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1.
K K Jain  P I John 《Pramana》1984,23(1):1-16
Experimental results on interaction of a rotating relativistic electron beam with plasma and neutral gas are presented. The rotating relativistic electron beam has been propagated up to a distance of 150 cm in a plasma. The response of the plasma to the rotating electron beam is found to be of magnetic diffusion type over a plasma density range 1011–1013 cm−3. Excitation of the axial and azimuthal return currents by the rotating beam and subsequent trapping of the azimuthal return current layer by the magnetic mirror field are observed. A field-reversed configuration has been formed by the rotating relativistic electron beam when injected into neutral hydrogen gas. We have observed field reversal up to three times the initial field in an axial length of 100 cm.  相似文献   

2.
The specific features of the beam-plasma instability in waveguide under very high beam current are shown analytically. The differences (as compared to conventional case of beam-plasma instability under low beam current) are due to change of physical mechanisms of beam-plasma interaction.  相似文献   

3.
Analysing the general dispersion relation numerically, the unstable regions of the relativistic electron-beam plasma system were determined. The external parameters were varied to ensure more effective instability excitations. The full charge and current compensation presumptions lead to new synchronism predictions. The return current's slow space charge wave and return current's slow cyclotron wave are synchronous with the plasma ion wave.  相似文献   

4.
通过箔 聚焦的电子束的包络方程研究了电子束的平衡与稳定特性,从而得到了能够传输的电子束的参数与箔之间距离和波导半径之间的关系。  相似文献   

5.
 通过箔 聚焦的电子束的包络方程研究了电子束的平衡与稳定特性,从而得到了能够传输的电子束的参数与箔之间距离和波导半径之间的关系。  相似文献   

6.
Microwave emission was measured from a system consisting of an unmagnetized plasma and a propagating electron beam. A 93-cm2 velvet cathode, with an anode-cathode gap of 5.9 cm, injects the electron current into the plasma through an aluminized Mylar anode. Measurements were made of the diode voltage and current in the 6-μV water dielectric accelerator and net current through the beam-plasma system. The unmagnetized plasma is produced by a 90-μs, 90-Å current pulse, emitted from a thermionic LaB6 electron source, that preionizes argon fill in a 1-m-long, 15-cm-diameter Lucite tube. A microwave spectrometer detects the radio-frequency output in the 2-18, 18-26, and 26-47 GHz bands, filters, and then separates into narrower subbands. The emission takes place in two distinct phases. The 2-GHz output rises promptly with the current pulse and then decays. At 6-GHz and above, a low-level microwave prepulse appears simultaneously with the 2-6 GHz output. This output rises sharply 25 ns after the current pulse begins and includes frequencies out to and beyond 40 GHz. The radio-frequency output falls off before the current pulse ends. The microwave intensity decays monotonically with frequency  相似文献   

7.
《Physics letters. A》2006,352(6):520-523
The effects of the thermal motion of the charged particles in the dissipative instability of the under and over-limiting currents of a relativistic electron beam in a fully magnetized beam-plasma waveguide is investigated. It is shown that by increasing the temperature of the plasma electrons, the resonant frequency of the waveguide slightly increases and the growth rates of the instability development decreases. In addition, an increase of the temperature of the plasma electron can change the dissipative hydrodynamic instability to the collisionless kinetic instability. Furthermore, the dissipative instability of the overlimiting electron beam is shown to be more sensitive with respect to the electron plasma temperature compared to the underlimiting electron beam case.  相似文献   

8.
相对论Birkhoff系统的平衡稳定性   总被引:2,自引:0,他引:2       下载免费PDF全文
傅景礼  陈立群  薛纭  罗绍凯 《物理学报》2002,51(12):2683-2689
研究相对论Birkhoff系统的平衡稳定性.给出相对论Birkhoff自治系统、半自治系统和非自治系统的平衡方程、受扰运动方程和一次近似方程;给出判定平衡稳定性的一次近似方法及其判据;讨论相对论Birkhoff系统平衡稳定性和经典Birkhoff系统平衡稳定性的关系.给出实例以说明方法的应用 关键词: 相对论 Birkhoff系统 平衡稳定性 一次近似方法  相似文献   

9.
It is strong that beam-plasma systems can be stabilized if a strong circularly polarized electromagnetic wave is applied. New unstable modes may, however, also be generated.  相似文献   

10.
We explore from a numerical point of view the validity of the Vlasov equation as a semi-classical approximation of time-dependent Hartree-Fock and time-dependent LDA theories, in terms of the survival of the Pauli principle. The fermionic properties are investigated by using a Na9+ cluster as test case and solving the Vlasov equation with the test particle method. This allows to derive a time span for which the Vlasov equation provides an acceptable approximation.  相似文献   

11.
The influence of conduction electron damping on the possibility of excitonic coupling in the intermediate valence systems is considered. The scattering by the internal degrees of freedom of f?-shells is shown to be the main mechanism for this damping. It is shown that both the excitonic energy gap and the damping are proportional to s-f? Coulomb integral, so the scattering considered prevents s- and f?-electrons from anomalous coupling. The growth of the resistivity near the point of valence change can be understood as the manifestation of this scattering.  相似文献   

12.
转动相对论Birkhoff系统的平衡稳定性   总被引:1,自引:1,他引:1       下载免费PDF全文
傅景礼  陈立群  薛纭 《物理学报》2003,52(2):256-261
研究转动相对论Birkhoff系统的平衡稳定性,给出转动相对论Birkhoff自治系统、半自治系统和非自治系统的平衡方程和转动相对论Birkhoff自治系统的受扰运动方程和一次近似方程;给出转动相对论Birkhoff自治系统平衡稳定性的一次近似方法及其判据;并给出转动相对论Birkhoff自治系统平衡稳定性的直接方法及其判据;讨论转动相对论Birkhoff系统平衡稳定性和经典转动Birkhoff系统平衡稳定性的关系.给出实例以说明方法的应用. 关键词: 相对论 转动Birkhoff系统 平衡稳定性 一次近似方法  相似文献   

13.
In this paper, the stability of equilibrium state manifold for relativistic Birkhoffian systems in studied. The equilibrium state equations, the disturbance equations and their first approximation are presented. The criteria of stability for the equilibrium state manifold are obtained. The relationship between the stability of the equilibrium-state manifold of relativistic Birkhoffian systems and that of classical Birkhoffian systems is discussed. An example is given to illustrate the results.  相似文献   

14.
介绍了采用双膜法测量神龙一号直线感应加速器靶区回流离子效应的实验工作,通过一片厚度数十μm的靶膜产生回流离子,并采用基于光学渡越辐射的电子束剖面测量系统记录时间分辨的束斑,首次证实了神龙一号加速器靶区存在回流离子。通过采用不同材料的靶膜,实验观测到了不同离子发射情况下回流离子对强流相对论电子束传输的影响,结果发现采用金属靶膜时,回流离子导致电子束部分汇聚、部分发散,而采用聚合物薄膜时,回流离子会导致电子束剖面出现剧烈的变化。  相似文献   

15.
In this paper We study the properties of electron motion when a nonneutral electron beam goes through a static magnetic field. The self-electronic and magnetic fields also affects on the test electron. The Hamiltonian equations of electron motion are deduced and the Poincare surface of section and the Lyapunov exponent are used to prove that the electron motion becomes chaotic when the fields are strong enough.  相似文献   

16.
徐慧  盛政明  张杰 《物理学报》2007,56(2):968-976
通过数值求解符拉索夫方程和泊松方程,研究了相对论效应和温度效应对等离子体振荡破裂的影响. 不考虑相对论效应情况下,初始扰动幅度较小时,不会发生等离子体振荡破裂,系统具有时间周期性. 此时电子温度的增加,会使得等离子体振荡最大幅度减小. 考虑相对论效应时,即使初始的等离子体电子密度扰动幅度不大,随着时间演化,相对论效应也能导致等离子体振荡破裂,而且初始电子密度扰动越小,产生等离子体振荡破裂所需时间越长. 在初始电子密度扰动较大时,无论考虑和不考虑相对论效应都会出现波破裂,但两者的结果有很大不同. 此外温度效应会降低能发生等离子体波破裂的阈值;等离子体波的相速度越大,能产生的波破裂现象也越明显. 关键词: 等离子体振荡 相对论效应 振荡破裂  相似文献   

17.
18.
利用相对论平均自洽场理论,研究了电子相对论径向波函数的基本特征.电子相对论径向波函数大小分量的数量级通常相差悬殊且不"同步",核外电子的径向分布没有严格的零概率点;束缚电子相对论径向波函数大小分量的节点个数为n-l-1、波腹个数为n-l,而自由电子的节点和波腹数则趋于无穷大.电子相对论径向波函数反映了相对论效应的基本特征:相对论效应越强,小分量振幅相对越大,自由电子径向波函数振荡越剧烈.  相似文献   

19.
The influence of self-fields on the cyclotron maser instability in a hollow electron beam propagating parallel to a uniform axial magnetic field B 0 ê z in a dielectric loaded waveguide is investigated. The theoretical analysis is carried out within the framework of linearized Vlasov-Maxwell equations. It is assumed that the beam is thin with the radial thickness much smaller than the beam radius. A new dispersion relation for azimuthally symmetric electromagnetic perturbation is derived and analyzed numerically. The influence of self-fields on the cyclotron maser instability in a dielectric loaded waveguide for different dielectric medium is studied. It is found that unlike the hollow waveguide the growth rate is increased by increasing self-fields. The instability band width decreases due to the increasing self-fields. The maximum growth rate increases gradually as self-fields increase as regards a different dielectric medium.  相似文献   

20.
The question of the influence of the environment on the structure and thermodynamic state of a bimetallic cluster is examined, using Metropolis Monte Carlo methods. An embedded atom model is used to estimate metal energies. The environment is modeled at a generic level as a rigid matrix which atoms interact with the atoms of an embedded Au-Pd cuboctahedral cluster via a Lennard Jones (LJ) potential. The high sensitivity of the cluster properties on its environment is demonstrated by scaling the LJ potential. It is found that the strength of the interfacial interactions completely determines surface segregation. Full segregation with either Au or Pd at the surface favors the occurrence of stable alloy phases in the cluster core while the subsurface layer acts as a buffer accommodating both the induced surface segregation and the inner composition constrained by phase stability. Cluster surface disorder induced by an amorphous matrix limits interface segregation and phase stability in the cluster core, even when the interfacial interaction strength is weak. The contrast between the epitaxial and amorphous matrix cases over a wide range of interface energies suggests the importance in the thermodynamic properties of the cluster core of the interfacial atomic arrangement in the matrix.  相似文献   

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