Multipactor Breakdown Prediction in a Rectangular Waveguide: Statistical Theory and Simulation Results

Statistical theory of the initial study of the multipactor discharge in a rectangular waveguide is constructed. The recurrent relation between the emission phase and position distributions is derived taking into account the velocity spread of secondary electrons. A general integral equation allowing prediction of the threshold value of the secondary yield (above which electron multipaction occurs) is formulated. It has been found that the presence of directional anisotropy can significantly alter the multipacting discharge cutoff conditions in comparison with isotropic emission. It has been established that the combined action of tangential velocity components and magnetic field leads to an increase of the threshold of multipactor growth. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

高功率盒形窗内次级电子倍增效应

以S波段高功率盒型窗为对象,采用Monte Carlo模拟方法对盒型窗内的次级电子倍增效应进行研究,探索次级电子的倍增规律。模拟得到了盒型窗内TE11模和TM11模共同作用下,两种陶瓷窗片表面次级电子倍增活跃的区域随传输功率的变化特点。在低传输功率下,次级电子仅在未镀膜窗片表面被激励,并以双面倍增的方式在金属法兰与镀膜窗片相对应的区域增长;在较高的传输功率下,窗片表面的次级电子将以单面倍增的方式活跃在窗片表面与波导口相对的区域。传输功率的升高使得镀膜窗片表面的次级电子倍增活跃区域转移到矩形波导窄边对应的区域,并加剧了未镀膜窗片表面的局部倍增效应。     

金属壁与介质窗之间次级电子倍增效应的研究

高功率盒形窗内的TM11模法向电场对次级电子倍增现象具有较大的影响,特别是在介质窗片与金属波导壁相对的区域,易发生双面次级电子倍增.采用蒙特卡罗粒子模拟方法,研究了法向电场作用下氧化铝陶瓷窗片与铜波导壁之间的双面倍增敏感曲线、倍增阈值电压、粒子数量的演变过程以及粒子运动轨迹.通过对相关参数的分析,获得了金属壁与陶瓷窗片之间双面谐振倍增和非谐振倍增的规律以及双面倍增向单面倍增转变的特点.此研究可为分析窗片失效机理提供理论依据.     

高功率盒形窗内次级电子倍增效应

以S波段高功率盒型窗为对象,采用Monte Carlo模拟方法对盒型窗内的次级电子倍增效应进行研究,探索次级电子的倍增规律。模拟得到了盒型窗内TE11模和TM11模共同作用下,两种陶瓷窗片表面次级电子倍增活跃的区域随传输功率的变化特点。在低传输功率下,次级电子仅在未镀膜窗片表面被激励,并以双面倍增的方式在金属法兰与镀膜窗片相对应的区域增长;在较高的传输功率下,窗片表面的次级电子将以单面倍增的方式活跃在窗片表面与波导口相对的区域。传输功率的升高使得镀膜窗片表面的次级电子倍增活跃区域转移到矩形波导窄边对应的区域,并加剧了未镀膜窗片表面的局部倍增效应。     

Multipactor Discharge in Single-Gap Bunchers at 80 MHz

Physics of Atomic Nuclei - The results of calculating the threshold voltage levels causing multipactor discharge in single-gap buncher cavities at 80 MHz are presented in the article. Two types of...     

大功率铁磁性微波部件微放电演变机理与抑制

铁氧体环行器是承载航天器微波系统大功率的关键器件,其大功率微放电效应是影响航天器在轨安全、可靠运行的瓶颈问题。从影响微放电效应的关键因素——二次电子发射特性出发,提出铁磁性微波部件微放电效应物理演变模型,揭示了铁磁性微波部件内部初始自由电子与二次电子运动的空间规律;通过改变铁磁性微波部件表面二次电子发射特性,揭示了铁磁性微波部件抗微放电优化设计的物理原理。在S频段铁氧体环行器中验证了基于表面二次电子发射特性的微放电效应抑制,将器件的微放电阈值从380 W提高至3400 W以上,提升效率大于900%。     

Saturation of a One-Sided Multipactor in Crossed Fields

We analyze the saturation mechanism of a vacuum resonance microwave discharge (multipactor) for systems in which a magnetostatic field returns electrons to the metal surface with secondary-emission multiplying. The steady-state model suggested earlier is improved essentially. In particular, we take into account the near-surface interaction of saturated electron bunches during the limited time of discharge-electron-surface impact. It is found that the Coulomb defocusing of electron bunches prevails over their microwave focusing (toward the resonance phase of the field), making it possible to extract superfluous secondary electrons when the electron bunches are reproduced on the discharge surface. Basic characteristics of the discharge, such as its existence conditions and proper fields and phase disposition of the resonance electron bunches, are determined as functions of the magnetostatic field and the secondary-emission coefficient. The results are discussed in comparison with the data of known experiments. An explanation of some differences related to both the observation conditions and the used analytical model is given.     

微脉冲电子枪的初步实验研究

给出了微脉冲电子枪的模拟计算及其初步实验结果. 该电子枪采用铜铝镁合金作为冷阴极材料, 在以磁控管作为微波功率源的出束实验中得到了100mA/cm²的电流密度.实验结果与次级电子倍增解析计算和SEEG程序的模拟计算结果基本符合, 初步验证了微脉冲电子枪的基本原理, 为今后实验中得到更大的电流密度打下了基础.     

Statistical Mechanics Approach to Coding Theory

We propose a method based on cluster expansion to study the optimal code with a given distance between codewords. Using this approach we find the Gilbert–Varshamov lower bound for the rate of largest code.     

Statistical Models in Theory of Polarization Bremsstrahlung

Universal relations have been derived to describe the spectral-angular dependence of the polarization bremsstrahlung of a fast charged particle, based on a statistical model for the electron skeleton of the target. Three statistical atomic models are considered in terms of which the target characteristics that determine the cross section for polarization bremsstrahlung are calculated and analyzed.     

Quantum Statistical Theory of Polarization Mode Dispersion

Polarization mode dispersion is modelled as decoherence of polarization under the disturbance of environment and the coupling with frequency. This model is described by the quantum master equation and the Langevin equation. It can be predicted that the optical beam is depolarized exponentially in a fibre and the differential group delay （DGD） is proportional to the square root of the propagation distance. The distribution of the DGD can also be calculated.     

Statistical Theory of Bremsstrahlung in Plasma-Molecular Systems

Different approaches to the statistical theory of bremsstrahlung in nonequilibrium plasma-molecular systems are compared. The spectra of bremsstrahlung, as well as collision integrals and effective dissipation constants are calculated for such systems within the framework of both classical and quantum theory.     

Mathematical Theory of Non-Equilibrium Quantum Statistical Mechanics

We review and further develop a mathematical framework for non-equilibrium quantum statistical mechanics recently proposed in refs. 1–7. In the algebraic formalism of quantum statistical mechanics we introduce notions of non-equilibrium steady states, entropy production and heat fluxes, and study their properties. Our basic paradigm is a model of a small (finite) quantum system coupled to several independent thermal reservoirs. We exhibit examples of such systems which have strictly positive entropy production.     

Statistical Theory of the Many-Body Nuclear System

A recently proposed statistical theory of the mean fields associated with the ground and excited collective states of a generic many-body system is extended by increasing the dimensions of the P-space. In applying the new framework to nuclear matter, in addition to the mean field energies we obtain their fluctuations as well, together with those of the wavefunctions, in first order of the expansion in the complexity of the Q-space states. The physics described by the latter is assumed to be random. To extract numerical predictions from our scheme we develop a schematic version of the approach, which, while much simplified, yields results of significance on the size of the error affecting the mean fields, on the magnitude of the residual effective interaction, on the ground state spectroscopic factor, and on the mixing occurring between the vectors spanning the P-space.     

同轴传输线微放电的统计理论稳态建模及敏感区域计算

为准确有效地预测微波器件的微放电阈值,提出了一种可以同时考虑同轴结构微放电过程中单边与双边碰撞的统计理论稳态模型.考虑到同轴结构中场分布的非均匀性以及二次电子的出射随机性,采用微扰法近似推导电子轨迹表达式,并基于电子出射速度与渡越时间之间的隐式关联性,构建用于计算同轴结构内、外导体处电子渡越时间概率分布的联合概率密度函数.通过电子出射相位分布的稳态假设,推导用于描述同轴结构中微放电倍增过程的稳态积分方程组,并提出一种通用的联立迭代求解方法.采用稳态模型分别计算银、铜、铝与阿洛丁等工程常用镀膜材料的同轴传输线微放电敏感区域,并分析了同轴传输线径比对微放电阈值的影响.与欧空局的微放电实验结果对比表明,稳态模型能够准确有效地计算同轴传输线的微放电阈值,同时发现平行平板与同轴结构微放电的敏感曲线之间存在显著差异.研究提供了一种精确有效的同轴传输线微放电阈值分析方法,并为实际工程中"免微放电"微波器件的设计与优化提供参考与依据.     

A Framework for Non-Equilibrium Statistical Ensemble Theory

Since Gibbs synthesized a general equilibrium statistical ensemble theory, many theorists have attempted to generalized the Gibbsian theory to
non-equilibrium phenomena domain, however the status of the theory of non-equilibrium phenomena can not be said as firm as well established as the
Gibbsian ensemble theory. In this work, we present a framework for the non-equilibrium statistical ensemble formalism based on a subdynamic kinetic
equation (SKE) rooted from the Brussels-Austin school and followed by some up-to-date works. The constructed key is to use a similarity transformation between Gibbsian ensembles formalism based on Liouville equation and the subdynamic ensemble formalism based on the SKE. Using this formalism, we study the spin-Boson system, as cases of weak coupling or strongly coupling, and obtain the reduced density operators for the Canonical ensembles easily.     

Statistical Mechanical Theory of a Closed Oscillating Universe

Based on Newton’s laws reformulated in the Hamiltonian dynamics combined with statistical mechanics, we formulate a statistical mechanical theory supporting the hypothesis of a closed universe oscillating in phase-space. We find that the behavior of this universe as a whole can be represented by a free entropic oscillator whose lifespan is nonhomogeneous, thus implying that time is shorter or longer according to the state of this universe given through its entropy. We conclude that time reduces to the entropy production of this universe and that a nonzero entropy production means that local fluctuations could exist giving rise to the appearance of masses and to the curvature of the space.     

部分相干离焦散斑照相的统计理论

运用散斑统计理论，探讨了部分相干离焦散斑照相的统计规律，指出了影响条纹质量的各种因素，并给出了实验验证。     

How to Measure a Two-Sided Market

Applying the theories of complex network and entropy measurement to the market, the two-sided market structure is analyzed in constructing the O2O platform transaction on the entropy measurement of the nodes and links. Market structure entropy (MSE) is initially introduced to measure the consistency degree of the individuals and the groups in the O2O market, according to the interaction in the profits, the time/space, and the information relationship. Considering that the market structure entropies are changing upward or downward, MSE is used to judge the consistency degree between the individuals and the groups. Respectively, considering the scale, the cost and the value dimensions, MSE is expanded to explain the market quality entropy, the market time-effect entropy, and the market capacity entropy.MSE provides a methodology in studying the O2O platform transaction and gives the quantitative index in the evaluation of the O2O market state.