小功率微波微等离子体源的集成研究

提出了一种小功率集成微波微等离子体源的结构,通过平面微带渐变螺旋电感耦合线圈激励微波微等离子体。研究表明,该集成微波微等离子体源具有频率可调、功率可调的特点,频率范围为2. 3 ~ 2. 6GHz,输出功率范围为20 ~40dBm。在频率为2477MHz、空气真空度为3. 7 Torr,输入功率为2. 15W 时,平面微带渐变螺旋电感耦合线圈能较好激励起微波微等离子体,这为微波微等离子体源的小型化研究提供了基础。     

平面螺旋电感耦合微波等离子体源的建模分析

介绍了一种小型化的2.45GHz小功率平面螺旋电感耦合微波等离子体源的建模方法.根据等效电路,推导出平面螺旋电感线圈的品质因数,并进行数值分析.研究表明:无载品质因数随结构、尺寸和频率等的变化而变化,并在谐振频率附近达到最大值.这为小功率电感耦合微波等离子体源的优化设计提供了理论依据.     

等离子体辅助镀膜

本文介绍了等离子体辅助镀膜技术以及相应的高真空等离子体源.这种新型等离子体源属于空心冷阴极结构,工作气压在1×10-3pa～10-1pa,它的最大优点在于能够直接电离氧化性气体而不烧毁阴极.采用探针法测定了氩等离子体中辅助离子的能量范围在50～80Ve之间,并在氩气、氧气的等离子体中分别沉积了单层ZnS薄膜和SiO2薄膜.实验结果表明,生成的薄膜具有良好的光学和机械性能.     

THz时域光谱诊断激光等离子体密度和碰撞频率

从电子在THz波电场中的运动方程出发,讨论了THz波在等离子体中的传播规律.从而可以得到由等离子体电子密度和碰撞频率决定的THz波的复折射率.该复折射率决定了THz波在等离子体中的传播,即THz脉冲相位和振幅变化.THz时域光谱系统可以测量THz波传播的相位和振幅,因此可以利用THz时域光谱来诊断等离子体密度和碰撞频率.由于受到等离子体色散关系的限制,该方法测量的等离子体密度有一定范围.在等离子体电子密度位于10~(12)~10~(16)/cm~3之间内,该方法可以得到较好的应用.     

小功率平面螺旋电感耦合微波等离子体源的研究

 本文提出一种基于平面螺旋微带的2.45GHz小功率电感耦合微波等离子体源,根据等效变压器耦合模型分析等离子体源的谐振特性,通过微波等离子体吸收功率与等离子体阻抗之间的关系,研究不同气压条件下的放电规律.研究表明,在低气压条件下,输入功率不超过220mW时,空气开始放电;而在常压条件下,输入功率不超过1.5W时,氩气开始放电;随着微波等离子体的激励,小功率微波等离子体源的谐振频率和S参数都发生变化.这为电感耦合微波等离子体源的小型化研究提供了理论基础.     

张衡一号卫星观测的地基VLF波电离层加热扰动特征

电离层扰动主要由太阳活动和地球表面活动引起,通过对已知地基甚低频（very low frequency, VLF）波发射源引发的等离子体扰动进行特征研究,对于认识电离层环境变化具有重要的参考意义. 文中主要介绍了张衡一号01卫星原位探测科学载荷等离子体分析仪（plasma analyzer package, PAP）观测系统和数据产出,对该载荷在507 km轨道原位观测的、由地基NWC站大功率VLF人工源辐射引起的电离层加热扰动现象及特征进行了总结和分析. 观测结果表明:氧离子密度、离子温度、离子漂移速度等多个原位观测量在夜侧轨道均同时记录到NWC站上空北侧约50～500 km区域出现的电离层加热扰动现象,扰动持续范围约为300～400 km;通过对相同轨道电场数据进行功率谱计算可知,该区域电场增强主要频率与NWC站发射频率相同. 上述观测结果验证了张衡一号01卫星PAP对电离层离子参量扰动现象具有一定的探测分辨能力,地基大功率VLF电波能够对电离层等离子体环境产生明显的扰动影响,且扰动区域相对于发射源位置向磁赤道方向发生偏移.     

波导型表面等离子体共振传感器传感特性计算

介绍了集成波导型表面等离子体共振传感器工作原理和基本结构,用传统波导模式的分析法结合表面等离子体波的色散方程,计算集成波导型表面等离子体共振传感器理论模型的共振波长。通过基于菲涅耳方程的解析分析,得到了含有表面等离子体共振吸收峰的透射谱。通过比较不同折射率被测物的透射谱,粗略确定了集成波导型表面等离子体传感器的检测范围。     

激波管等离子体中太赫兹波传输特性仿真与实验研究

研究了太赫兹波在透射波窗口封闭的激波管中的等离子体中的传输特性,获得了传输衰减量随等离子体电子密度、碰撞频率、透波窗口材料以及电磁波频率的变化规律,并比较了相同条件下毫米波的传输特性.利用激波管为实验平台模拟产生高速飞行器等离子体,开展了太赫兹波在等离子体中传输特性实验.结果表明,太赫兹波在相同电子密度和碰撞频率的等离子体中衰减量比毫米波小得多;随着等离子体碰撞频率的增加,太赫兹波传输衰减量先增加后减小,透波窗口增加了太赫兹波的传输衰减;随着窗口材料的介电常数增加,太赫兹波反射率增加,太赫兹波传输衰减曲线出现周期性振荡,振荡周期约5 GHz;太赫兹波通信可能作为一种解决再入飞行器黑障问题的有效技术途径.     

电感耦合等离子体源的研究进展

在简要回顾传统高密度等离子体源的基础上,重点介绍了新一代的低温高密度等离子体--电感耦合等离子体源(ICP)的放电机理,并结合最近的研究进展,系统分析了ICP的性能影响因素,总结了ICP目前存在的问题,展望了其应用前景.     

基于半导体等离子体频率光学调控的太赫兹波调制系统

介绍了一种太赫兹波光学调制系统,该系统首先通过刀片与半导体之间的狭缝实现太赫兹波和太赫兹表面等离子体波之间的耦合,然后通过改变照射到本征半导体表面的光强用以调控半导体表面的等离子体频率,使得半导体表面的等离子体频率在有光照和无光照条件下分别大于和小于其上传输的太赫兹表面等离子体波的频率,从而实现对在半导体表面传输的太赫兹表面等离子体波以及由其耦合出的太赫兹波的强度调控。该调制方法与传统方法相比具有调控频带宽、速度快、成本低、常温工作等优点,可用于太赫兹波通讯。仿真和实验结果进一步验证了该调制系统应用的可行性。     

Helicon Plasma Source

A spiral-antenna helicon plasma source is characterized experimentally at applied magnetic flux densities below 60 G and applied RF powers below 800 W. It is shown that, for a given RF power, a magnetostatic field applied to an inductively coupled plasma increases the electron concentration fourfold.     

Plasma Parameters in the Reactor with Simultaneous Magnetron Discharge and Inductive Radio-Frequency Discharge in the Presence of External Magnetic Field

A plasma reactor that contains vacuum–arc and magnetron sputtering sources and radio-frequency discharge that generates high-density plasma in the presence of external magnetic field is developed, constructed, and optimized. The reactor can be used for deposition of various functional coatings with ion stimulation. The parameters of the inductive radio-frequency discharge generated in the presence of external magnetic field that serves as a source of assisting ions are optimized. It is shown that the working interval of the induction of external magnetic field corresponds to the resonant excitation of the coupled helicon and Trivelpiece–Gold waves. The effect of magnitude and configuration of magnetic field on the parameters of gas-discharge plasma and ion current in the substrate region is studied in the presence of separately and simultaneously initiated magnetron and inductive discharges. The effect of ion flux that is incident on the films in the course of growth on the structure of functional coatings is analyzed.     

Influence of external conditions on physical processes and plasma parameters in a model of a high-frequency hybrid plasma system

The results of the experimental investigation into parameters of the helicon discharge plasma in a model of high-frequency hybrid plasma system equipped with a solenoidal antenna are presented. It is shown that an increase in the external magnetic field causes the formation of the plasma column and the displacement of the ion current over the discharge axis towards the lower model flange. The variation in the magnetic field configuration makes it possible to control the shape of the plasma column.     

表面波放电狭缝天线辐射电磁场的三维数值分析

针对平板型表面波放电等离子体源,建立了表面波放电狭缝天线辐射电磁波模型,对狭缝天线辐射电磁场分布进行了三维数值计算,并与表面波电磁场进行对比分析,讨论了平板型表面波放电机理。结果表明:整个狭缝天线阵激发的电磁场是每个狭缝天线激发电磁场的线性叠加;狭缝天线阵直接激发的电磁场强度在临近波导壁面处很大,并且随着空间距离的增大迅速衰减;狭缝天线阵直接激发和表面波的电场均远大于各自的磁场,分析电、磁场对带电粒子的力作用时可以忽略磁场力的作用;表面波电磁场远大于狭缝天线阵直接辐射的电磁场,强电磁场范围也远大于狭缝天线阵直接激发的强电磁场范围,等离子体有增强电磁场强度、扩大强电磁场范围的作用。     

A Helicon Plasma Source

The parameters of a helicon plasma source was studied for an rf power to 500 W and a magnetic field ranging from 0 to 200 G under an argon pressure of 3 mtorr. The electron density in the plasma was found to reach 10¹² cm^–3. Axial and radial electron distributions were studied. Helicon waves were excited by antennas of three types, a loop antenna being the most efficient. It is shown that the electron density in the plasma can significantly be increased if the system is under a nonuniform magnetic field such that its lower-value (relative to the rest of the system) part is applied to the antenna.     

Radiation from an electromagnetic source in a half-space of compressible plasma-surface waves

The radiation characteristics of a line source of magnetic current are studied for the case in which the source is situated in a half-space of isotropic, compressible plasma which is bounded on one side by a perfectly conducting, rigid plane screen. In addition to the electromagnetic and plasma space waves, the line source excites a boundary wave. This boundary wave is a coupled wave. It has associated with it both a magnetic field component and the pressure term. This is in contrast to the space waves which can be decomposed into an electromagnetic (EM) mode with no pressure term and a plasma (P) mode with no magnetic field associated with it. The characteristics of this boundary wave are evaluated. The boundary wave propagates for all frequencies and the power carried by the boundary wave becomes smaller as the frequency is increased.     

Plasma Induced Wiggler Magnetic Field in a Cavity

The transformation of an elliptically polarized standing wave in a cavity by a suddenly and uniformly created plasma is discussed. Theoretical expressions for the plasma induced wiggler magnetic field as well as the frequency-upshifted standing wave are derived. By choosing appropriate values of the source wave parameters and plasma parameters, one can get wiggler magnetic field of desired magnitude, direction and wiggler wavelength. A few representative results are discussed.     

Frequency Transformer: Appropriate and Different Models for a Building-up and Collapsing Magnetoplasma Medium

The interaction of an electromagnetic wave with a time varying medium is governed by the property of conservation of the wavenumber. This property can be utilized to construct a frequency transformer. The time variation in the relative permittivity of the medium is easily produced in a magnetoplasma medium by altering the ionization level. The change of the ionization level can be produced by the dynamic control of the source of ionization. The switching-on action of the source produces a build-up plasma, whereas a switching-off action produces a decaying plasma. Simple mathematical models, however, for the two cases are different. In the case of building-up plasma, the model has to ensure the continuity of the current density and in the case of decaying plasma, the average drift velocity of the surviving electrons has to be continuous. Using these two appropriate models, the effect of the time variation of the plasma frequency as well as the background magnetic field of the magnetoplasma medium are studied. Switching off the external magnetic field for the wave in the magnetoplasma medium converts a whistler wave to a wiggler magnetic field. Similar results are obtained with an intensification of the source wave as well as frequency upshift of the whistler wave for the collapsing plasma medium. By controlling the static magnetic field parameters and the level of ionization, the frequency shift ratio can be changed and the frequency transformer becomes tunable. The principle of frequency up-shifting using plasma permits the generation of signals from easily obtainable frequency bands and upshifts them into frequency bands not easily obtainable by other methods.     

Radiation from a uniaxially anisotropic plasma half space

A line source of magnetic currents is located in a half space with uniaxially anisotropic dielectric constant, with the optic axis inclined at an arbitrary angle to the interface. This two-dimensional, scalar diffraction problem is solved by Fourier integral techniques, and the solution is examined in the asymptotic range of large distance from the source. The radiation field comprises incident, reflected and refracted ray contributions whose properties are determined from a study of the refractive index curves for the medium. In addition, there may exist a lateral wave which is excited by a critically refracted incident ray, and which sheds energy back into the anisotropic medium by refraction. If the medium is a plasma with an externally impressed infinite dc magnetic field, and if the source oscillates below the plasma frequency, there exist shadow regions from which the direct and reflected rays are excluded but which can be penetrated by the lateral waves.     

Normal mode formulation of spin wave—Helicon wave interactions in ferromagnetic semiconductors

The linear interactions between spin waves and (drifted) helicon waves in p-type ferromagnetic semiconductors are analyzed in terms of the spatial normal modes of the uncoupled system. The coupled mode equations are investigated in the region of phase synchronism between the negative-energy-carrying helicon mode and the positive-energy-carrying spin wave mode. If these modes are weakly coupled, a convective instability is indicated when the carrier plasma frequency ωpis less than the spin precession frequency ωo.