高压氦风机的主要技术特点及运行情况

介绍了用于高压氦气试验回路的二级涡轮式氦气循环风机，由于采用了平衡结构、气动轴承、置入式电机、抽气冷却和交直流机组调速等手段，该风机具有轴向推力小、无油、无动密封、不引入其它介的南和调速方便等特点，本文将这些特点和高温气冷堆一回路氦气风机的技术要求作了比较。     

Preparation of high Tc (Yb,Y)Ba2Cu3O7-δ thin films by co-evaporation from effusion cells

We have prepared superconducting thin films of (Yb,Y)Ba₂Cu₃O_7-δ by evaporation of copper, ytterbium or yttrium, and barium fluoride from Knudsen effusion cells. A simple two chamber vacuum system produced stable evaporation rates of 5–10 nm/min using various Knudsen cells without realtime feedback control. Excellent stoichiometry was obtained in the films by optimizing the deposition of Cu from a dual filament cell, Yb from a single filament cell and Y and BaF₂ from high temperature cells. Films were deposited mainly on SrTiO₃ substrates at temperatures ranging from 120 to 600° C and O₂ partial pressure up to 1.5 ⋻ 10⁻⁵ Torr. Post deposition anneals in O₂ and O₂ + H₂O produced films with room temperature resistivities as low as 227μΩ-cm andT _c (R = 0) at 91 K. Films were characterized using x-ray diffractometry, Rutherford backscattering spectrometry, energy dispersive x-ray analysis, scanning electron microscopy as well as electronic transport measurements.     

Losses in a twisted multifilamentary superconducting composite submitted to any space and time variations of the electromagnetic surrounding

Using a circuit model, loss calculations have been carried out for coils and short samples, made of twisted multifilamentary composites or flat braided cables, which undergo any space and time-variations of the magnetic induction, of the transport current and of the temperature. This model has been tested by measuring losses in short samples submitted to a rotating magnetic field and to a longitudinal magnetic field and in solenoids and ‘special coils’ which look like small Tokamaks, where the composite which carries a time dependent current, is submitted to simultaneous transverse and longitudinal magnetic induction changes. Experimental and theoretical values are in good agreement within about 20% for hysteretic losses and for eddy current losses.     

Fabrication of Nb3Sn superconductors by the solid-liquid diffusion method using Sn rich CuSn alloy

Superconducting composite wires having thick Nb₃Sn layers (? 20 μm) and high current carrying capacities were fabricated by the diffusion reaction between Nb (solid) and Sn rich CuSn alloy (liquid): the solid-liquid diffusion method. Composite wires with a fine inner core of Cu 12 at % Sn alloy surrounded by Nb were produced by cold drawing and heat treated at about 700°C. The Sn rich intermetallic compounds which formed initially were transformed to Nb₃Sn in 50 ～ 100 h, as the Cu concentration in the CuSn alloy core increased due to the consumption of Sn. The process produced thick Nb₃Sn layers, in comparison with the bronze method, because of the high Sn content in CuSn alloy core. The mechanism of enhanced Nb₃Sn formation by Cu was also studied, and it was clarified that the Cu in CuSn alloy lowers the activity of Sn so that the formation of Sn poor intermetallic compounds Nb₃Sn becomes advantageous in the diffusion reaction as compared with other Sn rich compounds.     

Multifilamentary superconducting materials for large scale applications

The February 1971 edition of this journal carried a ten page article by the author and his colleagues reviewing the then ‘state of the art’ in multifilamentary superconducting composites.¹ At the time we attempted to cover in a fairly comprehensive manner the first decade of development of these materials since the construction of the first high field superconducting magnet.² Now more than another decade of development has passed and obviously the field can no longer be reviewed comprehensively in the same few pages. This article will attempt to give a brief overview of these materials from the point of view of one engaged in their development and supply for large applications. Hopefully, the references to books,^3,4 review articles,^5,6 and the proceedings of the various conferences^7–11 will serve as a source of further information for those who require more details.     

Mathematical Model of Ni3Al Compound Synthesis from Powder Mixture Under Pressure

The mathematical model of nonisothermal chemical synthesis of a 3Ni + Al two-component powder mixture in the thermal explosion regime under condition of forced densification by an external load has been constructed. Influence of applied pressure on completeness of the Ni₃Al intermetallic synthesis and material density was investigated by a numerical method. It was determined that during existence of the mixture in solid-liquid state the greatest degree of conversion and maximum densification of the synthesized product were reached at moderate pressures.     

New Thorium-Doped YBa2(1 ? x)SrxThxCu3O7 ? δ High-Tc Superconductors

Thorium-doped YBa_{2(1 – x)}Sr _x Th _x Cu₃O_{7 –} high-T _c ceramic superconductors (with x = 0.1, 0.15, 0.2, and 0.3) have been carefully prepared by the usual ceramic procedure and sintering technique, with intermediate grindings and annealing under a stream of compressed-air atmosphere. The structural parameters of the prepared samples are calculated and interpreted using X-ray diffraction analysis. The electrical properties are also carefully investigated in the present work using the four-probe technique. Results obtained were compared, explained, interpreted, and discussed in detail; meanwhile, the major goal of the present work and promising deductions are attained at.     

Theoretical Analysis of Responsivity of a High Temperature Superconductor (HTSC)—Hot Electron Far Infrared Bolometer (HEFIB)

The use of hot electron phenomena is very attractive from the point of view of making fast, high performance infrared detectors for the giga hertz – tera hertz frequency range. Low temperature superconductors at present provide efficient materials in this area but with the constraint of using nano meter thin films and milli Kelvin operating temperatures. This paper explores the possibility of exploiting high temperature superconductor materials for the hot electron far infrared bolometer, using 77 K as the operating temperature and micron thick films. Two temperature (electron and phonon) time dependent heat transfer equations involving electron and phonon interactions within the sensor lattice and the heat exchange with the substrate are developed and solved. A detailed mathematical analytic expression for the responsivity is presented. Computational analysis of responsivity choosing various combinations of involved parameters is carried out. Some important results for a 1 thick sensor of 1 mm × 1 mm crosssectional area are presented.     

铋铜氧化物超导体的霍尔效应

测量了铋铜氧化物超导体的霍尔系数实验结果及其温度依赖性．对不同样品进行了Ｘ射线结构分析，给出了载流子浓度与相结构之间关系．发现，转变温度较低的（２２１２）相样品的载流浓度较高，平均每个ＣＵ离子有０．２１个空穴．     

高温超导及其在电力工业中的应用

简要介绍了超导电力技术的一些基本概念,高温超导的特性,高温超导装置的发展过程、特点及其在电力系统中应用的优越性能.