基于高温超导量子干涉仪的超低场核磁共振成像研究

对基于高温超导量子干涉仪的低场核磁共振成像进行了较为系统的探索.首先对低场核磁共振系统进行了改进和完善,使得装置能够用于成像实验.在此基础上进行了一维、二维成像实验并取得了成功.二维成像分别采用了直接背投影成像法和傅里叶变换重建法.采用直接背投影方法成功获得了不同水样品分布的图形并与实物符合较好,同时还尝试对生物样品如青椒和芹菜的切片进行了成像,也得到了符合原物的二维投影像.尝试用傅里叶变换法对水样品进行成像,得到的图形能够显示样品轮廓,但信噪比偏低.对两种二维成像方法进行了比较和讨论.     

C波段卫星通信中高温超导双工器的研制

文中提出一种紧凑型的c波段高温超导双工器的设计方法,利用一个公共输入节点和两个带通滤波器组成双工器。公共节点是由中心谐振频率处在防护频带上的开环微带环实现,每个带通滤波器都包括四个矩形螺旋线谐振器。双工器的中心频率为4GHz,带宽为0.23GHz。该双工器采用氧化镁衬底双面镝钡铜氧高温超导薄膜加工而成,薄膜上下表面均溅射金保护层。将超导双工器封装在铜制屏蔽盒中并在机械制冷机(77K温度条件)中测试。实验结果表明,每个信道的插入损耗低于0.1dB,两个信道间的隔离度超过40dB。仿真和实验结果达到很好的吻合,有效的说明了设计方法的正确性。     

ITER CC导体测试装置数据采集系统的设计与应用

系统介绍了ITER CC性能认证超导导体测试装置数据采集系统的硬件设计。该系统可以对温度、压力、流量、液位、电流、磁场、电阻、电压降等物理量进行测量,并能根据实际需要进行系统扩展。另外还对基于VC++6.0编程环境下的数据采集系统的程序设计进行了介绍。通过对软件和硬件的集成调试,该系统实现了高速高精度的数据采集。     

高温超导直流电缆现状

文中对高温超导直流电缆现状进行了介绍。高温超导直流电缆是用于直流输电的高温超导电缆。高温超导直流电缆发展相对落后于高温超导交流电缆,国际上示范项目也较少。但随着轻型直流输电应用的逐渐发展,高温超导直流电缆越来越引起人们的重视。高温超导直流电缆的本体结构和高温超导交流电缆本体结构类似。高温超导直流电缆具有输电损耗小、适合长距离输电、增加电网稳定等功能。比较适用于背靠背直流输电,工业直流输电,互联网数据中心直流供电,远距离、大容量直流输电等场合。此外,还介绍了目前国际上主要的超导直流电缆项目及研究机构情况。     

基于校园网的开放式物理实验教学及管理模式的研究与应用

在进行物理实验教学体系改革的基础上,研究基于校园网的开放式物理实验教学及管理模式,探索地方工科院校的物理实验教学改革模式并在实验教学中应用。     

含超导材料Cantor序列一维光子晶体的传输特性

利用传输矩阵法研究了按分形三分Cantor序列构成的一维超导光子晶体的传输特性。数值结果表明,与传统电介质材料构成的光子晶体的频谱不同,这种光子晶体频谱没有展现出自相似性。此外,当构成光子晶体的两种材料的光学厚度相同时,光子晶体的频谱具有明显的周期性,并且在光子带隙中间成对地出现缺陷模。这种特性可以用于设计通道滤波器。     

创建“开放式”物理课堂,提高教学有效性

如何在教学过程中,转变教学理念,立足长远,用当代教育观来教育和培养学生,把握学科重点和难点,合理选择教学模式和教学策略是新课标改革后给教师们留下的一道作业题.创建“开放式”物理教学课堂,增加师生教学互动,是为了引导学生自主合作学习,进行探究性学习,是提高教学质量的有效途径,可以帮助学生养成独立思考习惯、树立学无止境的观念,充分体现了新课程标准的根本理念.教师应在教学实践中,努力发掘学生的创新能力,发挥学生的主动性和创造性,构建丰富多彩、多元发展的物理课堂.     

Design and study of a high-current 5-cell superconducting rf cavity

The Advanced Photon Source （APS） at Argonne National Laboratory is considering the development of a superconducting linac-based fourth-generation hard X-ray source to meet future scientific needs of the hard X-ray user community. This work specifically focuses on the design of an optimized 5-cell superconducting radio-frequency structure well suited for a high-energy, high-beam-current energy recovery linac. The cavity design parameters are based on the APS storage ring nominal 7 GeV and 100 mA beam operation. A high-current 5-cell cw superconducting cavity operating at 1.4 GHz has been designed. In order to achieve a high current, the accelerating cavity shape has been optimized and large end-cell beam pipes have been adopted. The beam break-up threshold of the cavity has been estimated using the code TDBBU, which predicts a high threshold beam current for a 7 GeV energy recovery linac model. A copper prototype cavity has been fabricated that uses half-cell modules, initially assembled by clamping the cells together.     

Electron-phonon Coupling in Gallium-Doped Germanium

The electronic structure, lattice dynamics, and electron-phonon coupling of gallium-doped germanium are inves- tigated using ab initio supercell methods. Our results indicate the superconducting transition in gallium-doped germanium can be explained within a standard phonon mediated mechanism. The contribution of acoustic modes to the coupling constant A almost entirely comes from Ga related modes, and - 25% to λ. The calculated coupling constant is 0.35 and the corresponding transition temperature is 0.44 K for the gallium-doped germanium with 6.25% gallium content using Coulomb pseudopotential μ^＊ = 0.1, in agreement well with the experimental data.     

Overdoped High Current Density Bi2-xPbxSr2CaCu2O8＋δ Intrinsic Josephson Junction Mesas and Their Switching Current Distributions

Small and thin mesa structures of intrinsic Josephson junctions 1- 2μm on a side and 1.5-7.5 nm in thickness are fabricated from single crystals of Bi2-xPbxSr2CaCu2O8＋δ with a nominal Pb content x from 0.2 to 0.5. The Josephson critical current density jc is found to be pronouncedly large, ranging from 10 to 50 kA/cm^2. Switching current probability measurements for these mesa samples show an indication of a crossover to the macroscopic quantum tunneling region.