The influence of a planar input coil on the V-1 characteristics of a dc-SQUID (superconducting quantum interference device) has been analyzed by means of computation and experimental investigation. An extended electrical model of the input coil based on transmission lines has been proposed. The frequency behavior of this model has been validated with an expanded copper model. The V-I characteristics of dc-SQUID's have been calculated with this extended circuit model using a SPICE-type circuit analysis program. The results have been compared with measurements of niobium dc-SQUID'S. In this paper the relationship between the V-I Characteristics of the SQUID and the coupling impedance of the washer is demonstrated.
Single layer YBaCuO-Gradiometer galvanically coupled to DC-SQUIDS were prepared on bicrystal substrates. The devices were operated at 77 K without any shielding. The best performance obtained was a field gradient resolution of 0,s pTlemdHz for a device with a baseline of 7 mm and a pickup-area of 2 cm2.
For many SQUID applications such as biomagnetism or non-destructive evaluation it is convenient or even necessary to work without the restrictions of a magnetically shielded room. This contribution deals with two sensors appropriate for this purpose.In the first concept we present a flip chip arrangement of a single-layer flux transformer and a single-layer SQUID, taking advantage of a simple technology. The SQUID was prepared on a 15 × 15 mm 2 SrTiO 3 24 • bicrystal and located in the common line of two-parallel-loop arrangements. The flipped antenna was designed as a two-parallel-loop gradiometer with 26 mm baseline on a 10 × 40 mm 2 LaAlO 3 single-crystal substrate. A field gradient sensitivity of 1 nT cm −1 0 was obtained. We could demonstrate a field gradient resolution of 20 fT cm −1 Hz 1/2 at 1 kHz in an unshielded environment.In the second concept we integrated both the flux antenna and the SQUID on a SrTiO 3 bicrystal. The tighter coupling scheme results in smaller devices for similar field gradient sensitivities. The integrated SQUID is designed as a 3 × 8 mm 2 device on a 10 × 10 mm 2 bicrystal substrate. The remaining space is used for test structures and SQUIDs without antennae, in order to control the technology as well as the SQUID design. Parallel processed dummy substrates were used to monitor the quality of film growth by x-ray analysis. The quality of our SQUID design will be discussed on the basis of the measured field gradient sensitivity and noise. The reliability of the devices is demonstrated by an NDE type measurement.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.