Spontaneous transition of the plasma confinement mode was observed in thehelical-axis heliotron device 'Heliotron J' for three different plasma heating schemes, i.e.ECH-only, NBI-only and the combination of EC...Spontaneous transition of the plasma confinement mode was observed in thehelical-axis heliotron device 'Heliotron J' for three different plasma heating schemes, i.e.ECH-only, NBI-only and the combination of ECH and NBI. The transition seems to occur above a certaincritical density. In addition to the confinement transition, a spontaneous shift of the hittingposition of the divertor plasma flux on the wall was observed. This shift could be related with thechange of the edge field topology caused by non-inductive toroidal currents.展开更多
Since runaway electrons and magnetohydrodynamics activity can contribute to serious damage and energy losses in tokamaks, the effect of an external electric field on runaway electrons and hard x-ray spectra is investi...Since runaway electrons and magnetohydrodynamics activity can contribute to serious damage and energy losses in tokamaks, the effect of an external electric field on runaway electrons and hard x-ray spectra is investigated. Parameters such as the plasma current, the hard x-ray photons count and the mean energy of runaway electrons are measured. Positive and negative voltages of 300 V are applied at lOms after the plasma initiation （while the plasma is forming）, at 15ms （while the plasma is stable） and at 20ms （while the plasma is fading away） to attain the most effective time of applying the external electric field. The number of hard x-ray photons has the most changes in the range of O-200 keV when the external electric fields are applied. Also in the duration of 20-30ms of plasma the greatest number of hard x-ray spectra is detected. When the external electric fields are applied, the mean energy of runaway electrons reduces significantly, especially at 15 ms （while the plasma is stab/e）.展开更多
This paper describes a Mach/Langmuir probe array with five pins and six pins, which can measure not only parallel flows and the flow perpendicular to the magnetic field but also the radial and the poloidal electric fi...This paper describes a Mach/Langmuir probe array with five pins and six pins, which can measure not only parallel flows and the flow perpendicular to the magnetic field but also the radial and the poloidal electric field E. arid E as well. Experimental measurements of the edge fluctuations, velocities of the toroidal, the poloidal flow and electric field have been carried out on both of SOL and the boundary region of HL-1M for Ohmic, biased H-mode, Lower Hybrid Current Drive (LHCD), Supersonic Molecular Beam Injection (MBI), Multi-shot Pellet Injection (MPI), Neutral Beam Injection (NBI), Ion Cyclotron Resonance Heating (ICRH) and Electric Cyclotron Resonance Heating (ECRH) discharges. The results show that the suppressions of the fluctuations are related to poloidal rotations produced by different discharge modes in the improved particle confinement property, simultaneously the change of the radial and poloidal electric field is generated and becomes more negative at the Tokamak plasma edge, and the sheared poloidal flow is related to the reduction in fluctuation level, and the poloidal velocity is mainly dominated by the E × B drift.展开更多
Carbon encapsulated Fe nanoparticles were successfully prepared via confined arc plasma method. The composition, morphology, microstructure, specific surface area and particle size of the product were characterized vi...Carbon encapsulated Fe nanoparticles were successfully prepared via confined arc plasma method. The composition, morphology, microstructure, specific surface area and particle size of the product were characterized via X-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray spectrometry and Brunauer-Emmett-Teller N2 adsorption. The experiment results show that the carbon encapsulated Fe nanoparticles have clear core-shell structure. The core of the particles is body centered cubic Fe, and the shell is disorder carbons. The particles are in spherical or ellipsoidal shapes. The particle size of the nanocapsules ranges from 15 to 40 nm, with the average value of about 30 nm. The particle diameter of the core is 18 nm, the thickness of the shells is 6-8 nm, and the specific surface area is 24 m2/g.展开更多
Engineering ceramics are typical difficult-to-machine materials because of high hardness and brittleness. PAC (Plasma Arc Cutting) is a very important thermal cutting process and has been successfully used in cutting ...Engineering ceramics are typical difficult-to-machine materials because of high hardness and brittleness. PAC (Plasma Arc Cutting) is a very important thermal cutting process and has been successfully used in cutting stainless steel and other difficult-to-machine alloys. PAC’s application in cutting ceramics, however, is still limited because the most ceramics are not good electronic conducts, and transferred plasma arc cannot be produced between cathode and work-piece. So we presented a method of plasma arc cutting engineering ceramics with additional anode. To reduce the kerf width and to improve the kerf quality, the hydro-magnetically confined plasma arc is used to cut engineering ceramic plates. By experiments and analyses the mechanism and characteristics of hydro-magnetic confined plasma are discussed and the effects of secondary confinement on cutting quality, arc properties, and optimal process parameters are presented. When the nozzle diameter is 3 mm, the kerf width of the Al 2O 3 ceramic plate with 6 mm thickness is less than 4.6 mm, and the cutting speed reaches to 0.9～1.2 m/min. Both theoretical analysis and experimental results have proved the feasibility and validity of the newly advanced hydro-magnetic plasma arc cutting, and the following conclusion can be drawn: (1)Synthesizing the advantages of both the water-constriction and magnetic constriction, the hydro-magnetic constriction of plasma arc forms a three-dimensional constriction with improved shape and uniformity of arc column, narrower kerfs, minimal beveling of cuts and higher dross-free cutting speeds than those under either water-constriction or magnetic constriction alone.(2)Hydro-magnetic constriction is capable of improving arc stability, which is reflected in the higher arc voltage at which arc-extinction occurs, than that under any single constriction. (3)For a given diameter of nozzle, quality cut can be produced by using a lower arc current than usually required in conventional plasma arc cutting, but ensuring fine arc shape and capability of cutting simply by employing hydro-magnetic constriction. Meanwhile, the heat load on nozzle could be reduced and service life of nozzle raised.展开更多
ICF(inertial confinement fusion)holds significant potential for achieving controlled nuclear fusion,but challenges related to efficient energy transfer and plasma stabilization remains.This article explores the ion-bu...ICF(inertial confinement fusion)holds significant potential for achieving controlled nuclear fusion,but challenges related to efficient energy transfer and plasma stabilization remains.This article explores the ion-bubble trigger mechanism as a promising solution for improving the compression and energy deposition processes in ICF,particularly when coupled with external magnetic fields,wigglers,undulators,and trapped magnetic fields.The ion-bubble mechanism enhances energy transfer by creating localized heating in the plasma,increasing the likelihood of fusion ignition.External magnetic fields,through their interaction with plasma particles,can optimize ion-bubble interactions by influencing particle trajectories and stabilizing plasma instabilities.Additionally,wigglers and undulators—devices that create oscillating magnetic fields—offer a means to fine-tune the interaction between plasma and electromagnetic radiation,further enhancing the ion-bubble effect.Trapped magnetic fields,formed through plasma compression,also contribute to plasma confinement and stability,offering further support for the ion-bubble trigger mechanism.By combining these factors,the ion-bubble trigger mechanism in ICF could significantly improve fusion efficiency and bring us closer to realizing sustainable fusion energy.展开更多
This paper generally compares the essential features between tokamaks and stellarators,based on previous review work individually made by authors on several specific topics,such as theories,bulk plasma transport and e...This paper generally compares the essential features between tokamaks and stellarators,based on previous review work individually made by authors on several specific topics,such as theories,bulk plasma transport and edge divertor physics,along with some recent results.It aims at summarizing the main results and conclusions with regard to the advantages and disadvantages in these two types of magnetic fusion devices.The comparison includes basic magnetic configurations,magnetohydrodynamic(MHD)instabilities,operational limits and disruptions,neoclassical and turbulent transport,confinement scaling and isotopic effects,plasma rotation,and edge and divertor physics.Finally,a concept of quasi-symmetric stellarators is briefly referred along with a comparison of future application for fusion reactors.展开更多
This paper describes the control software together with the operational hardware, which successfully realizes the operation of a new fully programmable imaging system with high spatial and temporal resolutions on the ...This paper describes the control software together with the operational hardware, which successfully realizes the operation of a new fully programmable imaging system with high spatial and temporal resolutions on the KT5D magnetic torus, for observing the visible l ight emission from the plasma discharge.展开更多
A new high repetition rate Nd：YAG Thomson scattering system is developed for the Heliotron J helical device. A main purpose of installing the new system is the temporal evolution measurement of a plasma profile for i...A new high repetition rate Nd：YAG Thomson scattering system is developed for the Heliotron J helical device. A main purpose of installing the new system is the temporal evolution measurement of a plasma profile for improved confinement physics such as the edge transport barrier （H-mode） or the internal transport barrier of the helical plasma. The system has 25 spatial points with -10 mm resolution. Two high repetition Nd：YAG lasers （〉 550 m J@ 50 Hz） realize the measurement of the time evolution of the plasma profile with ~10 ms time intervals. Scattered light is collected by a large concave mirror （D----800 mm, f/2.25） with a solid angle of -100 mstr and transferred to interference filter polychromators by optical fiber bundles in a staircase form. The signal is amplified by newly designed fast preamplifiers with DC and AC output, which reduces the low frequency background noise. The signals are digitized with a multi-event QDC, fast gated integrators. The data acquisition is performed by a VME-based system operated by the CINOS.展开更多
An electromagnetic calculation and the parameters of the magnet system of the magnetically confined plasma rocket were established. By using ANSYS code, it was found that the leakage rate depends on the current intens...An electromagnetic calculation and the parameters of the magnet system of the magnetically confined plasma rocket were established. By using ANSYS code, it was found that the leakage rate depends on the current intensity of the magnet and the change of the magnet position.展开更多
A phase-controlled lower hybrid wave （LHW） multi-junction （M J） coupler （3（rows）×4（columns）×4 （subwaveguides）） has been developed in the HT-7 tokamak. Simulations show that it is more effective f...A phase-controlled lower hybrid wave （LHW） multi-junction （M J） coupler （3（rows）×4（columns）×4 （subwaveguides）） has been developed in the HT-7 tokamak. Simulations show that it is more effective for driving plasma current than an ordinary phase-controlled LHW antenna （3（rows）× 12（columns）） （traditional coupler）. The plasm-wave coupling experiments show that the reflection coefficient （RC） is below 10%, implying that the MJ grill can launch the wave into the plasma effectively. The effect of power spectrum launched by the MJ coupler on RC indicates that an optimal condition is requisite for a better coupling in the lower hybrid current drive （LHCD） experiments, Studies indicate that the drive efficiency of the MJ antenna is higher than that of the traditional one, which is mainly ascribed to the discrepancy in impurity concentration, plasma temperature, and spectrum directivity. An improved confinement with an electron internal transport barrier is obtained by LHCD. The analysis shows that the modified negative （low） magnetic shear and the change of radial electric field profile due to LHCD are possible factors responsible for the eITB formation.展开更多
This paper reviews the energetic particle（EP） experiments during electron cyclotron resonance heating（ECRH） and neutral beam injection in the HL-2 A tokamak.A number of important results are summarized,which relat...This paper reviews the energetic particle（EP） experiments during electron cyclotron resonance heating（ECRH） and neutral beam injection in the HL-2 A tokamak.A number of important results are summarized,which relate to ITER physics,including the behavior of the multi-mode instability,the nonlinear interaction between wave-wave and wave-particles,the losses of EP induced by the instabilities,the effect of the EP instabilities on the thermal plasma confinement and the control of the EP instabilities by means of ECRH.Systematic experiments indicate that when the drive is great enough,the nonlinear effects and the multi-mode coexistence may play an important role,which affect the transport both of the EPs and the background plasma confinement,and these instabilities could be controlled.Some new phenomena about the EP induced instabilities discovered recently on the device,such as high frequency reversed shear Alfvén eigenmodes,Alfvénic ion temperature gradient modes,the geodesic acoustic mode induced by energetic electrons excited by interaction between tearing mode and beta induced Alfvén eigenmode and double e-fishbone in negative magnetic shear discharges etc,have also been presented in the paper.展开更多
The high confinement mode （H-mode） operation is recently obtained in HL-2A divertor configuration, the corresponding edge localized mode （ELM） is recognized as being of type III. Time intervals in ELM time series ...The high confinement mode （H-mode） operation is recently obtained in HL-2A divertor configuration, the corresponding edge localized mode （ELM） is recognized as being of type III. Time intervals in ELM time series are analysed to obtain the information about the ELM process. Signatures of unstable periodic orbits （UPOs） are detected, which are indicators of chaos and may be used to control the big ELM events.展开更多
One of the reasons for increased material removal rate in magnetic field assisted dry electrical discharge machining （EDM） is confinement of plasma due to Lorentz forces. This paper presents a mathematical model to ...One of the reasons for increased material removal rate in magnetic field assisted dry electrical discharge machining （EDM） is confinement of plasma due to Lorentz forces. This paper presents a mathematical model to evaluate the effect of external magnetic field on crater depth and diameter in single- and multiple-discharge EDM process. The model incorporates three main effects of the magnetic field, which include plasma confinement, mean free path reduction and pulsating magnetic field effects. Upon the application of an external magnetic field, Lorentz forces that are developed across the plasma column confine the plasma column. Also, the magnetic field reduces the mean free path of electrons due to an increase in the plasma pressure and cycloidal path taken by the electrons between the electrodes. As the mean free path of electrons reduces, more ionization occurs in plasma column and eventually an increase in the current density at the inter-electrode gap occurs. The model results for crater depth and its diameter in single discharge dry EDM process show an error of 9%-10% over the respective experimental values.展开更多
The implementation of magnetic islands in gyrokinetic simulation has been verified in the gyrokinetic toroidal code（GTC）.The ion and electron density profiles become partially flattened inside the islands.The densit...The implementation of magnetic islands in gyrokinetic simulation has been verified in the gyrokinetic toroidal code（GTC）.The ion and electron density profiles become partially flattened inside the islands.The density profile at the low field side is less flattened than that at the high field side due to toroidally trapped particles in the low field side,which do not move along the perturbed magnetic field lines.When the fraction of trapped particles decreases,the density profile at the low field becomes more flattened.展开更多
In the quest for a sustainable and abundant energy source, nuclear fusion technology stands as a beacon of hope. This study introduces a groundbreaking quantum mechanically effective induction system designed for magn...In the quest for a sustainable and abundant energy source, nuclear fusion technology stands as a beacon of hope. This study introduces a groundbreaking quantum mechanically effective induction system designed for magnetic plasma confinement within fusion reactors. The pursuit of clean energy, essential to combat climate change, hinges on the ability to harness nuclear fusion efficiently. Traditional approaches have faced challenges in plasma stability and energy efficiency. The novel induction system presented here not only addresses these issues but also transforms fusion reactors into integrated construction systems. This innovation promises compact fusion reactors, marking a significant step toward a clean and limitless energy future, free from the constraints of traditional power sources. This revolutionary quantum induction system redefines plasma confinement in fusion reactors, unlocking clean, compact, and efficient energy production.展开更多
Recent results of JT-60U towards establishment of physics basis for ITER andadvanced tokamak operation are presented. Progress in high integrated performance is achieved withimprovement of N-NB and ECRF heating system...Recent results of JT-60U towards establishment of physics basis for ITER andadvanced tokamak operation are presented. Progress in high integrated performance is achieved withimprovement of N-NB and ECRF heating systems. In the next experimental campaign 2003～2004,discharge duration with 17 MW heating will be extended up to 30s for sustaining high-beta plasmalonger than the current diffusion time. Superconducting modification of JT-60 is planned todemonstrate high-beta plasma sustainment exceeding ideal MHD instability limit without wallstabilization.展开更多
The energy loss of charged particles, including electrons, protons, and α-particles with tens keV initial energy E0, traveling in the hot dense carbon(C) plasma for densities from 2.281 to 22.81 g/cm3 and temperature...The energy loss of charged particles, including electrons, protons, and α-particles with tens keV initial energy E0, traveling in the hot dense carbon(C) plasma for densities from 2.281 to 22.81 g/cm3 and temperatures from 400 to 1500 eV is systematically and quantitatively studied by using the dimensional continuation method. The behaviors of different charged particles are readily distinguishable from each other. Firstly, because an ion is thousands times heavier than an electron, the penetration distance of the electron is much longer than that of proton and α-particle traveling in the plasma. Secondly, most energy of electron projectile with E0 < 100 keV deposits into the electron species of C plasma, while for the cases of proton and α-particle with E0 < 100 keV,about more than half energy transfers into the ion species of C plasma. A simple decreasing law of the penetration distance as a function of the plasma density is fitted, and different behaviors of each projectile particle can be clearly found from the fitted data.We believe that with the advanced progress of the present experimental technology, the findings shown here could be confirmed in ion-stopping experiments in the near future.展开更多
Two dark solitons are considered in a two-component Bose-Einstein condensate with an external magnetic trap, and effects of the trap potential on their dynamics are investigated by the numerical simulation. The result...Two dark solitons are considered in a two-component Bose-Einstein condensate with an external magnetic trap, and effects of the trap potential on their dynamics are investigated by the numerical simulation. The results show that the dark solitons attract, collide and repel periodically in two components as time changes, the time period depends strictly on the initial condition and the potential, and there are obvious self-trapping effects on the two dark solitons.展开更多
We report the experimental achievement of ^（87）Rb Bose-Einstein condensation in a magnetic trap with microwave and radio frequency（RF） induced evaporation.Evaporative cooling is realized by using 6.8 GHz microwave...We report the experimental achievement of ^（87）Rb Bose-Einstein condensation in a magnetic trap with microwave and radio frequency（RF） induced evaporation.Evaporative cooling is realized by using 6.8 GHz microwave radiation driving the ^（87）Rb atoms to transit from the ground-state hyperfine state ｜F=2,m_F= 2〉to ｜F=l,m_F=1〉.Compared with RF-induced evaporation,^（87）Rb atoms are hardly to achieve pure condensate by microwave evaporation cooling due to the effect of atoms in the ｜F=1,m_F=1〉state being pumped back into the trapping ｜F=2,m_F=1〉state.展开更多
基金The project partially supported by the Grant-in-Aid for Science Research of MEXT in Japan and by the Collaboration Program of the Laboratory for Complex Energy ProcessesIAEKyoto University
文摘Spontaneous transition of the plasma confinement mode was observed in thehelical-axis heliotron device 'Heliotron J' for three different plasma heating schemes, i.e.ECH-only, NBI-only and the combination of ECH and NBI. The transition seems to occur above a certaincritical density. In addition to the confinement transition, a spontaneous shift of the hittingposition of the divertor plasma flux on the wall was observed. This shift could be related with thechange of the edge field topology caused by non-inductive toroidal currents.
文摘Since runaway electrons and magnetohydrodynamics activity can contribute to serious damage and energy losses in tokamaks, the effect of an external electric field on runaway electrons and hard x-ray spectra is investigated. Parameters such as the plasma current, the hard x-ray photons count and the mean energy of runaway electrons are measured. Positive and negative voltages of 300 V are applied at lOms after the plasma initiation （while the plasma is forming）, at 15ms （while the plasma is stable） and at 20ms （while the plasma is fading away） to attain the most effective time of applying the external electric field. The number of hard x-ray photons has the most changes in the range of O-200 keV when the external electric fields are applied. Also in the duration of 20-30ms of plasma the greatest number of hard x-ray spectra is detected. When the external electric fields are applied, the mean energy of runaway electrons reduces significantly, especially at 15 ms （while the plasma is stab/e）.
文摘This paper describes a Mach/Langmuir probe array with five pins and six pins, which can measure not only parallel flows and the flow perpendicular to the magnetic field but also the radial and the poloidal electric field E. arid E as well. Experimental measurements of the edge fluctuations, velocities of the toroidal, the poloidal flow and electric field have been carried out on both of SOL and the boundary region of HL-1M for Ohmic, biased H-mode, Lower Hybrid Current Drive (LHCD), Supersonic Molecular Beam Injection (MBI), Multi-shot Pellet Injection (MPI), Neutral Beam Injection (NBI), Ion Cyclotron Resonance Heating (ICRH) and Electric Cyclotron Resonance Heating (ECRH) discharges. The results show that the suppressions of the fluctuations are related to poloidal rotations produced by different discharge modes in the improved particle confinement property, simultaneously the change of the radial and poloidal electric field is generated and becomes more negative at the Tokamak plasma edge, and the sheared poloidal flow is related to the reduction in fluctuation level, and the poloidal velocity is mainly dominated by the E × B drift.
基金Project(208151)supported by the Key Project of Ministry of Education,ChinaProject(1014RJZA035)supported by the Natural Science Foundation of Gansu Province,China
文摘Carbon encapsulated Fe nanoparticles were successfully prepared via confined arc plasma method. The composition, morphology, microstructure, specific surface area and particle size of the product were characterized via X-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray spectrometry and Brunauer-Emmett-Teller N2 adsorption. The experiment results show that the carbon encapsulated Fe nanoparticles have clear core-shell structure. The core of the particles is body centered cubic Fe, and the shell is disorder carbons. The particles are in spherical or ellipsoidal shapes. The particle size of the nanocapsules ranges from 15 to 40 nm, with the average value of about 30 nm. The particle diameter of the core is 18 nm, the thickness of the shells is 6-8 nm, and the specific surface area is 24 m2/g.
文摘Engineering ceramics are typical difficult-to-machine materials because of high hardness and brittleness. PAC (Plasma Arc Cutting) is a very important thermal cutting process and has been successfully used in cutting stainless steel and other difficult-to-machine alloys. PAC’s application in cutting ceramics, however, is still limited because the most ceramics are not good electronic conducts, and transferred plasma arc cannot be produced between cathode and work-piece. So we presented a method of plasma arc cutting engineering ceramics with additional anode. To reduce the kerf width and to improve the kerf quality, the hydro-magnetically confined plasma arc is used to cut engineering ceramic plates. By experiments and analyses the mechanism and characteristics of hydro-magnetic confined plasma are discussed and the effects of secondary confinement on cutting quality, arc properties, and optimal process parameters are presented. When the nozzle diameter is 3 mm, the kerf width of the Al 2O 3 ceramic plate with 6 mm thickness is less than 4.6 mm, and the cutting speed reaches to 0.9～1.2 m/min. Both theoretical analysis and experimental results have proved the feasibility and validity of the newly advanced hydro-magnetic plasma arc cutting, and the following conclusion can be drawn: (1)Synthesizing the advantages of both the water-constriction and magnetic constriction, the hydro-magnetic constriction of plasma arc forms a three-dimensional constriction with improved shape and uniformity of arc column, narrower kerfs, minimal beveling of cuts and higher dross-free cutting speeds than those under either water-constriction or magnetic constriction alone.(2)Hydro-magnetic constriction is capable of improving arc stability, which is reflected in the higher arc voltage at which arc-extinction occurs, than that under any single constriction. (3)For a given diameter of nozzle, quality cut can be produced by using a lower arc current than usually required in conventional plasma arc cutting, but ensuring fine arc shape and capability of cutting simply by employing hydro-magnetic constriction. Meanwhile, the heat load on nozzle could be reduced and service life of nozzle raised.
文摘ICF(inertial confinement fusion)holds significant potential for achieving controlled nuclear fusion,but challenges related to efficient energy transfer and plasma stabilization remains.This article explores the ion-bubble trigger mechanism as a promising solution for improving the compression and energy deposition processes in ICF,particularly when coupled with external magnetic fields,wigglers,undulators,and trapped magnetic fields.The ion-bubble mechanism enhances energy transfer by creating localized heating in the plasma,increasing the likelihood of fusion ignition.External magnetic fields,through their interaction with plasma particles,can optimize ion-bubble interactions by influencing particle trajectories and stabilizing plasma instabilities.Additionally,wigglers and undulators—devices that create oscillating magnetic fields—offer a means to fine-tune the interaction between plasma and electromagnetic radiation,further enhancing the ion-bubble effect.Trapped magnetic fields,formed through plasma compression,also contribute to plasma confinement and stability,offering further support for the ion-bubble trigger mechanism.By combining these factors,the ion-bubble trigger mechanism in ICF could significantly improve fusion efficiency and bring us closer to realizing sustainable fusion energy.
文摘This paper generally compares the essential features between tokamaks and stellarators,based on previous review work individually made by authors on several specific topics,such as theories,bulk plasma transport and edge divertor physics,along with some recent results.It aims at summarizing the main results and conclusions with regard to the advantages and disadvantages in these two types of magnetic fusion devices.The comparison includes basic magnetic configurations,magnetohydrodynamic(MHD)instabilities,operational limits and disruptions,neoclassical and turbulent transport,confinement scaling and isotopic effects,plasma rotation,and edge and divertor physics.Finally,a concept of quasi-symmetric stellarators is briefly referred along with a comparison of future application for fusion reactors.
基金The project supported by Chinese National Science Foundation (Nos. 10335060, 10235010) and Creative Project Grants of ChineseAcademy of Science
文摘This paper describes the control software together with the operational hardware, which successfully realizes the operation of a new fully programmable imaging system with high spatial and temporal resolutions on the KT5D magnetic torus, for observing the visible l ight emission from the plasma discharge.
基金supported by the Collaboration Program of the Laboratory for Complex Energy Processes,IAE,Kyoto Universitythe NIFS Collaborative Research Program (NIFS10KUHL030,NIFS09KUHL028,NIFS10KUHL033)
文摘A new high repetition rate Nd：YAG Thomson scattering system is developed for the Heliotron J helical device. A main purpose of installing the new system is the temporal evolution measurement of a plasma profile for improved confinement physics such as the edge transport barrier （H-mode） or the internal transport barrier of the helical plasma. The system has 25 spatial points with -10 mm resolution. Two high repetition Nd：YAG lasers （〉 550 m J@ 50 Hz） realize the measurement of the time evolution of the plasma profile with ~10 ms time intervals. Scattered light is collected by a large concave mirror （D----800 mm, f/2.25） with a solid angle of -100 mstr and transferred to interference filter polychromators by optical fiber bundles in a staircase form. The signal is amplified by newly designed fast preamplifiers with DC and AC output, which reduces the low frequency background noise. The signals are digitized with a multi-event QDC, fast gated integrators. The data acquisition is performed by a VME-based system operated by the CINOS.
基金the Fund of Knowledge Innovation Program of Chinese Academy of Sciences(No.KJCX2-SW-N19)
文摘An electromagnetic calculation and the parameters of the magnet system of the magnetically confined plasma rocket were established. By using ANSYS code, it was found that the leakage rate depends on the current intensity of the magnet and the change of the magnet position.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10205015 and 10575104）.Acknowledgement 0ne of the authors, Ding B J, would like to thank the members of HT-7 Team for their cooperation and kindly help.
文摘A phase-controlled lower hybrid wave （LHW） multi-junction （M J） coupler （3（rows）×4（columns）×4 （subwaveguides）） has been developed in the HT-7 tokamak. Simulations show that it is more effective for driving plasma current than an ordinary phase-controlled LHW antenna （3（rows）× 12（columns）） （traditional coupler）. The plasm-wave coupling experiments show that the reflection coefficient （RC） is below 10%, implying that the MJ grill can launch the wave into the plasma effectively. The effect of power spectrum launched by the MJ coupler on RC indicates that an optimal condition is requisite for a better coupling in the lower hybrid current drive （LHCD） experiments, Studies indicate that the drive efficiency of the MJ antenna is higher than that of the traditional one, which is mainly ascribed to the discrepancy in impurity concentration, plasma temperature, and spectrum directivity. An improved confinement with an electron internal transport barrier is obtained by LHCD. The analysis shows that the modified negative （low） magnetic shear and the change of radial electric field profile due to LHCD are possible factors responsible for the eITB formation.
基金supported by National Natural Science Foundation of China under Grant Nos.11005035,11475058the National Magnetic Confinement Fusion Science Program of China(ITERCN) under Grant Nos.2013GB104001 and 2013GB106004
文摘This paper reviews the energetic particle（EP） experiments during electron cyclotron resonance heating（ECRH） and neutral beam injection in the HL-2 A tokamak.A number of important results are summarized,which relate to ITER physics,including the behavior of the multi-mode instability,the nonlinear interaction between wave-wave and wave-particles,the losses of EP induced by the instabilities,the effect of the EP instabilities on the thermal plasma confinement and the control of the EP instabilities by means of ECRH.Systematic experiments indicate that when the drive is great enough,the nonlinear effects and the multi-mode coexistence may play an important role,which affect the transport both of the EPs and the background plasma confinement,and these instabilities could be controlled.Some new phenomena about the EP induced instabilities discovered recently on the device,such as high frequency reversed shear Alfvén eigenmodes,Alfvénic ion temperature gradient modes,the geodesic acoustic mode induced by energetic electrons excited by interaction between tearing mode and beta induced Alfvén eigenmode and double e-fishbone in negative magnetic shear discharges etc,have also been presented in the paper.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10990213)
文摘The high confinement mode （H-mode） operation is recently obtained in HL-2A divertor configuration, the corresponding edge localized mode （ELM） is recognized as being of type III. Time intervals in ELM time series are analysed to obtain the information about the ELM process. Signatures of unstable periodic orbits （UPOs） are detected, which are indicators of chaos and may be used to control the big ELM events.
文摘One of the reasons for increased material removal rate in magnetic field assisted dry electrical discharge machining （EDM） is confinement of plasma due to Lorentz forces. This paper presents a mathematical model to evaluate the effect of external magnetic field on crater depth and diameter in single- and multiple-discharge EDM process. The model incorporates three main effects of the magnetic field, which include plasma confinement, mean free path reduction and pulsating magnetic field effects. Upon the application of an external magnetic field, Lorentz forces that are developed across the plasma column confine the plasma column. Also, the magnetic field reduces the mean free path of electrons due to an increase in the plasma pressure and cycloidal path taken by the electrons between the electrodes. As the mean free path of electrons reduces, more ionization occurs in plasma column and eventually an increase in the current density at the inter-electrode gap occurs. The model results for crater depth and its diameter in single discharge dry EDM process show an error of 9%-10% over the respective experimental values.
基金supported by National Special Research Program of China for ITER(Nos.2013GB111000 and 2014GB107004)China Scholarship Council(No.2011601098)U.S.DOE Grants DE-SC0010416 and DE-FG02-07ER54916
文摘The implementation of magnetic islands in gyrokinetic simulation has been verified in the gyrokinetic toroidal code（GTC）.The ion and electron density profiles become partially flattened inside the islands.The density profile at the low field side is less flattened than that at the high field side due to toroidally trapped particles in the low field side,which do not move along the perturbed magnetic field lines.When the fraction of trapped particles decreases,the density profile at the low field becomes more flattened.
文摘In the quest for a sustainable and abundant energy source, nuclear fusion technology stands as a beacon of hope. This study introduces a groundbreaking quantum mechanically effective induction system designed for magnetic plasma confinement within fusion reactors. The pursuit of clean energy, essential to combat climate change, hinges on the ability to harness nuclear fusion efficiently. Traditional approaches have faced challenges in plasma stability and energy efficiency. The novel induction system presented here not only addresses these issues but also transforms fusion reactors into integrated construction systems. This innovation promises compact fusion reactors, marking a significant step toward a clean and limitless energy future, free from the constraints of traditional power sources. This revolutionary quantum induction system redefines plasma confinement in fusion reactors, unlocking clean, compact, and efficient energy production.
文摘Recent results of JT-60U towards establishment of physics basis for ITER andadvanced tokamak operation are presented. Progress in high integrated performance is achieved withimprovement of N-NB and ECRF heating systems. In the next experimental campaign 2003～2004,discharge duration with 17 MW heating will be extended up to 30s for sustaining high-beta plasmalonger than the current diffusion time. Superconducting modification of JT-60 is planned todemonstrate high-beta plasma sustainment exceeding ideal MHD instability limit without wallstabilization.
基金supported by the National Natural Science Foundation of China(Grant Nos.11575032,11274049,U1530258,11205019 and11304009)the National Magnetic Confinement Fusion Energy Research Project of China(Grant No.2015B108002)+1 种基金the Presidential Foundation of China Academy of Engineering Physics(CAEP)(Grant No.YZ2015014)the Foundation for the Development of Science and Technology of CAEP(Grant No.2014B0102015)
文摘The energy loss of charged particles, including electrons, protons, and α-particles with tens keV initial energy E0, traveling in the hot dense carbon(C) plasma for densities from 2.281 to 22.81 g/cm3 and temperatures from 400 to 1500 eV is systematically and quantitatively studied by using the dimensional continuation method. The behaviors of different charged particles are readily distinguishable from each other. Firstly, because an ion is thousands times heavier than an electron, the penetration distance of the electron is much longer than that of proton and α-particle traveling in the plasma. Secondly, most energy of electron projectile with E0 < 100 keV deposits into the electron species of C plasma, while for the cases of proton and α-particle with E0 < 100 keV,about more than half energy transfers into the ion species of C plasma. A simple decreasing law of the penetration distance as a function of the plasma density is fitted, and different behaviors of each projectile particle can be clearly found from the fitted data.We believe that with the advanced progress of the present experimental technology, the findings shown here could be confirmed in ion-stopping experiments in the near future.
基金the Scientific and Technological Research Program of Education Department of Hubei Province (No.Z200722001)the Middleaged and Young People Excellent Innovation Team of Science and Technology of Hubei Province (No.2003-7)the Research Program of The Hong Kong Polytechnic University (No.A-PA2Q).
文摘Two dark solitons are considered in a two-component Bose-Einstein condensate with an external magnetic trap, and effects of the trap potential on their dynamics are investigated by the numerical simulation. The results show that the dark solitons attract, collide and repel periodically in two components as time changes, the time period depends strictly on the initial condition and the potential, and there are obvious self-trapping effects on the two dark solitons.
基金supported in part by the National Natural Science Foundation of China for Distinguished Young Scholars(No.10725416)National Basic Research Program of China(No.2006CB921101)+1 种基金the National Natural Science Foundation of China for Excellent Research Team(No.60821004)the National Natural Science Foundation of China(No.60678029)
文摘We report the experimental achievement of ^（87）Rb Bose-Einstein condensation in a magnetic trap with microwave and radio frequency（RF） induced evaporation.Evaporative cooling is realized by using 6.8 GHz microwave radiation driving the ^（87）Rb atoms to transit from the ground-state hyperfine state ｜F=2,m_F= 2〉to ｜F=l,m_F=1〉.Compared with RF-induced evaporation,^（87）Rb atoms are hardly to achieve pure condensate by microwave evaporation cooling due to the effect of atoms in the ｜F=1,m_F=1〉state being pumped back into the trapping ｜F=2,m_F=1〉state.
