Hefei Science Center,CAS(No.2019HSC-KPRD001)partly supported by the Collaborative Research Program of the Research Institute for Applied Mechanics,Kyushu University.
文摘A millimeter wave solid state source—far infrared laser combined interferometer system(MFCI)consisting of a three-channel 890 GHz hydrogen cyanide(HCN)laser interferometer and a threechannel 340 GHz solid state source interferometer(SSI)is developed for real-time line-integrated electron density feedback and electron density profile of the EXL-50 spherical tokamak device.The interferometer system is a Mach–Zehnder type,with all probe-channels measured vertically,covering the plasma magnetic axis to the outermost closed magnetic plane.The HCN laser interferometer uses an HCN laser with a frequency of 890 GHz as a light source and modulates a100 k Hz beat signal by a rotating grating,giving a temporal resolution of 10μs.The SSI uses two independent 340 GHz solid-state diode sources as the light source,the frequency of the two sources is adjustable,and the temporal resolution of SSI can reach 1μs by setting the frequency difference of the two lasers at 1 MHz.The main optical path of the two interferometers is compactly installed on a set of double-layer optical platform directly below EXL-50.Dual optical path design using corner cube reflectors avoids the large support structures.Collinear the probebeams of two wavelengths,then the phase error caused by vibration can be compensated.At present,the phase noise of the HCN Interferometer is 0.08 rad,corresponding to a line-integrated electron density of 0.88×10^(17)m^(-2),one channel of measuring result was obtained by the MFCI system,and the highest density measured is about 0.7×10^(19)m^(-2).
文摘EHL-2 spherical torus(ST)is one of the key steps of p-^(11)B(proton-boron or hydrogen-boron)fusion energy research in ENN.The fusion produced energy is carried mainly by alpha particles of average energy 3 MeV,which ideally can be converted to electricity with high efficiency(>80%).However,there exist serious difficulties to realize such conversion in a fusion device,due to the high energy density and high voltage required.To comprehensively describe the progress of the EHL-2 physics design,this work presents preliminary considerations of approaches for achieving energy conversion,highlighting critical issues for further investigation.Specifically,we provide an initial simulation of alpha particle extraction in the EHL-2 ST configuration as a starting point for p-^(11)B fusion energy conversion.
基金supported by the ENN Group and the ENN Energy Research Institute.
文摘The EHL-2(ENN He-Long 2)spherical torus(ST)project focuses on advancing spherical torus technology to address the unique challenges of p-^(11)B fusion,which demands significantly higher ion temperature and heat flux to the divertor plate compared to traditional deuterium-tritium fusion.With a major radius of 1.05 m and a plasma current of 3 MA,the project aims to evaluate and optimize advanced divertor configurations,specifically the Super-X and X-point target(XPT)divertors.The design incorporates an up-down double-null configuration featuring a conventional inner divertor and an XPT outer divertor to effectively reduce the heat flux.The poloidal field(PF)coil system is meticulously optimized to balance engineering constraints with the flexibility in equilibrium configurations.This design is expected to provide a reference equilibrium configuration for other physics design issues and offer critical insight into heat load management.
基金supported by the Open Fund of Magnetic Confinement Laboratory of Anhui Province(No.2023 AMF03005)the China Postdoctoral Science Foundation(No.2021M703256)+4 种基金the Director Funding of Hefei Institutes of Physical Science,Chinese Academy of Sciences(No.YZJJ2022QN16)the National Key R&D Program of China(Nos.2022YFE03050003,2019YFE03080200,2019Y FE03040002,and 2022YFE03070004)National Natural Science Foundation of China(Nos.12075284,12175277,12275315 and 12275311)the National Magnetic Confinement Fusion Science Program of China(No.2022YFE03040001)the Science Foundation of the Institute of Plasma Physics,Chinese Academy of Sciences(No.DSJJ-2021-08)。
文摘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.
文摘A three-fluid equilibrium plasma with bulk plasma and energetic electrons has been observed on the Xuanlong-50(EXL-50) spherical torus, where the energetic electrons play a crucial role in sustaining the plasma current and pressure. In this study, the equilibrium of a multi-fluid plasma was investigated by analyzing the relationship between the external vertical magnetic field(B_(V)),plasma current(I_(p)), the poloidal ratio(β_(p)) and the Shafranov formula. Remarkably, our research demonstrates some validity of the Shafranov formula in the presence of multi-fluid plasma in EXL-50 spherical torus. This finding holds significant importance for future reactors as it allows for differentiation between alpha particles and background plasma. The study of multi-fluid plasma provides a significant reference value for the equilibrium reconstruction of burning plasma involving alpha particles.
基金supported by ENN Group and ENN Energy Research Institute.
文摘This paper presents the first comprehensive simulation study of p-11B fusion reactions in a spherical torus.We developed relevant program modules for fusion reactions based on energetic particle simulation frameworks and analyzed the two main fusion channels:thermal and beam-thermal.Using EHL-2 design parameters with n_(boron)=007n_(ion)and a hydrogen beam at 200 keV and 1 MW,our simulation indicates that p-11B reactions produce approximately 1.5×10^(15)αparticles per second(~0.7 kW)from the thermal channel,and5.3×10^(14)(~0.25 kW)from the beam-thermal channel.We conducted parameter scans to establish a solid physics foundation for the high ion temperature conditions(T_(i)>26ke V)designed for EHL-2.This work also laid the groundwork for studying various operation modes to explore different reaction channels.The simulation results suggest that the conditions in EHL-2 could be sufficient for investigating p-11B thermonuclear reactions.In addition,we found that EHL-2 offered good confinement for energetic particles,allowing us to research the interactions between these ions and plasmas.This research enhances our understanding of burning plasma physics.
基金supported by the ENN Group,the ENN Energy Research Institute and National Natural Science Foundation of China(No.12205122).
文摘EHL-2 is a compact,high-field spherical tokamak designed to explore the potential of an advanced p-11B nuclear fusion reactor.Due to its high plasma current and thermal energy,it is crucial to mitigate the impact associated with disruptions to ensure the safe operation of EHL-2.This paper evaluates the performance requirements of the disruption prediction system on EHL-2,with a particular focus on applying generalizable knowledge transfer from existing devices to future ones.Furthermore,the key characteristics of disruption mitigation strategies are analyzed,and their overall mitigation performance on EHL-2 is assessed.This insight provides valuable guidance for optimizing the engineering design of EHL-2 and identifying its optimal operational regime.
基金supported by ENN Group and ENN Energy Research Institute.
文摘The EXL-50U is China’s first large spherical torus device with a toroidal field reaching 1 T.The major radius of the EXL-50U ranges from 0.6 m to 0.8 m,with an aspect ratio of 1.4−1.8.The goal of plasma current in the first experimental phase is 500 kA,and in the future second phase,the goal of plasma current is 1 MA.On the EXL-50U project,the ENN fusion team expeditiously accomplished a series of comprehensive tasks including physical and engineering design,main component construction installation,and system commissioning,all within a mere eighteen-month timeframe.In the experiments of 2024,the EXL-50U achieved a 500 kA limiter configuration discharge using ECRH(Electron Cyclotron Resonance Heating)for non-inductive current start-up and a current ramp-up with the synergetic effect of ECRH and central solenoid(CS).Preliminary divertor configuration plasmas were also obtained under 200 kA plasma current.The core ion temperature of 1 keV was achieved with low-power NBI heating,and the energy confinement time of 30 ms was reached with Ohmic heating in the flat-top phase.The current and future experiments of EXL-50U will strongly support the physical design and operational scenarios of EHL-2 in the areas of current drive,high ion temperature exploration,energy transport and confinement,and hydrogen-boron physical characteristics.At the same time,the experience in the design,construction,and commissioning of the engineering,heating,and diagnostics systems on EXL-50U is also very beneficial for enhancing the feasibility of the engineering design for EHL-2.
基金the auspices of National Natural Science Foundations of China(Nos.12075284 and 12205157)supported by the High-End Talents Program of Hebei Province,Innovative Approaches towards Development of Carbon-Free Clean Fusion Energy(No.2021HBQZYCSB006).
文摘The EHL-2 spherical torus is designed to demonstrate proton-boron(p-11B)fusion within a compact spherical tokamak.Its planned heating system includes a negative ion-based neutral beam injection(N-NBI),two positive ion-based NBI systems(P-NBI),electron cyclotron resonance heating(ECRH),ion cyclotron resonance heating(ICRH),and high harmonic fast wave(HHFW),with a total power output of 31 MW.According to scaling law estimates,the device is capable of achieving H-mode operation.The plasma density,,n_(e,min)at the minimum L-H power threshold,P_(lh),is estimated to be 4.4×10^(19)m^(-3).The pedestal parameters were calculated using the REPED model.Assuming B as the primary impurity ion,the predicted pedestal width and height are lower compared to the typical case with carbon impurities.The pedestal collisionality for EHL-2 is estimated to range between 0.06 and 0.17,indicating the potential for significant energy loss due to edge localized modes(ELMs).The heat flux on the divertor plate has been calculated using the JOREK code.The peak heat fluxes during ELM bursts are approximately 31.0 MW/m^(2)at the lower inboard target and 39.5 MW/m^(2)at the lower outboard target.A preliminary design of the resonant magnetic perturbation(RMP)coils has been completed to both control type-I ELMs and correct error fields.The system comprises 16 coils arranged into 24 pairs.In ELM control mode,a 14/2 component is generated at 1.7 G/kAt,with a current of 4.9 kA required to achieveσChirikow=1 at the resonant surface,where the normalized poloidal magnetic flux is 0.85.In error field(EF)modulation mode,2/1 and 3/1 components are generated at 3.5 G/kAt and 2.8 G/kAt,respectively.
基金sponsored by the Fundamental Research Funds for the Central Universities(No.232024G-10)and National Natural Sciences Foundation of China(Nos.12075052,12275098 and 12275307)the ENN Group and the ENN Energy Research Institute.
文摘The divertor design is critical to heat load handling and thus to achievements of highperformance plasma operations in the EHL-2(ENN He-Long 2)tokamak.This paper presents the design of an X-point target(XPT)divertor,featuring a conventional inner divertor and an XPT outer divertor,aimed at the effective control of heat loads,which may be extremely high during high ion temperature scenarios.The divertor target plates are made from carbon-based materials,which can handle heat loads of up to 5 MW/m².Divertor performances,including the heat load controllability,the onset of detachment and the in-out/up-down asymmetry,etc.,are evaluated using both the simple particle-tracking strategy and the complicated SOLPS-ITER code.Special attention is paid to the drift effects on particle/heat transport in the divertor/scrape-off layer region and on the divertor heat loads,focusing on the semi-detached/detached operation regimes.Results from SOLPS-ITER simulations demonstrated that the currently designed magnetic equilibrium and divertor configuration can effectively handle the power heat load in EHL-2.
文摘The next generation fusion device listed on ENN’s fusion roadmap,named as(ENN He-Long)EHL-2,is under both physics and engineering designs.The instabilities of ideal magnetohydrodynamics(MHD)mode and neoclassical tearing mode(NTM)stabilized by electron cyclotron current drive(ECCD)for EHL-2’s two typical operation scenarios are analyzed.For high-ion-temperature operating(HITO)scenario,the vertical displacement event(VDE)could be a big challenge to the device safety.For the steady-state operating(SSO)scenario,the limitation may rise from the ideal MHD mode,NTM,etc.This suggests that the MHD analysis of both operation scenarios should be done with different focusing.Preliminary analysis based on the current physics and engineering design of both two scenarios is given in this paper.Based on the analysis result of above,the future assessments might target at active control method and the effect of boron on MHD activities.
基金supported by ENN Group and ENN Energy Research Institute.The authors would like to express their gratitude for the contributions of the ENN fusion team and collaborators,such as Tiantian Sun,Haojie Ma,and Yong Guo,in supporting these endeavours.The authors also acknowledge the support of the National SuperComputer Center in Tianjin and Beijing PARATERA Tech Corp.,Ltd.,for providing HPC resources that have contributed to the research results reported in this paper.This work was partly supported by National Natural Science Fundation of China(Nos.12375215 and 12475210).
文摘ENN He Long-2(EHL-2)is the next-generation large mega-Ampere(MA)spherical torus(ST)proposed and funded by the ENN company.The design parameters are:Ti0>30 keV,n_(e0)~1×10^(20)m^(-3),Ip~3 MA,Bt~3 T.One of the biggest challenges of EHL-2 is how to achieve several MA current flat-tops with limited voltage-seconds(Vs)of the center solenoid(CS)coils.In order to minimize the consumption of Vs,a fully non-inductive start-up by electron cyclotron resonance heating(ECRH)will be applied in EHL-2.The ramp-up phase will be accomplished with the synergetic mode between the CS and non-inductive methods.The strategy of non-inductive start-up and ramp-up with synergetic mode has been verified on EXL-50U’s experiments.Based on this strategy,numerical simulations indicate the feasibility of EHL-2 achieving 3 MA plasma current.A high-performance steady-state scenario with Ip~1.5 MA is also designed.In this scenario,the bootstrap current fraction fBS>70%,the safety factor q at the magnetic axis q0>2,the minimum safety factor qmin>1,the poloidal betaβp>3 and normalized betaβN>2.3.Each design iteration integrates the validation of physical models with the constraints of engineering implementation,gradually optimizing the performance of the heating and current drive(H&CD)systems.Numerical simulation results for general auxiliary H&CD systems such as neutral beam injection(NBI),electron cyclotron(EC)wave,ion cyclotron wave(ICW),and lower hybrid wave(LHW)are presented.These simulation results ensure that the 31 MW H&CD systems comprehensively cover all scenarios while maintaining engineering feasibility.
基金funded by the compact fusion project in the ENN group。
文摘Preionization has been widely employed to create initial plasma and help the toroidal plasma current formation.This research focuses on implementing a simple,economical and practical electron cyclotron resonance(ECR)preionization technique on the newly constructed EXL-50 spherical tokamak,and evaluating the effectiveness on improving the plasma current startup.Two types ECR microwave preionization experiments for the plasma initialization without the central solenoid are reported:(1)2.45 GHz microwave preionization and current startup with2.45 GHz ECR source;(2)2.45 GHz microwave preionization and current startup with 28 GHz ECR source.Application of the 2.45 GHz ECR microwave preionization to the experiments has contributed to(1)getting rid of the plasma breakdown delay;(2)the significant improvement of the discharge quality:the discharge is much longer and more stable while the driven plasma current is larger,compared to the discharge without preionization.
基金supported by National Natural Science Foundation of China(Nos.12075057,11775069,11320101005,51821005 and 11875020)Jiangxi Provincial Natural Science Foundation(No.20202ACBL201002)+1 种基金Doctoral Foundation(Nos.DHBK2017134 and DHBK 2018059)Grant-in-Aid for Scientific Research of JSPS(Nos.15H02155,15H02335,16H02442)。
文摘The toroidal component of the velocity for geodesic acoustic modes(GAMs)is first demonstrated.Multiple Langmuir probe arrays set up near the top tokamak of the J-TEXT were utilized for this study.A significant peak at the GAM frequency is observed in Mach number fluctuations.The toroidal velocity for the GAMs is estimated as 10–100 ms-1 and increases with the poloidal velocity.The ratio of toroidal component to the poloidal one of the velocity is mainly located in the interval between 0.3 and 1.0.With higher safety factors q,the ratio almost does not change with decreasing the safety factor,whereas it goes up sharply at low q.The coherencies between poloidal electric fields and Mach number fluctuations in turbulence frequency bands are also evaluated,and are higher than those between radial electric fields and Mach number fluctuations.
基金supported by National Natural Science Foundation of China(Nos.12175277 and 11975271)the National Key R&D Program of China(No.2022YFE 03050003)。
文摘A neural network model with a classical annotation method has been used on the EXL-50tokamak to predict impending disruption.However,the results revealed issues of overfitting and overconfidence in predictions caused by inaccurate labeling.To mitigate these issues,an improved training framework has been proposed.In this approach,soft labels from previous training serve as teachers to supervise the further learning process;this has lead to a significant improvement in predictive model performance.Notably,this enhancement is primarily attributed to the coupling effect of the soft labels and correction mechanism.This improved training framework introduces an instance-specific label smoothing method,which reflects a more nuanced model assessment on the likelihood of a disruption.It presents a possible solution to effectively address the challenges associated with accurate labeling across different machines.
基金supported by Shenzhen Clean Energy Research Institutesupported by the National Key R&D Program of China (No. 2017YFE0301205)National Natural Science Foundation of China (Nos. 11875289, 11975271, 11605244, 11675211, 12075284, 12075283, 12075155 and 11875294)
文摘The influence of a molybdenum dust buildup on plasma edge turbulence has been studied in the EAST tokamak.The motion of the dust from the upper divertor region is detected by a fast visible CCD camera,the XUV spectrometer arrays,and the EUV spectrometer.The MoXV emission intensity sharply increases compared with the spectral lines of various ionization states of other elements,which implies that the dust particles are the molybdenum impurities.The radial distribution of Mo^(14+)ion simulated by a simplified 1 D transport model indicates that the molybdenum dust mainly deposits in the pedestal bottom region.Moreover,it is observed that the coherent mode(CM)appears atρ=0.94 after the molybdenum impurities enter the main plasma region.The influx of molybdenum impurities results in increasing pedestal electron density and decreasing pedestal electron temperature in contrast to that before the event of impurities dropping.It is also found that the electron density gradient in the pedestal increases when the ablation of the molybdenum impurities is observed in the pedestal region.The qualitative experimental results indicate that the onset of CM is likely related to the increase of the density gradient and edge collisionality in the pedestal.In comparison to the density gradient,the enhancement of CM amplitude largely depends on the increase of the edge collisionality.
基金the support of National Key Research and Development Program of China (No. 2022YFA1604600)State Key Laboratory of Advanced Electromagnetic Technology。
文摘The poloidal magnetic field( B_(p)) plays a critical role in plasma equilibrium, confinement and transport of magnetic confinement devices. Multiple diagnostic methods are needed to complement each other to obtain a more accurate B_(p) profile. Recently, the laser-driven ion-beam trace probe(LITP) has been proposed as a promising tool for diagnosing B_(p) and radial electric field( E_(r)) profiles in tokamaks [Yang X Y et al 2014 Rev. Sci. Instrum. 85 11E429]. The spherical tokamak(ST) is a promising compact device with high plasma beta and naturally large elongation. However, when applying LITP to diagnosing B_(p) in STs, the larger B_(p) invalidates the linear reconstruction relationship for conventional tokamaks, necessitating the development of a nonlinear reconstruction principle tailored to STs. This novel approach employs an iterative reconstruction method based on Newton's method to solve the nonlinear equation. Subsequently,a simulation model to reconstruct the B_(p) profile of STs is developed and the experimental setup of LITP is designed for EXL-50, a middle-sized ST. Simulation results of the reconstruction show that the relative errors of B_(p) reconstruction are mostly below 5%. Moreover, even with 5 mm measurement error on beam traces or 1 cm flux surface shape error, the average relative error of reconstruction remains below 15%, initially demonstrating the robustness of LITP in diagnosing B_(p) profiles in STs.
基金supported by the National Magnetic Confinement Fusion Science Program of China (No. 2019YFE 03030004)National Natural Science Foundation of China (Nos. 11535013 and 11975232)
文摘Ultrafast charge exchange recombination spectroscopy(UF-CXRS)has been developed on the EAST tokamak(Yingying Li et al 2019 Fusion Eng.Des.146522)to measure fast evolutions of ion temperature and toroidal velocity.Here,we report the preliminary diagnostic measurements after relative sensitivity calibration.The measurement results show a much higher temporal resolution compared with conventional CXRS,benefiting from the usage of a prismcoupled,high-dispersion volume-phase holographic transmission grating and a high quantum efficiency,high-gain detector array.Utilizing the UF-CXRS diagnostic,the fast evolutions of the ion temperature and rotation velocity during a set of high-frequency small-amplitude edgelocalized modes(ELMs)are obtained on the EAST tokamak,which are then compared with the case of large-amplitude ELMs.
基金supported by Shenzhen Clean Energy Research Institute,the National MCF Energy R&D Program of China(Nos.2018YFE0311200 and 2022YFE03070004)National Natural Science Foundation of China(Nos.U1967206 and 12075155)+1 种基金the China Postdoctoral Science Foundation(No.2021M702270)the Fundamental Research Funds for the Central Universities(No.WK3420000018)。
文摘To interpret the common symmetric peaks caused by the large-scale structure in the complex S(f)spectrum from the heterodyne Doppler reflectometry(DR)measurement in EAST,a 2D circular-shaped O-mode full-wave model based on the finite-difference time-domain method is built.The scattering characteristics and the influences on the DR signal from various scales are investigated.When the structure is located around the cutoff layer,a moving radial or poloidal large-scale structure k_(θ)k_(θ),match(k_(θ),match is the theoretic wavenumber of Bragg scattering)could both generate an oscillation phase term called‘phase modulation’,and symmetrical peaks in the complex S(f)spectrum.It was found that the image-rejection ratio A_(−1)/A_(+1)(A_(±1)represents the amplitudes of±1 order modulation peaks)could be a feasible indicator for experiment comparison.In the case when the structure is near the cutoff layer with the same arrangement as the experiment for the edge DR channel,the curve of A_(−1)/A_(+1)versus kθcan be divided into three regions,weak asymmetrical range with k_(θ)/k_(0)0.15(k_(0)is the vacuum wavenumber),harmonics range with 0.15k_(θ)/k_(0)0.4,and Bragg scattering range of 0.4k_(θ)/k_(0)0.7.In the case when the structure is located away from the cutoff layer,the final complex S(f)spectrum is the simple superimposing of modulation and Bragg scattering,and the modulation peaks have an amplitude response nearly proportional to the local density fluctuation,called the‘propagationroute effect’.Under the H-mode experiment arrangement for the core DR,a critical fluctuation amplitude Amp(n_(e,Mod.@route))/Amp(n_(e,Tur.@MSA)∼1.3–4.1(Amp(n_(e,Mod.@route))refers to the pedestal large-scale structure amplitude and Amp(ne,Tur.@MSA)refers to turbulence amplitude at the main scattering area)is needed for the structure in the pedestal to be observed by the core DR measurement.The simulations are well consistent with the experimental results.These effects need to be carefully considered during the DR signal analyses as the injecting beam passes through the plasma region with large-scale structures.
基金supported by the National Key R&D Program of China (Nos. 2022YFE03100004, 2017YFE0302000, and 2017YFE0301100)National Natural Science Foundation of China (Nos. 12275097, 12275096, 11875292, 11675059, 11905079, 11305071, and 51821005)+5 种基金the Ministry of Science and Technology of China (No. 2013GB112002)the Project of Science and Technology Department of Sichuan Province (No. 2022NSFSC1791)the Natural Science Foundation of Anhui Province (No. 2208085J39)the Fundamental Research Funds for the Central Universities, HUST: (Nos. 2019kfy XMBZ034 and 2021XXJS007)the Initiative Postdocs Supporting Program of China (No. BX20180105)the US Department of Energy, Office of Science, Office of Fusion Energy Sciences (Nos. DEFG02-04ER54738 and DE-SC-0020287)。
文摘Following the reconstruction of the TEXT tokamak at Huazhong University of Science and Technology in China, renamed as J-TEXT, a plethora of experimental and theoretical investigations has been conducted to elucidate the intricacies of turbulent transport within the tokamak configuration. These endeavors encompass not only the J-TEXT device's experimental advancements but also delve into critical issues pertinent to the optimization of future fusion devices and reactors. The research includes topics on the suppression of turbulence, flow drive and damping, density limit, non-local transport, intrinsic toroidal flow, turbulence and flow with magnetic islands, turbulent transport in the stochastic layer, and turbulence and zonal flow with energetic particles or helium ash. Several important achievements have been made in the last few years, which will be further elaborated upon in this comprehensive review.
