神龙二号热阴极注入器束流调试

神龙二号注入器是一台感应叠加型强流脉冲电子束源，采用热阴极工作模式，为神龙二号加速器提供间隔可调的三脉冲电子束。该注入器的束流调试采取PIC模拟和实验调试交互验证、互相促进的方式，先是通过束斑测量确定引导线圈磁场的加载范围，然后通过PIC方法逐级梳理阳极段束线各线圈的磁场配置，再通过束斑测量加以确认。通过这种束流调试方法，获得了保持束流脉冲平顶完整通过的三种磁场配置，以适应下游加速段束流传输的不同要求。讨论了影响束流调试效果的因素，认为提升神龙二号注入器性能的关键是进一步改进大面积热阴极发射的均匀性。     

CSR60°二极C型铁磁场特性的研究

兰州重离子加速器冷却储存环主环注入线二极C型磁铁首次采用了磁极头中埋置垫补线圈调整磁场均匀度的设计.在其磁场测量中,使用了点测和积分测量的方法对其各方面特性参数进行了测量,并对积分场的测量结果以及内置垫补线圈对均匀场的垫补效果进行了详细的非线性分析.     

HIAF-BRing快脉冲二极磁铁磁场测量系统

介绍了强流重离子加速器装置HIAF(High Intensity heavy-ion Accelerator Facility)项目增强器BRing(Booster Ring)快脉冲二极磁铁的性能指标、测量要求和测量方法,描述了快脉冲二极磁铁稳态磁场测量系统及动态磁场测量系统的构成。在稳态磁场测量中,为提高积分磁场测量精度和测量效率,长线圈测量系统采用了on fly技术;在动态磁场测量中,研制了用于磁场延迟及磁场畸变测量的矩阵线圈。通过样机磁铁的测量,完成了测量系统的性能指标验证和磁铁的稳态磁场测量。实测结果表明,样机磁铁的设计和制造均达到了预期指标,并依据测量数据完成了磁铁的二次削斜。     

基于电磁感应法测量亥姆霍兹线圈磁场的改进

本文在电磁感应法的基础上,通过与亥姆霍兹线圈串联使电容达到谐振的改进方法,测量了不同电容参数下的亥姆霍兹线圈磁场分布,并利用Origin软件拟合分析了亥姆霍兹线圈磁场与中心轴线位置的关系.实验结果表明,基于电磁感应的改进方法测得的亥姆霍兹线圈磁场精确度在一定程度上均大于传统电磁感应法的测量结果,3种电容选择中,串联电容为0.099×10^-6F时,精确度最高,拟合的亥姆霍兹线圈磁场与中心轴线位置的关系式与理论状态下的公式基本吻合.改进方法的实验效果明显,精确度高,科学可行,是一种值得推广的测量亥姆霍兹线圈磁场的改进方法.     

脉冲线积分场测量系统的研制

介绍了脉冲线测量插入件磁场一二次积分的原理和测量装置的组成,分析了重力、噪声和反射波等因素对测量精度的影响,并采用对称安装金属线、夜间测量、油滴吸收反射波等方法减小了这些因素对测量的影响。脉冲线测量系统的测量结果与霍尔点测法相比符合得较好。利用该装置对实验室即将投入应用的电磁型圆极化波荡器进行了测量,验证了校正线圈和主线圈电流之间的关系。     

镀膜陶瓷真空室脉冲磁场穿透特性研究

介绍了合肥电子储存环新凸轨注入系统中将采用的超高真空陶瓷镀钛真空室的研制状况。对穿过真空室镀膜的脉冲磁场特性进行了理论分析与计算。讨论了不同的镀膜厚度及方式对脉冲磁场均匀性的影响,用跟踪程序计算了注入过程磁场径向不均匀性对束流轨道的扰动,给出了涡流引起的磁场径向不均匀性最大允许值。     

HL-2A装置周围杂散磁场测量与分析

在装置外侧进行中性粒子测量和中性束注入实验时，为了更好的屏蔽外部磁场，需要准确测定设备周围的磁场分布情况，即HL-2A装置的励磁线圈在装置外侧产生的杂散磁场的分布情况，本实验主要完成该分布的测量与分析，这对于以后装置外杂散磁场的测量与分析方法的改进完善也有其独立的意义。     

镀膜陶瓷真空室脉冲磁场穿透特性研究

 介绍了合肥电子储存环新凸轨注入系统中将采用的超高真空陶瓷镀钛真空室的研制状况。对穿过真空室镀膜的脉冲磁场特性进行了理论分析与计算。讨论了不同的镀膜厚度及方式对脉冲磁场均匀性的影响,用跟踪程序计算了注入过程磁场径向不均匀性对束流轨道的扰动,给出了涡流引起的磁场径向不均匀性最大允许值。     

强干扰环境下微秒级脉冲磁场与纳秒级主机同步器的研制

 同步器采用单稳态延时电路、脉冲陡化电路和抗干扰技术,解决了微秒级脉冲磁场与纳秒级主机的同步问题,同步延时在100 μs范围内可调。     

强干扰环境下微秒级脉冲磁场与纳秒级主机同步器的研究

同在采用单稳态延时电路、脉冲陡化电路和抗干扰技术,解决了微秒级脉冲磁场人秒级主机的同步问题,同步延时在１００μｓ范围内可调。     

On the effect of a longitudinal magnetic field on oscillatory characteristics of a subnormal region in discharge in argon

Oscillating nature of current pulses under d.c. excitation in subnormal region with longitudinal magnetic field at pressure range 0.20 torr to 0.85 torr have been studied. The frequency, bandwidth, peak-peak voltage, cut-off current and rise time of the current pulses have been observed with pressure, average tube current and magnetic field. A study of these oscillograms in magnetic field, average tube current and pressure are presented. The probable mechanism for the generation of oscillation based on space-charge field modification with magnetic field is discussed     

一种新的求解脑磁逆问题的搜索方法

给出一种新的求解真实头模型下脑磁逆问题的搜索方法.通过不同位置的源的相互关系，由上一个搜索源的计算结果通过简单计算，直接得到下一个搜索源的结果，避免了繁琐耗时的边界元积分方法，简化了求解过程，提高了求解速度. 关键词： 脑磁图 逆问题 搜索方法     

HL-2M装置5 MW中性束加热束线离子源放电室研制

为了给HL-2M装置建设一条5 MW中性束加热束线,开展了中性束加热用热阴极弧放电离子源放电室的研制。这条中性束束线包含4套80 kV/45 A/5 s离子源,放电室的设计指标为850 A/5 s。首先采用CST软件中的电磁工作室对特定几何结构的放电室会切磁场进行了模拟计算,得到了会切磁场分布,验证了会切磁场布局的合理性。针对放电室加工工艺和实验过程中局部拉弧等问题,对放电室结构进行了不断改进。放电室侧壁由40列会切磁体改为7圈环形磁体,阴极灯丝结构从灯丝板结构最终改为陶瓷可伐结构,并且在放电室和加速器之间增加了陶瓷屏蔽。在阴极板结构放电室和阴极陶瓷可伐结构放电室内都获得了正常的弧放电。最终定型的放电室采用周边7圈环形会切磁体和陶瓷可伐结构。在定型的放电室内达到了5 MW中性束束线离子源弧放电的指标。弧放电时间接近5 s,最大弧放电电流达到1 000 A。     

Specific features of magnetic field penetration into granular superconductors and possible sensitivity of magnetic sensors based on them

The results of experimental and theoretical studies of the magnetic properties of a superconducting ceramic with the composition YBa₂Cu₃O_{7 ? x} are presented. The limiting sensitivity of magnetic field sensors on the basis of a high-temperature superconducting ceramic is discussed.     

Single point measurements of magnetic field gradient waveform

Pulsed magnetic field gradients are fundamental to spatial encoding and diffusion weighting in magnetic resonance. The ideal pulsed magnetic field gradient should have negligible rise and fall times, however, there are physical limits to how fast the magnetic field gradient may change with time. Finite gradient switching times, and transient, secondary, induced magnetic field gradients (eddy currents) alter the ideal gradient waveform and may introduce a variety of undesirable image artifacts. We have developed a new method to measure the complete magnetic field gradient waveform. The measurement employs a heavily doped test sample with short MR relaxation times (T(1), T(2), and T(2)(*)<100 micros) and a series of closely spaced broadband radiofrequency excitations, combined with single point data acquisition. This technique, a measure of evolving signal phase, directly determines the magnetic field gradient waveform experienced by the test sample. The measurement is sensitive to low level transient magnetic fields produced by eddy currents and other short and long time constant non-ideal gradient waveform behaviors. Data analysis is particularly facile permitting a very ready experimental check of gradient performance.     

1.5 T磁感应强度水冷式螺线管线圈结构设计及仿真研究

介绍T量级水冷式螺线管线圈的结构设计及仿真研究工作。采用多层水冷结构设计,对不同温升导致的变形量进行计算并校核,最后利用POISSON程序对线圈磁场进行仿真计算。计算表明:最大温升60℃时,整个结构变形量小于0.07 mm,即探头相对位置变化量可小于0.1 mm;96.6 A电流加载时,中心区最大磁感应强度为1.5 T;0.01%精度轴向磁场宽度为40 mm,0.1%精度轴向磁场宽度为140 mm。从仿真结果来看,设计的水冷式螺线管线圈可满足磁场探头校准测量要求。     

Two-dimensional imaging with a single-sided NMR probe

A new low field unilateral NMR sensor equipped with a two-dimensional gradient coil system was built. A new NMR-MOUSE concept using a simple bar magnet instead of the classical U-shaped geometry was used to produce magnetic field profiles comparatively homogeneous in extended lateral planes defining a suitable field of view for 2D spatial localization. Slice selection along the depth direction is obtained by means of the highly constant static magnetic field gradient produced by this magnet geometry. Implementing a two-dimensional phase-encoding imaging method 2D cross sections of objects were obtained with high spatial resolution. By retuning the probe it was possible to change the depth of the selected slice obtaining a 3D imaging method. The details of the construction of the new device are presented together with imaging tests to show the quality of space encoding.     

Magnetic control of crystal chirality and the existence of a large magneto-optical dichroism effect in CuB2O4

The possibility of a magnetic field controlling the chirality of matter has been debated for a long time. Here, we report the successful induction of chirality in the noncentrosymmetric canted antiferromagnet, CuB2O4, by application of a low intensity static magnetic field. The chirality is reversed by a 90 degrees rotation of the direction of the magnetic field. The induction of chirality by a magnetic field gives rise to a gigantic enhancement of magnetochiral dichroism in this material. The ability to switch handedness in combination with this large magnetochiral optical effect allows us to design new optical devices such as a magnetically controllable isolator.     

Pulsed magnetization of uniaxial films with arbitrarily oriented axis of easy magnetization

The particular features of the pulsed magnetization of thin metal magnetic films with an axis of easy magnetization lying in the plane of the film are investigated. The dynamics of the transition of the magnetization from one stable state to another, due to the action of a controlling plane magnetic field, depends very much on the mutual orientation of the axis of easy magnetization and the magnetizing field. By solving the equations of motion of the magnetic moment numerically, the time dependences of the orientation of the magnetic moment, corresponding to the process of magnetization due to the action of an increasing pulsed magnetic field with a rise time of τ, are obtained. By analyzing the solutions obtained, the angular dependences of the magnetization time, the dependence on the amplitude and rise time of the magnetizing field, and the damping parameter are constructed. Using the Bogolyubov-Krylov method, approximate analytic solutions of the dynamic equations are obtained, which agree with a high degree of accuracy with the numerical solutions for times exceeding τ. Ul'yanovsk State University, Ul'yanovsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 41, No. 12, pp. 72–77, December, 1998.