Charged particle energy analyzer based on a modified cylindrical mirror in the ring-axis focusing mode

The electron-optical properties of systems with a modified structure of the energy analyzer in the form of a cylindrical mirror proposed earlier are investigated. The analyzer operating mode in which the source of charged particles is in the inner cylinder and the detector is on the cylinder axis (ring-axis focusing) is considered. It is shown using numerical simulation that the modified structure ensures higher focusing quality as compared to the traditional cylindrical mirror. The optimal structure and voltage supply are determined for which spherical aberration is five times smaller than with a conventional cylindrical mirror.     

New electrostatic cylindrical energy analyzer

The focusing properties of an ideal cylindrical field in full relativistic field have been investigated for charged particles originating from an extended source and an analytical solution for the equations of motion has been provided. This focusing system can be used for production of electrostatic energy analyzer provided surface analysis from an extended area.     

Charged particle energy analyzer based on a modified cylindrical mirror

A modified design of an electrostatic energy analyzer of the cylindrical mirror type is suggested. The outer electrode of the modified analyzer consists of three cylinders with equal radii and different potentials. The electron-optical properties of the analyzer are numerically simulated, and it is demonstrated that it may offer a much higher focusing quality than a conventional cylindrical mirror. Optimal design and operating conditions are found for which the spherical aberration decreases fivefold compared with the conventional mirror.     

Scaling Theory of Strongly Charged Cylindrical Polyelectrolyte Brushes

Scaling theory of charged cylindrical polyelectrolyte brushes is developed. The dependence of brush thickness on the grafting density, charge fraction, and chain length is analyzed. A full phase diagram is established. Characteristics and boundaries between different regimes of cylindrical polyelectrolyte brushes are summarized. Special attentions are paid to electrostatic interaction induced stiffening and counterion condensation effects. If the Bjerrum length of the solution is larger than the Kuhn length of the polyelectrolyte chains, counterion condensation occurs in the strongly charged polyelectrolyte brushes. On the contrary, the electrostatic interaction stretches the strongly charged grafted polyelectrolyte chains to their contour length.     

High-resolution spectroscopy of low-energy electrons emitted in nuclear transformations

Some measurements of low-energy converslon electrons and photoelectrons are presented. The results were obtained using electrostatic cylindrical mirror analyzers.     

A tunable bragg cavity for an efficient millimeter FEL driven by electrostatic accelerators

A comparison between three possible cavity configurations, the confocal cavity, the ring cavity and the Bragg cavity is presented for a millimeter FEL set within the high voltage head of an electrostatic accelerator. A simple mechnical design to make the Bragg cavity tunable is proposed. The usual theory of the sinusoidal Bragg corrugation, in cylindrical geometry, is extended to the rectangular corrugation and, further, the theory of the Bragg mirror is extended to rectangular geometry. The features of a Bragg mirror in cylindrical and rectangular geometry are compared.     

Half-open Penning trap with efficient light collection for precision laser spectroscopy of highly charged ions

We have conceived, built and operated a ’half-open’ cylindrical Penning trap for the confinement and laser spectroscopy of highly charged ions. This trap allows fluorescence detection employing a solid angle which is about one order of magnitude larger than in conventional cylindrical Penning traps. At the same time, the desired electrostatic and magnetostatic properties of a closed-endcap cylindrical Penning trap are preserved in this configuration. We give a detailed account on the design and confinement properties, a characterization of the trap and show first results of light collection with in-trap produced highly charged ions.     

用于三维全电磁粒子模拟的电荷守恒共形发射技术北大核心CSCD

给出了满足电荷守恒的共形发射技术。首先阴极表面由三角网格共形描述,发射带电粒子时,根据电荷和电流线性分配方式和离散高斯定律,带电粒子的初始位置设置在与三角面元处于同一个网格元胞内,离三角面元最近且处于金属内部的网格点上。带电粒子的初始运动由两部分组成:一是由三角面上的法向场推进所产生的运动;二是使发射粒子在阴极面上分布呈随机性而设定的随机运动。运动产生的电流按照电荷守恒定律分配到离散网格中,并且由于粒子的初始位置设置在整网格点上,带电粒子的共形发射不会产生非物理的静电累加。最后通过同轴二极管模型来验证共形发射模型的正确性。     

分离圆柱面与偏心圆柱面静电场问题的镜象解

基于静电场的叠加原理和唯一性定理,用镜象法求解由两圆柱导体所组成的分离圆柱面与偏心圆柱面静电场边值问题,推导出分离圆柱面与偏心圆柱面静电场边值问题的解析解。     

带电粒子与静电波相互作用单粒子方程的严格解

研究了带电粒子与静电波之间的相互作用, 给出了带电粒子运动方程的严格解, 得出了粒子的速度的解析表达式, 同时推导出了带电粒子被静电波俘获的数学条件, 讨论了粒子与波能量交换的物理过程, 对现有等离子体物理的教材中相关的问题是一个补充. 本文结果对带电粒子加速器、微波管以及基础等离子体问题的研究有一定参考意义.     

Design Calculation of a Improved ECR Ion Source

The design of a ECR ion source in a working mode with a ω_ecr resonance surfaces and a 2ω_rf enclosed surface is presented.The 0.8T axial mirror field and 0.8T radial hexapole field are introduced with detailed discussions.The computational results show that the axial length of the ω_ecr resonance surface in the improved ECR ion source is extended significantly compared with the original CAPRICE one and a closed 2ω_rf equigauss surface is also formed.The new topology of the magnetic field in the improved ECR ion source will largely raise the intensity of high charged ion on the basis of the analysis of ionization mechanism.     

Vacuum ultraviolet resonance line radiation source from rare gas atoms and ions for UHV photoelectron spectroscopy

A source and differential pumping system for producing high intensity resonance line radiation from rare gas atoms and ions for ultrahigh vacuum (UHV) photoelectron spectroscopy has been developed. Photoelectron count rates from a gold sample, as measured with a double-pass cylindrical mirror analyzer at pass energy 15 eV and 0.10 eV resolution, are ～ 300,000 c s^?1 for the He(I) (21.22 eV) line and ～30000 c s^?1 for the He(II) (40.81 eV) line. The source design is based on the principle of the electrostatic charged particle oscillator and is capable of sustaining discharges over the pressure range 1 to ～ 10^?6 torr. The discharge segment consists of a cylindrical cold cathode surrounding two tungsten rod anodes which are held at high positive potential. Three stages of differential pumping are employed in order that the vacuum in the main spectrometer chamber can be maintained at 2 × 10^?10 torr during operation. The calculated helium flow reaching the main chamber under these conditions is < 101 s^?1. Details of the construction and operating characteristics of the source are presented.     

Numerical study on electrostatic potential distribution of large cylindrical oil tanks

This study carried out a numerical simulation of electrostatic potential distribution in the cylindrical oil tank, focusing on spatial distribution of electrostatic potential and the variation tendency of the potential in the filling operation. Electrostatic potential distribution of stationary oil was illustrated, and the relationship between the electrostatic potential distribution and some parameters of the tank and oil was analyzed as well. Dynamic electrostatic distribution was studied when charged oil is filling into the tank, and ESD prevention measures’ effects on electrostatic potential distribution were simulated. Finally, calculation results of two other types of oil tanks were presented in brief.     

High-dispersion energy analyzer of charged particles in the form of two coaxial cylinders with an end diaphragm

We propose an energy analyzer of charged particles based on the coaxial electrostatic lens that has been studied earlier. The optimal regimes of operation of such an analyzer are determined using numerical simulation by varying four independent parameters. It is found that linear energy dispersion is an order of magnitude higher than the dispersion of widely used energy analyzers of the type of a plane and cylindrical mirrors, as well as a number of other devices for analyzing the energy of charged particles.     

Specific boundary conditions for the simulation of extraction for ECRIS,LIS, and H−-sources

The necessity of a three-dimensional simulation of the extraction has been accepted for electron cyclotron resonance ion sources (ECRIS) as well as for negative ion sources. For an ECRIS, the magnetic hexapole together with the solenoidal mirror field defines a minimum B structure which confines the plasma. Depending on the magnetic flux density distribution, the plasma density in front of the extraction electrode might be non-homogeneous. In H^?-sources, magnetic filter fields are used to separate electrons with different energies or to separate electrons from negative ions. These magnetic filters influence the ions as well. Besides these asymmetry effects other quantities have to be considered, namely the correct formulation of initial conditions of all present charged particles. For ECRIS the initial conditions for ions are assumed to be in the electronvolt range, whereas it can be in the kilo electronvolt range for laser ion sources. Another quantity of interest is the electron energy and the distribution of electrons in real space and their movability if magnetic fields are present.     

The dust acoustic wave in a bounded dusty plasma with strong electrostatic interactions between dust grains

The dispersion relation for the dust acoustic wave (DAW) in an unmagnetized dusty plasma cylindrical waveguide is derived, accounting for strong electrostatic interactions between charged dust grains. It is found that the boundary effect limits the radial extent of the DAW. The present result should be helpful for understanding the frequency spectrum of the DAW in a dusty plasma waveguide with strongly coupled charged dust grains.     

Dispersion relation of dust acoustic waves in metallic multi-walled carbon nanotubes

In this paper,a charged multi-walled carbon nanotube(MWCNT),which is surrounded by charged nanoparticles,is modeled as a cylindrical shell of electron-ion-dust plasma.By employing classical electrodynamics formulations and the linearized hydrodynamic model,the dispersion relation of the dust acoustic wave oscillations in the composed system is investigated.We obtain a new low-frequency electrostatic excitation in the MWCNT,i.e.dust acoustic wave oscillations.     

静电六极装置电场分布的数值计算方法及在N2O分子转动态选择、取向中的应用

阐述求解极性分子转动态选择及取向静电六极装置中势能分布、电场分布的数值计算方法.为了获得电场分布公式,需通过数值迭代求解势能满足的Laplace方程,获取数值分布点,通过数值分布点,由待定系数的多级展开势能解析表达式进行最小二乘拟合获得势能分布公式,由势能对空间向量的微分获得电场分布.分子在六极电场中的运行轨迹采用经典Newton方程描述,并通过四阶龙格-库塔方法(Four Order Runge-Kutta Method)实现数值求解,其中能量处理采用量子力学方法.应用此方法给出静电六极装置的电场分布公式,运用获得的电场分布公式计算和讨论电场对极性分子N₂O的静电六极转动态选择、取向所带来的影响.