Accurate measurement of the average plasma parameters in the edge region,including the temperature and density of electrons and ions,is critical for understanding the characteristics of the scrape-off layer(SOL) and d...Accurate measurement of the average plasma parameters in the edge region,including the temperature and density of electrons and ions,is critical for understanding the characteristics of the scrape-off layer(SOL) and divertor plasma transport in magnetically confined fusion research.On the J-TEXT tokamak,a multi-channel retarding field analyzer(RFA) probe has been developed to study average plasma parameters in the edge region under various poloidal divertor and island divertor configurations.The edge radial profile of the ion-to-electron temperature ratio,τ_(i/e),has been determined,which gradually decreases as the SOL ion self-collisionality,v_(SOL)*,increases.This is broadly consistent with what has been observed previously from various tokamak experiments.However,the comparison of experimental results under different configurations shows that in the poloidal divertor configuration,even under the same v_(SOL)*,τ_(i/e) in the SOL region becomes smaller as the distance from the X-point to the target plate increases.In the island divertor configuration,τ_(i/e) near the O-point is higher than that near the X-point at the same v_(SOL)*,and both are higher than those in the limiter configuration.These results suggest that the magnetic configuration plays a critical role in the energy distributions between electrons and ions at the plasma boundary.展开更多
A toroidal soft x-ray imaging(T-SXRI)system has been developed to investigate threedimensional(3D)plasma physics on J-TEXT.This T-SXRI system consists of three sets of SXR arrays.Two sets are newly developed and locat...A toroidal soft x-ray imaging(T-SXRI)system has been developed to investigate threedimensional(3D)plasma physics on J-TEXT.This T-SXRI system consists of three sets of SXR arrays.Two sets are newly developed and located on the vacuum chamber wall at toroidal positionsφof 126.4°and 272.6°,respectively,while one set was established previously atφ=65.50.Each set of SXR arrays consists of three arrays viewing the plasma poloidally,and hence can be used separately to obtain SXR images via the tomographic method.The sawtooth precursor oscillations are measured by T-SXRI,and the corresponding images of perturbative SXR signals are successfully reconstructed at these three toroidal positions,hence providing measurement of the 3D structure of precursor oscillations.The observed 3D structure is consistent with the helical structure of the m/n=1/1 mode.The experimental observation confirms that the T-SXRI system is able to observe 3D structures in the J-TEXT plasma.展开更多
The J-TEXT tokamak has been operated for ten years since its first plasma obtained at the end of 2007. The diagnostics development and main modulation systems, i.e. resonant magnetic perturbation (RMP) systems and m...The J-TEXT tokamak has been operated for ten years since its first plasma obtained at the end of 2007. The diagnostics development and main modulation systems, i.e. resonant magnetic perturbation (RMP) systems and massive gas injection (MGI) systems, will be introduced in this paper. Supported by these efforts, J-TEXT has contributed to research on several topics, especially on RMP physics and disruption mitigation. Both experimental and theoretical research show that RMP could lock, suppress or excite the tearing modes, depending on the RMP amplitude, frequency difference between RMP and rational surface rotation, and initial stabilities. The plasma rotation, particle transport and operation region are influenced by the RMP. Utilizing the MGI valves, disruptions have been mitigated with pure He, pure Ne, and a mixture of He and Ar (9:1). A significant runaway current plateau could be generated with moderate amounts of Ar injection. The RMP has been shown to suppress the generation of runaway current during disruptions.展开更多
In order to measure boundary electrostatic and magnetic fluctuations simultaneously,a combined Langmuir-magnetic probe(CLMP)has been designed and built on joint-Texas experimental tokamak.The probe consists of 8 graph...In order to measure boundary electrostatic and magnetic fluctuations simultaneously,a combined Langmuir-magnetic probe(CLMP)has been designed and built on joint-Texas experimental tokamak.The probe consists of 8 graphite probe pins and a 3D magnetic probe,driven by a mechanical pneumatic device.By means of simulation,the shielding effect of the graphite sleeve on the magnetic fluctuation signal is explored,and the influence of the eddy current was reduced by cutting the graphite sleeve.In the experiment,it has been verified that the mutual inductance of electromagnetic signals can be ignored,and a 70–90 k Hz electromagnetic mode is observed around the last closed magnetic surface.The establishment of CLMP provides data for the exploration of the coupling of electrostatic and magnetic fluctuations.展开更多
The three-dimensional(3D) magnetic configuration system in the J-TEXT tokamak has featured in many experimental studies.The system mainly consists of three subsystems:the static resonant magnetic perturbation(SRMP) sy...The three-dimensional(3D) magnetic configuration system in the J-TEXT tokamak has featured in many experimental studies.The system mainly consists of three subsystems:the static resonant magnetic perturbation(SRMP) system,the dynamic resonant magnetic perturbation(DRMP) system and the helical coil system.The SRMP coil system consist of two kinds of coils,i.e.three six-loop coils and two five-loop coils.It can suppress tearing modes with a moderate strength,and may also cause mode locking with larger amplitude.The DRMP coil system consists of 12 single-turn saddle coils(DRMP1) and 12 double-turn saddle coils(DRMP2).Its magnetic field can be rotated at a few kHz,leading to either acceleration or deceleration of the tearing mode velocity and the plasma rotation.The helical coil system consists of two closed coils,and is currently under construction to provide external rotational transform in J-TEXT.The 3D magnetic configuration system can suppress tearing modes,preventing and avoiding the occurrence of major disruption.展开更多
The effect of externally applied resonant magnetic perturbation(RMP)on carbon impurity behavior is investigated in the J-TEXT tokamak.It is found that the m/n=3/1 islands have an impurity screening effect,which become...The effect of externally applied resonant magnetic perturbation(RMP)on carbon impurity behavior is investigated in the J-TEXT tokamak.It is found that the m/n=3/1 islands have an impurity screening effect,which becomes obvious while the edge magnetic island is generated via RMP field penetration.The impurity screening effect shows a dependence on the RMP phase with the field penetration,which is strongest if the O point of the magnetic island is near the low-field-side(LFS)limiter plate.By combining a methane injection experimental study and STRAHL impurity transport analysis,we found that the variation of the impurity transport dominates the impurity screening effect.The impurity diffusion at the inner plasma region(r/a<0.8)is enhanced with a significant increase in outward convection velocity at the edge region in the case of the magnetic island’s O point near the LFS limiter plate.The impurity transport coefficient varies by a much lower level for the case with the magnetic island’s X point near the LFS limiter plate.The interaction of the magnetic island and the LFS limiter plate is thought to contribute to the impurity transport variation with the dependence on the RMP phase.A possible reason is the interaction between the magnetic island and the LFS limiter.展开更多
In J-TEXT tokamak,fast electron bremsstrahlung diagnostic with 9 chords equipped with multichannel analyzer enables detailed studies of the generation and transport of fast electrons.The spatial profiles and energy sp...In J-TEXT tokamak,fast electron bremsstrahlung diagnostic with 9 chords equipped with multichannel analyzer enables detailed studies of the generation and transport of fast electrons.The spatial profiles and energy spectrum of the fast electrons have been measured in two ECCD cases with either on-axis or off-axis injection,and the profiles processed by Abel-inversion are consistent with the calculated power deposition locations.Moreover,it is observed that the energy of fast electrons increases rapidly after turning off the ECCD,which may be attributed to the acceleration by the recovered loop voltage at low electron density.展开更多
The main works on disruption mitigation including suppression and mitigation of runaway current on the J-TEXT tokamak are summarized in this paper.Two strategies for the mitigation of runaway electron(RE) beams are ap...The main works on disruption mitigation including suppression and mitigation of runaway current on the J-TEXT tokamak are summarized in this paper.Two strategies for the mitigation of runaway electron(RE) beams are applied in experiments.The first strategy enables the REs to be completely suppressed by means of supersonic molecular beam injection and resonant magnetic perturbation which can enhance RE loss,magnetic energy transfer which can reduce the electric field,and secondary massive gas injection(MGI) which can increase the collisional damping.For the second strategy,the runaway current is allowed to form but should be dissipated or soft landed within tolerance.It is observed that the runaway current can be significantly dissipated by MGI,and the dissipation rate increases with the injected impurity particle number and eventually stabilizes at 28 MA s^(-1).The dissipation rate of the runaway current can be up to 3 MA s^(-1)by ohmic field.Shattered pellet injection has been chosen as the main disruption mitigation method,which has the capability of injecting material deeper into the plasma for higher density assimilation when compared to MGI.Moreover,simulation works show that the RE seeds in the plasma are strongly influenced under different phases and sizes of 2/1 mode locked islands during thermal quench.The robust runaway suppression and runaway current dissipation provide an important insight on the disruption mitigation for future large tokamaks.展开更多
A heterodyne collective scattering system has been designed and developed to investigate the turbulent transport of core plasma on J-TEXT.A dual-HCN laser which consists of two separately pumped HCN gas lasers at 337...A heterodyne collective scattering system has been designed and developed to investigate the turbulent transport of core plasma on J-TEXT.A dual-HCN laser which consists of two separately pumped HCN gas lasers at 337μm has been developed as the laser source of the scattering system.The intermediate frequency(IF)is~1 MHz when there is a 4μm cavity length difference and capable to maintain stability more than 5 h without manual operation.Detection channels at three different angles(2≤k_(⊥)≤12 cm^(-1))have been installed with Schottky barrier diode mixers of 893 GHz.The sampling frequency of the acquisition system is6 MHz to observe low-frequency density fluctuations.Initial experimental results have been detected and more results can be expected in future experiments.展开更多
The application of resonant magnetic perturbation(RMP)coils could break the initial axisymmetry and change the magnetic topology in tokamak systems.To understand the plasma equilibrium response to the RMP fields,three...The application of resonant magnetic perturbation(RMP)coils could break the initial axisymmetry and change the magnetic topology in tokamak systems.To understand the plasma equilibrium response to the RMP fields,three-dimensional(3 D)non-linear magnetohydrodynamics equilibrium calculations have been carried out using the HINT code for an RMP field-penetration experiment on J-TEXT.The HINT code does not assume perfectly nested flux surfaces,and is able to consider directly the change of magnetic topology due to the RMP field penetrations.Correlations between 3 D equilibrium calculations and experimental observations are presented.The magnetic topologies calculated by HINT were compared with the field topologies obtained from a vacuum approximation method.It turns out that the effects of redistribution of plasma pressure and current due to the formation of magnetic islands at various resonant rational surfaces should be considered self-consistently for understanding the change of magnetic structure.Such changes include changes in the shape and size of magnetic islands,and the distribution of stochastic fields around the magnetic islands and at the plasma boundary,which plays an important role for plasma-wall interactions.展开更多
High-density experiments in the high-field-side mid-plane single-null divertor configuration have been performed for the first time on J-TEXT.The experiments show an increase in the highest central channel line-averag...High-density experiments in the high-field-side mid-plane single-null divertor configuration have been performed for the first time on J-TEXT.The experiments show an increase in the highest central channel line-averaged density from 2.73×10^(19)m^(-3) to 6.49×10^(19)m^(-3),while the X-point moves away from the target by increasing the divertor coil current.The corresponding Greenwald fraction rises from 0.50 to 0.79.For the impurity transport,the density normalized radiation intensity(absolute extreme ultraviolet and soft x-ray)of the central channel density decreased significantly(>50%)with an increase in the plasma density.To better understand the underlying physics mechanisms,the 3 D edge Monte Carlo code coupled with EIRENE(EMC3-EIRENE)has been implemented for the first time on J-TEXT.The simulation results show good agreement with the experimental findings.As the X-point moves away from the target,the divertor power decay length drops and the scrape-off layer impurity screening effect is enhanced.展开更多
Nonlinear magnetohydrodynamic(MHD) simulations of an equilibrium on the J-TEXT tokamak with applied resonant magnetic perturbations(RMPs) are performed with NIMROD(non-ideal MHD with rotation,open discussion).Nu...Nonlinear magnetohydrodynamic(MHD) simulations of an equilibrium on the J-TEXT tokamak with applied resonant magnetic perturbations(RMPs) are performed with NIMROD(non-ideal MHD with rotation,open discussion).Numerical simulation of plasma response to RMPs has been developed to investigate magnetic topology,plasma density and rotation profile.The results indicate that the pure applied RMPs can stimulate 2/1 mode as well as 3/1 mode by the toroidal mode coupling,and finally change density profile by particle transport.At the same time,plasma rotation plays an important role during the entire evolution process.展开更多
基金supported by the National Magnetic Confinement Fusion Energy R&D Program of China (No.2018YFE0309100)National Natural Science Foundation of China (No.51821005)。
文摘Accurate measurement of the average plasma parameters in the edge region,including the temperature and density of electrons and ions,is critical for understanding the characteristics of the scrape-off layer(SOL) and divertor plasma transport in magnetically confined fusion research.On the J-TEXT tokamak,a multi-channel retarding field analyzer(RFA) probe has been developed to study average plasma parameters in the edge region under various poloidal divertor and island divertor configurations.The edge radial profile of the ion-to-electron temperature ratio,τ_(i/e),has been determined,which gradually decreases as the SOL ion self-collisionality,v_(SOL)*,increases.This is broadly consistent with what has been observed previously from various tokamak experiments.However,the comparison of experimental results under different configurations shows that in the poloidal divertor configuration,even under the same v_(SOL)*,τ_(i/e) in the SOL region becomes smaller as the distance from the X-point to the target plate increases.In the island divertor configuration,τ_(i/e) near the O-point is higher than that near the X-point at the same v_(SOL)*,and both are higher than those in the limiter configuration.These results suggest that the magnetic configuration plays a critical role in the energy distributions between electrons and ions at the plasma boundary.
基金supported by the National Magnetic Confinement Fusion Energy R&D Program of China(Nos.2018YFE0309100 and 2019YFE03010004)National Natural Science Foundation of China(No.51821005)。
文摘A toroidal soft x-ray imaging(T-SXRI)system has been developed to investigate threedimensional(3D)plasma physics on J-TEXT.This T-SXRI system consists of three sets of SXR arrays.Two sets are newly developed and located on the vacuum chamber wall at toroidal positionsφof 126.4°and 272.6°,respectively,while one set was established previously atφ=65.50.Each set of SXR arrays consists of three arrays viewing the plasma poloidally,and hence can be used separately to obtain SXR images via the tomographic method.The sawtooth precursor oscillations are measured by T-SXRI,and the corresponding images of perturbative SXR signals are successfully reconstructed at these three toroidal positions,hence providing measurement of the 3D structure of precursor oscillations.The observed 3D structure is consistent with the helical structure of the m/n=1/1 mode.The experimental observation confirms that the T-SXRI system is able to observe 3D structures in the J-TEXT plasma.
基金supported by the National Magnetic Confinement Fusion Science Program of China(Nos.2014GB118000,2014GB106001,2015GB111001,2015GB111002 and 2015GB120003)National Natural Science Foundation of China(Nos.11505069,11275079 and 11405068)
文摘The J-TEXT tokamak has been operated for ten years since its first plasma obtained at the end of 2007. The diagnostics development and main modulation systems, i.e. resonant magnetic perturbation (RMP) systems and massive gas injection (MGI) systems, will be introduced in this paper. Supported by these efforts, J-TEXT has contributed to research on several topics, especially on RMP physics and disruption mitigation. Both experimental and theoretical research show that RMP could lock, suppress or excite the tearing modes, depending on the RMP amplitude, frequency difference between RMP and rational surface rotation, and initial stabilities. The plasma rotation, particle transport and operation region are influenced by the RMP. Utilizing the MGI valves, disruptions have been mitigated with pure He, pure Ne, and a mixture of He and Ar (9:1). A significant runaway current plateau could be generated with moderate amounts of Ar injection. The RMP has been shown to suppress the generation of runaway current during disruptions.
基金supported by the National Key R&D Program of China(No.2018YFE0309100)National Natural Science Foundation of China(No.51821005)。
文摘In order to measure boundary electrostatic and magnetic fluctuations simultaneously,a combined Langmuir-magnetic probe(CLMP)has been designed and built on joint-Texas experimental tokamak.The probe consists of 8 graphite probe pins and a 3D magnetic probe,driven by a mechanical pneumatic device.By means of simulation,the shielding effect of the graphite sleeve on the magnetic fluctuation signal is explored,and the influence of the eddy current was reduced by cutting the graphite sleeve.In the experiment,it has been verified that the mutual inductance of electromagnetic signals can be ignored,and a 70–90 k Hz electromagnetic mode is observed around the last closed magnetic surface.The establishment of CLMP provides data for the exploration of the coupling of electrostatic and magnetic fluctuations.
基金supported by the National Magnetic Confinement Fusion Energy R&D Program of China(Nos.2018YFE0309100 and 2018YFE0310300)National Natural Science Foundation of China(Nos.12075096,11905077,11905078,11905079,11905080,12047526 and 51821005)
文摘The three-dimensional(3D) magnetic configuration system in the J-TEXT tokamak has featured in many experimental studies.The system mainly consists of three subsystems:the static resonant magnetic perturbation(SRMP) system,the dynamic resonant magnetic perturbation(DRMP) system and the helical coil system.The SRMP coil system consist of two kinds of coils,i.e.three six-loop coils and two five-loop coils.It can suppress tearing modes with a moderate strength,and may also cause mode locking with larger amplitude.The DRMP coil system consists of 12 single-turn saddle coils(DRMP1) and 12 double-turn saddle coils(DRMP2).Its magnetic field can be rotated at a few kHz,leading to either acceleration or deceleration of the tearing mode velocity and the plasma rotation.The helical coil system consists of two closed coils,and is currently under construction to provide external rotational transform in J-TEXT.The 3D magnetic configuration system can suppress tearing modes,preventing and avoiding the occurrence of major disruption.
基金supported by the National Key R&D Program of China(Nos.2017YFE0301301 and 2017YFE0302000)National Natural Science Foundation of China(Nos.11805135 and 11805131)the Ministry of Science and Technology(No.2015GB103001).
文摘The effect of externally applied resonant magnetic perturbation(RMP)on carbon impurity behavior is investigated in the J-TEXT tokamak.It is found that the m/n=3/1 islands have an impurity screening effect,which becomes obvious while the edge magnetic island is generated via RMP field penetration.The impurity screening effect shows a dependence on the RMP phase with the field penetration,which is strongest if the O point of the magnetic island is near the low-field-side(LFS)limiter plate.By combining a methane injection experimental study and STRAHL impurity transport analysis,we found that the variation of the impurity transport dominates the impurity screening effect.The impurity diffusion at the inner plasma region(r/a<0.8)is enhanced with a significant increase in outward convection velocity at the edge region in the case of the magnetic island’s O point near the LFS limiter plate.The impurity transport coefficient varies by a much lower level for the case with the magnetic island’s X point near the LFS limiter plate.The interaction of the magnetic island and the LFS limiter plate is thought to contribute to the impurity transport variation with the dependence on the RMP phase.A possible reason is the interaction between the magnetic island and the LFS limiter.
基金the National Key R&D Program of China(Nos.2017YFE0302000,2018YFE0309103,2019YFE030-10004,2017YFE0300501,2018YFE0310300,2018YFE0309100)National Natural Science Foundation of China(Nos.11775089,51821005,11905077 and 11575068)the China Postdoctoral Science Foundation(No.2019M652615)。
文摘In J-TEXT tokamak,fast electron bremsstrahlung diagnostic with 9 chords equipped with multichannel analyzer enables detailed studies of the generation and transport of fast electrons.The spatial profiles and energy spectrum of the fast electrons have been measured in two ECCD cases with either on-axis or off-axis injection,and the profiles processed by Abel-inversion are consistent with the calculated power deposition locations.Moreover,it is observed that the energy of fast electrons increases rapidly after turning off the ECCD,which may be attributed to the acceleration by the recovered loop voltage at low electron density.
基金supported by the National MCF Energy R&D Program of China(Nos.2019YFE03010004,2018YFE0309103,2018YFE0310300,2018YFE0309100,2017YFE0302000,2017YFE0300501)National Natural Science Foundation of China(Nos.11775089,51821005,12205122,11905077 and 11575068)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.21KJB140025)
文摘The main works on disruption mitigation including suppression and mitigation of runaway current on the J-TEXT tokamak are summarized in this paper.Two strategies for the mitigation of runaway electron(RE) beams are applied in experiments.The first strategy enables the REs to be completely suppressed by means of supersonic molecular beam injection and resonant magnetic perturbation which can enhance RE loss,magnetic energy transfer which can reduce the electric field,and secondary massive gas injection(MGI) which can increase the collisional damping.For the second strategy,the runaway current is allowed to form but should be dissipated or soft landed within tolerance.It is observed that the runaway current can be significantly dissipated by MGI,and the dissipation rate increases with the injected impurity particle number and eventually stabilizes at 28 MA s^(-1).The dissipation rate of the runaway current can be up to 3 MA s^(-1)by ohmic field.Shattered pellet injection has been chosen as the main disruption mitigation method,which has the capability of injecting material deeper into the plasma for higher density assimilation when compared to MGI.Moreover,simulation works show that the RE seeds in the plasma are strongly influenced under different phases and sizes of 2/1 mode locked islands during thermal quench.The robust runaway suppression and runaway current dissipation provide an important insight on the disruption mitigation for future large tokamaks.
基金the National Key R&D Program of China(Nos.2017YFE0302000,2018YFE0310300 and 2018YFE0309101)National Natural Science Foundation of China(Nos.51821005 and 11905080)。
文摘A heterodyne collective scattering system has been designed and developed to investigate the turbulent transport of core plasma on J-TEXT.A dual-HCN laser which consists of two separately pumped HCN gas lasers at 337μm has been developed as the laser source of the scattering system.The intermediate frequency(IF)is~1 MHz when there is a 4μm cavity length difference and capable to maintain stability more than 5 h without manual operation.Detection channels at three different angles(2≤k_(⊥)≤12 cm^(-1))have been installed with Schottky barrier diode mixers of 893 GHz.The sampling frequency of the acquisition system is6 MHz to observe low-frequency density fluctuations.Initial experimental results have been detected and more results can be expected in future experiments.
基金supported by the National Key R&D Program of China(No.2018YFE0309100)by National Natural Science Foundation of China(No.51821005)。
文摘The application of resonant magnetic perturbation(RMP)coils could break the initial axisymmetry and change the magnetic topology in tokamak systems.To understand the plasma equilibrium response to the RMP fields,three-dimensional(3 D)non-linear magnetohydrodynamics equilibrium calculations have been carried out using the HINT code for an RMP field-penetration experiment on J-TEXT.The HINT code does not assume perfectly nested flux surfaces,and is able to consider directly the change of magnetic topology due to the RMP field penetrations.Correlations between 3 D equilibrium calculations and experimental observations are presented.The magnetic topologies calculated by HINT were compared with the field topologies obtained from a vacuum approximation method.It turns out that the effects of redistribution of plasma pressure and current due to the formation of magnetic islands at various resonant rational surfaces should be considered self-consistently for understanding the change of magnetic structure.Such changes include changes in the shape and size of magnetic islands,and the distribution of stochastic fields around the magnetic islands and at the plasma boundary,which plays an important role for plasma-wall interactions.
基金supported by the National Magnetic Confinement Fusion Energy R&D Program of China (Nos.2018YFE0301104 and 2018YFE0309100)National Natural Science Foundation of China (No. 51821005).
文摘High-density experiments in the high-field-side mid-plane single-null divertor configuration have been performed for the first time on J-TEXT.The experiments show an increase in the highest central channel line-averaged density from 2.73×10^(19)m^(-3) to 6.49×10^(19)m^(-3),while the X-point moves away from the target by increasing the divertor coil current.The corresponding Greenwald fraction rises from 0.50 to 0.79.For the impurity transport,the density normalized radiation intensity(absolute extreme ultraviolet and soft x-ray)of the central channel density decreased significantly(>50%)with an increase in the plasma density.To better understand the underlying physics mechanisms,the 3 D edge Monte Carlo code coupled with EIRENE(EMC3-EIRENE)has been implemented for the first time on J-TEXT.The simulation results show good agreement with the experimental findings.As the X-point moves away from the target,the divertor power decay length drops and the scrape-off layer impurity screening effect is enhanced.
基金supported by the National Magnetic Confinement Fusion Science Programs(No.2015GB104004 and No.2015GB111002)partially supported by National Natural Science Foundation of China(No.11575068)
文摘Nonlinear magnetohydrodynamic(MHD) simulations of an equilibrium on the J-TEXT tokamak with applied resonant magnetic perturbations(RMPs) are performed with NIMROD(non-ideal MHD with rotation,open discussion).Numerical simulation of plasma response to RMPs has been developed to investigate magnetic topology,plasma density and rotation profile.The results indicate that the pure applied RMPs can stimulate 2/1 mode as well as 3/1 mode by the toroidal mode coupling,and finally change density profile by particle transport.At the same time,plasma rotation plays an important role during the entire evolution process.