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低密度等离子体融断开关的粒子模拟研究 总被引:4,自引:4,他引:0
采用2.5维柱坐标粒子模拟程序研究了低密度等离子体融断开关(PEOS)工作过程中的物理现象,介绍了计算模型的建立和复杂边界的算法处理。模拟结果表明,在PEOS导通电流的过程中,电流通道最初在等离子体的发生器端形成,并且随着导通时间的增大而向负载端漂移。离子的空间分布并没有明显的变化,当PEOS发生断路时,等离子体离子的密度会迅速降低,并最终导致PEOS阴极附近的等离子体的密度已接近为零,此时,阴极电子完全受磁场箍缩作用而不能到达阳极,PEOS完全断开。 相似文献
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利用空心阴极放电产生了尺寸为60 cm× 60 cm× 2 cm的大面积等离子体面. 在实验室条件下对大面积等离子体片的密度分布进行了测量. 由于高压放电脉冲脉宽较短, 实验中改变了测量方法, 同时, 在中等磁场影响下, 为了得到真实的等离子体密度, 进行了必要的数值修正.在放电电流为1---6 A时, 测量了二维的电子密度分布. 另外, 测量并讨论了其他环境参数对等离子体密度的影响. 电子密度的分布情况对与微波波束切换相当重要. 由空心阴极增强型放电产生的大面积等离子体面具有反射X波段(8---12 GHz) 微波需要的足够稠密的电子密度和足够均匀的密度分布, 这是等离子体面在雷达系统中取代金属面板的有利条件. 相似文献
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Radiation loss in a compound plasma system with high and low temperature regions 总被引:1,自引:0,他引:1
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A code has been developed for calculating the non-coronal radiation of impurity in a compound plasma system which consists of high and low temperature regions. The radiation loss of impurity carbon in this system is calculated and analysed. The cooling rate in this system is smaller than that in a homogeneous plasma system due to the particle exchange between the two regions of the system. The volumetric radiation is much bigger in the low temperature region than in the high temperature region because of the relatively low temperature and high electron density, despite the much smaller volume. 相似文献
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Energy loss of a fast-electron beam due to the excitation of collective oscillation in hot plasma
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Energy loss due to a fast-electron beam interacting with the hot plasma at a high density is analysed theoretically. By splitting the particle density fluctuations into the individual part due to the random thermal motion of the individual electrons and the collective part due to plasma-wave excitation, we are concerned with the collective interaction of the relativistic plasma electrons resulting from the Coulomb interactions. Consequently, we derive the frequency of the hot plasma and the "Debye length" with the modification of the relativistic effect. And finally we calculate the energy loss of a fast-electron beam due to the excitation of collective oscillation in the hot plasma. 相似文献
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利用自行研制的2-1/2维全电磁柱坐标粒子模拟程序对等离子体融断开关磁场渗透机制进行了模拟研究。模拟结果表明在磁场Hall渗透机制特征长度远远小于等离子体离子的无碰撞趋肤深度的条件下,等离子体内部磁场渗透过程主要由电子流体运动的Hall项来控制。对于等离子体空间分布存在较大的密度梯度的物理问题,必须考虑二维空间特性对磁场渗透速度的影响。在磁场已渗透经过的等离子体区域中,等离子体呈现非电中性,离子受静电场的作用会加速运动到达阴极,最终形成真空鞘层。 相似文献
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基于单粒子理论模型及积分算法,编写了单粒子轨道数值模拟程序———ALFA,分析了柱形和球形两种边界位形磁化等离子体靶中非热α粒子通过库仑碰撞对D-T等离子体加热的能量沉积率。在均匀背景磁场及相同的D-T等离子体密度、温度条件下,柱形边界中非热α粒子能量沉积率比球形边界更高。在相同等离子体温度及密度条件下,α粒子的能量沉积率随磁场的增大而增大,但计算结果表明,磁场的有效作用区域存在明显的上下限值,当等离子体内磁场小于下限阈值时,磁场增加对α粒子能量沉积率的提高贡献不大,而且当等离子体内磁场超过上限阈值后,磁场再增加对提高α粒子能量沉积率的作用也不明显。对不同几何尺寸的磁化等离子体靶,磁场有效作用区域的上下限值不同,靶尺寸越大,相应的上下限阈值越小。提高等离子体密度,可增加α粒子能量沉积率,也能降低磁场有效作用区域的上下限阈值。 相似文献
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Plasma is a significant medium in high-energy density physics since it can hardly be damaged. For some applications such as plasma based backward Raman amplification(BRA), uniform high-density and large-scale plasma channels are required. In the previous experiment, the plasma transverse diameter and density are 50–200 μm and 1–2 × 10~(19)cm~(-3),here we enhance them to 0.8 mm and 8 × 10~(19)cm~(-3), respectively. Moreover, the gradient plasma is investigated in our experiment. A proper plasma gradient can be obtained with suitable pulse energy and delay. The experimental results are useful for plasma physics and nonlinear optics. 相似文献
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Particle simulation on electron acceleration process by the laser ponderomotive force in inhomogeneous underdense plasma layers
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The mechanism of electron ponderomotive acceleration due to increasing group velocity of laser pulse in inhomogeneous underdense plasma layers is studied by two-dimensional relativistic parallel particle-in-cell code. The electrons within the laser pulse move with it and can be strongly accelerated ponderomotively when the duration of laser pulse is much shorter than the duration of optimum condition for acceleration in the wake. The extra energy gain can be attributed to the change of laser group velocity. More high energy electrons are generated in the plasma layer with descending density profile than that with ascending density profile. The process and character of electron acceleration in three kinds of underdense plasma layers are presented and compared. 相似文献
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研究高功率微波作用下等离子体中的雪崩效应,对于研究等离子体防护技术具有重要意义.通过采用等离子体流体近似方法,建立等离子体中的波动方程、电子漂移-扩散方程和重物质传递方程,表征电磁波在等离子体中的传播以及等离子体内部带电粒子的变化情况,分析研究了高功率微波作用下雪崩效应的产生过程和变化规律.研究表明,入射电磁波功率决定了雪崩效应的产生;初始电子密度能够影响雪崩效应产生的时间;入射电磁波的激励作用初始表现为集聚效应,当激励能量积累到一定阈值时,雪崩效应才会产生;在雪崩效应产生过程中,等离子体内部电子密度的变化非常迅速并且比较复杂.雪崩效应产生后,等离子体内截止频率会远超过入射波频率,电磁波不能在等离子体中传播,从而起到防护高功率微波的效果. 相似文献
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邓佳川 赵永涛 程锐 周贤明 彭海波 王瑜玉 雷瑜 刘世东 孙渊博 任洁茹 肖家浩 麻礼东 肖国青 R. Gavrilin S. Savin A. Golubev D. H. H. Hoffmann 《物理学报》2015,64(14):145202-145202
实验测量了100 keV的质子束穿过部分电离氢等离子体靶后的能量损失. 等离子体靶由气体放电方式产生, 其自由电子密度在1016 cm-3量级, 电子温度约1–2 eV, 维持时间在微秒量级. 研究结果表明: 质子束在等离子体靶中的能量损失与自由电子密度密切相关且明显大于在同密度条件下中性气体靶中的能量损失; 在自由电子密度达到峰值处, 通过实验结果计算得到此时的自由电子库仑对数约为10.8, 与理论计算结果符合较好, 该值比Bethe公式给出的中性气体靶中束缚电子库仑对数高4.3倍,相应的能损增强因子为2.9. 相似文献
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Lin Chen Jing Ren Fan Guo LiangJi Zhou Ye Li An He Wei Jiang 《中国科学:物理学 力学 天文学(英文版)》2014,57(3):442-446
To understand the formation process of vacuum gap in coaxial microsecond conduction time plasma opening switch (POS), we have made measurements of the line-integrated plasma density during switch operation using a time-resolved sensitive He-Ne interferometer. The conduction current and conduction time in experiments are about 120 kA and 1 μs, respectively. As a result, more than 85% of conduction current has been transferred to an inductive load with rise time of 130 ns. The radial dependence of the density is measured by changing the radial location of the line-of-sight for shots with the same nominal POS parameters. During the conduction phase, the line-integrated plasma density in POS increases at all radial locations over the gun-only case by further ionization of material injected from the guns. The current conduction is observed to cause a radial redistribution of the switch plasma. A vacuum gap forms rapidly in the plasma at 5.5 mm from the center conductor, which is consistent with the location where magnetic pressure is the largest, allowing current to be transferred from the POS to the load. 相似文献
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A code named LARWM with non-ideal magnetohydrodynamic equations in cylindrical model is used to describe the instability in Tokamak plasma surrounded by a conducting wall with finite resistivity. We mainly take three factors related to the shear equilibrium plasma flow into consideration to study the stabilizing effect of the shear flow on the resistive wall modes (RWMs). The three factors are the velocity amplitude of flow, the shear rate of flow on plasma surface, and the inertial energy of equilibrium plasma flow. In addition, a local shear plasma flow is also calculated by the LARWM code. Consequently, it is found that the inertial energy of the shear equilibrium plasma flow has an important role in the stabilization of the RWMs. 相似文献
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A simpler analytical approach is employed to obtain energy integral equation for a pseudo‐particle in a pseudo‐potential, which admits double layer (DL) solutions for the non‐linear low‐frequency electrostatic perturbations in non‐uniform plasma consisting of electrons and two kinds of ions. One of the ion species has field‐aligned shear flow and electrons are superthermal kappa distributed. This theoretical model is applied to the upper ionospheric oxygen‐dominated plasma that has small concentration of protons along with upward flow of oxygen ions. Under suitable boundary conditions, both rarefactive (density dip) and compressive (density hump) DLs are obtained solving energy integral equation using the plasma parameters of ionosphere around altitude of 800 km. The amplitude and width of the DLs depend upon the scale lengths of density and temperature gradients as well as on the ratio of equilibrium densities of oxygen and hydrogen. 相似文献