In this study,a two-dimensional fluid model is proposed to simulate the underwater discharge in a He/H2O-filled bubble at atmospheric pressure.The molar fraction of water vapor is varied in the range of 0.01%-1%to inv...In this study,a two-dimensional fluid model is proposed to simulate the underwater discharge in a He/H2O-filled bubble at atmospheric pressure.The molar fraction of water vapor is varied in the range of 0.01%-1%to investigate the dependence of discharge dynamics and reaction products on water vapor concentration(WVC).The numerical results show that most properties of the discharge sensitively depend on the WVC.The increase of WVC leads to an increase in the electron density and discharge propagation velocity,which is attributed to Penning ionization between He*and H2O.The main positive ion switches from He+to H2O+,while the WVC increases from 0.01%to 1%.The dominant reactive oxygen species is OH,whose peak density is about two orders of magnitude higher than that of O.Besides,the densities of OH and O radicals increase with the increasing WVC.It is shown that the formation mechanism of O radicals is significantly affected by the WVC.The dominant reaction creating O radicals changes from the charge exchange between He2+and H2O to the electron impact dissociation of H2O as the WVC increases from 0.01%to 1%.This study is helpful for better understanding the application of non-thermal plasmas discharges in water,such as biomedical,environmental engineering.展开更多
A one-dimensional hybrid model was developed to study the electrical asymmetry effect（EAE） caused by the fourthorder harmonic in a dual-frequency capacitively coupled Ar plasma.The self-bias voltage caused by the fo...A one-dimensional hybrid model was developed to study the electrical asymmetry effect（EAE） caused by the fourthorder harmonic in a dual-frequency capacitively coupled Ar plasma.The self-bias voltage caused by the fourth-order frequency changes periodically with the phase angle,and the cycle of self-bias with the phase angle is π/2,which is half of that in the second-order case.The influence of the phase angle between the fundamental and its fourth-order frequency on the ion density profiles and the ion energy distributions（IEDs） were studied.Both the ion density profile and the IEDs can be controlled by the phase angle,which provides a convenient way to adjust the sheath characters without changing the main discharge parameters.展开更多
An experimental investigation of the saturation ion current densities （Jions） in hydrogen inductively coupled plasma （ICP） produced by a large-power （2-32 kW） radio frequency （RF） generator is reported, then s...An experimental investigation of the saturation ion current densities （Jions） in hydrogen inductively coupled plasma （ICP） produced by a large-power （2-32 kW） radio frequency （RF） generator is reported, then some reasonable explanations are given out. With the increase of RF power, the experimental results show three stages： in the first stage （2-14 kW）, the electron temperature will rise with the increase of RF power in the ICP, thus, the Jions increases continually as the electron temperature rises in the ICP. In the second stage （14 20 kW）, as some H- ions lead to the mutual neutralization （MN）, the slope of Jio^s variation firstly decreases then increases. In the third stage （20-32 kW）, both the electronic detachment （ED） and the associative detachment （AD） in the ICP result in the destruction of H- ions, therefore, the increased amplitude of the Jions in the third stage is weaker than the one in the first stage. In addition, with the equivalent transformer model, we successfully Explain that the Jions at different radial locations in ICP has the same rule. Finally, it is found that the Jions has nothing to do with the outer/inner puffing gas pressure ratio, which is attributed to the high-speed movement of hydrogen molecules.展开更多
A two-dimensional hybrid simulation scheme is proposed to study the characteristics of dual-frequency （DF） capacitively coupled plasma （CCP） discharge based on the geometry of real device. Given the experimental p...A two-dimensional hybrid simulation scheme is proposed to study the characteristics of dual-frequency （DF） capacitively coupled plasma （CCP） discharge based on the geometry of real device. Given the experimental parameters for argon plasma, the output from the fluid module such as ion density, number flux, electron temperature and the Monte-Carlo collision （MCC） results of ion energy distribution function （IEDF） as well as electron energy distribution function （EEDF） are obtained and discussed in detail. A novel complete floating double probe is designed to measure both density and temperature of electron and a quadrupole mass spectrometer is also equipped for IEDF investigations. The measurements on the density of bulk plasma, electron temperature and IEDF agree well, qualitatively, with the simulated results. A comparison with experimental results indicates that, since the structure of real device is taken into account, this model is capable of describing the global dynamic characteristics occurred in DF-CCP and presenting more reliable results than the model with an ideal chamber structure.展开更多
A high-density RF ion source is an essential part of a neutral beam injector. In this study, the authors attempt to retrofit an original regular RF ion source reactor by inserting a thin dielectric tube through the sy...A high-density RF ion source is an essential part of a neutral beam injector. In this study, the authors attempt to retrofit an original regular RF ion source reactor by inserting a thin dielectric tube through the symmetric axis of the discharge chamber. With the aid of this inner tube, the reactor is capable of generating a radial magnetic field instead of the original transverse magnetic field, which solves the E × B drift problem in the current RF ion source structure. To study the disturbance of the dielectric tube, a fluid model is introduced to study the plasma parameters with or without the internal dielectric tube, based on the inductively coupled plasma（ICP） reactor. The simulation results show that while introducing the internal dielectric tube into the ICP reactor, both the plasma density and plasma potential have minor influence during the discharge process, and there is good uniformity at the extraction region. The influence of the control parameters reveals that the plasma densities at the extraction region decrease first and subsequently slow down while enhancing the diffusion region.展开更多
基金This work was supported by National Natural Science Foundation of China(No.11705022)Innovation and Entrepreneurship Plan of Dalian Nationalities University(No.201912026182).
文摘In this study,a two-dimensional fluid model is proposed to simulate the underwater discharge in a He/H2O-filled bubble at atmospheric pressure.The molar fraction of water vapor is varied in the range of 0.01%-1%to investigate the dependence of discharge dynamics and reaction products on water vapor concentration(WVC).The numerical results show that most properties of the discharge sensitively depend on the WVC.The increase of WVC leads to an increase in the electron density and discharge propagation velocity,which is attributed to Penning ionization between He*and H2O.The main positive ion switches from He+to H2O+,while the WVC increases from 0.01%to 1%.The dominant reactive oxygen species is OH,whose peak density is about two orders of magnitude higher than that of O.Besides,the densities of OH and O radicals increase with the increasing WVC.It is shown that the formation mechanism of O radicals is significantly affected by the WVC.The dominant reaction creating O radicals changes from the charge exchange between He2+and H2O to the electron impact dissociation of H2O as the WVC increases from 0.01%to 1%.This study is helpful for better understanding the application of non-thermal plasmas discharges in water,such as biomedical,environmental engineering.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11305032,11305028,11375163,and 11275039)the Scientific Foundation of Ministry of Education of China(Grant No.N130405008)
文摘A one-dimensional hybrid model was developed to study the electrical asymmetry effect（EAE） caused by the fourthorder harmonic in a dual-frequency capacitively coupled Ar plasma.The self-bias voltage caused by the fourth-order frequency changes periodically with the phase angle,and the cycle of self-bias with the phase angle is π/2,which is half of that in the second-order case.The influence of the phase angle between the fundamental and its fourth-order frequency on the ion density profiles and the ion energy distributions（IEDs） were studied.Both the ion density profile and the IEDs can be controlled by the phase angle,which provides a convenient way to adjust the sheath characters without changing the main discharge parameters.
基金supported by the National Magnetic Confinement Fusion Science Program of China(Nos.2011GB108011 and 2010GB103001)the Major International(Regional)Project Cooperation and Exchanges of China(No.11320101005)the Startup Fund from Fuzhou University(No.510071)
文摘An experimental investigation of the saturation ion current densities （Jions） in hydrogen inductively coupled plasma （ICP） produced by a large-power （2-32 kW） radio frequency （RF） generator is reported, then some reasonable explanations are given out. With the increase of RF power, the experimental results show three stages： in the first stage （2-14 kW）, the electron temperature will rise with the increase of RF power in the ICP, thus, the Jions increases continually as the electron temperature rises in the ICP. In the second stage （14 20 kW）, as some H- ions lead to the mutual neutralization （MN）, the slope of Jio^s variation firstly decreases then increases. In the third stage （20-32 kW）, both the electronic detachment （ED） and the associative detachment （AD） in the ICP result in the destruction of H- ions, therefore, the increased amplitude of the Jions in the third stage is weaker than the one in the first stage. In addition, with the equivalent transformer model, we successfully Explain that the Jions at different radial locations in ICP has the same rule. Finally, it is found that the Jions has nothing to do with the outer/inner puffing gas pressure ratio, which is attributed to the high-speed movement of hydrogen molecules.
基金supported by National Natural Science Foundation of China (No. 10635010)Specialized Research Fund for the Doctoral Program of Higher Education of China (No.20090041110026)
文摘A two-dimensional hybrid simulation scheme is proposed to study the characteristics of dual-frequency （DF） capacitively coupled plasma （CCP） discharge based on the geometry of real device. Given the experimental parameters for argon plasma, the output from the fluid module such as ion density, number flux, electron temperature and the Monte-Carlo collision （MCC） results of ion energy distribution function （IEDF） as well as electron energy distribution function （EEDF） are obtained and discussed in detail. A novel complete floating double probe is designed to measure both density and temperature of electron and a quadrupole mass spectrometer is also equipped for IEDF investigations. The measurements on the density of bulk plasma, electron temperature and IEDF agree well, qualitatively, with the simulated results. A comparison with experimental results indicates that, since the structure of real device is taken into account, this model is capable of describing the global dynamic characteristics occurred in DF-CCP and presenting more reliable results than the model with an ideal chamber structure.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11305028,11305032,and 11320101005)
文摘A high-density RF ion source is an essential part of a neutral beam injector. In this study, the authors attempt to retrofit an original regular RF ion source reactor by inserting a thin dielectric tube through the symmetric axis of the discharge chamber. With the aid of this inner tube, the reactor is capable of generating a radial magnetic field instead of the original transverse magnetic field, which solves the E × B drift problem in the current RF ion source structure. To study the disturbance of the dielectric tube, a fluid model is introduced to study the plasma parameters with or without the internal dielectric tube, based on the inductively coupled plasma（ICP） reactor. The simulation results show that while introducing the internal dielectric tube into the ICP reactor, both the plasma density and plasma potential have minor influence during the discharge process, and there is good uniformity at the extraction region. The influence of the control parameters reveals that the plasma densities at the extraction region decrease first and subsequently slow down while enhancing the diffusion region.
