大有效面积的高Tc rf SQUID

关键词： c rf SQUID')" href="#">高T_c rf SQUID 新型结构 大有效面积 磁通聚焦器     

高Tc双晶结rf SQUID

我们成功地在ＹＳＺ双晶衬底上制备了性能优良的高Ｔｃ 双晶结ｒｆ ＳＱＵＩＤ．在相同的测量条件下,得到与衬底台阶结ｒｆ ＳＱＵＩＤ 相同或相近的器件性能指标,磁场分辨率达到８４ｆＴ／Ｈｚ１／２ ．     

用于HTc rf SQUID的新型超导共面谐振器

在10mm*10mm*1mm的LaAlO3基片上设计和制成了一种新结构的800MHz超导共面谐振器,它可以和外尺寸9mm*9mm的垫片式rfSQUID器件实现有效的耦合,对于使用超导共面谐振器的rf SQUID,该方案为提高器件有效面积和磁场灵敏度提供了新的方法.     

高温rf SQUID的电压-电流特性曲线

对于采用电感耦合谐振回路的２００ＭＨｚ 高温超导ＹＢＣＯｒｆＳＱＵＩＤ 系统,我们测量了它的输出电压偏置电流幅度的特性曲线（ 即ＶＴＩｒｆ 曲线） ,发现当ｒｆ ＳＱＵＩＤ 工作在非回滞模式并且采用混频器作为检波器时,曲线的形状与通常所观察到的ＶＴＩｒｆ 曲线有显著的不同,我们认为这是相位信号和振幅信号共同作用的结果,根据这一思想我们选用高温超导ｒｆ ＳＱＵＩＤ参数并利用低温超导ｒｆ ＳＱＵＩＤ 理论进行一些模拟计算,获得和实验非常一致的结果,这说明低温超导ｒｆ ＳＱＵＩＤ 理论仍可用来解释一些高温超导ｒｆ ＳＱＵＩＤ实验现象     

基于USB传输的rf SQUID自动测量系统

本文报告了基于USB传输的计算机控制的射频超导量子干涉器(rf SQUID)自动控制测量系统的实现,系统可对rf SQUID的工作点进行调整和显示.本文将对系统工作原理、硬件电路和软件的设计做简要介绍.     

用于高TcrfSQUID的高Tc超导平面谐振器

我们设计并制备了用于高ＴｃｒｆＳＱＵＩＤ的超导平面谐振器，并测量了其谐振参数。实验表明，超导平面谐振器与分立元件式谐振器相比具有很高的品质因数，约为１０００－６０００。通过调节衬底材料，设计尺寸可以调节谐振频率。     

含有两个约瑟夫森结的射频SQUID的本征磁通噪声

我们研究了双结射频超导量子干涉器件（rf SQUID）的含时特性，给出了总磁通的动力学方程，并分析了在回滞模式和非回滞模式下的本征磁通噪声。结果显示：两个结的临界电流差别越大则越有助于获得小的本征噪声，在这种情况下，双结rf SQUID的本征磁通噪声会比单结rf SQUID的噪声稍大，但不超过一个数量级。     

用穿透场测量高Tc超导体样品有效钉扎势方法研究

在不同温度下测量了不同磁场扫描速率所对应的样品磁滞回线，据此定出样品的穿透场，利用穿透场与磁场扫描速率的关系得出了样品有效钉扎势，相对于其它方法而言，我们的方法具有数据处理的特点，用穿透场测量样品有效钉扎势，可能成为研究高温超导体的又一新方法。     

高Tc铜氧化物超导体的结晶化学和分块设计

本文简要地描述了已发现的铜氧化物超导体的不同结构类型,并按其中CuO平面的不同连接和分隔方式做了分块划分。利用这些连接、分隔的不同方式可以组合出新的结构类型。这种思想已被铅系的Pb-2222(PbBaSr(NdCe_2)Cu_3O_y),LaBa(NdCe)_2Cu_3O_y和Ta-1222等新化合物的设计和成功制备所证实。最后提出了寻求新型层状铜氧化物和超导新体系的可能方向。     

虚拟仪器在射频超导量子干涉仪控制电路中的应用

本文简要介绍LabVIEW开发的射频超导量子干涉器（rf SQUID）自动控制系统的虚拟仪器，系统可对超导量子干涉器的工作点进行调整和显示，实现了LabVIEW软件系统与第三方硬件的结合．本文将对系统工作原理、硬件电路组成和软件的设计做简要介绍．     

虚拟仪器在射频超导量子干涉仪控制电路中的应用

本文简要介绍LabVIEW开发的射频超导量子干涉器(rf SQUID)自动控制系统的虚拟仪器,系统可对超导量子干涉器的工作点进行调整和显示,实现了LabVIEW软件系统与第三方硬件的结合.本文将对系统工作原理、硬件电路组成和软件的设计做简要介绍.     

Development of 1.3GHz high-T-c rf SQUID

A new high-T_c (HT_c) rf SQUID working at around 1.3GHz has been developed to avoid electromagnetic interference such as growing mobile communication jamming. This new system works in a frequency range from 1.23 to 1.42GHz (centred at 1.3GHz), which is not occupied by commercial communication. The sensor used in the 1.3GHz rf SQUID is made of a HT_c coplanar superconducting resonator and a large-area HT_c superconducting film concentrator. We have achieved in the 1.3GHz HT_c rf SQUID system a minimal flux noise of 2.5×10^{-5}Φ_0/\sqrt{Hz} and a magnetic field sensitivity of 38fT/\sqrt{Hz} in white noise range, respectively. The effective area of the concentrator fabricated on a 15×15mm^2 substrate is 1.35mm^2. It is shown that the 1.3GHz rf SQUID system has a high field sensitivity. Design and implementation of 1.3GHz HT_c rf SQUID offers a promising direction of rf SQUID development for higher working frequency ranges.     

Development of 1.3GHz high-T-c rf SQUID

A new high-T_c (HT_c) rf SQUID working at around 1.3GHz has been developed to avoid electromagnetic interference such as growing mobile communication jamming. This new system works in a frequency range from 1.23 to 1.42GHz (centred at 1.3GHz), which is not occupied by commercial communication. The sensor used in the 1.3GHz rf SQUID is made of a HT_c coplanar superconducting resonator and a large-area HT_c superconducting film concentrator. We have achieved in the 1.3GHz HT_c rf SQUID system a minimal flux noise of 2.5×10^{-5}Φ_0/\sqrt{Hz} and a magnetic field sensitivity of 38fT/\sqrt{Hz} in white noise range, respectively. The effective area of the concentrator fabricated on a 15×15mm^2 substrate is 1.35mm^2. It is shown that the 1.3GHz rf SQUID system has a high field sensitivity. Design and implementation of 1.3GHz HT_c rf SQUID offers a promising direction of rf SQUID development for higher working frequency ranges.     

基于嵌入式系统的射频超导量子干涉仪控制系统

本文介绍了嵌入式系统在射频超导量子干涉仪控制系统中的应用,提出了嵌入式系统的整体方案,并对系统工作原理以及设计思想做了简要介绍.     

基于嵌入式系统的射频超导量子干涉仪控制系统

本文介绍了嵌入式系统在射频超导量子干涉仪控制系统中的应用，提出了嵌入式系统的整体方案，并对系统工作原理以及设计思想做了简要介绍．     

Peculiarities of rf SQUID response in finite magnetic fields

Single-layer washer-type high-T_c YBa₂Cu₃O_7−x rf SQUIDs with grain-boundary Josephson junctions, as well as low-T_c Nb rf SQUIDs with Nb–Al₂O₃–Nb tunnel junctions, have been investigated in finite magnetic fields. It was shown experimentally that the suppression of the critical current of the Josephson junction due to the magnetic field leads to a modulation of the amplitude of the SQUID output signal. The role of the “unwanted” junction in high-T_c rf SQUIDs, which is formed by the grain boundary running through the washer of the SQUIDs on bicrystal substrates, has also been clarified. The drop of the SQUID signal at a finite magnetic field is originated by the penetration of the magnetic field into the unwanted junction. Based on these results, a direct radio-frequency method for the determination of the first critical field H_c1 for long Josephson junctions has been developed.     

Observation of rf SQUID characteristics in YBCO bulk at 77 K

The online version of the original article can be found at     

Observation of rf SQUID characteristics in YBCO bulk at 77 K

RF SQUID behaviour due to grain boundary weak links in a bulk YBCO is observed at 77 K using modified commercial rf electronics. Porous samples with lowI _c are found to show this characteristic whereas dense samples with higherI _c do not show SQUID behaviour.V-B modulation characteristic is found to be better when the rf pumping frequency is kept slightly higher than the resonance frequency of the tank circuit. Designing of coil for tank circuit with appropriateQ has been found to be very crucial for seeing the SQUID behaviour. Estimation of parameters such as coupling constant, mutual inductance, inductance and radius of the SQUID loop, have been made and their significance is discussed. Flux noise spectrum of the bulk rf SQUID in flux locked mode is also reported.