质子照相磁透镜的优化设计

 对质子照相系统中Zumbro磁透镜的参数进行了优化,使成像系统造成的图像模糊最小化,结果表明:构成Zumbro磁透镜的四极透镜对内外漂移段长度相等时,成像系统获得最小的图像模糊。对成像系统的视场进行了分析,表明视场对Zumbro透镜的参数不敏感。给出了质子能量为20 GeV时Zumbro透镜的参数,Geant4蒙特卡罗计算表明:所给的Zumbro透镜参数能正确成像。     

Imaging beamline for high energy proton radiography

Proton radiography is a new tool for advanced hydrotesting. This article will discuss the basic concept of proton radiography first, especially the magnetic lens system. Then a scenario of 50 GeV imaging beamline will be described in every particular, including the matching section, Zumbro lens system and imaging system. The simulation result shows that the scenario of imaging beamline performs well, and the influence of secondary particles can be neglected.     

11 MeV能损型质子照相空间分辨能力模拟

透射质子的能损和散射角是质子照相成像模糊的主要来源。基于Zumbro聚焦成像磁透镜的质子照相技术,可基本消除散射角引起的成像模糊,实现几十μm的空间分辨,但无法对能损信息进行优化是其空间分辨能力难以进一步提升的主要原因。为利用透射质子的能损信息,进一步提高质子照相的空间分辨能力,提出了一种新型的成像磁透镜,称之为能损型聚焦成像磁透镜。基于11 MeV低能能损型质子照相的实验束线和Geant4模拟软件,建立全过程照相模型,研究11 MeV能损型成像束线的空间分辨能力。模拟研究表明:对于10 μm厚的Al箔,考虑点扩散函数等测量系统成像模糊的影响,11 MeV能损型成像束线可实现约30 μm的空间分辨。与等大型Zumbro磁透镜相比,空间分辨能力得到显著提升。     

时间分辨电子显微镜中放大成象系统的设计

本文介绍了时间分辨电子显微镜中的放大成象系统。该系统由物镜，第一，第二中间镜及投影镜等磁透镜组成，其电子束交叉截面位于远离投影镜极靴中心的位置，且具有细而长的腰部；该系统可提供大于一万倍的放大倍率，最大放大倍率可达十万倍，从而为提高时间分辨电子显微镜的空间分辨本领和时间分辨率提供了良好的条件。     

考虑磁透镜边缘场的质子成像系统优化设计

高能质子照相系统由四极磁透镜和准直器组成,实际透镜的边缘场将影响成像系统的性能.本文将含边缘场的磁场梯度用贝尔函数近似,提出了一种含边缘场的成像系统优化方法.通过Geant 4程序模拟了能量为1.6 GeV的质子成像系统,并通过优化方法给出了考虑边缘场的优化后的系统参数.研究了考虑边缘场时的成像系统参数对准直器孔径的影响.通过对比理想成像系统和优化前后的成像系统在使用准直器时的客体通量分布,研究了边缘场对质子通过客体的通量影响.结果表明,优化后的成像系统可以减小质子通过客体后的通量误差,并且积分差值在10^–2量级时,准直器的孔径参数变化亦在10^–2量级.     

阴极透镜象差的变分理论

本文运用变分原理研究了电磁复合聚焦阴极透镜的象差理论,导出了在任意象平面中象差系数的普遍公式。它们可以用Glaser导出的象差系数的线性组合来表示。这就表明了宽束与细束电子光学系统的象差都可以用统一的变分方法处理,并建立了两者之间的联系,本文采用矢量形式描写阴极透镜的近轴轨迹,并采用矩阵形式描写象差。本文所得的象差系数较之文献上已有结果形式更为简洁且适用于计算机计算。本文考虑了阴极面上磁场和横向电场不为零的情况,因而所得结果较为普遍。 关键词：     

多焦距光学系统的小型化设计

提出了一种多焦距短筒功率谱采集透镜(PSCL)系统设计方案,系统由前组透镜、后组透镜和4倍透镜组组成。F500傅里叶透镜作为前组透镜固定,加后组透镜,实现焦距F500至F800或F1000的切换。在F500或F1000系统后增加4倍透镜组,实现F2000或F4000的光学系统。设计结果表明,该方案缩短了透镜系统筒长,且像质良好。该透镜系统适用于多种焦距值切换的光学系统和仪器的小型化。     

A study on effect of current density on magnetic lenses

Attention has been concentrated on the effect of the current density on magnetic objective lens design. The optical properties of various objective lens types have been investigated in terms of current density σ. Arrangement of energizing coil on symmetric magnetic electron lenses also, has been examined. Favorable current density σ regions are estimated for the iron polepiece and iron free magnetic lenses.     

A different algebraic method for the fifth-order combined geometric-chromatic aberrations of practical magnetic electron lenses

In this paper, differential algebraic (DA) method is applied to fifth-order combined geometric-chromatic aberrations of practical magnetic electron lenses. The magnetic fields of magnetic electron lenses, which are computed by FEM or FDM method, are in the form of discrete arrays. Thus the developed new DA method is applicable to engineering design and programs were written for computing the fifth-order combined geometric-chromatic aberrations of practical magnetic electron lenses. An example is given. The combined geometric-chromatic aberrations up to fifth order are calculated. It is proved that the numerical results for the magnetic fields in the form of discrete arrays have good accuracy compared with the results computed by using the magnetic fields expressed in analytical form. The accuracy is limited only by the accuracy of the numerical computation of the fields and the arithmetic errors. Finally, a practical magnetic electron lens is analyzed and discussed as an example.     

Study on rotation-free combined immersion magneto-electrostatic lenses

Demagnified rotation-free image formed by combined immersion magneto-electrostatic lenses is beneficial for projection lithography systems with respect to pattern stitching. Based on Busch theorem, the image-rotation in combined immersion magnetic electrostatic lenses is investigated, and consequently this image-rotation free condition is derived. A practical lens based upon this condition is constructed by parametrically optimizing its magnetic field. The numerically computed results show that its image-rotation-angle for this system is close to zero.     

Spiral distortion of magnetic lenses with fields of the form B(z) ∝ z, n = 2, 3, 4

The spiral distortion of magnetic lenses with a field distribution in the form of an inverse power law has been studied. The spiral distortion coefficient can be evaluated explicitly in terms of Bessel function. For spherical field (B ∝ Z⁻³), which is useful for the study of single pole magnetic lens, the spiral distortion coefficient was analytically expressed.     

Aberration-corrected catadioptric magnifiers useful for simple microfiche readers

The present paper considers the magnifying power and aberration properties of three different catadioptric magnifying systems useful for application as simple hand-held microfiche readers. These are in the form of a plano-convex lens, a meniscus lens and an achromatic doublet lens and all their outer surfaces have been coated with a semi-reflecting film so that they behave like catadioptric elements. These can be designed to give magnification in the range of 15 × to 25 × with sufficient eye relief. Using such magnifiers, it is possible to read microfiche having frame sizes of 16 × 12 mm and 12 × 9 mm. The cemented achromatic doublet coated on the outer surfaces seems to give a very good image for use in microfiche reader.     

Design and fabrication of fluid controlled dynamic optical lens system

A novel small fluid controlled optical lens system that is capable of displaying dynamic variation of its focal length and field-of-view (FOV) is designed and fabricated. In this active lens system, appropriate volume of the optical fluid can be pumped into or out of the lens chamber to provide double-convex (DCX) or double-concave (DCV) lens effect. Simple optical imaging experiments were performed using different sets of glass lenses with fixed focal lengths to determine the optimum lens configuration required for designing a dynamic optical lens system. The experimental results obtained from the glass lenses demonstrate that a combination of a single DCX lens with three DCV lenses provides a wider FOV. The flexible membranes for fluid controlled lenses were fabricated using polydimethylsiloxane polymer material, which has good optical transparency and elasticity. A simple fluid injection system is used to vary the radius of curvature of the lenses, and thereby to change the focal length. A dynamic optical lens system with a combination of one DCX and multiple variable focal length DCV lenses as designed here can image an object with a wide range of focal length and FOV. With this fluid controlled optical system, the FOV and focal length could be continuously varied and a maximum FOV of 118.3° could be achieved. The smallest f-number (f_/#) for this fluid controlled single lens system was found to be 1.3, which corresponds to the numerical aperture value of 0.35.     

The nonlinear transformation of an ion beam in the plasma lens

The plasma lens can carry out not only sharp focusing of ions beam. At those stages at which the magnetic field is nonlinear, formation of other interesting configurations of beams is possible. Plasma lens provides formation of hollow beams of ions. Application of the several plasma lenses allow to get a conic and a cylindrical beams. The plasma lens can be used for obtaining a beams with homogeneous spatial distribution. Calculations and measurements were performed for a C⁺⁶ and Fe⁺²⁶ beams of 200?C300 MeV/a.u.m. energy. The obtained results and analysis are reported.     

周期场透镜的成象特性

由三个或五个透镜元素组成的周期场,可以作为离子透镜使离子束成象。通常它具有比单个透镜元素强得多的聚焦能力(在相同的电压比下)。这种周期场透镜曾用于静电加速器离子源初聚系统中,但它的成象特性尚未有详细的分析。本文提出一种研究这类透镜特性的方法。将周期场看作由若干个透镜元素合成的组合透镜,然后以Ferraris特征行列式求它的基点表示式。作为普遍情况,以浸没透镜作为透镜元素,导得了三个和五个透镜元素的周期场透镜基点表示式。式中只包含透镜元素的基点参量和电极系统的几何参量。式子十分简洁,便于计算,并有足够的精确度。通过解析表示式中各个因子的分析,可以方便地掌握透镜的特性。由短磁透镜组合的周期磁场是上述普遍情况的一个特例。文中以等径小间隙双圆筒透镜为浸没透镜元素,对周期场透镜的特性用导得的基点表示式进行了计算和分析。     

一种具有Luneburg透镜特性的轴向GRIN介质透镜

本文给出一种轴向GRIN(梯度折射率)介质透镜。这种透镜具有 Luneburg(卢内堡)透镜的特性。它可以使无限远光线锐成象;亦可用于点—点锐成象系统,光准直或光准直—聚焦系统;在微波频谱区域及有声成象、天线设计方面有一定应用价值。     

Mini lenses for tiny low-voltage electron-beam devices

The peculiarities of the design of tiny elements of electron optics—electron lenses used in the microsystem electron-beam technique, and their difference from conventional electron lenses that are applied in modern electron-beam equipment have been considered. Lenses with a two-functional magnetic circuit are analyzed. The magnetic circuit in such lenses, along with its direct destination, serves simultaneously as an electrode to which necessary potentials are applied. A lens with a coil playing the role of an electrode is considered as well. This approach allows more compact location of elements of electronic optics in an electron-optical system and simultaneous implementation of new properties of tiny lenses. The problem of fabrication of the excitation coil in the form of an Archimedes spiral is studied. The possibilities of application of new materials (high-temperature conductors, solid electrolytes, ferrites, etc.) that could not be previously used due to the large sizes of the elements of conventional electron optics are analyzed.     

Two-photon excited fluorescence of the lens for the diagnosis of presbyopia

Presbyopia is a wide spread phenomenon in elder people and is caused by the hardening of the lens in human eyes. Research is performed to make such lenses again more flexible by application of geometrically optimised cuts through the lens with a femtosecond-laser. Different protein agglomerations are responsible for the flexibility reduction of the lens. Two-photon excited fluorescence of the lens can be used as a diagnostic tool to localise such protein accumulations. In in-vitro experiments with human cataract lenses and also lenses of the Philly-mouse it could be demonstrated that with age the fluorescence increases as presbyopia proceeds. The distribution of the fluorescing compounds are not homogeneous but rather cloudy. Discrimination of the compounds by fluorescence lifetime measurements in relation of the depth in the lens is possible.     

头盔式单目微光夜视仪中光学系统的设计

为提高头盔式单目微光夜视仪中光学系统的成像质量，并满足夜视仪结构紧凑、质量小的指标要求，提出在微光夜视仪光学系统设计中引入高次项非球面透镜的设计方法。针对具体的头盔式微光夜视仪，根据微光物镜、目镜系统技术参数计算理论，确定该微光夜视仪光学系统的技术参数，应用光学设计软件ZEMX上机调试，并在光学系统设计中引入高次非球面透镜，使物镜系统镜片数由原来的9片减少为6片，目镜系统由原来的9片减少为7片，简化了结构，并提高了成像质量。设计结果表明：在头盔式微光夜视系统中采用非球面透镜可以提高系统成像质量，简化系统结构。     

Far-field pattern analysis of 94 GHz extended hemispherical lens monopulse antennas

In this paper, the far-field patterns are investigated for double-slot antenna array placed on extended hemispherical lenses. The radiation patterns of the extended hemispherical lens fed by single double-slot antenna or double-slot antenna array are computed using ray-tracing inside the dielectric lens and electric and magnetic field integration on the spherical dielectric surface. The computation results show that the sharp null of the difference pattern is below -37dB.