Castellation of plasma facing components is foreseen as the best solution for ensuring the lifetime of future fusion devices. However, the gaps between the resulting surface elements can increase fuel retention and co...Castellation of plasma facing components is foreseen as the best solution for ensuring the lifetime of future fusion devices. However, the gaps between the resulting surface elements can increase fuel retention and complicate fuel removal issues. To know how the fuel is retained inside the gaps, the plasma sheath around the gaps needs to be understood first. In this work, a kinetic model is used to study plasma characteristics around the divertor gaps with the focus on the H＋ penetration depth inside the poloidal gaps, and a rate-theory model is coupled to simulate the hydrogen retention inside the tungsten gaps. By varying the magnetic field strength and plasma temperature, we find that the H＋ cyclotron radius has a significant effect on the penetration depth. Besides, the increase of magnetic field inclination angle can also increase the penetration depth. It is found in this work that parameters as well as the penetration depth strongly affect fuel retention in tungsten gaps.展开更多
In this paper, the characteristics of an atmospheric pressure helium plasma jet generated by a dual-power electrode （DPE） configuration are investigated by using a two-dimensional fluid model. The effect of a needle...In this paper, the characteristics of an atmospheric pressure helium plasma jet generated by a dual-power electrode （DPE） configuration are investigated by using a two-dimensional fluid model. The effect of a needle electrode on the discharge is studied by comparing the results of the DPE configuration with those of the single ring electrode configuration. It is found that the existence of the needle leads to the generation of a helium plasma jet with a higher propagation velocity, higher species density, and larger discharge width. Furthermore, the influences of the needle radius and needle-to-ring discharge gap on the generation of a plasma jet are also studied. The simulation results indicate that the needle electrode has an evident influence on the plasma jet characteristics.展开更多
The influence of the J×B force on the topographical modification of W targets during a type-I-like ELM in ITER has been studied numerically. A two-dimensional(2D) fluid dynamics model is employed by solving liqui...The influence of the J×B force on the topographical modification of W targets during a type-I-like ELM in ITER has been studied numerically. A two-dimensional(2D) fluid dynamics model is employed by solving liquid hydrodynamic Navier-Stokes equation with the 2D heat conduction equation in addition to driving forces for surface topography, such as surface tension and pressure gradient, the J×B force is particularly addressed. The governing equations are solved with the finite volume method by adequate prediction of the moving solid-liquid interface. Numerical simulations are carried out for a range of type-I ELM characteristic parameters. Our results indicate that both the surface tension and the J×B force contributes to the melt motion of tungsten plates when the energy flux is under 3000 MW·m^(-2), the surface tension is a major driving force while the pressure gradient is negligible. Our results also indicate that the J×B force makes the small hills grow at different rates at both the crater edges under a type-I-like ELM heat load with a Gaussian power density profile.展开更多
This paper performs a numerical simulation of concentric-ring discharge structures within the scope of a twodimensional diffusion-drift model at atmospheric pressure between two parallel circular electrodes covered wi...This paper performs a numerical simulation of concentric-ring discharge structures within the scope of a twodimensional diffusion-drift model at atmospheric pressure between two parallel circular electrodes covered with thin dielectric layers. With a relative high frequency the discharge structures present different appearances of ring structures within different radii in time due to the evolvement of the filaments. The spontaneous electron density distributions help understanding the formation and development of self-organized discharge structures. During a cycle the electron avalanches are triggered by the electric field strengthened by the feeding voltage and the residual charged particles on the barrier surface deposited in the previous discharges. The accumulation of charges is shown to play a dominant role in the generation and annihilation of the discharge structures. Besides, the rings split and unify to bring and annihilate rings which form a new discharge structure.展开更多
The characteristics of homogeneous discharges in mixed gases of hydrogen diluted silane and argon at atmospheric pressure are investigated numerically based on a one-dimensional fluid model. This model takes into acco...The characteristics of homogeneous discharges in mixed gases of hydrogen diluted silane and argon at atmospheric pressure are investigated numerically based on a one-dimensional fluid model. This model takes into account the primary processes-excitation and ionization, sixteen reactions of radicals with radicals in silane/hydrogen/argon discharges-and therefore, can adequately represent the discharge plasma. We analyze the effects of very high frequency （VHF） on the densities of species （e, H, SiH3, SiH＋ and SiH2） in such discharges using the model. The simulation results show that the densities of SiH3, SiH＋, H, and SiH2 increase with VHF when the VHF ranges from 30 MHz to 150 MHz. It is found that the deposition rate of uc-Si：H film depends on the concentration of SiH3, SiH＋, SiH2, and H in the plasma. The effects of VHF on the deposition rate and the amount of crystallized fraction for uc-Si：H film growth is also discussed in this paper.展开更多
基金supported by the National Magnetic Confinement Fusion Science Program,China(Grant No.2013GB109001)the National Natural Science Foundation of China(Grant Nos.11275042 and 11305026)the Fundamental Research Funds for the Central Universities of Ministry of Education of China(Grant No.DUT14RC(3)039)
文摘Castellation of plasma facing components is foreseen as the best solution for ensuring the lifetime of future fusion devices. However, the gaps between the resulting surface elements can increase fuel retention and complicate fuel removal issues. To know how the fuel is retained inside the gaps, the plasma sheath around the gaps needs to be understood first. In this work, a kinetic model is used to study plasma characteristics around the divertor gaps with the focus on the H＋ penetration depth inside the poloidal gaps, and a rate-theory model is coupled to simulate the hydrogen retention inside the tungsten gaps. By varying the magnetic field strength and plasma temperature, we find that the H＋ cyclotron radius has a significant effect on the penetration depth. Besides, the increase of magnetic field inclination angle can also increase the penetration depth. It is found in this work that parameters as well as the penetration depth strongly affect fuel retention in tungsten gaps.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10775026,11275042,11305026,and 11405042)
文摘In this paper, the characteristics of an atmospheric pressure helium plasma jet generated by a dual-power electrode （DPE） configuration are investigated by using a two-dimensional fluid model. The effect of a needle electrode on the discharge is studied by comparing the results of the DPE configuration with those of the single ring electrode configuration. It is found that the existence of the needle leads to the generation of a helium plasma jet with a higher propagation velocity, higher species density, and larger discharge width. Furthermore, the influences of the needle radius and needle-to-ring discharge gap on the generation of a plasma jet are also studied. The simulation results indicate that the needle electrode has an evident influence on the plasma jet characteristics.
基金Project supported by the Scientific Research Foundation of Liaoning Province,China(Grant No.2016J027)the Open Research Project of Key Laboratory of Materials Modification by Laser,Ion and Electron Beams,Ministry of Education(Grant No.KF1705)the National Key Research and Development Program of China(Grant Nos.2017YFA0402500,2017YFE0300400,and 2017YFE0301200)
文摘The influence of the J×B force on the topographical modification of W targets during a type-I-like ELM in ITER has been studied numerically. A two-dimensional(2D) fluid dynamics model is employed by solving liquid hydrodynamic Navier-Stokes equation with the 2D heat conduction equation in addition to driving forces for surface topography, such as surface tension and pressure gradient, the J×B force is particularly addressed. The governing equations are solved with the finite volume method by adequate prediction of the moving solid-liquid interface. Numerical simulations are carried out for a range of type-I ELM characteristic parameters. Our results indicate that both the surface tension and the J×B force contributes to the melt motion of tungsten plates when the energy flux is under 3000 MW·m^(-2), the surface tension is a major driving force while the pressure gradient is negligible. Our results also indicate that the J×B force makes the small hills grow at different rates at both the crater edges under a type-I-like ELM heat load with a Gaussian power density profile.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.50537020 and 50528707)
文摘This paper performs a numerical simulation of concentric-ring discharge structures within the scope of a twodimensional diffusion-drift model at atmospheric pressure between two parallel circular electrodes covered with thin dielectric layers. With a relative high frequency the discharge structures present different appearances of ring structures within different radii in time due to the evolvement of the filaments. The spontaneous electron density distributions help understanding the formation and development of self-organized discharge structures. During a cycle the electron avalanches are triggered by the electric field strengthened by the feeding voltage and the residual charged particles on the barrier surface deposited in the previous discharges. The accumulation of charges is shown to play a dominant role in the generation and annihilation of the discharge structures. Besides, the rings split and unify to bring and annihilate rings which form a new discharge structure.
基金supported by National Natural Science Foundation of China(Nos.10775026,50537020,and50528707)
文摘The characteristics of homogeneous discharges in mixed gases of hydrogen diluted silane and argon at atmospheric pressure are investigated numerically based on a one-dimensional fluid model. This model takes into account the primary processes-excitation and ionization, sixteen reactions of radicals with radicals in silane/hydrogen/argon discharges-and therefore, can adequately represent the discharge plasma. We analyze the effects of very high frequency （VHF） on the densities of species （e, H, SiH3, SiH＋ and SiH2） in such discharges using the model. The simulation results show that the densities of SiH3, SiH＋, H, and SiH2 increase with VHF when the VHF ranges from 30 MHz to 150 MHz. It is found that the deposition rate of uc-Si：H film depends on the concentration of SiH3, SiH＋, SiH2, and H in the plasma. The effects of VHF on the deposition rate and the amount of crystallized fraction for uc-Si：H film growth is also discussed in this paper.
