Berger Jorge
Department of Physics and Optical Engineering, Ort Braude College, 21982 Karmiel, Israel.
J Phys Condens Matter. 2017 Jul 26;29(29):29LT01. doi: 10.1088/1361-648X/aa75c4. Epub 2017 May 30.
The standard operation of a dc SQUID leads to oscillatory electric fields that emit electromagnetic radiation. We estimate the effect that this radiation could have on the measured sample. A stationary SQUID could be advantageous if the oscillation contribution to back action on the measured sample has to be avoided. We study a superconducting loop that encloses a magnetic flux, connected to a superconducting and to a normal electrode, when a fixed electric current between the electrodes flows across the loop. The considered circuit does not contain Josephson junctions. We find that in a very broad range of parameters the current flow converges to a stationary regime, i.e. the densities of normal current and of supercurrent become functions of position only, independent of time. The potential difference between the electrodes depends on the magnetic flux, so that measuring this voltage would provide information on the enclosed flux. The influence of thermal noise was estimated. The sizes of the voltage and of the power dissipation could be appropriate for the design of a practical fluxmeter. We found narrow ranges of flux at which the voltage varies sharply with the flux.
直流超导量子干涉仪（dc SQUID）的标准操作会产生振荡电场，进而发射电磁辐射。我们估算了这种辐射可能对被测样品产生的影响。如果必须避免振荡对被测样品的反作用，那么静态超导量子干涉仪可能具有优势。我们研究了一个包围磁通量的超导环，该超导环连接到一个超导电极和一个正常电极，当电极之间的固定电流流过该环时。所考虑的电路不包含约瑟夫森结。我们发现，在非常广泛的参数范围内，电流流动会收敛到一个稳定状态，即正常电流密度和超电流密度仅成为位置的函数，与时间无关。电极之间的电位差取决于磁通量，因此测量该电压将提供有关所包围磁通量的信息。我们估算了热噪声的影响。电压和功耗的大小可能适合实际磁通计的设计。我们发现了磁通的狭窄范围，在这些范围内电压随磁通急剧变化。
