一种粒子谱仪用高均匀性高磁通密度永磁组件

研制的永磁组件采用主辅永磁体和匀场技术相结合的改进C型磁路结构,利用计算机仿真技术对组件磁路结构进行验证及优化。仿真分析及实验结果表明：采用这种磁路结构扩大了均匀区的范围,提高了磁场均匀性。按这种结构制造的永磁组件在20 mm气隙、中心平面200 mm120 mm均匀区内气隙磁通密度达到0.75 T,不均匀度为0.67%。另外,也对永磁组件在高低温下的磁性能进行了仿真计算,结果表明:在-55~70 ℃温度范围内均匀区的气隙磁通密度变化为4%左右。     

永磁体外部磁场的不均匀性研究

从永磁体的分子电流观点、退磁场、工艺等出发, 以矩形永磁体为例, 从理论上分析了影响永磁体外部磁场不均匀性的各种因素.研究结果表明, 永磁体外部磁场宏观不均匀性(好场区均匀度和面积相对大小) 和空间距离及永磁体的外形设计密切相关. 退磁场对永磁体外部磁场微观不均匀性有着复杂影响. 永磁体工艺如粉末颗粒、取向度、烧结凝固、机械加工等将影响永磁体外部磁场的不均匀性, 如磁化偏角、对称性、光滑性等. 关键词： 永磁体 外部磁场 不均匀性 退磁场     

Active ferromagnetic shimming of the permanent magnet for magnetic resonance imaging scanner

This paper presents an approach of active ferromagnetic shimming for C-type permanent magnetic resonance imaging (MRI) magnet.It is designed to reduce inhomogeneity of magnetostatic field of C-type permanent magnet to meet the stringent requirement for MRI applications.An optimal configuration (locations and thicknesses) of active ferromagnetic pieces is generated through calculation according to the initial field map and the demanded final homogeneity specifications.This approach uses a minimisation technique which makes the sum of squared magnetic moment minimum to restrict the amount of the active ferromagnetic material used and the maximal thickness of pieces stacked at each hole location in the shimming boards.Simulation and experimental results verify that the method is valid and efficient.     

高功率光隔离器永磁系统的理论研究与优化

基于阵列永磁体的特点以及光隔离器对磁场的需求设计了两种适用于高功率隔离器的永磁系统,分析了其磁场分布、磁场非均匀性对隔离度的影响,研究了磁体装配误差对磁场的影响。研究结果表明：通过引入斜向磁化永磁体,选择合适的磁化角度和磁体长度,可以提高永磁体的磁场强度,大幅度减小旋转器所需磁光晶体长度;受磁场非均匀性影响的隔离度与磁光晶体的孔径、长度以及入射激光的光斑半径有关,当晶体长度一定时,减小晶体半径和入射光的半径可以显著提高隔离度。在入射光半径为1.5 mm、磁光晶体半径5 mm时,对应的隔离度分别为105.8 dB和45.4 dB。     

高功率光隔离器永磁系统的理论研究与优化

基于Halbach阵列永磁体的特点以及光隔离器对磁场的需求,设计了两种适用于高功率隔离器的永磁系统,分析了其磁场分布、磁场非均匀性对隔离度的影响,研究了磁体装配误差对磁场的影响。研究结果表明:通过引入斜向磁化永磁体,选择合适的磁化角度和磁体长度,可以提高永磁体的磁场强度,大幅度减小旋转器所需磁光晶体长度;受磁场非均匀性影响的隔离度与磁光晶体的孔径、长度以及入射激光的光斑半径有关,当晶体长度一定时,减小晶体半径和入射光的半径可以显著提高隔离度。在入射光半径为1.5mm、磁光晶体半径5mm时,对应的隔离度分别为105.8dB和45.4dB。     

多注行波管周期永磁聚焦系统

 利用自行开发的3维行波管仿真软件研究了五注耦合腔行波管周期永磁聚焦系统,分析了各个电子注通道内的静磁场分布和电子注聚焦性能。讨论了在有无初始横向速度的情况下各电子注的聚焦情况。并对外层电子注通道内的横向磁场的性质和其造成的对电子注聚焦的影响进行了分析,结果表明:该多注周期永磁聚焦系统具有良好的静磁场分布特性与电子注聚焦性能,在结构设计合理时,横向磁场对外层通道内电子注的聚焦影响很小,可以忽略。     

几组特殊形状永磁体的磁场及梯度COMSOL分析

利用COMSOL"静磁场,无电流"的应用模式给出了相对放置的永磁条、具有磁回路结构的磁轭磁极、环形磁体的磁场分布图,并分析了这3组磁体的磁场和梯度情况,更关注于均匀磁场和恒梯度磁场的分布情况。     

磁场可调永磁离子源

研制了一台磁场可调微波离子源, 在离子源放电室处需要的磁场由一组永久磁铁产生, 永久磁铁外部安装了铁磁回路, 铁磁回路的结构可以很容易的手动调整, 通过调整铁磁回路的结构, 可以在放电室产生要求的磁场. 在调试过程中, 也可以调整铁磁回路以改变离子源内部磁场结构, 有利于获得最佳放电条件. 该源在测试中, 从3mm直径的引出孔引出了17mA的离子束.     

Development of the relativistic backward wave oscillator with a permanent magnet

Firstly, an X-band relativistic backward wave oscillator with a low guiding magnetic field is simulated, whose output microwave power is 520 MW. Then, an experiment is carried out on an accelerator to investigate a relativistic backward wave oscillator with a permanent magnetic field whose strength is 0.46 T. When the energy of the electron is 630 keV and the current of the electron beam is 6.7 kA, a 15 ns width pulsed microwave with 510 MW output power at 8.0 GHz microwave frequency is achieved.     

Low-field nuclear magnetic resonance spectrometer for non-invasive monitoring of fluctuations in blood glucose in the human finger

A low-field nuclear magnetic resonance spectrometer for non-invasive monitoring of human finger blood glucose fluctuations was developed. Saline solution and blood serum samples with different glucose concentrations were first detected by the spectrometer and it has been found that there was a high-linear correlation between the glucose concentration and the transverse relaxation time. Then, the spectrometer was employed to noninvasively measure a finger from each of the several volunteers. The experiment results showed that the transverse relaxation time of the human finger increases with human blood glucose concentration. In conclusion, the human finger nuclear magnetic resonance spectrometer could be a potential tool to noninvasive monitoring of human body’s blood glucose fluctuations in the future.