A novel approach for x-ray scattering experiments in magnetic fields utilizing trapped flux in type-II superconductors

We introduce a novel approach to x-ray scattering studies in applied magnetic fields by exploiting vortices in superconductors. This method is based on trapping magnetic flux in a small disk-shaped superconductor (known as a trapped field magnet, TFM) with a single-crystal sample mounted on or at close proximity to its surface. This opens an unrestricted optical access to the sample and allows magnetic fields to be applied precisely along the x-ray momentum transfer, facilitating polarization-sensitive experiments that have been impractical or impossible to perform to date. The TFMs used in our study remain stable and provide practically uniform magnetic fields for days, which are sufficient for comprehensive x-ray diffraction experiments, specifically x-ray resonance exchange scattering (XRES) to study field-induced phenomena at a modern synchrotron source. The TFM instrument has been used in a "proof-of-principle" XRES study of a meta-magnetic phase in a rare-earth compound, TbNi(2)Ge(2), in order to demonstrate its potential.     

Development of an x-ray diffraction camera used in magnetic fields up to 10 T

A high-field x-ray diffraction (HF-XRD) camera was developed to observe structural changes of magnetic materials in magnetic fields up to 10 T. The instrument mainly consists of a Debye-Scherrer-type camera with a diameter of 80.1 mm, a 10-T cryocooled superconducting magnet with a 100-mm room-temperature bore, an x-ray source, a power supply, and a chiller for the x-ray source. An x-ray detector (image plate) in the HF-XRD camera can be taken out and inserted into the magnet without changing the sample position. The performance of the instrument was tested by measuring the HF-XRD for silicon and ferromagnetic MnBi powders. A change of x-ray diffraction pattern was observed due to the magnetic orientation of MnBi, showing that the instrument is useful for studying field-induced orientation processes and structural properties of field-controlled materials.     

外加磁场对磁流体润滑油膜轴承的影响

为了研究磁流体润滑油膜轴承内磁场的分布情况,分别通过永磁铁、螺线管及亥姆赫兹线圈对其施加3种不同形式的外磁场。通过磁场二维实体有限元模型的数值仿真,分析在3种模型下磁流体润滑油膜轴承的磁场分布特性,并比较磁场在油膜区的分布情况。结果表明,永磁铁模型的磁场主要分布在永磁铁、油膜、轴承座以及靠近磁铁的轧辊部分,螺线管模型的磁场主要分布在油膜、轴承座以及靠近磁铁的轧辊部分,亥姆霍兹线圈模型的磁场主要分布在线圈以及油膜的端部;3种模型在油膜区磁场分布沿轴向均呈现中间小、两端大的不均匀现象,且具有端部效应;永磁铁模型和螺线管模型在油膜区磁场沿径向分布均匀,亥姆霍兹线圈模型沿径向分布不均匀。     

材料自蔓延合成磁场环境的产生方法及强磁体研制

为了研究磁场环境对自蔓延高温合成的影响,从而利用磁场环境合成出所需材料,本文设计和制作了用于开展磁场环境下自蔓延高温合成(SHS)材料试验的强磁体。通过永磁铁磁场和通电线圈产生磁场的叠加,在实验区域产生特斯拉级强度。其中的关键技术有:同时改变永磁铁磁场方向或通电线圈中电流大小,实现连续改变实验区磁场强度(0~1 T),采用蓄电池供给短时间大电流。与同等强度的传统磁体比较,该磁体重量和成本降低1/10。     

偏置磁场对磁致伸缩液位传感器检测电压的影响

为了提高磁致伸缩液位传感器的检测精度,研究了磁致伸缩液位传感器中产生偏置磁场的浮子磁铁的放置方式及其对检测电压的影响。利用ANSYS软件对浮子磁铁不同放置方式下形成的偏置磁场进行了有限元分析,分析显示:采用3块磁铁互成120°N极N极S极(NNS)放置或者采用圆环磁铁作为偏置磁场时检测效果比较理想。实验研究了磁致伸缩液位传感器的偏置磁场对检测电压的影响,并在浮子磁铁不同放置方式下进行多次实验。结果表明:偏置磁铁为3块磁铁互成120°NNS放置时或者为圆环磁铁时,检测电压的幅值达到50mV,比其它放置方式提高了近30mV。研究表明:磁致伸缩液位传感器应选择3块磁铁NNS放置或者选择圆环磁铁作为偏置磁场。     

Manufacturing of a superconducting magnet system for 28 GHz electron cyclotron resonance ion source at KBSI

A magnet system for a 28 GHz electron cyclotron resonance ion source is being developed by the Korea Basic Science Institute. The configuration of the magnet system consists of 3 solenoid coils for a mirror magnetic field and 6 racetrack coils for a hexapole magnetic field. They can generate axial magnetic fields of 3.6 T at the beam injection part and 2.2 T at the extraction part. A radial magnetic field of 2.1 T is achievable at the plasma chamber wall. A step type winding process was employed in fabricating the hexapole coil. The winding technique was confirmed through repeated cooling tests. Superconducting magnets and a cryostat system are currently being manufactured.     

A permanent-magnet-based attached instrument used to inspect articles on the basis of their coercive force

An attached magnetic instrument that uses two permanent magnets to magnetize and demagnetize an article is considered. When one of the magnets is set at a fixed angle, the rotation angle of the other magnet is proportional to the coercive force of an article and is used as the tested parameter.     

A 30 T pulsed magnet with conical bore for synchrotron powder diffraction

We report on the design, construction, and operation of a horizontal field, 30 T magnet system with a conical bore optimized for synchrotron x-ray powder diffraction. The magnet offers ±31° optical access downstream of the sample, which allows to measure a sufficiently large number of Debye rings for an accurate crystal structure analysis. Combined with a 290 kJ generator, magnetic field pulses of 60 ms length were generated in the magnet, with a rise time of 4.1 ms and a repetition rate of 6 pulses/h at 30 T. The coil is mounted inside a liquid nitrogen bath. A liquid helium flow cryostat reaches into the coil and allows sample temperature between 5 and 250 K. The setup was used on the European Synchrotron Radiation Facility beamlines ID20 and ID06.     

Note: unique characterization possibilities in the ultra high vacuum scanning transmission x-ray microscope (UHV-STXM) "MAXYMUS" using a rotatable permanent magnetic field up to 0.22 T

Using the x-ray magnetic circular dichroism effect, the soft x-ray range provides powerful detection capabilities concerning element specific structural, chemical, and magnetic properties. We present the implementation of a variable 0.22 T magnet system based on permanent magnets into the new UHV scanning microscope "MAXYMUS" at HZB/BESSY II, allowing surface sensitive and simultaneous standard transmission microscopic investigations in a variable external magnetic field. The outstanding potential of these new investigation possibilities will be demonstrated showing the development of the magnetic domain structure concurrently at the surface and in the bulk, providing a profound understanding of fundamental mechanisms in coupled magnetic systems.     

永磁体形性特征对磁水复合支撑式艉轴承润滑特性的影响

螺旋桨重力会导致船舶推进轴系发生挠曲,造成艉轴承边缘润滑状态恶劣。采用一种磁水复合支撑形式的艉轴承,通过引入永磁体磁力作用,改善桨重因素对艉轴承边缘润滑状态的不利影响;构建永磁体三维磁力特性分析方法,探究不同永磁体材料磁性质和布置形式对磁力承载性能的影响规律;基于艉轴承弹性流体动压润滑分析方法,获取永磁体形性特征对润滑特性的影响规律。结果表明：磁承载力受永磁体材料剩磁的影响明显,材料剩磁越大,永磁体承载力越大,轴承润滑状态相对越好;沿周向增加磁块数目或增加永磁块轴向长度可以增大永磁体的承载力,但永磁体承载效率可能下降,设计时需综合考虑;磁体的布置形式也对磁力承载性能和润滑性能影响显著,在永磁体体积相同的情况下,更为合理的布置形式可使永磁体承载力与艉轴承最小水膜厚度明显增大。     

The INE-Beamline for actinide science at ANKA

Since its inauguration in 2005, the INE-Beamline for actinide research at the synchrotron source ANKA (KIT North Campus) provides dedicated instrumentation for x-ray spectroscopic characterization of actinide samples and other radioactive materials. R&D work at the beamline focuses on various aspects of nuclear waste disposal within INE's mission to provide the scientific basis for assessing long-term safety of a final nuclear waste repository. The INE-Beamline is accessible for the actinide and radiochemistry community through the ANKA proposal system and the European Union Integrated Infrastructure Initiative ACTINET-I3. Experiments with activities up to 1 × 10(+6) times the European exemption limit are feasible within a safe but flexible containment concept. Measurements with monochromatic radiation are performed at photon energies varying between ~2.1 keV (P K-edge) and ~25 keV (Pd K-edge), including the lanthanide L-edges and the actinide M- and L3-edges up to Cf. The close proximity of the INE-Beamline to INE controlled area labs offers infrastructure unique in Europe for the spectroscopic and microscopic characterization of actinide samples. The modular beamline design enables sufficient flexibility to adapt sample environments and detection systems to many scientific questions. The well-established bulk techniques x-ray absorption fine structure (XAFS) spectroscopy in transmission and fluorescence mode have been augmented by advanced methods using a microfocused beam, including (confocal) XAFS/x-ray fluorescence detection and a combination of (micro-)XAFS and (micro-)x-ray diffraction. Additional instrumentation for high energy-resolution x-ray emission spectroscopy has been successfully developed and tested.     

Design of a vector magnet for the measurements of anisotropic magnetoresistance and rotational magneto-optic Kerr effect

A vector magnet is designed and assembled with two electromagnets to produce a rotational magnetic field in any direction within a plane. This design allows a rotation of the magnetic field without a mechanical rotation of the magnets. The fast speed of the field rotation (~10 s for a complete 360° rotation) and the stability against mechanical vibration easily overcome the slow drifting effect in anisotropic magnetoresistance (AMR) and rotational magneto-optic Kerr effect (ROTMOKE) measurements. As an example we applied this vector magnet to carry out AMR and ROTMOKE measurements on epitaxial growth of Fe(10 nm)∕MgO(001) films. The result demonstrates the stability and high quality of the vector magnet in determining the magnetic anisotropy of magnetic thin films using AMR and ROTMOKE techniques.     

胶囊机器人磁驱动力建模与测量

可吞式无线磁驱胶囊机器人在胃肠道内的诊疗效果与机器人受到的外部磁驱动力密切相关。本文建立了外部磁驱动力的理论模型,基于等效磁荷模型推导了两径向充磁环形永磁体相互作用的数学表达式,采用自适应递归式计算方法开展了数值计算。此外,发展了环形永磁体间磁力实时测量方法,并开发了磁力-间距同步测量仪器开展实验研究,且建立了3D环形永磁体有限元仿真模型。实验测量磁力-间距关系曲线与理论计算和有限元仿真结果吻合较好,误差小于4%,验证了理论模型和有限元仿真模型的准确性和可靠性。通过参数分析,揭示了胶囊机器人内置永磁体长度、厚度和体积对磁力的影响规律。研究结果为精准驱动胶囊机器人在胃肠道内运动奠定了理论基础。     

电液伺服转阀耐高压双向旋转比例电磁铁

针对传统旋转比例电磁铁不耐高压的不足,提出一种耐高压的旋转比例电磁铁结构。永磁体产生的极化磁通与线圈产生的控制磁通相互叠加,使电磁铁输出与控制电流成比例的双向转矩(转角)。通过磁路、磁场仿真分析和试验研究,分析其静态力矩特性和动态幅频特性,仿真结果与试验结果基本吻合,表明该旋转比例电磁铁结构紧凑、无控制零位死区、输出力矩大(最大输出力矩为±0.65 N•m)、响应快(幅频宽约为190 Hz),具有正磁弹簧刚度、良好的线性度(非线性误差小于3％)及较小的滞环(小于4.5％),可用于直接驱动电液伺服转阀。     

Vector potential photoelectron microscopy

A new class of electron microscope has been developed for the chemical microanalysis of a wide range of real world samples using photoelectron spectroscopy. Highly structured, three-dimensional samples, such as fiber mats and fracture surfaces can be imaged, as well as insulators and magnetic materials. The new microscope uses the vector potential field from a solenoid magnet as a spatial reference for imaging. A prototype instrument has demonstrated imaging of uncoated silk, magnetic steel wool, and micron-sized single strand tungsten wires.     

Magnetic circuit design by topology optimization for Lorentz force maximization in a microspeaker

Bipolar magnets are common in most magnetic circuits, but circuit efficiency can be enhanced if multipolar magnets are used instead. However, the use of multipolar magnets is rare. In this investigation, the possibility of using multipolar magnets for maximizing the Lorentz force in a microspeaker is considered. The design problem of a multipolar magnetic circuit is formulated as a topology optimization problem. The circuit design region is discretized by finite elements, and a material state among a multipolar magnet, a yoke and air for every element is so determined as to maximize a desired Lorentz force component. Numerical results show that multipolar magnetic circuits obtained by the topology optimization outperform a conventional bipolar circuit.     

A polyvalent harmonic coil testing method for small-aperture magnets

A method to characterize permanent and fast-pulsed iron-dominated magnets with small apertures is presented. The harmonic coil measurement technique is enhanced specifically for small-aperture magnets by (1) in situ calibration, for facing search-coil production inaccuracy, (2) rotating the magnet around its axis, for correcting systematic effects, and (3) measuring magnetic fluxes by stationary coils at different angular positions for measuring fast pulsed magnets. This method allows a quadrupole magnet for particle accelerators to be characterized completely, by assessing multipole field components, magnetic axis position, and field direction. In this paper, initially the metrological problems arising from testing small-aperture magnets are highlighted. Then, the basic ideas of the proposed method and the architecture of the corresponding measurement system are illustrated. Finally, experimental validation results are shown for small-aperture permanent and fast-ramped quadrupole magnets for the new linear accelerator Linac4 at CERN (European Organization for Nuclear Research).     

磁力齿轮内转子护套过盈量计算及其应力分析

针对磁力齿轮中转子在旋转时产生的离心力容易导致表贴式永磁体损坏的问题,将一个高强度过盈配合的保护套应用到永磁体的保护中。对内转子保护套与永磁体间的过盈配合量及其应力的计算方法进行了分析,对一台内转子速度为56 r/min,传动比为8的磁力齿轮,计算了内转子护套和永磁体的应力值以及护套的过盈量,并根据计算出的过盈量利用ANSYS Workbench15.0分析了护套和永磁体的应力,通过建立试验平台对稳定运行一段时间的样机进行了拆分,观察护套效果。研究结果表明:仿真结果接近理论计算值,内转子护套表面光滑无凸起,证明数值计算的准确性,该护套可用于保护永磁体。     

Development of an optimised magnetic field source for flowmeter applications

Sensitivity of a magnetic flowmeter relies on many factors like magnetic field strength, gap between electrodes, material properties, magnet temperature etc. For a given measuring conditions, a strong magnetic field source can produce highest sensitivity for the flowmeter. An economic design of magnetic field source would be to produce the strongest magnetic field from a given amount of magnetic material. In this paper, various magnet configurations are analyzed using FEM and the flowmeter sensitivity using such magnet configurations are compared. It is observed that magnets arranged in a Halbach fashion produce the highest sensitivity for the flowmeter using a given amount of magnetic material. The major challenge for the development of such a magnetic field source is its fabrication from its constituent magnets, combatting their huge attractive/repulsive forces (∼2500 N for our case). Therefore, a specific mechanical tool has been designed for assembling the magnetic field source and a robust assembly technique has been devised using numerical computations. The designed magnetic field source produces a peak magnetic field of 0.78 T in the pole cross section of 50 mm × 50 mm.     

三稳态压电能量采集器的动态特性与实验

为了探究三稳态压电振动能量采集器的动力学特性,以磁-机-压电耦合型三稳态压电振动能量采集器(tristable piezoelectric vibration energy harvester,简称TPVEH)为研究对象,利用磁荷法、力平衡和基尔霍夫定律分别建立了采集器末端磁铁与外部磁铁之间的非线性磁力模型和系统集总参数动力学模型。仿真分析了磁铁间距、激励加速度幅值和频率等参数对采集器动力学特性和采集电压的影响。研制了三稳态压电振动能量采集器原理样机,搭建了实验测试平台,实验验证了仿真结果的正确性。研究结果表明,随着激励加速度幅值增大,能量采集器依次经历单稳态、双稳态和三稳态3种运动状态,且三稳态运动时的工作频带和输出性能(位移、速度和采集电压)比双稳态和单稳态时要高。