Density modulation experiments are powerful experimental schemes for the study of particle transport. The diffusion coefficients (D) and convection velocity (V), which cannot be evaluated from the particle balance...Density modulation experiments are powerful experimental schemes for the study of particle transport. The diffusion coefficients (D) and convection velocity (V), which cannot be evaluated from the particle balance in the equilibrium state, can be obtained separately. Further, the estimated values of D and V are determined independent of the absolute value of the particle source rate, which is difficult to obtain experimentally. However, the sensitivities and interpretation of D and V from the modulation experiments need to be considered. This paper describes numerical techniques for solving the particle balance equation of the modulation components. Examples of the analysis are shown regarding the data of LHD experiments, and the results of the modulation experiments are discussed.展开更多
The impact of the E×B flow shear stabilization on particle transport and density peaking at JET is analyzed in the framework of integrated modelling with the CRONOS code.For that purpose,plasmas from a power scan...The impact of the E×B flow shear stabilization on particle transport and density peaking at JET is analyzed in the framework of integrated modelling with the CRONOS code.For that purpose,plasmas from a power scan which show a significant increasing of density peaking with the injected neutral beam injection power have been used as a modeling basis.By means of simulations with the quasilinear model GLF23 for the heat and particle transport,a strong link between the particle confinement and E×B flow shear stabilization is found.This is particularly important close to the pedestal region where the particle pinch direction becomes strongly inward for high E×B flow shear values.Such impact introduces some non-negligible deviation from the well-known collisonality dependence of the density peaking,whose general trend has been also obtained in the framework of this modelling by performing pedestal density scans.展开更多
The fusion performance and particle confinement of an international thermonuclear experimental reactor(ITER)-like fusion device have been modeled by numerically solving the energy transport equation and the particle...The fusion performance and particle confinement of an international thermonuclear experimental reactor(ITER)-like fusion device have been modeled by numerically solving the energy transport equation and the particle transport equation. The effect of fuelling depth has been investigated. The plasma is primarily heated by the fusion produced alpha particles and the loss process of particles and energy in the scrape-off layer has been taken into account. To study the effect of fuelling depth on fusion performance, the ITERH-98P(y,2) scaling law has been used to evaluate the transport coefficients. It is shown that the particle confinement and fusion performance are significantly dependent on the fuelling depth. Deviation of 10% of the minor radius on fuelling depth can make the particle confinement change by ~ 61% and the fusion performance change by ~ 108%. The enhancement of fusion performance is due to the better particle confinement induced by deeper particle fuelling.展开更多
A quasi-stationary alternating current (AC) operation assisted by lower hybrid waves (LHW) was achieved recently in HT-7. It is found that the particle confinement time of the positive current plasma is lower than...A quasi-stationary alternating current (AC) operation assisted by lower hybrid waves (LHW) was achieved recently in HT-7. It is found that the particle confinement time of the positive current plasma is lower than that of the negative current plasma. The particle transport coefficients are investigated in AC plasmas by a gas puff modulation method. It is observed that the particle diffusion coefficient for the positive plasma current case is almost the same as that for the negative one, but the absolute value of inward pinch velocity for the positive current plasma is much lower than Vhat of the negative one. The result of the particle transport model study is in agreement with the experimental confinement study. The intensity of Hα emission and impurities emission of CⅢ, OII and OV for the negative current plasma are much lower than that for the positive current plasma. The radiation from Hα, OⅡ, CⅢ and ECE signals from the negative to the positive current phase showed less ionization and lower parameters than those from the positive to the negative one. The difference of particle transport and confinement in AC plasmas is not predicted by the current theory.展开更多
Different types of models for describing the motion of a kicked ion were suggested and studied. It is shown that certain kinds of jumping behavior of the exerting electromagnetic field can lead to a type of noninverti...Different types of models for describing the motion of a kicked ion were suggested and studied. It is shown that certain kinds of jumping behavior of the exerting electromagnetic field can lead to a type of noninvertible property, which changes this conservative system into a 'quasi-dissipative' one. The quasi-dissipative behaviors allow the particle to move along a confined chaotic 'quasi-attractor' in many regions of the parameter space. If the exerting electromagnetic field is discontinuous but the system is still invertible, it will take an unbounded chaotic diffusion with similar parameter values. We hope that this discovery could provide a helpful idea for confining the plasma.展开更多
In the experimental advanced superconducting tokamak,density pump-out phenomena were observed by using a multi-channel polarimeter-interferometer system under different heating schemes of ion cyclotron resonant heatin...In the experimental advanced superconducting tokamak,density pump-out phenomena were observed by using a multi-channel polarimeter-interferometer system under different heating schemes of ion cyclotron resonant heating,electron cyclotron resonance heating,and neutral beam injection.The density pump-out was also induced with application of resonant magnetic perturbation,accompanied with a degradation of particle confinement.For the comparison analysis in all heating schemes,the typical plasma parameters are plasma current 400 k A,toroidal field 2 T,and line average density 2×10^19m^-3.The experimental results show that the degree of pump-out is concerned with electron density and heating power.Low density deuterium low confinement(L-mode) plasmas(〈3.5×10^19m^-3) show strong pump-out effects.The density pump-out correlated with a significant drop of particle confinement.展开更多
Ion Bernstein waves (IBWs) have been proposed to be useful for heating and improving transport in tokamak plasmas. An Ion Bernstein wave heating experiment using different frequency (27 MHz and 30 MHz) was carried...Ion Bernstein waves (IBWs) have been proposed to be useful for heating and improving transport in tokamak plasmas. An Ion Bernstein wave heating experiment using different frequency (27 MHz and 30 MHz) was carried out on HT-7 superconducting tokamak in recent experiments. At a frequency of 30 MHz, ne peaked and Ha dropped have been pervasively observed, Tp was improved by a factor of 2 - 4, and Te increased by a factor of 1 - 1.5. An obvious confinement of particle was observed during the IBW pulse. At 27MHz, both global and localized electron heating were observed depending on the location of the ion resonant layer by changing Bt. Central electron heating effect was obtained in the global heating mode and electron temperature strongly increased near the 2 ΩD resonant layer for localized heating mode.展开更多
Edge plasma characteristics were studied by a fast-scanning 4-probe array and a Much/Reynolds stress/Langmuir 10-probe movable array in the boundary region. These probes could measure the edge plasma temperature, dens...Edge plasma characteristics were studied by a fast-scanning 4-probe array and a Much/Reynolds stress/Langmuir 10-probe movable array in the boundary region. These probes could measure the edge plasma temperature, density, poloidal electric field, radial electric field, Reynolds stress, poloidal rotation velocities and their profiles, which could be obtained by changing the radial positions of the probe array shot by shot. The measured results were used to analyse plasma confinement, turbulent fluctuations and correlations. The fixed flush 3-probe arrays were mounted on the 4-divertor neutralization plates at the same toroidal cross-section in the divertor chamber. These probes were used to measure the profiles of the electron temperature, density and float potential in the divertor chamber. Edge plasma behaviours in both limiter configuration and divertor configuration are compared. The decay lengths of the edge temperature and density were measured and is emphasized for plasma behaviours of the supersonic molecular beam injection and lower hybrid current drive. The dependence of the radial gradient of Reynolds stress on the poloidal flow and the radial gradient of the electric field on turbulent loss are discussed.展开更多
We study the uncertainty relation for three quantum systems in the N-dimensional space by using the virial theorem (VT). It is shown that this relation depends on the energy spectrum of the system as well as on the sp...We study the uncertainty relation for three quantum systems in the N-dimensional space by using the virial theorem (VT). It is shown that this relation depends on the energy spectrum of the system as well as on the space dimension N. It is pointed out that the form of lower bound of the inequality, which is governed by the ground state, depends on the system and on the space dimension N. A comparison between our result for the lower bound and recent results, based on information-theoretic approach, is pointed out. We examine and analyze these derived uncertainties for different angular momenta with a special attention made for the large N limit.展开更多
Dispersion and surface deposition of charged particles by gas-solids jets in confined chambers are constantly encountered in many industrial applications such as in electrostatic precipitation and dry powder coating p...Dispersion and surface deposition of charged particles by gas-solids jets in confined chambers are constantly encountered in many industrial applications such as in electrostatic precipitation and dry powder coating processes. Understanding and control of flow patterns and trajectories of charged particles are important to the optimal design and operation of such devices. In this study, modeling of flow fields and particle trajectories of dilute gas-solid two-phase flows with charged particles in confined chambers is performed. The dilute gas-solid two-phase flows are simulated by use of a hybrid Eulerian-Lagrangian approach with the one-way coupling between the gaseous phase and particle phase. The space charge distribution is included as a source term in equations of motion or Lagrangian equation of charged particles, which in turn depends on the particle trajectories that determine the space charge distribution. Our modeling predictions suggested that the electrostatic charge plays a significant role in particle radial dispersion. Effect of voltage has limited influence on particle trajectories however it can have a big impact on the residence time. Cone angle has a significant effect on the structure of flow field. For cone with a larger cone angle (typically over 15°), there will be a flow separation along the side wall near the flow entrance region. By comparing with the conical chamber, the cylindrical chamber has a big vortex and three smaller vortexes in the lower part of the chamber, which would complicate the particle dispersion with or without the coupling of charging.展开更多
基金supported in part by the JSPS-CAS Core-University Program in the field of Plasma and Nuclear Fusion
文摘Density modulation experiments are powerful experimental schemes for the study of particle transport. The diffusion coefficients (D) and convection velocity (V), which cannot be evaluated from the particle balance in the equilibrium state, can be obtained separately. Further, the estimated values of D and V are determined independent of the absolute value of the particle source rate, which is difficult to obtain experimentally. However, the sensitivities and interpretation of D and V from the modulation experiments need to be considered. This paper describes numerical techniques for solving the particle balance equation of the modulation components. Examples of the analysis are shown regarding the data of LHD experiments, and the results of the modulation experiments are discussed.
基金supported by The Franco-Thai scholarship program and Development and Promotion of Science and Technology Talents Projectbeen carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No.633053。
文摘The impact of the E×B flow shear stabilization on particle transport and density peaking at JET is analyzed in the framework of integrated modelling with the CRONOS code.For that purpose,plasmas from a power scan which show a significant increasing of density peaking with the injected neutral beam injection power have been used as a modeling basis.By means of simulations with the quasilinear model GLF23 for the heat and particle transport,a strong link between the particle confinement and E×B flow shear stabilization is found.This is particularly important close to the pedestal region where the particle pinch direction becomes strongly inward for high E×B flow shear values.Such impact introduces some non-negligible deviation from the well-known collisonality dependence of the density peaking,whose general trend has been also obtained in the framework of this modelling by performing pedestal density scans.
基金supported by National Natural Science Foundation of China(Nos.11175178 and 11375196)the National Magnetic Confinement Fusion Science Program of China(No.2014GB113000)
文摘The fusion performance and particle confinement of an international thermonuclear experimental reactor(ITER)-like fusion device have been modeled by numerically solving the energy transport equation and the particle transport equation. The effect of fuelling depth has been investigated. The plasma is primarily heated by the fusion produced alpha particles and the loss process of particles and energy in the scrape-off layer has been taken into account. To study the effect of fuelling depth on fusion performance, the ITERH-98P(y,2) scaling law has been used to evaluate the transport coefficients. It is shown that the particle confinement and fusion performance are significantly dependent on the fuelling depth. Deviation of 10% of the minor radius on fuelling depth can make the particle confinement change by ~ 61% and the fusion performance change by ~ 108%. The enhancement of fusion performance is due to the better particle confinement induced by deeper particle fuelling.
基金National Natural Science Foundation of China (No.10675125)the JSPS-CAS Core-University Program in the field of Plasma and Nuclear Fusion
文摘A quasi-stationary alternating current (AC) operation assisted by lower hybrid waves (LHW) was achieved recently in HT-7. It is found that the particle confinement time of the positive current plasma is lower than that of the negative current plasma. The particle transport coefficients are investigated in AC plasmas by a gas puff modulation method. It is observed that the particle diffusion coefficient for the positive plasma current case is almost the same as that for the negative one, but the absolute value of inward pinch velocity for the positive current plasma is much lower than Vhat of the negative one. The result of the particle transport model study is in agreement with the experimental confinement study. The intensity of Hα emission and impurities emission of CⅢ, OII and OV for the negative current plasma are much lower than that for the positive current plasma. The radiation from Hα, OⅡ, CⅢ and ECE signals from the negative to the positive current phase showed less ionization and lower parameters than those from the positive to the negative one. The difference of particle transport and confinement in AC plasmas is not predicted by the current theory.
基金the National Natural Foundation of China under Grant No. 19975039.
文摘Different types of models for describing the motion of a kicked ion were suggested and studied. It is shown that certain kinds of jumping behavior of the exerting electromagnetic field can lead to a type of noninvertible property, which changes this conservative system into a 'quasi-dissipative' one. The quasi-dissipative behaviors allow the particle to move along a confined chaotic 'quasi-attractor' in many regions of the parameter space. If the exerting electromagnetic field is discontinuous but the system is still invertible, it will take an unbounded chaotic diffusion with similar parameter values. We hope that this discovery could provide a helpful idea for confining the plasma.
基金Supported by the National Magnetic Confinement Fusion Program of China(Nos.2012GB101002 and 2014GB106002)National Nature Science Foundation of China(Nos.11375237 and 11105184)
文摘In the experimental advanced superconducting tokamak,density pump-out phenomena were observed by using a multi-channel polarimeter-interferometer system under different heating schemes of ion cyclotron resonant heating,electron cyclotron resonance heating,and neutral beam injection.The density pump-out was also induced with application of resonant magnetic perturbation,accompanied with a degradation of particle confinement.For the comparison analysis in all heating schemes,the typical plasma parameters are plasma current 400 k A,toroidal field 2 T,and line average density 2×10^19m^-3.The experimental results show that the degree of pump-out is concerned with electron density and heating power.Low density deuterium low confinement(L-mode) plasmas(〈3.5×10^19m^-3) show strong pump-out effects.The density pump-out correlated with a significant drop of particle confinement.
基金The project supported by the Meg-science Engineering Project of the Chinese Academy of Sciences
文摘Ion Bernstein waves (IBWs) have been proposed to be useful for heating and improving transport in tokamak plasmas. An Ion Bernstein wave heating experiment using different frequency (27 MHz and 30 MHz) was carried out on HT-7 superconducting tokamak in recent experiments. At a frequency of 30 MHz, ne peaked and Ha dropped have been pervasively observed, Tp was improved by a factor of 2 - 4, and Te increased by a factor of 1 - 1.5. An obvious confinement of particle was observed during the IBW pulse. At 27MHz, both global and localized electron heating were observed depending on the location of the ion resonant layer by changing Bt. Central electron heating effect was obtained in the global heating mode and electron temperature strongly increased near the 2 ΩD resonant layer for localized heating mode.
基金supported by the National Natural Science Foundation of China(Nos.10375020 and 10235010)
文摘Edge plasma characteristics were studied by a fast-scanning 4-probe array and a Much/Reynolds stress/Langmuir 10-probe movable array in the boundary region. These probes could measure the edge plasma temperature, density, poloidal electric field, radial electric field, Reynolds stress, poloidal rotation velocities and their profiles, which could be obtained by changing the radial positions of the probe array shot by shot. The measured results were used to analyse plasma confinement, turbulent fluctuations and correlations. The fixed flush 3-probe arrays were mounted on the 4-divertor neutralization plates at the same toroidal cross-section in the divertor chamber. These probes were used to measure the profiles of the electron temperature, density and float potential in the divertor chamber. Edge plasma behaviours in both limiter configuration and divertor configuration are compared. The decay lengths of the edge temperature and density were measured and is emphasized for plasma behaviours of the supersonic molecular beam injection and lower hybrid current drive. The dependence of the radial gradient of Reynolds stress on the poloidal flow and the radial gradient of the electric field on turbulent loss are discussed.
文摘We study the uncertainty relation for three quantum systems in the N-dimensional space by using the virial theorem (VT). It is shown that this relation depends on the energy spectrum of the system as well as on the space dimension N. It is pointed out that the form of lower bound of the inequality, which is governed by the ground state, depends on the system and on the space dimension N. A comparison between our result for the lower bound and recent results, based on information-theoretic approach, is pointed out. We examine and analyze these derived uncertainties for different angular momenta with a special attention made for the large N limit.
文摘Dispersion and surface deposition of charged particles by gas-solids jets in confined chambers are constantly encountered in many industrial applications such as in electrostatic precipitation and dry powder coating processes. Understanding and control of flow patterns and trajectories of charged particles are important to the optimal design and operation of such devices. In this study, modeling of flow fields and particle trajectories of dilute gas-solid two-phase flows with charged particles in confined chambers is performed. The dilute gas-solid two-phase flows are simulated by use of a hybrid Eulerian-Lagrangian approach with the one-way coupling between the gaseous phase and particle phase. The space charge distribution is included as a source term in equations of motion or Lagrangian equation of charged particles, which in turn depends on the particle trajectories that determine the space charge distribution. Our modeling predictions suggested that the electrostatic charge plays a significant role in particle radial dispersion. Effect of voltage has limited influence on particle trajectories however it can have a big impact on the residence time. Cone angle has a significant effect on the structure of flow field. For cone with a larger cone angle (typically over 15°), there will be a flow separation along the side wall near the flow entrance region. By comparing with the conical chamber, the cylindrical chamber has a big vortex and three smaller vortexes in the lower part of the chamber, which would complicate the particle dispersion with or without the coupling of charging.