共查询到18条相似文献,搜索用时 140 毫秒
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等离子体参数的变化对在其中传播的电磁波有重要影响,文章采用周期性边界条件的二维PIC粒子模拟程序对电磁波在等离子中的传播过程进行了数值模拟,给出了电磁波在不同密度等离子体中传播的色散关系,得到了电磁波在等离子体中的传播特性。其结果,将作为进一步实现电磁波与等离子体中空间电荷波产生波-波相互作用过程模拟的基础。 相似文献
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本文导出了无外磁场电子注在等离子体约束下其上传播的空间电荷波波动方程,详细讨论了该条件下的波特性,并对等离子 频率降低因子进行了分析。研究了离子体填充状况空间电荷波性质影响甚大,选择等离子体填充因子对空间电荷波性质进行适当的控制。 相似文献
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目前对涡旋电磁波的产生方法及应用已经有很多理论及实验上的研究,但对于其传播过程的研究还非常缺乏,尤其是在电离层等离子体中的传播过程的研究.本文建立了柱坐标系下的时域有限差分方法模型,推导了柱坐标系下的边界吸收方法,在此基础上计算了涡旋电磁波在真空及等离子体中的传播过程,同时模拟了等离子体密度在涡旋电磁波作用下的时空演化过程.模拟结果表明:通过阵列天线模型产生的涡旋电磁波在真空中传播时涡旋的形状不会改变;在等离子体介质中,涡旋波的传播依然遵循线性理论,当涡旋电磁波遇到截止频率的等离子体时也会有明显的反射,并产生驻波;同时,在等离子体中涡旋波依然可以保持涡旋形态;涡旋波对等离子体的线性作用使得等离子体也呈现出涡旋态,与实验中的观测相符.以上的模拟结果能为涡旋电磁波加热电离层的实验以及未来在短波通信方面的应用提供理论支持.本文建立的涡旋波在等离子体中的传播模型也为进一步研究涡旋波与等离子体的非线性相互作用打下了基础. 相似文献
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本文研究了相对论电子注中的空间电荷波,建立了相对论空间电荷波的一般理论。导出了空间电荷波方程,定义了相对论动电压,并探讨了它的物理含义;导出了相对论电子注的动功率流定律,求得了相对论空间电荷波的正规模式。 相似文献
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本文给出了采用球形收敛枪的功率行波管噪声系数的计算方法。在单速、一维假定下,推导了球形收敛电子注上的空间电荷波传播方程和噪声阻抗的变换过程。计算表明:改变收敛角、阴极曲率半径、阳极电压及漂移区长度等,可以使功率行波管获得较低的噪声系数。通过几个实际管子噪声系数的测量,对本文所得的结果进行了验证。 相似文献
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弹性声波与表面缺陷相互作用的数值模拟 总被引:1,自引:1,他引:0
为了分析材料表面缺陷对声表面波传播的影响,以弹性动力学理论为基础,采用有限元方法数值模拟了声表面波沿金属表面传播及其与表面缺陷的相互作用.通过数值模拟弹性声表面波与不同深度、不同宽度的表面缺陷相互作用过程,得到了声表面波经不同表面缺陷后的反射和透射表面波波形,并对波形进行快速傅里叶变换分析.结果表明,弹性声表面波与表面缺陷相互作用后,产生反射Rayleigh波和透射Rayleigh波:随着表面缺陷深度和宽度的增加,Rayleigh波反射率相应增加,而透射率相应减小. 相似文献
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《Electron Devices, IEEE Transactions on》1959,6(4):419-428
The Amplitron device is analyzed from a normal mode viewpoint based on predominance of the reentrant character of the stream; the analysis is therefore valid for devices with short electron recirculation times and moderate signal levels. The nature of the space charge deduced from the above hypothesis is that of a rotating set of identical spokes having equal angular spacing in the interaction space. The induction effects of this space charge configuration upon the delay line are calculated, accounting for the periodic nature and the short length of the delay line. It is found that both forward-and backward-traveling waves are appreciable and must be considered. The fields in the interaction space are resolved into Fourier component traveling waves. The amplitude of the synchronously interacting wave is related to 1) the input signal, 2) the forward-traveling wave resulting from space charge induction, and 3) the backward-traveling wave resulting from space charge induction. Use is made of the phase relation (adiabatic theory) between the space charge and the synchronously traveling wave to obtain a consistent solution determining the phase relation between the input wave and the space charge. The above relationship between the space charge and the input signal allows the calculation of complex (vector) gain of the Amplitron. It is thus shown that the Amplitron is a nonlinear, or saturated, amplifier. A limit to the gain is observed; the backward-traveling wave is essential in determining it. Phase-dependence on operating RF level, or RF phase pushing, is noted; this type of phase variation does not exceed 90°. Calculations as a function of frequency show the bandwidth to be expected. It is found that conditions may lead to oscillation; feedback mechanisms reside in the backward-traveling wave and in the stream reentrance. The degree of input mismatch of the operating tube is discussed. 相似文献
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S. Koshevaya V. GrimalskyJ. Escobedo-Alatorre M. Tecpoyotl-Torres 《Microelectronics Journal》2003,34(4):231-235
A superheterodyne amplification of sub-millimeter electromagnetic waves in GaAs due to the negative differential mobility is analyzed. The nonlinearity arises from the modulation of concentration, due to a space charge wave, and from the ponderomotive force, due to electromagnetic waves. The case of resonant interaction of two traveling counter propagating electromagnetic waves and the space charge wave in a thin n-GaAs film placed into a dielectric waveguide is considered. The case of 2D electron gas is also analyzed. The simulation of this nonlinear interaction shows a certain increment of the amplification. 相似文献
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Cooke S.J. Chia-Lie Chang Antonsen T.M. Jr. Chernin D.P. Levush B. 《Electron Devices, IEEE Transactions on》2005,52(5):764-773
We describe a new model for calculating the ac space charge in a linear-beam traveling wave tube (TWT) large-signal simulation code when the true three-dimensional (3-D) geometry of the interaction circuit is taken into account. We use the 3-D electromagnetic simulation code CTLSS to characterize the ac space charge fields generated by a set of test currents placed inside the periodic interaction structure. This information, expressed in matrix form, is used by the large-signal simulation codes CHRISTINE-1D and CHRISTINE-3D to compute self-consistently the additional space charge field terms due to the structure in response to the beam evolution during the simulation. We present the formulation, and describe the implementation in both CTLSS and the large-signal codes. We validate the model by comparison with the analytical sheath helix model, and evaluate the importance of including this correction for modeling a number of helix and coupled-cavity TWT devices. 相似文献
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主要研究了飞秒等离子间相互的非线性作用对超高频电磁波——太赫兹波产生的影响。国内外许多研究机构已经证实,在太赫兹波产生的过程中,等离子体间的相互非线性作用会对太赫兹波产生影响。笔者结合理论分析设计并搭建一种了双束等离子体重合产生太赫兹波的测试系统,研究发现等离子体间相互非线性作用时,会产生三阶非线性光学效应,等离子体的折射率和相位发生变化形成非均匀场导致了太赫兹波辐射能量的降低,并在实验测量研究中发现随着等离子体波长双束等离子波长的增加,等离子体密度增加,导致太赫兹波的辐射能量的降低现象更加明显,另外,等离子体功率越大,太赫兹波吸收越大。同时,研究发现等离子体周围惰性气体分子质量影响太赫兹降低程度,气体分子质量决定着飞秒激光聚焦空气电离出的等离子体所形成的电场强度,分子质量越高,所形成的电场强度越强,双束等离子体重合时对太赫兹波降低的辐值越大。这些为研究等离子体间非线性作用对太赫兹波的影响提供了更加全面的理论支撑,有助于推动太赫兹波技术在军事及民用领域的快速发展。 相似文献
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本文在考虑等离子体厚度效应的情况上,详尽地推导了充填圆环状等离子体的圓柱波导中TM模慢电磁波的色散方程;利用相对论空间电荷波理论,导出了相对论电子注在轴向磁场引导下沿等离子体内表面传输时的空间电荷波方程;求得了电子注和慢空间电荷波相互作用的线性增益和频率漂移;讨论了等离子体厚度、密度对色散特性和互作用增益的影响。 相似文献
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Doping profiles in bipolar devices are numerically calculated taking into account the actual space charge produced during the diffusion process, which is described by standard models based upon effective diffusivities. The influence of this charge on the diffusion of dopants was examined for arsenic/boron double diffusion in order to evaluate the errors on profiles obtained using the well-known approximation of space-charge neutrality. Numerical results show that this approximation satisfactorily predicts practical doping profiles except for short-time low-temperature diffusion 相似文献
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本文的工作是利用在光折变晶体Ce:KNSBN中,其光生载流子的迁移机制在空间电荷场形成过程中是以扩散为主的特性,使得能量从变形的泵浦光转移到信号光上去,而无相位转移,从而实现泵浦光的整形。 相似文献