Heat Treatment of Nd1＋x Ba2-x Cu3o7-δ Superconductors

ComparedwithYBaCuOsuperconductor ,theNdBaCuOhashighercriticalcurrentdensity (Jc)inhighmagneticfield[1] .Jc equalsabout 1× 10 3A·cm- 2 in 10TfieldforNdBaCuOwhereasforYBaCuOitis 1× 10 2 A·cm- 2 atthesamefieldatliquidnitro gentemperature .NdBaCuOshowedhighergrowthspeedwhenBridgmenmethodwasusedtopreparetheorientedmaterial[2 ] .Ataspeedof 5 0mm·h- 1,thesamplecouldstillgethighdegreeoforientationforNdBaCuO ,butforYBaCuOthegrowthspeedwaslim itedtoonly 1or 2mm·h- 1.Becauseofitshighcr…     

Chemical bond properties and Moessbauer spectroscopy in （La1—xMx）2 CuO4（M=Ba,Sr）

By using the average band-gap model,the chemical bond properties of (La1-xMx)2CuO4(M=Ba,Sr) were calculated.The calculated covalencies for Cu-O and La-O bond in the compounds are 0.3 and 0.03 respectively.Moessbauer isomer shifts of ^57Fe doped in La2CuO4 and ^119Sn doped in La2CuO4 were calculated by using the chemical surrounding factor defined by covalency and electronic polarizability.Four valence state tin and three valence iron sites were identified in ^57Fe and ^119Sn doped La2CuO4.     

变形及退火处理后MgB2/Fe复合线的特性

MgB2 属于低TcBCS机制超导体 ,转变温度极易达到最佳值 39K ,且容易制备、不存在弱连接、具有高临界电流密度 ,而且几乎各项同性。所有这些性质 ,使它成为很有工程应用前途的超导体。制备MgB2 超导体线带最简单、最便宜的方法就是使用先位法 (exsitu)粉末装管技术 (PIT)。纯铁是最佳的外壳材料。将变形后的先位线带进行热处理 ,使MgB2 核心再结晶 ,电流密度提高到10 6A/cm2 (在 4 2K ,B =0T)。斯洛伐克电气工程学院最近研究了变形模式对MgB2 /Fe(Fe合金 )复合线传输电流密度、MgB2 与Fe(SS)壳之间的反应以及对这种复合线工程电流…     

Superconducting Busline Design for HT—7U Tokamak

Superconducting (SC) tokamak HT-7U has seven pairs of buslines connecting toroidal/Poloidal coils and the current leads,These SC buslines(SCBLs) share a common cryostat and are made of the calbe in conduit conductors(CICCs) arranged as a decoupling configuration.In order to reduce the heat loads conducted from the seven current leads with a capacity of 15kA during the magnets cooldown.the buslines with a much lower thermal conduction were employed in comparison with the current leads,and a special cooling loop was designed.     

科学家竞相研究的C60球状碳分子：C60的发现及其意义

过去人们只知道自然界存在石墨和金刚石两种纯碳形态。1985年9月美国化学家意外地发现纯碳的第三种形态:由60个碳原子组成的球状碳分子C_(60)。目前,全世界至少有50个研究小组竞相研究这种球状碳分子的结构和性能。美、日科学家巳研究出具有超导性的掺杂钾或铯、铷的C_(60),临界超导温度最高达33K。     

YBa2Cu3O7—δ超导体的磁穿透深度及相对能隙

根据测得的表面电阻R_S(T),通过在BCS理论框架中引入一个修正电导率,计算出YBa_2Cu_3O_(7-δ)(YBCO)超导材料的磁穿透深度和简约能隙与温度的相关性.引入修正电导率主要是根据YBCO超导体中电子结构表示Cu-O链对微波表面电阻的贡献.计算得到的磁穿透深度和相对能隙与实验结果符合得相当好.     

A Calculation of Steady Pressure Drop and an Analysis of HT—7U CICC

Under the condition of steady,the pressure drop of coolant is mainly caused by friction along the cable.in the CICC(cable-in-conduit-conductor).helium flow within the conductor consists of two parallel interconnected tubes.The velocity distribution has some differece between the central channel and conductor space.The region of Reynolds number is from 10^3 to 10^6.This paper describes the calculation of pressure drop of HT-7U CICC at various mass flows.It is assumed that the coolant flows in two parallel,rough tudes during the caclulation.