共查询到19条相似文献,搜索用时 453 毫秒
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力学变形诱导的Nb_3Sn超导临界性能退化给超导磁体装置的电磁性能指标和安全运行造成了极其不利的影响.由于对Nb_3Sn超导临界性能应变退化效应认识的不足,目前仍缺乏统一适用于不同应变状态下的工程设计用一般本构模型.本文基于张量函数的表示理论和Nb_3Sn电子态密度Bhatt模型,建立了可以统一描述不同加载模式下Nb_3Sn费米面态密度变化的演化模型,并基于此给出了能够与不同实验结果吻合较好的刻画超导临界转变温度应变退化特征的分析模型.正作为国际热核聚变实验反应堆(ITER)、核磁共振(NMR)波谱仪以及高能物理(HEP)等超导磁体构件用超导材料之一,Nb_3Sn超导材料在高场超导磁体领域引起了广泛的研究关注[1-4].力学变形诱导的Nb_3Sn超导材料超导电性能(临界温度、上临界磁场、临界电流密度)退化,给超导磁体的安全稳定运行造成了极其不利的影响[4].针对Nb_3Sn超导材料变形-超导电性能耦合行为,Ekin进行了系列实验[5],实验结果表明,力学变 相似文献
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核磁共振成像和核磁共振谱仪是高场超导磁体的主要应用领域.高场超导磁体通常具有较高的磁场和运行电流,在运行过程中超导线会产生较高的电磁应力,其临界特性将发生退化,影响磁体的稳定性.开展高场超导磁体的电磁应力精确分析显得尤为必要.本文发展了一种快速有效的有限元分析方法,第一步,为整个超导磁体系统建立平均有限元模型,采用传统的电磁-结构耦合方法求解电磁应力,获得最大应力位置;第二步,对最大应力所在的超导线圈建立详细有限元模型,采用单积分-结构分析方法精确求解每一组分中电磁应力.基于该模型研究了500 MHz NMR超导磁体的电磁应力.该分析方法也可以用于超导磁体冷却过程中的热应力分析.为高场超导磁体设计和建造提供有益的理论依据. 相似文献
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从理论上对超导开关线的母材选择和参数设计进行了分析,并对超导开关线的合理使用提出了建议。采用低温电阻率ρ(4.2K)=38×10~(-6)Ω·cm的Cu-30Wt.%Ni合金作母材,成功地研制得NbTi芯径分别为18μm和10μm的CuNi-NbTi二组元多芯拧扭复合线。这种复合线具有满意的绝热稳定性和开关特性,并且与cu-NbTi多芯拧扭复合线两者之间的超导接头表现出良好的冷压焊接性能,是一种优良的可用作高稳定性超导磁体恒流闭路运行的超导开关线。 相似文献
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快速反应的热控式超导开关研究 总被引:2,自引:0,他引:2
高频运行的超导磁通泵面临的主要问题是超导开关的反应速度太慢。本从理论和实验上研究了这类开关运行的基本特点。采用合理的开关结构及工艺,超导开关的回复时间在1.2s以下,触发时间在40ms以下。 相似文献
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We further elaborate on the device proposed by Karimi et al. [15], in which coupled superconducting qubits can play the role of a quantum heat switch. In the present paper we analyze the performances of the switch if the number of qubits increases considering in details the cases of three and four qubits. To this aim we study the effect of the number of qubits on the transmitted power between baths. As the number of qubits increases, the transmitted power between baths increases as well. 相似文献
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Induced current of high temperature superconducting loops by combination of exciting coil and thermal switch 下载免费PDF全文
Jia-Wen Wang 《中国物理 B》2022,31(3):37402-037402
With its commercialization, the second-generation (2G) high temperature superconducting (HTS) RE—Ba—Cu—O (REBCO, RE is rare earth) tape is extensively applied to the superconducting magnets in the high magnetic fields. However, unlike low temperature superconducting (LTS) magnets, the HTS magnet cannot operate in the persistent current mode (PCM) due to the immature superconducting soldering technique. In this paper, an exciting method for two HTS sub-loops, so-called charging and load loops, is proposed by flux pump consisting of exciting coil and controllable thermal switch. Two HTS sub-loops are made of an REBCO tape with two slits. An exciting coil with iron core is located in one sub-loop and is supplied with a triangular waveform current so that magnetic field is generated in another sub-loop. The influence of magnetic flux on induced current in load loop is presented and verified in experiment at 77 K. The relationship between the induced magnetic flux density and the current on the sub-loops having been calibrated, magnetic flux density, and induced current are obtained. The results show that the HTS sub-loops can be excited by a coil with thermal switch and the induced current increases with magnetic flux of exciting coil increasing, which is promising for persistent current operation mode of HTS magnets. 相似文献
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Maly T Bryant J Ruben D Griffin RG 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2006,183(2):303-307
We describe a field-lock/field-sweep system for the use in superconducting magnets. The system is based on a commercially available field mapping unit and a custom designed broad-band 1H NMR probe. The NMR signal of a small water sample is used in a feedback loop to set and control the magnetic field to high accuracy. The current instrumental configuration allows field sweeps of +/-0.4 T and a resolution of up to 10(-5) T (0.1 G) and the performance of the system is demonstrated in a high-field electron paramagnetic resonance (EPR) application. The system should also be of utility in other experiments requiring precise and reproducible sweeps of the magnetic field such as DNP, ENDOR or PELDOR. 相似文献
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磁共振系统中的发射/接收(transmit/receive,T/R)开关用于收发通路的切换,要求在隔离大功率信号的同时具有较小的插入损耗;另外,在宽带磁共振谱仪中,一般的窄带T/R开关也不再适用.本文基于PIN(positive-intrinsic-negative)二极管设计了工作频率为10~100 MHz的宽带磁共振T/R开关.通过减小电平跳变、优化开关过冲和解决二极管被动导通等问题,获得了插入损耗小于1 dB、大功率信号隔离度大于75 dB、开关时间1 μs的整体性能.用本文设计的宽带T/R开关替代一般探头中的窄带T/R开关,在0.5 T核磁共振(NMR)波谱仪上测得了氢核和氟核两个不同频率的磁共振信号,验证了宽带T/R开关的宽带性能. 相似文献
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We study the superconducting and magnetic behaviour of Nb/Co superlattices, for superconducting Nb layer thickness of 44 nm and Co layer thickness less than 1 nm. In this limit no ferromagnetism is observed for Co. The superlattice behaves as independent superconducting Nb layers. We obtain the penetration depth and superconducting gap of the material, and analyze the results in terms of microscopic models and theories. 相似文献
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氮化铝(AlN)具有高热导性、高电绝缘性,是超导二元电流引线热截流结构中常用的材料之一。根据稳态导热法建立低温真空实验装置,实验研究了超导冷却系统热截流结构中,界面温度和接触压力对AlN块材与无氧铜(OFHC-Cu)块材间接触界面热阻的影响。在实验温度(90K-210K)和压力(0.273MPa-0.985MPa)条件下,AlN/OFHC-Cu接触界面热阻随接触压力的提高而降低,而当界面温度上升时界面热阻由于热载子热运动的强化而降低,温度较高时,接触界面热阻随压力变化的速率趋缓。低温下AlN/OFHC-Cu间的接触界面热阻是直接冷却超导系统的设计和超导系统的热稳定性方面必需解决的问题。 相似文献
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D. Rinaldi I. Pop R. Caciuffo G. Cone O. Francescangeli P. Mengucci A. Stepanescu I. Stirbat 《Il Nuovo Cimento D》1995,17(4):381-391
Summary The magnetic response of granular superconducting YBCO samples with different grain sizes is reported. The analysis is carried
out by measuring the low-frequency a.c. magnetic susceptibility as a function of the temperature with an applied magnetic
field of amplitude ranging between 0.4 and 800 A/m. The observed magnetic behaviour is interpreted in terms of grain size
and weak-links properties. The experimental results evidence the influence of the sample microstructure on the magnetic susceptibility.
The intergranular and intragranular onset temperatures are compared with the critical temperature of the samples obtained
by means of electrical-resistivity measurements. The temperature dependence of the intergranular critical current density
is derived from the susceptibility data. 相似文献