用于心磁图测量的基于高温超导量子干涉仪磁强计的有源补偿

我们建立了一套基于高温超导量子干涉仪(SQUID)的可靠的、经济型的单通道心磁图(MCG)系统,该系统在一个简易的磁屏蔽室(MSR)中运行.实验结果表明,对于消除心磁测量中的环境噪声,简易磁屏蔽室和有源补偿相结合是一个很合适的方案,这种方案对心磁图的普及有实际的帮助.同时,本文给出了一个有源补偿的简单模型,并将计算结果与实验数据进行了比较.     

Vortices in Josephson arrays interacting with non-classical microwaves: The effect of dissipation

Vortices circulating in a ring made from a Josephson array in the insulating phase are studied. The ring contains a `dual Josephson junction' through which the vortices tunnel. External non-classical microwaves are coupled to the device. The time evolution of this two-mode fully quantum mechanical system is studied, taking into account the dissipation in the system. The effect of the quantum statistics of the photons on the quantum statistics of the vortices is discussed. Entropic calculations quantify the entanglement between the two systems. Quantum phenomena in the system are also studied through Wigner functions. After a certain time (which depends on the dissipation parameters) these quantum phenomena are destroyed due to dissipation. Received 21 October 2002 / Received in final form 11 February 2003 Published online 11 April 2003 RID="a" ID="a"e-mail: a.konstadopoulou@brad.ac.uk     

Magnetic field dependencies of the critical current and of the resonant modes of dc SQUIDs fabricated from superconductors with s + id order-parameter symmetries

The magnetic field dependencies of the critical current and of the self-induced resonant modes of dc SQUIDs fabricated from superconductors with s + id order parameter symmetries are calculated. Combining the complementary results of the two dependencies, an unambiguous determination of the ratio of the s and d wave components is possible. Two cases of SQUID configurations are analyzed for which the flux coupled to the two Josephson junctions of the dc SQUID is either negligible or significant.