共查询到19条相似文献,搜索用时 187 毫秒
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非均匀磁场约束条件下的电子束空气等离子体特性 总被引:1,自引:0,他引:1
为了揭示大气环境电子束等离子体的性质,基于蒙特卡罗程序包Geant4建立了一个包含电离、激发以及轫致辐射等物理过程的计算模型,用于模拟非均匀磁场约束条件下高能强流稳态电子束的输运特性、以及大气环境等离子体的性质。结果表明:非均匀磁场可以有效控制电子束在空气中的输运轨迹,显著降低电子束的发散;随着电子束在空气中行程的增加,电子束能谱开始展宽并向低能区移动;输运装置出口能量损失比电子束射程末端高2个量级,且随着电子束输运距离的增加,等离子体密度降低;等离子体密度的高低与电子束能量直接相关。 相似文献
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为了研究高速动态气流中的电子束等离子体特性,建立了一个由蒙特卡罗模型、多组分等离子体模型与计算流体力学模型组成的多阶段耦合数值模型,在临近声速气流条件下,对1.33×104 Pa空气电子束等离子体特性进行了研究。结果表明,电子束能量沉积具有极强的空间不均性,电子束激发下的风洞流场呈现不同的性质,亚声速流场下游边界区密度减小,而在超声速流场中可诱发弱激波;相比于静止气体,在动态气流中等离子体密度下降,且存在额外的输运行为,使其向气流下游输运,但在临近声速条件下,气流速度大小对气流下游等离子体分布的影响不大;电子束入射角对等离子体空间分布和大小均有影响。 相似文献
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建立了一个四组分一维混合模型,对电子束注入大气产生大尺度等离子体的过程进行了数值模拟.结果表明了能量为140keV、流强为50mA/cm2的注入电子束,可以产生线度为0.5m,密度为1012cm-3量级的大气环境下等离子体.电子束所伴随的空间电荷效应由于等离子体的产生会很快消失,不影响后续的等离子体产生过程.电子束注入流强主要影响产生等离子体的密度,而电子束能量则同时影响其空间线度和密度.
关键词:
电子束
碰撞
电离 相似文献
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考虑相对论电子束入射等离子体所产生的离子通道的具体结构,利用线性电磁流体力学理论对离子通道摇摆电子束激发的纵向慢波电磁不稳定性进行研究.通过对导出的系统色散关系的数值分析,给出了系统中电磁波、空间电荷波以及两者在一定条件下互作用形成的电磁-静电混合模式的传播特性.研究发现系统在慢波区域存在电磁不稳定性,并揭示此慢波不稳定性是由电子束的betatron振荡所导致,且系统的不稳定性程度与betatron振动频率密切相关.对betatron振荡激发的慢波电磁不稳定性物理机理进行了分析,并给出了不稳定性存在的条件
关键词:
离子通道
betatron振荡
电磁不稳定性 相似文献
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黄林 《核聚变与等离子体物理》1982,(3)
本文研究了相对论电子束在磁化等离子体中的传输。采用电荷中和及磁中和模型,求解了束-等离子体系统的初值问题,得到了等离子体的响应函数。结果表明:与非磁化等离子体一样,磁化等离子体也可以传输任意大电流密度的电子束;在VA《γ_0m/m_i)~(1/2)c的条件下,弱纵向外磁场只对等离子体的响应函数有影响,不改变电子束的传输。 相似文献
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董克攻 吴玉迟 郑无敌 朱斌 曹磊峰 何颖玲 马占南 刘红杰 洪伟 周维民 赵宗清 焦春晔 温贤伦 魏来 臧华平 余金清 谷渝秋 张保汉 王晓方 《物理学报》2011,60(9):95202-095202
在激光尾波场电子加速机理中,为了有效地加速电子,需要抑制衍射散焦等造成的激光传输不稳定性问题. 激光脉冲的稳定传输不仅有利于能量耦合给等离子体波,而且对电子束的注入及稳定加速有着重要影响,具有一定横向密度分布的充气型放电毛细管可以有效引导激光脉冲的传输. 利用等离子体的Stark展宽效应对毛细管产生的等离子体进行密度测量,给出了等离子体密度与充气压强之间的关系. 利用磁流体程序CRMHA对毛细管的放电特性进行了模拟,研究了毛细管引导效应的形成机理.
关键词:
充气型放电毛细管
Stark展宽
磁流体模拟
引导 相似文献
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Physical properties of relativistic electron beam during long-range propagation in space plasma environment 下载免费PDF全文
《中国物理 B》2021,30(10):104103-104103
It is known that ion channel can effectively limit the radial expansion of an artificial electron beam during its longrange propagation in the space plasma environment. Most prior studies discussed the focusing characteristics of the beam in the ion channel, but the establishment process and transient properties of the ion channel itself, which also plays a crucial role during the propagation of the relativistic electron beam in the plasma environment, were commonly neglected. In this study, a series of two-dimensional(2 D) particle-in-cell simulations is performed and an analytical model of ion channel oscillation is constructed according to the single-particle motion. The results showed that when the beam density is higher than the density of plasma environment, ion channel can be established and always continues to oscillate periodically over the entire propagation. Multiple factors, including the beam electron density, initial beam radius, and the plasma density can affect the oscillation properties of ion channel. Axial velocity of the beam oscillates synchronously with the ion channel and this phenomenon will finally develop into a two-stream instability which can seriously affect the effective transport for relativistic electron beam. Choosing appropriate beam parameters based on various plasma environments may contribute to the improvement of the stability of ion channel. Additionally, radial expansion of the beam can be limited by ion channel and a stable long-range propagation in terrestrial atmosphere may be achieved. 相似文献
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Smith J.R. Shokair I.R. Struve K.W. Schamiloglu E. Werner P.W. Lipinski R.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1991,19(5):850-854
An intense relativistic electron beam may be transported in low-pressure gas using an ion channel which focuses and guides the beam. The beam can be unstable to the growth of transverse oscillations caused by the electric force between the beam and channel-the ion hose instability. Beam propagation on channels created by photoionization of gas with an excimer laser is discussed. Ion hose oscillations have been recorded which have a betatron wavelength of approximately 1.5 m. The growth rate of the ion hose instability in the linear regime was measured as 1.67±0.45. At this level of growth, the amplitude of beam oscillations equals the channel radius after a period of one-third of an ion oscillation time 相似文献
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The dynamics of a relativistic electron beam propagating in an ion channel with a periodically varying density is considered.
The behavior of the ion hose instability at different parameters of the beam-ion channel system is studied using the spread
mass model. Conditions are determined under which the ion hose instability does not hinder the beam propagation over distances
on the order of 100 betatron lengths of the beam. 相似文献
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V. I. Vysotskii M. V. Vysotskii 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2008,2(2):253-263
Features of parametric effects during channeling of atomic ions, nuclei, and relativistic electrons (positrons) in crystals were considered. It was shown that parametric coupling between ion channeling states in the field of crystal axes and planes and electronic states in the ion volume leads to the possibility of “parametric collapse” of the beam, i.e., a decrease in the oscillation amplitude of the atomic ion in the channel due to periodic transfer of the ion oscillation energy to the inner electron of the atom. The same effect can be used to cool beams due to energy transfer to intrinsic nuclear states with low energy levels. It was shown that parametric cooling of beams with a decrease in the transverse energy can also occur during axial channeling of relativistic electron beams. This process results from the parametric coupling between channeling states, which are caused by the particle charge and electron spin states in an effective magnetic field induced in the moving coordinate system. 相似文献
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We investigate the transverse expansion of a relativistic electron beam propagating in a rarefied gas-plasma medium in the ion focusing regime during the development of ion hose instability. The expression is constructed for the pinch potential of the beam as a function of the amplitude of transverse deviation of the beam and on the parameter characterizing the ratio of the characteristic radial scales of the ion channel and of the electron beam. It is shown that this potential becomes substantially lower upon an increase in the hose oscillation amplitude and when the ion channel expands relative to the transverse size of the beam cross section. 相似文献
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Ion-focused propagation of a relativistic electron beam in the self-generated plasma in atmosphere 下载免费PDF全文
Jian-Hong Hao 《中国物理 B》2022,31(6):64101-064101
It is known that ion-focused regime (IFR) can effectively suppress expansion of a relativistic electron beam (REB). Using the particle-in-cell Monte Carlo collision (PIC-MCC) method, we numerically investigate the propagation of an REB in neutral gas. The results demonstrate that the beam body is charge neutralization and a stable IFR can be established. As a result, the beam transverse dimensions and longitudinal velocities keep close to the initial parameters. We also calculate the charge and current neutralization factors of the REB. Combined with envelope equations, we obtain the variations of beam envelopes, which agree well with the PIC simulations. However, both the energy loss and instabilities of the REB may lead to a low transport efficiency during long-range propagation. It is proved that decreasing the initial pulse length of the REB can avoid the influence of electron avalanche. Using parts of REB pulses to build a long-distance IFR in advance can improve the beam quality of subsequent pulses. Further, a long-distance IFR may contribute to the implementation of long-range propagation of the REB in space environment. 相似文献
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The oblique propagation of the quantum electrostatic solitary waves in magnetized relativistic quantum plasma is investigated using the quantum hydrodynamic equations. The plasma consists of dynamic relativistic degenerate electrons and positrons and a weakly relativistic ion beam. The Zakharov‐Kuznetsov equation is derived using the standard reductive perturbation technique that admits an obliquely propagating soliton solution. It is found that two types of quantum acoustic modes, that is, a slow acoustic mode and fast acoustic mode, could be propagated in our plasma model. The parameter that determines the nature of soliton, that is, compressive or rarefactive soliton, for slow mode is investigated. Our numerical results show that for the slow mode, the determining parameter is ion beam velocity in the case of relativistic degenerate electrons. We also have examined the effects of plasma parameters (like the beam velocity, the density ratio of positron to electron, the relativistic factor, and the propagation angle) on the characteristics of solitary waves. 相似文献
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A study is made of the effect of the magnetic self-field of a relativistic electron beam propagating in the ion focus regime on the transverse dynamics of plasma electrons. For Gaussian radial profiles of the beam and the ion density in the channel, the maximum deviation of the plasma electrons from the axis of the beam-plasma system is determined as a function of the space-charge neutralization fraction, the ratio of the characteristic beam radius to the channel radius, and the net beam current. 相似文献
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《Waves in Random and Complex Media》2013,23(2):131-140
In the present work, numerical studies on the effects of weakly relativistic ponderomotive force and space charge in the nonlinear interaction of a high-power microwave beam with a plasma are carried out. It is shown that, the profiles of the electron density and dielectric permittivity contain high peaks, and modulation of wavelength occurs in electron density distribution by increasing the microwave energy flux. In addition, it is indicated that the profiles of the electric and magnetic fields in relativistic regime are lengthened more than non-relativistic regime by increasing the initial electron density and the relativistic effects cause the increase in oscillation wavelength of electron density, dielectric permittivity and space charge field, in comparison with the non-relativistic regime. Finally, the results of the research show that the steepening in electron density distributions and their oscillation wavelength are enhanced, when the relativistic effects appear. 相似文献