共查询到20条相似文献，搜索用时 15 毫秒
1.
A two-dimensional particle-in-cell plasma model is built in the R–Z plane to investigate the lowfrequency plasma oscillations in the discharge channel of a 5 kW LHT-140 Hall thruster. In addition to the elastic, excitation, and ionization collisions between neutral atoms and electrons,the Coulomb collisions between electrons and electrons and between electrons and ions are analyzed. The sheath characteristic distortion is also corrected. Simulation results indicate the capability of the built model to reproduce the low-frequency oscillation with high accuracy. The oscillations of the discharge current and ion density produced by the model are consistent with the existing conclusions. The model predicts a frequency that is consistent with that calculated by the zero-dimensional theoretical model. 相似文献
2.
Demai ZENG 《等离子体科学和技术》2022,24(7):74005
It is assumed that the shift of a strong magnetic field region with a positive gradient from exit plane to outside, namely the transit from a normal loaded magnetic field to an aft-loaded one, enhances the multiple ionization process in the magnetically shielded Hall thruster. To confirm this conjecture, a comparative study is carried out numerically with a particle-in-cell method. The simulation results prove that compared with the normal loaded magnetic field, the application of aft-loaded magnetic field enhances the multiple ionization process. This study further analyzes the ionization characteristics of the transition from low-charged ions to high-charged ions under two magnetic field conditions and the influence of the magnetic strength of aft-loaded magnetic field on the multiple ionization characteristics. The study described herein is useful for understanding the discharge characteristics of Hall thruster with an aft-loaded magnetic field. 相似文献
3.
The microwave discharge cusped field thruster is a novel concept of electric micropropulsion device, which operates μ N level thrust in low mass flow rate conditions, making use of a coaxial transmission line resonator. With its advantages of low thrust noise and high thrust resolution over a wide range of thrust, the thruster has emerged as a candidate thruster for the space-borne gravitational wave detection mission. The cathode effects commonly exist in many kinds of electric propulsion, and they are typically significant in micropropulsions. In order to find out the cathode position effects on a microwave discharge cusped field thruster, a thermionic cathode is mounted on a cross-slider for coupling. Under different cathode positions, the plume is analyzed by a Faraday probe and a retarding potential analyzer to analyze the performance and discharge characteristics. The results show that the magnetic mirror effect leads to significant degradation of anode current and an increase in low-energy ion ratio as the cathode moves away from the thruster exit. The electron conduction route also significantly impacts anode current efficiency, related to the cathode-exit distance and the thruster magnetic topology. 相似文献
4.
胡鹏;张文瀚;孙建冬;鹿畅;陈冲;韩亚杰;韩道满;刘旭辉;孙斌 《等离子体科学和技术》2025,27(6):064011-1-064011-9
A new magnetic field configuration is proposed by introducing a cusped field to the helicon plasma thruster (HPT), and the effects of the cusped field on the discharge characteristics of the HPT are investigated. The experimental results show that the thruster can still achieve a stable W mode discharge with the additional cusped field, while the discharge conditions have been changed so that a higher RF power is required to achieve the W mode under the same experimental conditions. However, the ion density in the plume region is increased by at least one order of magnitude and the ion flux density is increased by a factor of 4 to 5. The ionization enhancement is attributed to the change in magnetic field configuration, which improves the energy coupling efficiency and the ability to confine charged particles (particularly electrons). This magnetic confinement could employ more electrons to ionize the working medium atoms, and the ionization rate is enhanced. The increase in ion density leads to a reduction in the energy available for ion acceleration, resulting in a slight decrease in ion energy. 相似文献
5.
In this paper,a direct connection between the discharge current amplitude and the thruster performance is established by varying solely the capacitance of the filter unit of the Hall thrusters.To be precise,the variation characteristics of ion current,propellant utilization efficiency,and divergence angle of plume at different low-frequency oscillation amplitudes are measured.The findings demonstrate that in the case of the propellant in the discharge channel just meets or falls below the full ionization condition,the increase of low-frequency oscillation amplitude can significantly enhance the ionization degree of the neutral gas in the channel and increase the thrust and anode efficiency of thruster.On the contrary,the increase in the amplitude of low-frequency oscillation will lead to increase the loss of plume divergence,therefore the thrust and anode efficiency of thruster decrease. 相似文献
6.
Liang HAN 《等离子体科学和技术》2019,21(8):85502-69
This paper presents a method to measure the in situ magnetic field in a Hall thruster by optical non-invasive means, based on the optical Faraday rotation effect. This method does not affect the discharge of the thruster. Furthermore, its time resolution depends on the speed of the photodetector, and measurement at a MHz scale can be achieved. 相似文献
7.
A distribution of the magnetic field produced by permanent magnets in the DNB ion source is calculated and analyzed in order to understand the plasma confinement in a cusped magnetic field and optimize plasma discharge. A uniform plasma is obtained in the experiment. 相似文献
8.
DUAN Ping 《等离子体科学和技术》2016,18(5):525-530
The influences of the low-emissive graphite segmented electrode placed near the channel exit on the discharge characteristics of a Hall thruster are studied using the particlein-cell method.A two-dimensional physical model is established according to the Hall thruster discharge channel configuration.The effects of electrode length on the potential,ion density,electron temperature,ionization rate and discharge current are investigated.It is found that,with the increasing of the segmented electrode length,the equipotential lines bend towards the channel exit,and approximately parallel to the wall at the channel surface,the radial velocity and radial flow of ions are increased,and the electron temperature is also enhanced.Due to the conductive characteristic of electrodes,the radial electric field and the axial electron conductivity near the wall are enhanced,and the probability of the electron-atom ionization is reduced,which leads to the degradation of the ionization rate in the discharge channel.However,the interaction between electrons and the wall enhances the near wall conductivity,therefore the discharge current grows along with the segmented electrode length,and the performance of the thruster is also affected. 相似文献
9.
Xiaogang YUAN 《等离子体科学和技术》2020,22(9):94003-094003
To study the heating mechanism of electron cyclotron resonance thruster(ECRT) immersed in a non-uniform magnetic field, experiments and simulations are performed based on an electron cyclotron resonance plasma source at ASIPP. It is found that the first harmonic of electron cyclotron resonance is essential for plasma ignition at high magnetic field(0.0875 T), while the plasma can sustain without the first and second harmonics of electron cyclotron resonance at low magnetic field(till 0.0170 T). Evidence of radial hollow density profile indicates that upper hybrid resonance, which has strong edge heating effect, is the heating mechanism of low-field ECRT. The heating mode transition from electron cyclotron resonance to upper hybrid resonance is also revealed. Interestingly, the evolutions of electron temperature and electron density with input power experience a ‘delayed' jump, which may be correlated with the different power levels required for cyclotron and ionization. Moreover, when the field strength decreased, the variation of electron density behaves in an opposite trend with that of electron temperature,implying a possible competition of power deposition between them. The present work is of great interest for understanding the plasma discharge in ECRT especially immersed in a non-uniform magnetic field, and designing efficient ECRT using low magnetic field for economic space applications. 相似文献
10.
Yue YANG Boyuan LI Yuchi WU Bin ZHU Bo ZHANG Zhimeng ZHANG Minghai YU Feng LU Kainan ZHOU Lianqiang SHAN Lihua CAO Zongqing ZHAO Weimin ZHOU Yuqiu GU 《等离子体科学和技术》2021,23(1):15001-12
The transport of sub-picosecond laser-driven fast electrons in nanopore array targets is studied.Attributed to the generation of micro-structured magnetic fields, most fast electron beams are proven to be effectively guided and restricted during the propagation. Different transport patterns of fast electrons in the targets are observed in experiments and reproduced by particle-in-cell simulations, representing two components: initially collimated low-energy electrons in the center and high-energy scattering electrons turning into surrounding annular beams. The critical energy for confined electrons is deduced theoretically. The electron guidance and confinement by the nano-structured targets offer a technological approach to manipulate and optimize the fast electron transport by properly modulating pulse parameters and target design, showing great potential in many applications including ion acceleration, microfocus x-ray sources and inertial confinement fusion. 相似文献
11.
In order to investigate the effects of secondary electrons, which are emitted from the wall, on the performance of a thruster, a one-dimensional fluid model of the plasma sheath in double walls is applied to study the characteristics of a magnetized sheath. The effects of secondary electron emission (SEE) coefficients and trapping coefficients, as well as magnetic field, on the structure of the plasma sheath are investigated. The results show that sheath potential and wall potential rise with the increment of SEE coefficient and trapping coefficient which results in a reduced sheath thickness. In addition, magnetic field strength will influence the sheath potential distributions. 相似文献
12.
A 1D1V hybrid Vlasov-fluid model was developed for this study to elucidate discharge current oscillations of Hall thrusters (HTs). The Vlasov equation for ions velocity distribution function with ionization source term is solved using a constrained interpolation profile conservative semi-Lagrangian method. The fourth-order weighted essentially non-oscillatory (4th WENO) limiter is applied to the first derivative value to minimize numerical oscillation in the discharge oscillation analyses. The fourth-order accuracy is verified through a 1D scalar test case. Nonoscillatory and high-resolution features of the Vlasov model are confirmed by simulating the test cases of the Vlasov–Poisson system and by comparing the results with a particle-in-cell (PIC) method. A 1D1V HT simulation is performed through the hybrid Vlasov model. The ionization oscillation is analyzed. The oscillation amplitude and plasma density are compared with those obtained from a hybrid PIC method. The comparison indicates that the hybrid Vlasov-fluid model yields noiseless results and that the steady-state waveform is calculable in a short time period. 相似文献
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在使用自制外推电离室（以下简称外推室）,绝对测量国产JJ-2型电子静电加速器电子在硅材料深部剂量率实验中,加速器电子束流强度的不稳定将引起外推室所测电离电流的不稳定。有时束流强度不稳造成的电离电流变化量会大于因空腔体积改变所引起的电离电流变化量,致使外推室测量的数据无法进行体积外推,从而失去了外推室测剂量的意义。本实验采取单位束流强度剂量测量方法,在外推室进行测量的每一个极间距离上,由计算机快速同步地采集数十组电离电流和与之相应的束流强度值,剔除粗差后求单位束流强度下电子的平均电离电流值,进而使体积外推得以顺利进行。最后通过有关公式计算出单位束流强度下的电子平均吸收剂量率。 相似文献
15.
本文基于Bohr-Lindhard(B-L)模型,考虑了碰撞双方的电子密度分布,计算了能量为20~900keV/u的B2+、C3+、N4+及O5+等类锂离子与He原子碰撞中的单电子丢失(SEL)、伴随单电离的单电子丢失(SELSI)、伴随双电离的单电子丢失(SELDI)等截面对能量的依赖曲线,计算结果与已有的实验数据符合较好。分析发现,对于一给定的过程,较重的离子有较小的有效碰撞参数范围;对于同一种入射离子,SEL、SELSI和SELDI等过程对应的有效碰撞参数范围依次减小。 相似文献
16.
《Fusion Engineering and Design》2014,89(7-8):1019-1023
The generation and diffusion of runaway electrons (REs) during major disruptions in the HL-2A tokamak has been studied numerically. The diffusion caused by the magnetic perturbation is especially addressed. The simulation results show that the strong magnetic perturbation (δB/B ∼ 1.0 × 10−3) can cause a significant loss of REs due to the radial diffusion and restrain the RE avalanche effectively. The results also indicate that the REs are generated initially in the plasma core during disruptions, and that the toroidal electric field does not exhibit a centrally hollow phenomenon. In addition, it is found that the toroidal effects have little impact on the generation of RE and the evolution of toroidal electric field. 相似文献
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Yujun KE Xinfeng SUN Xuekang CHEN Licheng TIAN Tianping ZHANG Maofan ZHENG Yanhui JIA Haocheng JIANG 《等离子体科学和技术》2017,19(9):95503-095503
An ECR ion thruster with a diameter of 5 cm has been developed and tested.Four different antenna positions were experimentally and numerically investigated,and the results suggest that the optimal location for the antenna is where it is perfectly surrounded by the electron cyclotron resonance layer.We also evaluated two different antenna configurations,and found that the star configuration is preferable to the circular configuration,and also that the circular antenna is only 40％ as efficient as the star antenna.The experimental curve of the ion beam current and voltage agrees with the fitting results from the analytic solution.The simulation of the magnetic topology in the discharging chamber with different back yoke heights indicates that it needs to be further verified. 相似文献
19.
蒙特卡罗方法在器件屏蔽封装中的应用 总被引：3，自引：0，他引：3
用1.5MeV的电子对几种封装材料进行辐照,得到它的剂量深度分布曲线．同时用Monte-Carlo方法计算进行模拟,两着符合较好。高Z材料．如钨、钽是最好的屏蔽初级电子的材料．但从实用性设计考虑,这些材料都是导体,不利于对特殊结构器件进行包封,又设计了几种复合材料．这既达到了屏蔽的效果,又可以绝缘,可以直接对器件进行封装。建立的理论模拟方法,为预估二次封装器件的空间辐射环境抗总剂量能力提供了一种有效的方法。 相似文献