A magnetic field produced by a current flowing through the plasma grid(PG) is one of the solutions to reduce the collisional loss of negative ions in a negative ion source, which reduces the electron temperature in fr...A magnetic field produced by a current flowing through the plasma grid(PG) is one of the solutions to reduce the collisional loss of negative ions in a negative ion source, which reduces the electron temperature in front of the PG. However, the magnetic field diffused into the driver has some influence on the plasma outflowing. In order to investigate the effect of changing this magnetic field on the outflowing of plasma from the driver, a circular ring(absorber) of high permeability iron has been introduced at the driver exit, which can reduce the magnetic field around it and improve plasma outflowing. With the application of the absorber, the electron density is increased by about 35%, and the extraction current measured from the extraction grid is increased from 1.02 A to 1.29 A. The results of the extraction experiment with cesium injection show that both the extraction grid(EG) current and H-current are increased when the absorber is introduced.展开更多
In order to support the design, manufacture and commissioning of the negative- ion-based neutral beam injection （NBI） system for the Chinese Fusion Engineering Test Reactor （CFETR）, the Hefei utility negative ion ...In order to support the design, manufacture and commissioning of the negative- ion-based neutral beam injection （NBI） system for the Chinese Fusion Engineering Test Reactor （CFETR）, the Hefei utility negative ion test equipment with RF source （HUNTER） was proposed at ASIPP. A prototype negative ion source will be developed at first. The main bodies of plasma source and accelerator of the prototype negative ion source are similar to that of the ion source for EAST-NBI. But instead of the filament-arc driver, an RF driver is adopted for the prototype negative ion source to fulfill the requirement of long pulse operation. A cesium seeding system and a magnetic filter are added for enhancing the negative ion density near the plasma grid and minimizing co-extracted electrons. Besides, an ITER-like extraction system is applied inside the accelerator, where the negative ion beam is extracted and accelerated up to 50 kV.展开更多
Electric potential near a wall for plasma with the surface produced negative ions with magnetic field increasing toward a wall is investigated analytically. The potential profile is derived analytically by using a pla...Electric potential near a wall for plasma with the surface produced negative ions with magnetic field increasing toward a wall is investigated analytically. The potential profile is derived analytically by using a plasma-sheath equation, where negative ions produced on the plasma grid （PG） surface are considered in addition to positive ions and electrons. The potential profile depends on the amount and the temperature of the surface produced negative ions and the profile of the magnetic field. The negative potential peak is formed in the sheath region near the PG surface for the case of strong surface production of negative ions or low temperature negative ions. As the increase rate of the magnetic field near the wall becomes large, the negative potential peak becomes small.展开更多
Neutral beam injection(NBI)systems based on negative hydrogen ion sources-rather than the positive ion sources that have typically been used to date-will be used in the future magnetically confined nuclear fusion expe...Neutral beam injection(NBI)systems based on negative hydrogen ion sources-rather than the positive ion sources that have typically been used to date-will be used in the future magnetically confined nuclear fusion experiments to heat the plasma.The collisions between the fast negative ions and neutral background gas result in a significant number of high-energy positive ions being produced in the acceleration area,and for the high-power long-pulse operation of NBI systems,this acceleration of positive ions back to the ion source creates heat load and material sputtering on the source backplate.This difficulty cannot be ignored,with the neutral gas density in the acceleration region having a significant impact on the flux density of the backstreaming positive ions.In the work reported here,the pressure gradient in the acceleration region was estimated using an ionization gauge and a straightforward 1D computation,and it was found that once gas traveled through the acceleration region,the pressure dropped by nearly one order of magnitude,with the largest pressure drop occurring at the plasma grid.The computation also revealed that the pressure drop in the grid gaps was substantially smaller than that in the grid apertures.展开更多
A radio-frequency(RF) inductively coupled negative hydrogen ion source(NHIS) has been adopted in the China Fusion Engineering Test Reactor(CFETR) to generate negative hydrogen ions.By incorporating the level-lumping m...A radio-frequency(RF) inductively coupled negative hydrogen ion source(NHIS) has been adopted in the China Fusion Engineering Test Reactor(CFETR) to generate negative hydrogen ions.By incorporating the level-lumping method into a three-dimensional fluid model,the volume production and transportation of H^(-) in the NHIS,which consists of a cylindrical driver region and a rectangular expansion chamber,are investigated self-consistently at a large input power(40 k W) and different pressures(0.3–2.0 Pa).The results indicate that with the increase of pressure,the H^(-) density at the bottom of the expansion region first increases and then decreases.In addition,the effect of the magnetic filter is examined.It is noteworthy that a significant increase in the H^(-) density is observed when the magnetic filter is introduced.As the permanent magnets move towards the driver region,the H^(-) density decreases monotonically and the asymmetry is enhanced.This study contributes to the understanding of H-distribution under various conditions and facilitates the optimization of volume production of negative hydrogen ions in the NHIS.展开更多
In order to study the key technology and physics of RF driven negative ion source for neutral beam injector in China, the Hefei utility negative ions test equipment with RF source was developed at Institute of Plasma ...In order to study the key technology and physics of RF driven negative ion source for neutral beam injector in China, the Hefei utility negative ions test equipment with RF source was developed at Institute of Plasma Physics, Chinese Academy of Sciences（ASIPP）. Its negative ion source can be equipped with single or double RF drivers. There is a plasma expansion chamber with depth of 19 mm and an enhanced filter field. A three electrodes negative ion accelerator was employed to extract and accelerate the negative ions, which are plasma grid,extraction grid and ground grid. And there are several diagnostic tools for the plasma and beam parameters measurement. The characteristics of plasma generation, negative ion production and extraction were studied on the test equipment. The negative ion beam was extracted from the RF driven negative ion source for the first time. The detailed structure and main results are presented in this article.展开更多
In order to understand the physics and pre-study the engineering issues for radio frequency(RF)negative beam source,a prototype source with a single driver and three-electrode accelerator was developed.Recently,the be...In order to understand the physics and pre-study the engineering issues for radio frequency(RF)negative beam source,a prototype source with a single driver and three-electrode accelerator was developed.Recently,the beam source was tested on the RF source test facility with RF plasma generation,negative ion production and extraction.A magnetic filter system and a Cs injection system were employed to enhance the negative ion production.As a result,a long pulse of 105 s negative ion beam with current density of 153 A m-2 was repeatedly extracted successfully.The source pressure is 0.6 Pa and the ratio of co-extracted electron and negative ion current is around0.3.The details of design and experimental results of beam source were shown in this letter.展开更多
Huazhong University of Science and Technology has developed an experimental setup of a radio frequency(RF) driven negative hydrogen ion source,to investigate the physics of production and extraction of the H^(-)ions f...Huazhong University of Science and Technology has developed an experimental setup of a radio frequency(RF) driven negative hydrogen ion source,to investigate the physics of production and extraction of the H^(-)ions for neutral beam injection in nuclear fusion reactors.The main design parameters of the ion source are:RF power ≤40 kW;extraction voltage ≤10kV;accelerator voltage ≤20 kV.This paper gives an overview of the progress of the ion source with particular emphasis on some issues.The RF driver and source plasma are analyzed and optimized in terms of impedance matching,plasma characteristics and power coupling.In regard to the simulation analysis,a plasma model based on the particle-in-cell method and a beam trajectory model considering beam stripping loss are developed to investigate the plasma and negative ions transport inside the ion source.Furthermore,a collisional radiative model of H and H2is built for plasma optical diagnosis.展开更多
In the design of negative hydrogen ion sources,a magnetic filter field of tens of Gauss at the expansion region is essential to reduce the electron temperature,which usually results in a magnetic field of around 10 Ga...In the design of negative hydrogen ion sources,a magnetic filter field of tens of Gauss at the expansion region is essential to reduce the electron temperature,which usually results in a magnetic field of around 10 Gauss in the driver region,destabilizing the discharge.The magnetic shield technique is proposed in this work to reduce the magnetic field in the driver region and improve the discharge characteristics.In this paper,a three-dimensional fluid model is developed within COMSOL to study the influence of the magnetic shield on the generation and transport of plasmas in the negative hydrogen ion source.It is found that when the magnetic shield material is applied at the interface of the expansion region and the driver region,the electron density can be effectively increased.For instance,the maximum of the electron density is 6.7×10^(17)m^(-3)in the case without the magnetic shield,and the value increases to 9.4×10^(17)m^(-3)when the magnetic shield is introduced.展开更多
A three-dimensional fluid model is developed to investigate the radio-frequency inductively coupled H2 plasma in a reactor with a rectangular expansion chamber and a cylindrical driver chamber,for neutral beam injecti...A three-dimensional fluid model is developed to investigate the radio-frequency inductively coupled H2 plasma in a reactor with a rectangular expansion chamber and a cylindrical driver chamber,for neutral beam injection system in CFETR.In this model,the electron effective collision frequency and the ion mobility at high E-fields are employed,for accurate simulation of discharges at low pressures(0.3 Pa-2 Pa)and high powers(40 kW-100 kW).The results indicate that when the high E-field ion mobility is taken into account,the electron density is about four times higher than the value in the low E-field case.In addition,the influences of the magnetic field,pressure and power on the electron density and electron temperature are demonstrated.It is found that the electron density and electron temperature in the xz-plane along permanent magnet side become much more asymmetric when magnetic field enhances.However,the plasma parameters in the yz-plane without permanent magnet side are symmetric no matter the magnetic field is applied or not.Besides,the maximum of the electron density first increases and then decreases with magnetic field,while the electron temperature at the bottom of the expansion region first decreases and then almost keeps constant.As the pressure increases from 0.3 Pa to 2 Pa,the electron density becomes higher,with the maximum moving upwards to the driver region,and the symmetry of the electron temperature in the xz-plane becomes much better.As power increases,the electron density rises,whereas the spatial distribution is similar.It can be summarized that the magnetic field and gas pressure have great influence on the symmetry of the plasma parameters,while the power only has little effect.展开更多
The results on high power injection with the ueutral bean, injection （NBI） system for the Large Helical Device （LHD） are reported. The system consists of three beam-lines with two hydrogen negative ion （H^- ion）...The results on high power injection with the ueutral bean, injection （NBI） system for the Large Helical Device （LHD） are reported. The system consists of three beam-lines with two hydrogen negative ion （H^- ion） sources installed in each beam-line. In order to improve the injection power, a new beam accelerator with a multi-slot grounded grid （MSGG） has been developed and applied to one beam-line. Using the accelerator, a maximum power of 5.7 MW was achieved in 2003 and 2004, and the maximum energy of 189 keV was reached. The power and energy exceeded the design values of the individual beam-line for LHD. The other beam-lines also increased their injection power up to about 4 MW, and the total injection power of 13.1 MW was achieved with three beam-llnes in 2003. Although the accelerator had an advantage in high power beam injection, extracted beams expand in the short side direction of the ground-grid slot. The disadvantage has been resolved by modifying the aperture shapes of the steering grid.展开更多
We present an extended update on the status of a particle-in-cellwithMonte Carlo collisions(PIC-MCC)gun code developed at LosAlamos for the study of surfaceconverter H−ion sources.The programis fully kinetic.Some of t...We present an extended update on the status of a particle-in-cellwithMonte Carlo collisions(PIC-MCC)gun code developed at LosAlamos for the study of surfaceconverter H−ion sources.The programis fully kinetic.Some of the program’s features include:solution of arbitrary electrostatic and magnetostatic fields in an axisymmetric(r,z)geometry to describe the self-consistent time evolution of a plasma;simulation of a multi-species(e^(−),H^(+),H^(+)_(2),H^(+)_(3),H^(−))plasma discharge from a neutral hydrogen gas and filament-originated seed electrons;full 2-dimensional(r,z)3-velocity(v_(r),v_(z),vφ)dynamics for all species;detailed collision physics between charged particles and neutrals and the ability to represent multiple smooth(not stair-stepped)electrodes of arbitrary shape and voltage whose surfaces may be secondary-particle emitters(H^(−)and e^(−)).The status of this development is discussed in terms of its physics content and current implementation details.展开更多
The extraction of negative ions inevitably leads to the destruction of the original plasma state. To understand the effect of extraction on a plasma sheath under a weak magnetic filter field, the time-dependent behavi...The extraction of negative ions inevitably leads to the destruction of the original plasma state. To understand the effect of extraction on a plasma sheath under a weak magnetic filter field, the time-dependent behavior of H- ion extraction from a negative ion source has been studied by particle-in-cell simulation in the collisionless limit. The simulation results have shown that the plasma sheath would undergo a transient process, in which there exists an edge electrostatic wave that propagates counterclockwise along the wall with a velocity of 4 mm/ns until it reaches the other side of extraction aperture. The thickness of the plasma sheath and the plasma potential both increase greatly at the final quasi-steady-state. For comparison, the results of extracting positive ions are also given.展开更多
基金supported by the Comprehensive Research Facility for Fusion Technology Program of China(No.2018-000052-73-01-001228)National Natural Science Foundation of China(No.11975264)。
文摘A magnetic field produced by a current flowing through the plasma grid(PG) is one of the solutions to reduce the collisional loss of negative ions in a negative ion source, which reduces the electron temperature in front of the PG. However, the magnetic field diffused into the driver has some influence on the plasma outflowing. In order to investigate the effect of changing this magnetic field on the outflowing of plasma from the driver, a circular ring(absorber) of high permeability iron has been introduced at the driver exit, which can reduce the magnetic field around it and improve plasma outflowing. With the application of the absorber, the electron density is increased by about 35%, and the extraction current measured from the extraction grid is increased from 1.02 A to 1.29 A. The results of the extraction experiment with cesium injection show that both the extraction grid(EG) current and H-current are increased when the absorber is introduced.
基金supported by National Natural Science Foundation of China(Nos.11505224,11575240,11405207)the National Magnetic Confinement Fusion Science Program of China(Nos.2013GB101001,2013GB101002,2013GB101003)+1 种基金International Science and Technology Cooperation Program of China(No.2014DFG61950)Foundation of ASIPP(No.DSJJ-14-JC07)
文摘In order to support the design, manufacture and commissioning of the negative- ion-based neutral beam injection （NBI） system for the Chinese Fusion Engineering Test Reactor （CFETR）, the Hefei utility negative ion test equipment with RF source （HUNTER） was proposed at ASIPP. A prototype negative ion source will be developed at first. The main bodies of plasma source and accelerator of the prototype negative ion source are similar to that of the ion source for EAST-NBI. But instead of the filament-arc driver, an RF driver is adopted for the prototype negative ion source to fulfill the requirement of long pulse operation. A cesium seeding system and a magnetic filter are added for enhancing the negative ion density near the plasma grid and minimizing co-extracted electrons. Besides, an ITER-like extraction system is applied inside the accelerator, where the negative ion beam is extracted and accelerated up to 50 kV.
文摘Electric potential near a wall for plasma with the surface produced negative ions with magnetic field increasing toward a wall is investigated analytically. The potential profile is derived analytically by using a plasma-sheath equation, where negative ions produced on the plasma grid （PG） surface are considered in addition to positive ions and electrons. The potential profile depends on the amount and the temperature of the surface produced negative ions and the profile of the magnetic field. The negative potential peak is formed in the sheath region near the PG surface for the case of strong surface production of negative ions or low temperature negative ions. As the increase rate of the magnetic field near the wall becomes large, the negative potential peak becomes small.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFC2202700).
文摘Neutral beam injection(NBI)systems based on negative hydrogen ion sources-rather than the positive ion sources that have typically been used to date-will be used in the future magnetically confined nuclear fusion experiments to heat the plasma.The collisions between the fast negative ions and neutral background gas result in a significant number of high-energy positive ions being produced in the acceleration area,and for the high-power long-pulse operation of NBI systems,this acceleration of positive ions back to the ion source creates heat load and material sputtering on the source backplate.This difficulty cannot be ignored,with the neutral gas density in the acceleration region having a significant impact on the flux density of the backstreaming positive ions.In the work reported here,the pressure gradient in the acceleration region was estimated using an ionization gauge and a straightforward 1D computation,and it was found that once gas traveled through the acceleration region,the pressure dropped by nearly one order of magnitude,with the largest pressure drop occurring at the plasma grid.The computation also revealed that the pressure drop in the grid gaps was substantially smaller than that in the grid apertures.
基金supported by the National Key R&D Program of China (No. 2017YFE0300106)National Natural Science Foundation of China (Nos. 11935005 and 12075049)the Fundamental Research Funds for the Central Universities(Nos. DUT21TD104 and DUT21LAB110)。
文摘A radio-frequency(RF) inductively coupled negative hydrogen ion source(NHIS) has been adopted in the China Fusion Engineering Test Reactor(CFETR) to generate negative hydrogen ions.By incorporating the level-lumping method into a three-dimensional fluid model,the volume production and transportation of H^(-) in the NHIS,which consists of a cylindrical driver region and a rectangular expansion chamber,are investigated self-consistently at a large input power(40 k W) and different pressures(0.3–2.0 Pa).The results indicate that with the increase of pressure,the H^(-) density at the bottom of the expansion region first increases and then decreases.In addition,the effect of the magnetic filter is examined.It is noteworthy that a significant increase in the H^(-) density is observed when the magnetic filter is introduced.As the permanent magnets move towards the driver region,the H^(-) density decreases monotonically and the asymmetry is enhanced.This study contributes to the understanding of H-distribution under various conditions and facilitates the optimization of volume production of negative hydrogen ions in the NHIS.
基金supported by the Key Program of Research and Development of Hefei Science Center,CAS(No.2016HSCKPRD002)National Natural Science Foundation of China(Nos.11505224,11505225,11575240,11675215,11675216)
文摘In order to study the key technology and physics of RF driven negative ion source for neutral beam injector in China, the Hefei utility negative ions test equipment with RF source was developed at Institute of Plasma Physics, Chinese Academy of Sciences（ASIPP）. Its negative ion source can be equipped with single or double RF drivers. There is a plasma expansion chamber with depth of 19 mm and an enhanced filter field. A three electrodes negative ion accelerator was employed to extract and accelerate the negative ions, which are plasma grid,extraction grid and ground grid. And there are several diagnostic tools for the plasma and beam parameters measurement. The characteristics of plasma generation, negative ion production and extraction were studied on the test equipment. The negative ion beam was extracted from the RF driven negative ion source for the first time. The detailed structure and main results are presented in this article.
基金supported by the Comprehensive Research Facility for Fusion Technology Program of China(No.2018-000052-73-01-001228)
文摘In order to understand the physics and pre-study the engineering issues for radio frequency(RF)negative beam source,a prototype source with a single driver and three-electrode accelerator was developed.Recently,the beam source was tested on the RF source test facility with RF plasma generation,negative ion production and extraction.A magnetic filter system and a Cs injection system were employed to enhance the negative ion production.As a result,a long pulse of 105 s negative ion beam with current density of 153 A m-2 was repeatedly extracted successfully.The source pressure is 0.6 Pa and the ratio of co-extracted electron and negative ion current is around0.3.The details of design and experimental results of beam source were shown in this letter.
基金supported by the National Key R&D Program of China(No.2017YFE0300105)National Natural Science Foundation of China(Nos.11775088 and 12005074)the Fundamental Research Funds for the Central Universities,HUST(No.2021XXJS013)
文摘Huazhong University of Science and Technology has developed an experimental setup of a radio frequency(RF) driven negative hydrogen ion source,to investigate the physics of production and extraction of the H^(-)ions for neutral beam injection in nuclear fusion reactors.The main design parameters of the ion source are:RF power ≤40 kW;extraction voltage ≤10kV;accelerator voltage ≤20 kV.This paper gives an overview of the progress of the ion source with particular emphasis on some issues.The RF driver and source plasma are analyzed and optimized in terms of impedance matching,plasma characteristics and power coupling.In regard to the simulation analysis,a plasma model based on the particle-in-cell method and a beam trajectory model considering beam stripping loss are developed to investigate the plasma and negative ions transport inside the ion source.Furthermore,a collisional radiative model of H and H2is built for plasma optical diagnosis.
基金supported by the National Key R&D Program of China(No.2017YFE0300106)National Natural Science Foundation of China(No.12075049)the Fundamental Research Funds for the Central Universities(Nos.DUT20LAB201 and DUT21LAB110)。
文摘In the design of negative hydrogen ion sources,a magnetic filter field of tens of Gauss at the expansion region is essential to reduce the electron temperature,which usually results in a magnetic field of around 10 Gauss in the driver region,destabilizing the discharge.The magnetic shield technique is proposed in this work to reduce the magnetic field in the driver region and improve the discharge characteristics.In this paper,a three-dimensional fluid model is developed within COMSOL to study the influence of the magnetic shield on the generation and transport of plasmas in the negative hydrogen ion source.It is found that when the magnetic shield material is applied at the interface of the expansion region and the driver region,the electron density can be effectively increased.For instance,the maximum of the electron density is 6.7×10^(17)m^(-3)in the case without the magnetic shield,and the value increases to 9.4×10^(17)m^(-3)when the magnetic shield is introduced.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFE0300106)the National Natural Science Foundation of China(Grant No.12075049)the Fundamental Research Funds for the Central Universities,China(Grant Nos.DUT20LAB201 and DUT21LAB110).
文摘A three-dimensional fluid model is developed to investigate the radio-frequency inductively coupled H2 plasma in a reactor with a rectangular expansion chamber and a cylindrical driver chamber,for neutral beam injection system in CFETR.In this model,the electron effective collision frequency and the ion mobility at high E-fields are employed,for accurate simulation of discharges at low pressures(0.3 Pa-2 Pa)and high powers(40 kW-100 kW).The results indicate that when the high E-field ion mobility is taken into account,the electron density is about four times higher than the value in the low E-field case.In addition,the influences of the magnetic field,pressure and power on the electron density and electron temperature are demonstrated.It is found that the electron density and electron temperature in the xz-plane along permanent magnet side become much more asymmetric when magnetic field enhances.However,the plasma parameters in the yz-plane without permanent magnet side are symmetric no matter the magnetic field is applied or not.Besides,the maximum of the electron density first increases and then decreases with magnetic field,while the electron temperature at the bottom of the expansion region first decreases and then almost keeps constant.As the pressure increases from 0.3 Pa to 2 Pa,the electron density becomes higher,with the maximum moving upwards to the driver region,and the symmetry of the electron temperature in the xz-plane becomes much better.As power increases,the electron density rises,whereas the spatial distribution is similar.It can be summarized that the magnetic field and gas pressure have great influence on the symmetry of the plasma parameters,while the power only has little effect.
基金supported in part by the JSPS-CAS Core-University Program in the field of Plasma and Nuclear Fusion
文摘The results on high power injection with the ueutral bean, injection （NBI） system for the Large Helical Device （LHD） are reported. The system consists of three beam-lines with two hydrogen negative ion （H^- ion） sources installed in each beam-line. In order to improve the injection power, a new beam accelerator with a multi-slot grounded grid （MSGG） has been developed and applied to one beam-line. Using the accelerator, a maximum power of 5.7 MW was achieved in 2003 and 2004, and the maximum energy of 189 keV was reached. The power and energy exceeded the design values of the individual beam-line for LHD. The other beam-lines also increased their injection power up to about 4 MW, and the total injection power of 13.1 MW was achieved with three beam-llnes in 2003. Although the accelerator had an advantage in high power beam injection, extracted beams expand in the short side direction of the ground-grid slot. The disadvantage has been resolved by modifying the aperture shapes of the steering grid.
基金This research is supported by the US Department of Energy through contract DE-AC52-06NA25396.
文摘We present an extended update on the status of a particle-in-cellwithMonte Carlo collisions(PIC-MCC)gun code developed at LosAlamos for the study of surfaceconverter H−ion sources.The programis fully kinetic.Some of the program’s features include:solution of arbitrary electrostatic and magnetostatic fields in an axisymmetric(r,z)geometry to describe the self-consistent time evolution of a plasma;simulation of a multi-species(e^(−),H^(+),H^(+)_(2),H^(+)_(3),H^(−))plasma discharge from a neutral hydrogen gas and filament-originated seed electrons;full 2-dimensional(r,z)3-velocity(v_(r),v_(z),vφ)dynamics for all species;detailed collision physics between charged particles and neutrals and the ability to represent multiple smooth(not stair-stepped)electrodes of arbitrary shape and voltage whose surfaces may be secondary-particle emitters(H^(−)and e^(−)).The status of this development is discussed in terms of its physics content and current implementation details.
基金Supported by National Natural Science Foundation of China (11105130)Science and Technology Development Foundation of CAEP (2012B0402056)
文摘The extraction of negative ions inevitably leads to the destruction of the original plasma state. To understand the effect of extraction on a plasma sheath under a weak magnetic filter field, the time-dependent behavior of H- ion extraction from a negative ion source has been studied by particle-in-cell simulation in the collisionless limit. The simulation results have shown that the plasma sheath would undergo a transient process, in which there exists an edge electrostatic wave that propagates counterclockwise along the wall with a velocity of 4 mm/ns until it reaches the other side of extraction aperture. The thickness of the plasma sheath and the plasma potential both increase greatly at the final quasi-steady-state. For comparison, the results of extracting positive ions are also given.
