电磁聚焦成象系统中带不饱和磁铁聚焦磁场的约束逆设计

本文对电磁聚焦成像系统中带不饱和磁铁的聚焦磁场的逆设计进行了探讨,用约束优化方法——内罚函数法来设计能实现给定磁场分布的实际磁聚焦线圈系统。     

耦合腔行波管PPM聚焦系统横向磁场分析

借助三维静磁场分析软件,模拟仿真了两种非旋转对称PPM聚焦系统的内部磁场：极靴耦合槽分别呈180°和0°排列。根据仿真结果分析了阿良莫夫斯基关于PPM聚焦系统磁场实验中的横向磁场成因;总结了铁制加载头对PPM聚焦系统横向磁场的改善效果以及对磁饱和的影响。最后归纳出横向磁场的3种成因,分别阐述了铁制加载头对其影响;给出了...     

E波段折叠波导行波管集成极靴结构设计及仿真

为进一步提升毫米波折叠波导行波管的输出功率,通过整体加工的工艺方法,将折叠波导慢波结构和周期永磁聚焦系统在母材上同时加工,形成一种集成极靴结构。基于圆形注电子光学系统,设计了E波段折叠波导行波管的集成极靴结构。利用三维电磁场模拟软件(CST)的微波工作室,设计并模拟了慢波结构的冷特性参数,并根据慢波结构尺寸设计周期永磁聚焦系统。通过电磁工作环境仿真软件(OPERA)对磁场进行仿真验证,最终整管粒子数值模拟(PIC)计算结果表明,在61~71 GHz频带内可获得大于1 kW的饱和输出功率。该集成极靴结构在提供强轴向磁场的同时,具有结构紧凑、散热性好等优点。     

一维阵列电子注平面聚焦系统磁场分布特性

针对平面集成行波管对一维阵列电子注聚焦的应用需求,设计了4通道电子注平面磁聚焦系统。将各通道磁场轴向和横向分量沿轴分布特征计算结果与测试结果进行对比,确认了Opera软件计算磁场分布特征的准确性。为与轴对称周期永磁(PPM)聚焦系统电子注通道内磁场分布特性进行对比,建立了轴对称PPM聚焦系统模型,测试结果与计算结果一致性较好。通过平面聚焦系统与轴对称PPM聚焦系统电子注通道内的磁场纵向和横向分布特性对比表明,两种聚焦系统电子注通道内纵向和横向磁场具有相同的分布特征,在离轴相同位置的圆周上横向磁场分量与轴向分量的比值均为B_x/B_z≈0.11,该平面聚焦系统可实现一维阵列圆形电子注的良好聚焦。     

行波管长周期永磁聚焦系统的研究

对长周期永磁聚焦系统中电子注的脉动情况进行了系统的研究。在增大磁系统周期的时候,从理论上讨论了高次谐波,磁场参量和空间电荷参量对电子注脉动的影响,最后利用计算机仿真软件OPERA对电子注在长周期磁聚焦系统中的运动进行了模拟。结果表明,理论推导的结果与计算机模拟值相符,可以利用这种方法进行长周期聚焦系统的模拟和设计。     

缩小倍率型永磁聚焦天文成像探测器系统的研究

本文从当代天文光电成像探测器的发展现状与实际需要出发，着重探讨寻求允许输入像面不是平面、放大倍率不等于１的永磁聚焦磁场系统的设计途径，用约束变尺度法来设计在电磁聚焦成像系统中实现给定的不均匀磁场分布的实际永磁环磁路系统。     

行波管中聚焦磁场对互作用影响的研究

本文应用MAGIC模拟软件,研究了周期永磁聚焦螺旋线行波管中聚焦磁场的分布对电子轨迹的影响.分别模拟了电子的静态轨迹和互作用轨迹,通过对电子轨迹的分析,设计了一种渐变的磁场分布.应用MAGIC模拟软件对这种渐变磁场进行模拟仿真,结果显示这种渐变磁场可以有效抑制电子散焦,并通过仿真结果分析了如何设置这种新型磁场.     

具有任意设定图像转角的电磁聚焦成像

本文研究了实现图像有任意设定像转角的电磁聚焦成像理论，进一步发展了作者先前的电磁聚焦成像理论，导出了在设定图像转角下轴上电场和磁场应满足的条件，按照本理论不仅可获得直立式，而且可获得任意设定图像转角（或者倒像式）的电磁聚焦成像系统，作为例子，给出了一种解析的轴上电场和磁场分布，可实现设定图像转角且放大率Ｍ＝１或者Ｍ≠１的电磁聚焦成像。     

图象无旋转的曲轴电磁聚焦成象

在曲轴宽电子束聚焦理论和电磁聚焦成象系统理论的基础上,本文进一步发展了图象无旋转的曲轴电磁聚焦成象理论,给出了曲轴系统中获得图象无旋转的充要条件,并讨论了可获得图象无旋转系统的曲轴电场和磁场分布的若干特例。     

线性均衡器的研制

均衡器是重要的微波器件之一,用来改善微波系统的平坦度。研究了加载电阻的微带谐振器及其在微带均衡器中的应用。先用微波仿真软件Serenade对由加载电阻的微带谐振器构成的均衡器进行优化,再利用三维场仿真软件(HFSS)对电路进行电磁仿真检验,设计并制做了2～12GHz微带线性均衡器。均衡器在整个频带内约均衡5dB,输入与输出驻波比均小于2:1,最终实验结果与设计相吻合,满足了工程的需要。结果表明,这种加载电阻的微带谐振器方式适合线性均衡器的设计和制作。     

New method for energy compensation of free electron laser

In this paper the theory of FEL operation in a longitudinal uniform magnetic field integrated with a synchronous precessing electro-magnetic field is expounded in view of the main problems in FEL development. A new energy compensation method is suggested as a new way and basis for the development of FEL research.     

Design and Implementation of a Micromanipulation System Using a Magnetically Levitated MEMS Robot

Magnetic levitation of microrobots is presented as a new technology for micromanipulation tasks. The microrobots were fabricated based on microelectromechanical systems technology and weigh less than 1 g. The robots can be positioned in 3-D using magnetic field. It is shown that microrobots can be produced using commercially available magnets or electrodeposited magnetic films. A photothermal microgripper is integrated to the microrobots to perform micromanipulation operations. The microgrippers can be actuated remotely by laser focusing that makes the microrobot free of any wiring. This leads to increased motion range with more functionality in addition to dust-free motion and ability to work in closed environments. The 3-D motion capability of the microrobots is verified experimentally and it was demonstrated that the microgrippers can be operated in a vertical range of 4 mm and a horizonal range of 4 mm $,times,$5 mm. Micromanipulation experiments such as pick-and-place, pushing, and pulling were demonstrated using objects with 100 $mu$ m and 1 mm diameter.      

Electromagnetic considerations for RF current density imaging [MRI technique

Radio frequency current density imaging (RF-CDI) is a recent MRI technique that can image a Larmor frequency current density component parallel to B(0). Because the feasibility of the technique was demonstrated only for homogeneous media, the authors' goal here is to clarify the electromagnetic assumptions and field theory to allow imaging RF currents in heterogeneous media. The complete RF field and current density imaging problem is posed. General solutions are given for measuring lab frame magnetic fields from the rotating frame magnetic field measurements. For the general case of elliptically polarized fields, in which current and magnetic field components are not in phase, one can obtain a modified single rotation approximation. Sufficient information exists to image the amplitude and phase of the RF current density parallel to B(0) if the partial derivative in the B(0) direction of the RF magnetic field (amplitude and phase) parallel to B(0) is much smaller than the corresponding current density component. The heterogeneous extension was verified by imaging conduction and displacement currents in a phantom containing saline and pure water compartments. Finally, the issues required to image eddy currents are presented. Eddy currents within a sample will distort both the transmitter coil reference system, and create measurable rotating frame magnetic fields. However, a three-dimensional electro-magnetic analysis will be required to determine how the reference system distortion affects computed eddy current images.     

一种新型的中性原子交流电磁囚禁

提出了一种新型的冷原子强场seeking态磁势阱 ,利用的是原子在交变四极场中受到的梯度力。计算结果表明通过选择合适的参数 ,可以控制势阱在轴向和径向的势阱深度。在得到一个径向势阱深度达 0 6mK ,纵向深度为 0 5mK的交流磁势阱 ,可以将温度为～ 10 0 μK的冷原子囚禁在径向 1mm ,纵向 4mm的范围内。如果撤消轴向囚禁 ,还可以获得一个径向囚禁深度为 1 8mK ,能将温度为～ 10 0 μK的冷原子囚禁在径向 5 0 μm范围内的新型磁导管。     

Picosecond magnetic spectroscopy of two- and three-dimensionaldiluted magnetic semiconductors

The authors have developed a novel type of magnetic spectroscopy which relies on an integrated multichip SQUID (superconducting quantum interference devices) microsusceptometer to obtain nearly quantum-limited spin resolution. The susceptometer, including two DC SQUIDs, pickup loops, and field coils, was fabricated using VLSI technology to achieve an unprecedented scale of magnetic sensitivity, optimized for the study of microscopic samples or thin layers. Furthermore, in combination with an ultrafast pulsed laser system, measurements can be made at picosecond time scales, providing an understanding of the dynamics of the magnetic phenomena in these materials and the effects of quantum confinement on magnetic behavior     

浸没流多透镜多注电子光学系统的模拟研究

该文采用先2维后3维的计算方法,对L波段高峰值功率多注速调管电子光学系统进行了模拟设计。采用均匀场浸没流多透镜聚焦系统对电子注进行聚焦,获得了通过率100%,填充因子55%,特性良好的旁轴电子注。模拟计算表明,多透镜系统可有效调整电子注平衡半径,电子枪区均匀场可有效调整电子注波动性及层流性,聚集系统可在阴极磁感应强度为0.001~0.01 T,主磁场为0.06~0.13 T的范围内实现对旁轴电子注的良好聚焦。     

Equivalence of periodic magnetic field to uniform magnetic field in electron beam focusing

The general solution of the electron trajectory equation in a periodic magnetic field is derived in the form of series expansion, assuming laminar electron flow and small perturbation. It is concluded that if the cathode is not very heavily immersed in a magnetic field, beam focusing by a periodic magnetic field would be almost equivalent to that by a uniform magnetic field except near the unstable region. Under these restrictions, each focusing system would give almost the same beam ripple (in magnitude and phase) under the same injection conditions into the focusing system. It is also found that the first stable region of beam perturbation in the periodic magnetic field becomes narrower as the flux threading the cathode increases or the period of the magnetic field decreases, as far as linearization of the path equation is possible.