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根据研制的大口径、高场强的超导强磁装置的特点,选择基于LabVIEW的数据采集和测控系统。低温传感器共六支,分别安装于磁体氦槽和冷屏不同位置,其中碳电阻温度计Cernox三支,铂电阻温度计Pt100两支、Pt1000一只,用于监测磁体温度;超导氦液面计一个,用于监测氦液面高度;根据磁体参数匹配研制了一套可调励磁速率的磁体专用直流电源及其失超保护系统,保证磁体安全运行。所有数据通过NI公司内插DAQ6251数据采集卡的PX I采集,用LabVIEW编写数据采集程序和人机界面。 相似文献
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准确计算分析超导磁体低温系统的漏热量,是评价超导磁体低温绝热性能的重要依据。文中以一台自制的7 T磁共振成像系统(MRI)的超导磁体作为研究对象,对其低温系统进行了详细的漏热计算,分别得到了液氦容器和液氮容器的理论漏热量。将计算结果与实测数据进行比较,分析了磁体实际的低温性能。 相似文献
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N. Sato H. Shimawaki K. Yokoo J. Sakuraba Y. Yamada K. Watanabe 《International Journal of Infrared and Millimeter Waves》1999,20(6):979-989
A liquid helium free superconducting magnet was designed and fabricated and for an application to a millimeter wave gyrotron and a peniotron. The magnet generates a magnetic field of 5T in a 100mm room temperature bore and has been continuously working for more than 5,400 hours without troubles.The magnet system was applied to the millimeter wave gyrotron experiments to confirm the stability of the magnet. In the experiments, stable operations of the gyrotron were achieved in the frequency range of 30 - 133GHz. 相似文献
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磁共振成像(magnetic resonance imaging,MRI)是当今世界上最先进的医学影像技术之一,现阶段MRI技术正朝着成像质量更清晰、功能更强大、效率更高、个体化更强的趋势发展.与全身MRI设备相比,专科型MRI设备具有体积小、重量轻、成本低、病人舒适度高、成像质量高、功能更强等优点.但是关节专用超导MRI系统需要长度方向上被严格限制的超导磁体在160 mm直径球域(diameter sphere volume,DSV)内产生高均匀度的磁场.本文综合考虑了超导线用量、中心磁感应强度和成像区磁场不均匀度等因素,使用0-1规划和遗传算法相结合的方法设计了一种非屏蔽型1.5 T关节MRI超导磁体,该磁体的室温孔径为280 mm,总长度为520 mm,液氦量为30 L,载流区最大磁场为5.48 T,5高斯线范围为径向3.2 m、轴向2.6 m,160 mm DSV的磁场不均匀度设计值为22 ppm,考虑加工误差及冷缩因素,磁体加工完成并经过被动匀场后的预估值为60 ppm.经过绕制、固化、组装、焊接等工序,该磁体已制作完成.经过3次锻炼后成功励磁到1.5 T,经过被动匀场后160 mm DSV的磁场不均匀度达到50 ppm,各项指标均达到设计目标. 相似文献
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基于中国聚变工程实验堆(CFETR)接头的设计要求,提供了一种大孔径背景场磁体的设计方案。构造出大孔径背景场磁体的结构,利用背景场磁体来得到相应的磁场数据,对比研究磁体的参数对磁场的影响,得出相关参数的变化规律。利用Gandalf 程序模拟计算出CFETR 接头背景场磁体的分流温度,考虑到液氦的流体力学性能,采用Gandalf 程序模拟超导股线的失超行为,估算出较为精确的最小失超能。将最小失超能作为Q0 值代入到程序中得出热斑温度值,分析结果表明,设计符合要求,为CFETR 高温超导接头的制作和实验提供了可靠依据。 相似文献
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In an ADS injector Ⅰ, there are five superconducting magnets in each cryomodule. Each superconducting magnet contains a solenoid magnet, a horizontal dipole corrector (HDC), and a vertical dipole corrector (VDC). Six current leads will be required to power the electrical circuits, from room temperature to the 2.1 K liquid helium bath: two leads carry 100 A current for the solenoid magnet while the other four carry 12 A for the HDC and the VDC. This paper presents the principle of current lead optimization, which includes the cooling methods, the choice of material and structure, and the issues for current lead integration. 相似文献
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A design scheme of large aperture field magnet is provided based on the design requirements of the China Fusion Engineering Testing Reactor (CFETR) joints. Using the background field magnet to get the corresponding magnetic field data, the influence of the magnet parameter on the magnetic field is compared, and the corresponding magnetic field data are obtained. Gandalf program was used to simulate the shunt temperature of CFETR field magnet under operating conditions. Considering the hydrodynamic performance of liquid helium, Gandalf program was used to simulate the quench behavior of superconducting strands and to estimate the more accurate minimum quenching energy. The minimum quench value can be used as the Q0 value inputted into the program to obtain hot spot temperature value. The analysis shows that the design meets the requirements for the production of high temperature superconducting magnets and provide reliable basis for manufacture and experiments. 相似文献
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A high-pressure modification of Gallium was formed at liquid helium temperature by the application of a pressure in excess of 35000 atm. It was superconducting with a transition temperature of 6·38°K. The high-pressure form remained after the pressure was removed at helium temperature. This resulted, however in a shift in transition temperature to 7·5°K. The average derivativedT c/dp was ?3·10?5°K/atm. 相似文献
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介绍了EBIT(Electron Beam Ion Trap,电子束离子阱)装置零蒸发低温超导磁体系统的研制过程与超导磁体的性能测试结果。该系统中超导磁体由一对上下布置的分离线圈组成,中心最大磁场强度可达4.5T,在中心轴线上±10mm内磁场均匀度优于2×10-4,磁场衰减系数在8h小于1×10-4;同时其低温杜瓦系统采用双冷屏结构,并通过二级G-M制冷机冷却冷屏来降低液氦的蒸发量。超导磁体的性能测试结果表明满足用户基本要求。 相似文献
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A.L.S. Angelis H.-J. Besch B.J. Blumenfeld L. Camilleri T.J. Chapin R.L. Cool C. del Papa L. Di Lella Z. Dimčovski R.J. Hollebeek L.M. Lederman D.A. Levinthal J.T. Linnemann C. Newman N. Phinney B.G. Pope S.H. Pordes K.K. Young 《Physics letters. [Part B]》1979,87(4):398-402
An apparatus consisting of a superconducting solenoid magnet, cylindrical drift-chambers, and two arrays of lead-glass ?erenkov counters has been used at the CERN ISR to study the production of e+e? pairs of invariant mass above 6.5 GeV/c2. Cross sections for the continuum and the ? family of resonances are presented, as well as the mean transverse momentum 〈pT〉 of the electron-positron pairs in the continuum and resonance region. 相似文献
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Chang WH Chung CY Chen JH Hwang DW Hsu CH Yao C Hwang LP 《Magnetic resonance imaging》2011,29(6):869-876
This work presents a simple design for a mobile single-sided nuclear magnetic resonance (NMR) apparatus with a relatively homogeneous static magnetic field (B0) distribution. In the proposed design, the B0 magnetic field of the apparatus is synthesized using only two permanent magnet blocks, i.e., a cube (main) magnet and a small shim magnet placed above the main magnet. The magnetic flux of the shim magnet partially cancels out that of the main magnet, subsequently creating a smooth B0 profile above the shim magnet where low-resolution NMR experiments are performed. Compared with many previously published designs, this straightforward design simplifies the construction of the apparatus and simultaneously generates a B0 field parallel to the apparatus surface, allowing the use of a simple loop-type radiofrequency (RF) coil. Additionally, an apparatus prototype is constructed according to the proposed design. Weighing only 1.8 kg, the constructed apparatus has a compact structure and can be held in the palm of a hand. The apparatus generates a B0 strength of about 0.0746 T. Within a B0 field deviation of 3 mT, the region with a relatively homogeneous B0 distribution extends to about 11 mm above the shim magnet. The proposed apparatus can detect a clear Hahn echo or Carr-Purcell-Meiboom-Gill (CPMG) echoes of a pencil eraser block or a bottle of oil placed on the apparatus in 5 s with signal averaging using an RF transmitter power of only 19 W; the detection range of the apparatus exceeds 6 mm. The strength of the residual static magnetic field gradient of the apparatus is roughly estimated at 0.58 T/m. Applying different CPMG echo spacings in this residual static gradient leads to various transverse relaxation time (T2) contrasts for liquids with distinct viscosities such as water and oil. Two nondestructive inspection applications of the apparatus, including correlating the concentrations of magnetic nanoparticle solutions with their measured transverse relaxation rates (R2) and monitoring the outgassing from an opened bottle of oxygen-supersaturated water by measuring its longitudinal relaxation rate (R1), are also demonstrated. 相似文献
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This study presents a simple design for a mobile, single-sided nuclear magnetic resonance (NMR) apparatus which uses the magnetic flux parallel to the magnetization direction of a single, disc-shaped permanent magnet polarized in radial direction. The stray magnetic field above the magnet is approximately parallel to the magnetization direction of the magnet and is utilized as the B0 magnetic field of the apparatus. The apparatus weighs 1.8 kg, has a compact structure and can be held in one's palm. The apparatus generates a B0 field strength of about 0.279 T at the center of apparatus surface and can acquire a clear Hahn echo signal of a pencil eraser block lying on the RF coil in one shot. Moreover, a strong static magnetic field gradient exists in the direction perpendicular to the apparatus surface. The strength of the static magnetic field gradient near the center of the apparatus surface is about 10.2 T/m; one-dimensional imaging of thin objects and liquid self-diffusion coefficient measurements can be performed therein. The available spatial resolution of the one-dimensional imaging experiments using a 5×5 mm horizontal sample area is about 200 μm. Several nondestructive inspection applications of the apparatus, including distinguishing between polyethylene grains of different densities, characterizing epoxy putties of distinct set times and evaluating the fat content percentages of milk powders, are also demonstrated. Compared with many previously published designs, the proposed design bears a simple structure and generates a B0 magnetic field parallel to the apparatus surface, simplifying apparatus construction and simultaneously rendering the selection of the radiofrequency coil relatively flexible. 相似文献
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K. Yokoyama T. Oka K. Noto 《Physica C: Superconductivity and its Applications》2010,470(20):1201-1206
We study the construction of superconducting permanent magnets by RE123 bulk materials and the investigation of these industrial applications such as a magnetic separation. A bulk magnet can generate strong magnetic fields exceeding 2 T, which is the limit of ordinary iron-cored electromagnets, in a compact device with a low running cost. A magnetic field distribution of the bulk magnet is a cone shape, and it contributes to an increase of magnetic force which is proportional to the product of a magnetic field and its gradient. It is important to evaluate magnetic force when the application of the bulk magnet is discussed. In this paper, two Gd123 bulk materials of 65 mm in diameter were magnetized using a pair of superconducting bulk magnet system and three-axis components of magnetic flux density (Bx,⋅By, and Bz) in an open space between the magnetic poles were scanned with pitch of 2 mm in each direction. From these measured data, the axial and radial components of magnetic force factor, Bz⋅dBz/dz and Br⋅dBr/dr, were calculated. At 10 mm gap, the Bz⋅dBz/dz value reached 180.6 T2/m for a field of 2.33 T, which is comparable to Bz = 6.76 T for a common 10 T–100 mm∅ superconducting magnet. 相似文献
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The superconductivity and magnetoresistance (MR) of epitaxial bilayers consisting of YBa2Cu3O7?δ (YBCO) and La0.67Sr0.33MnO3 (LSMO) are investigated with respect to the proximity and spin polarization effects. In the region of the mixed vortex state near the onset temperature of the superconducting transition, the diffusion of the spin-polarized quasiparticles from the LSMO to the YBCO is evidenced by their distinct magnetotransport behaviors, which are characterized by two superconducting transitions. It is revealed that the second transition is strongly dependent on the applied magnetic field, demonstrating an abnormal pair-breaking effect. This effect, together with the reduced MR, is believed to arise from an increase in the spin injection efficiency induced by the suppressed interfacial spin scattering, disclosing a new perspective for understanding the magnetotransport phenomena in proximity-coupled superconductor/ferromagnet (S/F) hybrids. 相似文献
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《Infrared Physics & Technology》1999,40(3):219-230
We describe a high-resolution (0.015 cm−1) Fourier transform spectrometer which has been developed to investigate bulk and surface magnetic polaritons in magnetic media by far infrared magneto-optic spectroscopy. The spectrometer uses a novel combination of laser-controlled sampling of the interferogram and phase modulation of the infrared beam to combine very accurate sampling and low signal-to-noise ratio. The spectrometer is coupled to a liquid helium cryostat with a 7 T superconducting magnet, and a liquid helium-cooled silicon bolometer is used as the detector. Samples can be mounted in the cryostat for polarised oblique incidence reflection measurements in the Voigt geometry with the applied magnetic field vertical. Measurements on surface polaritons are made by using attenuated total reflection (ATR) spectroscopy with silicon prisms to obtain the necessary wave vector enhancement. The resolution of the instrument is demonstrated with measurements on the rotational lines of water vapour, and a selection of measurements on a bulk single crystal of FeF2, a uniaxial antiferromagnet, is presented to illustrate the performance of the instrument as a probe of magnetic excitations. 相似文献