电子注对谐振腔中TM模式谐振频率和电磁场分布的影响

将电子注视为等离子体柱,从填充等离子体柱的谐振腔的物理模型出发,推导了圆柱腔填充中心电子注时TM0m0模式的特征方程,并重点分析了填充电子注的圆柱腔中TM010模式和TM020模式的谐振频率和电磁场分布随等离子频率的变化情况。研究结果表明,随着电子注的等离子体频率不断增大,谐振频率也不断增大,谐振腔内电场和磁场的分布也随之发生改变。当电子注的等离子体频率超过谐振腔的谐振频率时,谐振腔内的电磁场分布将发生很大的变化,出现了电子注内外电场方向相反和趋肤效应等现象。     

Gas exposure tests of high field niobium X-band cavities

After exposing two high field TE₀₁₁ niobium X-band cavities to different gases including carbon dioxide, and one TM₀₁₀ cavity to air, no degradation was observed. The cavities were not protected with an anodic oxide layer.     

等效电路计算同轴输出腔TM310模式的间隙阻抗

设计了外Q值较小,工作于高阶横磁TM310模的X波段速调管单间隙同轴输出谐振腔。用微波等效电路理论计算了高阶横磁TM310模情形六个漂移管的等效间隙中心位置,由此计算腔内等效间隙中心到输出波导内横向膜片的等效长度。以MATLAB编程计算得到同轴谐振腔TM310模式加载矩形波导滤波器输出回路的间隙阻抗,其结果与传统冷测模拟法计算结果吻合。验证了等效长度计算方法的正确性,用于圆柱腔基模的传统微波等效电路理论能用于分析同轴谐振腔高阶横磁模式输出回路,且比传统的冷测模拟法及场分析法更为快捷。     

Computer Simulation of a 5.7GHz, 110kW Transit-Time Oscillator

A high-power transit-time oscillator producing 110kW at 5.7GHz in the TM₀₁₀ cavity mode is described. The device comprises a temperature-limited diode electron gun operating at 40A in the range from 28kV to 35kV and an intermediate coaxial cavity from which the microwave power is extracted through a TEM coaxial guide. The diode serves also as a resonant cavity, where electromagnetic oscillations are grown from noise. The effect of the applied voltage on both the output microwave power and the instability saturation time has been investigated leading to an optimal diode voltage of 33kV.     

有效抑制光子晶体加载矩形谐振腔中模式竞争的方法

研究了光子晶体加载矩形谐振腔,针对传统光子晶体加载无法完全抑制模式竞争的问题,提出了特性阻抗和介质加载方法进行改进,完全实现了谐振腔的高次模式的单模工作,为抑制高次模式工作的谐振腔中模式竞争的问题提供了一种新方法.在此基础之上,采用解析方法以及高频仿真软件HFSS,设计了一个采用TM₅₃₀高次模式工作的传统光子晶体加载的谐振腔,进一步采用了该新方法对其进行改进,并深入分析了采用这种方法抑制模式竞争的物理原因.计算结果表明,新方法能有效抑制模式竞争,实现谐振腔的高次工作模式的单模工作. 关键词： 光子晶体 谐振腔 模式竞争 特性阻抗     

The model oxidation catalyst α-V2O5: insights from contactless in situ microwave permittivity and conductivity measurements

The in situ microwave cavity perturbation technique was used to study the complex permittivity and conductivity of polycrystalline α-V₂O₅ in a tubular reactor under reactive high-temperature conditions with a TM₁₁₀ cavity resonating at 9.2 GHz. The sample was investigated at 400 °C in flowing air and air/n-butane mixtures while simultaneously measuring the total oxidation products CO and CO₂ by gas chromatography. The V₂O₅ powder was identified as an n-type semiconductor and the dynamic microwave conductivity correlated well with the near-infrared (NIR) absorption assigned to V3d¹ band gap states. Correlations between catalytic performance, real and imaginary parts of the permittivity, and NIR absorption allowed the differentiation between bulk and surface contributions to the charge transport in reactive atmospheres. The stability of the crystalline bulk phase was proven by in situ powder X-ray diffractometry for all applied testing conditions.     

Ein Verfahren zur Messung der komplexen Dielektrizitätszahl an kleinen Flüssigkeitsmengen im Frequenzbereich von 0,7–25 GHz mit Hohlraumresonatoren

A method is described for measuring the complex relative permittivity of liquids. Circular cylindrical TE₀₁₁-, TM₀₁₀- and coaxial-line-resonators are used. The liquid under test is contained in a narrow glass tube (volume<0.5 ml) which is placed concentrically along the axis of the cavity resonator. Besides the knowledge of the diameter of the glass tube and the dimensions of the resonator only frequency measurements are required. The accuracy of the method (error±5% of the absolute value for both, the real- and imaginary part of the permittivity) is comparable to other methods requiring a larger amount of liquid. Furthermore, permittivity variations can be measured very sensitively because these are indicated by shifts of the resonance frequency as well as changes of the quality constant, which can both be determined with an error smaller than 0.5%. Some experimental results for water and an aqueous phospholipid suspension are given to demonstrate the accuracy of the method.

     

Analysis for the new type long-pulsed and high efficient microwave amplifier—magnicon

This paper begins with the cylindrical cavity field expression of the rotating TM_n10 mode in magnicon, and obtains its dissipated power, cold quality formula and so on, which are different from those in the static state TM_n10. Furthermore starting from the dynamics equations, the passive deflect cavity electron velocity and position solution, as well as the interact instantaneous power solution between electron and wave have been solved. The cylindrical coordinate electron energy dynamics equation in the output cavity, and the modification of terminal parameter formula for relativity have also been discussed. This work is supported by the Sic. & Tech. Funds of CAEP.     

Effect of ionized plasma medium on the radiation from a RITMA structure on ferrite substrate

This paper presents theoretical investigations on the radiation properties of a right isosceles triangular microstrip antenna (RITMA) printed on a magnetized ferrite substrate Ni_0.62Co_0.02Fe_1.948O₄ in the presence of ionized plasma medium. The theoretical study on RITMA structure in free space is carried out in TM₁₁ mode of excitation by applying cavity model-based modal expansion technique while hydrodynamic theory is used for its analysis in plasma medium. By varying the bias magnetic field, far-field radiation patterns in free space and plasma medium are obtained which in turn are applied in computing radiated power, directivity, quality factor and bandwidth of antenna. It is found that the presence of plasma medium affects the performance of RITMA structure significantly Article presented at the International Conference on the Frontiers of Plasma Physics and Technology, 9–14 December 2002, Bangalore, India.     

The Dual Mode Microwave Afterglow Apparatus for Measuring the Electron Temperature Dependence of the Electron‐Ion Recombination

Three dual mode microwave apparatus (one using S ‐band and two using X ‐band) have been developed to determine ambipolar diffusion and electron‐ion recombination rates under conditions such that T_gas = 300K and T_e is varied from 300 K to 6300 K, in the afterglow period of the dc glow discharge. TheTM₀₁₀ cylindrical cavity (in S ‐band) and TM₀₁₁ open cylindrical cavity (X ‐band) are used to determine the electron density during the afterglow period and a non‐resonant waveguide mode is used to apply a constant microwave heating field to the electrons. To test the properties of the apparatus the neon afterglow plasma has been investigated. At T_e = 300 K a value of α (Ne⁺₂) = (1.7± 0.2) × 10^–7cm³/s is obtained which is in good agreement with values of other investigators. Also similar variations of α as T^–0.4_e (S ‐band) and as T^–0.42_e (X ‐band) obeyed over the range 300 ≤ Te ≤ 6300K are in good agreement with some other previous measurements. The simplicity of the X‐band microwave apparatus also allows the measurements of the gas temperature dependency and the study of electron attachment and may be used simultaneously with optical or mass spectrometry investigations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

矩形波导与圆柱波导或圆柱谐振腔间的小孔耦合

本文讨论了三种不同系统的小孔耦合的近似解法:矩形波导与圆柱波导的同轴耦合,矩形波导中的TE₁₀型波与圆柱谐振腔中的TM₁₂₀型波间的耦合和矩形波导中的TE₁₀型波与圆柱波导中的TM_mn型波间的耦合。通过这几个问题的解法,我们希望读者可以看到处理复杂微波元件问题时所需的从物理概念出发的灵活应用已有方法的必要性。这里提供的几个公式有着广泛的应用范围而是在现有文献中探讨得不够的。这里介绍的方法可以应用到其他新的微波网络问题中去。     

等离子体填充盘荷波导高频特性分析

从麦克斯韦方程和流体理论出发，推导了填充磁化等离子体慢波结构的基本方程.在大磁场情况下，对等离子体填充盘荷波导的色散特性和耦合阻抗作了研究，结果表明填充等离子体使色散曲线上移，耦合阻抗提高.等离子体填充产生出模式谱非常丰富的周期性低频等离子体模式(TG模式).当等离子体密度增加到一定程度后，场模TM₀₁模的频率范围和TG₀₁模的频率范围相近，两个模式互相耦合产生出新的混合模G₁,G₂.如果相对论行波管工作在混合模上，将会产生新的工作机理. 关键词： 盘荷波导 等离子体填充 色散特性 相对论行波管     

Numerical modelling of 8mm TM01-TE11 mode converter

A numerical study of TM₀₁-TE₁₁ circular waveguide mode converter, with its optimized size and structure, is presented in this paper. Many factors such as spurious modes, backward wave, perturbation functions of waveguide axis or radius, phase-rematching techniques and ohmic losses are taken into account for the influence to mode converter's efficiency and bandwidth. And the dimensions of an optimized model (f₀=35GHz. with input and output radius a₀=13.6mm) are given.     

A partially reflecting metal cladding: its effect on the modes of dielectric optical waveguides

If the metal cladding of a dielectric optical waveguide is sufficiently thin to be only partially reflecting, then the waveguide modes differ from those of the conventional metal-clad waveguide. The TE modes are little affected by a variation in the metal thickness but the TM modes change considerably due to a coupling between the waveguide modes and the surface plasma waves supported by both the metal: dielectric interfaces and the metal film. It is the refractive index of the dielectric cladding which is remote from the guiding core that determines whether the lowest order TM mode is the TM₀ or TM₁ mode. This dielectric cladding also strongly influences the attenuation of the TM modes and, if the guide supports a TM₀ mode, then the attenuation of the TM modes far from cut-off are an order of magnitude higher than that of the corresponding modes when the guide cannot support a TM₀ mode. If the guide can support a TM₀ mode then its dimensions can be chosen such that it will support the TE_N and TM_N modes with equal phase velocities. A lossless approximation is used to develop an expression which will specify the required guide dimensions directly and parametric plots of these dimensions are discussed.     

The cold quality Qcold for magnicon on resonator in the rotating TMn10 mode

Cold quality Q_cold is an important parameter in microwave electronic tube design. Magnicon works in a rotrating TM_n10 mode in the cylindracl cavity, its field distribution is different from the static state. But up to now researchers simply assume its cold quality to be two times of the static one, which usually results in big errors. Here in this paper, based on the rotating field distribution, and using the integrated Bessel function, we deduced the cavity’s storage and the rotating field dissipated power expressions, and obtained a modified cold quality formula for rotating TM_n10 mode in the magnicon, which shows a good agreement with the experimental data. This work supported sci. & Tech. Funds of CAEP. Associate professor.     

Study of Disk-Loaded Waveguide Filled with Plasma

Recently disk-loaded waveguide has been widely used in high-power traveling wave tubes (HPTWT). It has been shown in many experiments that the interaction efficiency and output power can be increased greatly by injecting plasma into the vacuum microwave device. Using field analysis, the dispersion characteristics and the interaction impedance of the disk-loaded waveguide filled with plasma are analyzed in a strong longitudinal magnetic field. In conclusion, the frequency of the TM₀₁ mode increases as the density of the plasma increases. It also can be found when the plasma density increases to a large scale, the TM₀₁ mode of the disk-loaded waveguide overlaps the TG mode, these two modes couple each other and form the new hybrid modes.     

The cold quality Qcold for magnicon on resonator in the rotating TMn10 mode

Cold quality Q_cold is an important parameter in microwave electronic tube design. Magnicon works in a rotrating TM_n10 mode in the cylindracl cavity, its field distribution is different from the static state. But up to now researchers simply assume its cold quality to be two times of the static one, which usually results in big errors. Here in this paper, based on the rotating field distribution, and using the integrated Bessel function, we deduced the cavity’s storage and the rotating field dissipated power expressions, and obtained a modified cold quality formula for rotating TM_n10 mode in the magnicon, which shows a good agreement with the experimental data. This work supported sci. & Tech. Funds of CAEP.     

Electron Temperature Dependence of the Dissociative Recombination Coefficient of Molecular Argon Ions Ar+2 with Electrons

A dual mode (TM₀₁₀ cylindrical cavity/cylindrical waveguide) microwave apparatus is used to study the ion mobility and dissociative recombination of molecular argon ions with electrons in the afterglow period of a d.c. glow discharge as a function of electron temperature when electrons were heated by microwaves up to T_e ≤ 10300K, with T₊ = T_gas = 300K. The electron temperature dependence of the total rate coefficient of dissociative recombination may be represented by α (Ar⁺₂) = (8.1 ± 0.5) × 10^–7[300/T_e(inK)]^0.64cm³s^–1 which is in very good agreement with most previous experimental results but not with the recent theoretical calculations (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Collisional Effects on the TM Modes in Parallel Plane Wave Guide Filled with Plasma

The reflection coefficient (C_R) and the transmission coefficient (C_T) of the TM modes in a half space (z < 0) parallel plane wave guide filled with homogeneous, collisional and moving plasma are derived and discussed. It is observed that C_R and C_T are modified depending upon the collision frequency of the electrons as well as that of the ions. There is a remarkable change in C_R due to ion-neutral collisions when the plasma moves against the direction of the TM modes.     

Effects of a lossy thin plasma-film on metal-diffused LiNbO3 optical waveguides

I intend to investigate the effects of different kinds of partially reflecting metal film (plasma layer) on the wave characteristics of a stratified titanium-diffused LiNbO₃ optical waveguide. The mode number, the equivalent indices, the extinction coefficients, the field distributions and the powers carried in each layer are given as a function of the free-space wavelength, of the diffusion parameters, and of the opticc-axis orientation. Of course, the power of TM-like hybrid waves flows in opposite directions in the plasma and the other regions.For ac-axis varying in the transverse plane, the ith-order hybrid mode is rather complicated in the guide with an aluminum layer. There, in fact, the field mapping can be seen as an overlap of a TE _i with a TM _i+1, mode because of a sudden transformation of the TM₀ mode into a superficial plasma wave (SPW). On the contrary, with a silver layer, the hybrid field is a simple combination of a TE _i with a TM _i mode with no SPW growing.The guide losses assume the lowest values (1 dB/cm) for an Ag layer which is the prime candidate for making electro-optical or acoustic-optical devices. On the other hand, the nickel film causes the highest losses (66 dB/cm).