The busbar system for Wendelstein 7-X prepared for assembly and operational loads

Forschungszentrum Jülich has taken over the design, manufacturing and assembly of the superconducting busbar system for the stellarator Wendelstein 7-X. This includes the busbars itself, the support structure consisting of supports and clamps, and the joints for electrical and hydraulic connection of the busbars and coil terminals. Apart from providing the required electrical connection scheme, the busbar system has to be designed for relevant electrical and mechanical loads. Numerous interfaces and geometric boundary conditions define the confined space to accommodate the busbars and their support elements. This article describes how the individual challenges to engineering have been met in the course of the project. This includes design concepts and the method for iterative design of supports with respect to the individual load distribution caused by the supports itself.     

Output properties of fiber optic sensor for micro-displacement measurement at 77 K and 4.2 K

Fiber optic sensors for micro-displacement measurement are applied to displacement measurement of superconductors. Output characteristics of a fiber optic sensor were measured at 77 K and 4.2 K. The results show that the linearity between output voltage ratio and displacement is good both at 77 K and at 4.2 K, and the sensitivity at 77 K is higher than that at 4.2 K.     

Y-Ba-Cu-O超导涂层的研制

用等离子喷涂工艺制备了 Y-Ba-Cu-O 高临界温度超导涂层,涂层的初始转变温度为101K、零电阻温度为86K。电阻率与磁化率的测量结果表明这种超导涂层具有与烧结超导块体相类似的性能,X 光衍射谱显示出涂层主要由 YBa_2Cu_3O_(?)单相化合物组成。     

核探测器的进展

本文介绍了几种基本核探测器的国外最新进展。     

An experimental investigation of YBa2Cu3O7 films at millimeter-wave frequencies

We have measured the millimeter-wave (100 GHz) surface resistance of high-quality laserdeposited YBa₂Cu₃O₇ films on SrTiO₃ and LaA10₃ substrates. Due to finite film thickness, radiation losses are important in the normal state and in the superconducting state nearT _c. These effects are calculated andR _s characteristic of the ohmics losses in the film are extracted from the data. The surface resistanceR _s drops rapidly atT _c, and a detailed comparison with calculations which include finite mean free path effects suggests a gap which exceeds the weak coupling BCS limit.     

High Tc Superconductor Theoretical Models and Electromagnetic Flux Characteristics

High Tc Superconductors (HTS) have special electromagnetic characteristics and phenomena. Effort has been made in order to theoretically understand the applied HTS superconductivity and HTS behaviors for practical applications, various theoretical models related to the HTS electromagnetic properties have been developed. The theoretical models and analytic methods are summarized with regard to understanding the HTS magnetic flux characteristic which is one of the most critical issues related to HTS applications such as for HTS magnetic levitation application.     

用SOI-Gel法制备Y_1Ba_2Cu_3O(7-δ)及超导电性

Y2O3、Ba2CO3；CuO作原料，将其制成相应的硝酸盐，利用柠檬酸强的蛰合作用，可以制得完、钡、铜稳定的配位化合物，形成溶胶，蒸发溶剂之后形成凝胶，加热到300℃时凝胶自燃，系统转变成Y2O3、Ba2CO3；CuO的超细粉体，经均匀混合后，压成413×1．5mm圆片，在930℃左右制成_1Ba_2Cu_3O(7-δ)超导体，经测试其零电阻转变温度为90．9K。     

A Numerical Treatment of the rf SQUID: I. General Properties and Noise Energy

We investigate the characteristics and noise performance of rf Superconducting Quantum Interference Devices (SQUIDs) by solving the corresponding Langevin equations numerically and optimizing the model parameters with respect to noise energy. After introducing the basic concepts of the numerical simulations, we give a detailed discussion of the performance of the SQUID as a function of all relevant parameters. The best performance is obtained in the crossover region between the dispersive and dissipative regimes, characterized by an inductance parameter β′ _L ≡2π LI ₀/Φ ₀≈1; L is the loop inductance, I ₀ the critical current of the Josephson junction, and Φ ₀ the flux quantum. In this regime, the lowest (intrinsic) values of noise energy are a factor of about 2 above previous estimates based on analytical approaches. However, several other analytical predictions, such as the inverse proportionality of the noise energy on the tank circuit quality factor and the square of the coupling coefficient between the tank circuit and the SQUID loop, could not be well reproduced. The optimized intrinsic noise energy of the rf SQUID is superior to that of the dc SQUID at all temperatures. Although for technologically achievable parameters this advantage shrinks, particularly at low thermal fluctuation levels, we give examples for realistic parameters that lead to a noise energy comparable to that of the dc SQUID even in this regime.      

Using ion implantation to adjust the transition temperature of superconducting films

We summarize a continuing investigation into using ion implantation to alter the transition temperature of superconducting thin films. The primary motivation for the work presented here was to study the feasibility of using magnetic ion doping to replace the bi-layer T_c control process currently used for certain cryogenic detector applications at National Institute for Standards and Technology. The results from work with various ion species implanted into aluminum, molybdenum, titanium and tungsten host films are presented.     

Dislocation Structures in a BulkPb－doped Bi－SrCa－Cu－O High Temperature Superconductor

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