Flip effect in the orientation of a magnet levitating over a superconducting torus in the Meissner state

The torque between a permanent magnet and a toroidal superconductor in the Meissner state is calculated using a model previously proposed based on London’s and Maxwell’s equations. A flip effect on the stable orientation of the magnet as a function of position is demonstrated. At large distances the magnet tends to be perpendicular to the axis of the torus, but when you approach it, at a certain point there is a flip and it tends to be parallel to that axis while being closer than a certain limit. This effect can be easily used as a binary detector for proximity.     

FAIR收集环二极超导实验磁体的研究

为验证国际反质子和离子加速器(Facility for Antiproton and Ion Research-FAIR)收集环(Collector Ring-CR)二极超导磁体工程设计的可靠性,设计并制造了用于导体性能测试的实验磁体,借助基于有限元的ANSYS软件对其进行了分析,达到了实验磁体的强度要求,实验结果表明导体在低温下性能稳定。进行的研究为收集环二极超导磁体的研发提供了有益的参考。     

Gyrotron based on a superconducting magnet

The replacement of conventional pulsed magnetic field coils previously used to generate the intra-cavity B-field with an 11T superconducting magnet is reported. The resulting more stable mm-wave output pulse is shown and the refurbishment requirements of both the field emission, field-immersed, cold cathode and Marx bank spark gaps demonstrated. This system proved to be tunable, oscillating from 20GHz up to 110GHz, with peak power levels of 450kW and 300kW respectively. Other operating parameters were also examined including mm-wave pulse length as a function of anode-cathode position. The pulse length increased from 87±6ns to 310±10ns with a 2.5 cm horizontal transit of the cathode away from the anode. A similar effect was witnessed with the increase of the intra-cavity B-field from 1.00T to 5.00T resulting in the mm-wave pulse duration increasing from 250±40ns. Second harmonic operation of the cavity resulted in 0.5kW of radiation observed at 96GHz. The pulse-to-pulse mm-wave stability coupled with the mode selectivity of the ohmic-Q-dominated cavity resulted in the identification of several oscillating modes including the TE₁₂, cut-off frequency 21.1 GHz, the TE₀₂, cut-off frequency 29.1 GHz, the TE₃₅ at 74 GHz and the TE_14,2, at 88GHz.     

基于迈斯纳效应超导电机的设计与电磁结构分析

本文对低温超导体在低温环境下表现出的迈斯纳效应进行了分析,并将这一现象产生的抗磁特性应用于电机驱动,设计出一种定子位于转子内部的超导电机。文章还阐述了电机的工作原理,结构设计方案。针对一种两相驱动的结构设计方案进行了电磁结构分析,得到具体的电机特性参数。     

Design of a superconducting magnet for CADS

This paper describes a superconducting magnet system for the China Accelerator Driven System (CADS). The magnetic field is provided by one main, two bucking and four racetrack coils. The main coil produces a central field of up to 7 T and the effective length is more than 140 mm, the two bucking coils can shield most of the fringe field, and the four racetrack superconducting coils produce the steering magnetic field. Its leakage field in the cavity zone is about 5× 10^-5 T when the shielding material Niobium and cryogenic permalloy are used as the Meissner shielding and passive shielding respectively. The quench calculations and protection system are also discussed.     

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阐述了FAIR收集环二极超导磁体电流引线的基本原理,给出了电流引线的主要参数及初步设计方案,提出了使用复合材料和通过结构优化以减小电流引线的漏热,并根据电流引线的传热特性进行了漏热的分析和计算,实验结果验证了概念设计的可行性。     

FAIR收集环二极超导磁体电流引线的概念设计

阐述了FAIR收集环二极超导磁体电流引线的基本原理,给出了电流引线的主要参数及初步设计方案,提出了使用复合材料和通过结构优化以减小电流引线的漏热,并根据电流引线的传热特性进行了漏热的分析和计算,实验结果验证了概念设计的可行性。     

Tailoring of the flip effect in the orientation of a magnet levitating over a superconducting torus: Geometrical dependencies

In a previous study, a general local model was used in order to demonstrate the apparition of a flip effect in the equilibrium orientation of a magnet when it is over a superconducting torus. This effect can be easily used in devices such as binary position detectors for magneto-microscopy, contactless sieves or magnetic levels amongst others.We present an initial study useful to design devices based on the flip effect between magnets and torus superconductors. It demonstrates that varying different geometrical parameters the flip effect point can be fixed. Also, it can be observed that increasing the inner radius of the torus elevates the flip effect point. A magneto-mechanical explanation of this phenomenon is exposed. For an increment of cross-section diameter occurs the same behavior. There are linear piecewises in the geometrical dependency functions that can be used for a more accurate fitting of the flip effect point.     

Vibration analysis of a rectangular thin isotropic plate with a part-through surface crack of arbitrary orientation and position

In this paper, vibration analysis of a rectangular thin isotropic plate with a part-through surface crack of arbitrary orientation and position is performed by using the Kirchhoff plate theory. Simply supported (SSSS), clamped (CCCC) and simply supported–clamped (SCSC) boundary conditions are considered for the analysis. First, the governing differential equation of a cracked plate is formulated. A modified line spring model is then used to formulate the crack terms in the governing equation. Next, by the application of Burger's formulation, the differential equation is transformed into the well-known Duffing equation with cubic and quadratic nonlinearities. The Duffing equation is then solved by the method of multiple scales (MMS) to extract the frequency response curve. Natural frequencies are evaluated for different values of length, angle and position of a part-through surface crack. Some results are compared with the published literature. Amplitude variation with different values of length, angle and position of a part-through surface crack are presented, for all three types of the plate boundary conditions.     

7T大口径NbTi超导磁体降温通电实验

介绍了用于超导导体测试用超导磁体降温通电实验,降温采用500W@4.5K制冷机系统。300—10K直接采用冷He气循环冷却超导磁体,温度低于10K直接输入LHe。该磁体在4.2K温度下可通1000A的电流,其中心磁场为7T,储能为3M J。     

Analysis of current ramp for a high-temperature superconducting magnet

In this paper, an equivalent electrical circuit for response of a high-temperature superconductor (HTS) system for arbitrary time varying transport current is considered and as well as an analysis of the generated resistance losses is given. Also, for the pancake coil made with superconducting Bi-2223/AgMg tape, hysteresis behavior on the voltage-current curve is examined as a function of the current rate during ramp up and down at liquid nitrogen temperature. Behavior of voltage versus current is in good agreement with considered theory.     

光在光轴取向任意条件下的晶体表面透射率

为了分析一束光在晶体表面的能量损失以及两束折射光的能量比,给出了一种求解反射率和透射率的方法。讨论了光从各向同性介质入射到单轴晶体表面时的折射和反射,注意到了e光线与e光波方向的不同,e光折射率与e光波法线折射率的不同,得出了在界面处应该满足的边界方程。在晶体光轴取向任意的条件下,给出了表明各光束间能量关系的折射率和反射率的理论表达式,为晶体器件特性的研究提供了有力的理论工具。数值模拟表明:得到的结果满足能量守恒;反射到各向同性介质中的光的电场(或磁场)与原入射光的电场(或磁场)不再平行;光轴的取向和入射角的大小对折射的o光、e光的能量比有很大的影响。     

CCT型超导磁体结构分析

CCT(Canted-Cosine-Theta)型超导磁体为一种新型的磁体结构,它的导体轨迹符合一定的空间曲线方程,磁场则是由多层线圈组合而产生.超导线绕制在骨架的特定线槽中,导线之间由骨架隔开,以阻断电磁力的累积.利用磁体周期性轴向对称特点建立了有限元分析模型,对磁体在降温和加载电磁力作用下进行了结构分析,通过研制样...     

一种基于迈斯纳效应的超导电机的驱动力的计算

超导体的迈斯纳效应是超导体的特有的性质之一,超导驱动的电机正是利用超导体的这个性质而设计的一种新型电机,由于驱动原理与传统的电机有很大的不同,这种电机的驱动力的计算一直是这种超导电机设计中要解决的主要问题,针对一种结构的电机,利用理论分析和数值计算的方法计算了一种基于超导体迈斯纳效应的超导电机驱动力的大小,为这种电机的设计提供了主要依据。     

Preparing arbitrary mode superconducting LC entangled coherent state via a superconducting charge qubit

We design a pure solid-device comprised by LC circuits, which are coupled to superconducting charge qubit to entangle superconducting LC coherent modes. The operation time of the state of the system does not increase with the increase of the number of LC modes. Based on the measurement of charge states, an arbitrary mode of the state can be easily generated. A brief discussion about the experimental feasibility of the scheme is also shown.     

Critical fluctuations in a mesoscopic superconducting ring

The nonlocal magnetoconductivity fluctuations in a superconducting submicron ring, with radius comparable to the Ginzburg-Landau coherence length, are studied. The order parameter mode separation yields to the solution of the time-dependent Ginzburg-Landau equation and the paraconductivity Fourier components are calculated in the vicinity of the critical temperature, including the critical fluctuation region. The homogeneous component has a logarithmic singularity at T(c) while the other components are found to be not singular.     

Properties of high-Tc superconducting circular waveguides with Meissner boundary

The propagation properties of the TE-modes in a high-temperature superconducting circular waveguide using the Mei\ner boundary conditions on the wall are presented for the first time. The results show that now the normalized cutoff parameterk _c R, (whereR is the radius of the superconducting circular waveguide andk _c the cutoff wavenumber,) is dependent on the radius unlike conventional metallic circular waveguide whose normalized cutoff parameterk _c R is a constant for a given mode and the filled dielectrics. Instead of TE₁₁-mode now TE₀₁ mode becomes the dominant mode and the normal component of magnetic field for the dominant mode is not equal to zero on the wall. Other unique results of high-T _c superconducting circular waveguides are illustrated, too.supported by Deutscher Akademischer Austauschdienst (DAAD)