Washer rf SQUID Magnetometers with Coplanar Resonators at 77K

Zhang, Y.; Wolters, N.; Zeng, X. H.; Schubert, J.; Zander, W.; Soltner, H.; Yi, Huan; Banzet, M.; Rüders, F.; Braginski, A. I.

doi:10.1016/s0964-1807(98)00083-0

Cited by 32 publications

(28 citation statements)

References 10 publications

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“…As a replacement for the conventional LC tank circuit, which not only provides less V spp but also takes more space, thus hindering the front-end assembly, thin film superconducting coplanar resonators were used and investigated in the flip chip configuration [7,8]. In the case of the coplanar resonator, we used either an 8 mm rectangular (SR8) or a 13.4 mm circular (SR13) layout design with integrated flux concentrators [7]. The difference between the performances of the rf SQUIDs using these couplings was investigated.…”

Section: Coupling Techniques Advantages and Disadvantagesmentioning

confidence: 99%

Signal enhancement techniques for rf SQUID based magnetic imaging systems

Akram¹,

Fardmanesh²,

Schubert³

et al. 2006

Supercond. Sci. Technol.

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We have investigated the rf SQUID (radio-frequency superconducting quantum interference device) and its coupling to tank circuit configurations to achieve an optimal front-end assembly for sensitive and high spatial resolution magnetic imaging systems. The investigation of the YBCO rf SQUID coupling to the conventional LC tank circuits revealed that coupling from the back of the SQUID substrate enhances the SQUID signal while facilitating the front-end assembly configuration. The optimal thickness of the substrate material between the SQUID and the tank circuit is 0.4 mm for LaAlO 3 resulting in an increase of the SQUID flux-voltage transfer function signal, V spp , of 1.5 times, and 0.5 mm for SrTiO 3 with an increase of V spp of 1.62 times compared to that for direct face to face couplings. For rf coupling with a coplanar resonator, it has been found that the best configuration, in which a resonator is sandwiched between the SQUID substrate and the resonator substrate, provides a V spp about 3.4 times higher than that for the worse case where the resonator and the SQUID are coupled back to back. The use of a resonator leads to a limitation of the achievable spatial resolution due to its flux focusing characteristics. This resulted in a favouring of the use of the conventional tank circuits when considering the desired high spatial resolution. The effect of the YBCO flip chip magnetic shielding of the SQUIDs in the back-coupling with the LC tank circuit configuration has also been investigated, with a view to reducing the SQUID effective area to increase the spatial resolution and also for studying the effect of the coupling of various kinds of transformers to the SQUIDs. It is revealed that there is no very considerable change in the flux-voltage transfer function signal level with respect to the effective shield area, while the lowest working temperature of the SQUIDs was slightly shifted higher by a couple of degrees, depending on the shield area.

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Section: Coupling Techniques Advantages and Disadvantagesmentioning

confidence: 99%

Signal enhancement techniques for rf SQUID based magnetic imaging systems

Akram¹,

Fardmanesh²,

Schubert³

et al. 2006

Supercond. Sci. Technol.

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“…9 This was the first demonstration of an rf SQUID coupled to a planar structure. For HTS magnetometers, a major breakthrough was made by Zhang et al 10,11 in singlelayer technology with the use of a superconducting coplanar resonator as the tank circuit. Figure 1͑a͒ shows the schematic layout of a superconducting coplanar resonator.…”

Section: Experiments a Tank Circuitmentioning

confidence: 99%

“…Unloaded quality factors as high as 2ϫ10 4 can be obtained. 11 A washer rf SQUID is coupled to the central hole of the superconducting flux concentrator by the flip-chip configuration, forming a magnetometer. A typical magnetic field noise measured for magnetometers fabricated on a 10ϫ10 mm 2 substrate was 30 fT/Hz 1/2 in the white noise regime.…”

Section: Experiments a Tank Circuitmentioning

confidence: 99%

Superconducting multiturn flux transformers for radio frequency superconducting quantum interference devices

Yi¹,

Zhang²,

Schubert³

et al. 2000

Journal of Applied Physics

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This article describes three planar layouts of superconducting multiturn flux transformers integrated with a coplanar resonator for radio frequency ͑rf͒ superconducting quantum interference device ͑SQUID͒ magnetometers. The best magnetic field noise values of 22 and 11.5 fT/Hz 1/2 in the white noise regime were obtained for the layout with two input coils and the layout with the labyrinth resonator, respectively. Excess low-frequency noise ͑about 200 fT/Hz 1/2 at 10 Hz͒ was present. Computer simulation showed that the loss in this trilayer system was dominated by the high loss tangent of the dielectric film used for the separation of the upper and lower superconducting films. The rf coupling coefficient k rf between the resonator and the flip-chip-coupled SQUID was also estimated. The values k rf 2 Ϸ14ϫ10 Ϫ3 obtained for the layout with two input coils, and k rf 2 Ϸ45 ϫ10 Ϫ3 for the layout with the labyrinth resonator were considerably higher than the typical value of k rf 2 Ϸ7ϫ10 Ϫ3 for the single-layer coplanar resonator. These high coupling coefficients have compensated the somewhat degraded unloaded quality factor of the resonator, thus securing the optimum operation of the rf SQUID.

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“…2 To further improve the field sensitivity, the use a superconducting flux transformer with a multiturn input coil coupled inductively to the SQUID is desirable. However, when the coplanar resonator was integrated with a multiturn flux transformer as shown in Fig.…”

Section: 2mentioning

confidence: 99%

Simulation of the superconducting multiturn flux transformer integrated with a coplanar resonator

Zhang

Klein

2000

Applied Physics Letters

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The analysis of the structure of a superconducting multiturn flux transformer integrated with a coplanar resonator for radio-frequency superconducting quantum interference devices is described. Electromagnetic simulations indicate that the loss is dominated by the high loss tangent of the dielectric film used for the separation of the upper and lower superconducting films. The simulated current distribution at its resonant frequency shows that the highest current density is distributed on the multiturn input coil. This current distribution leads to a very high loss when the loss tangent of the dielectric film is high. However, for the same loss tangent of the dielectric film, it is possible to get a reasonably high unloaded quality factor by providing a normal shunt for the multiturn input coil.

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Washer rf SQUID Magnetometers with Coplanar Resonators at 77K

Cited by 32 publications

References 10 publications

Signal enhancement techniques for rf SQUID based magnetic imaging systems

Signal enhancement techniques for rf SQUID based magnetic imaging systems

Superconducting multiturn flux transformers for radio frequency superconducting quantum interference devices

Simulation of the superconducting multiturn flux transformer integrated with a coplanar resonator

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