A comparison is made between the critical current (Ic) versus bending strain and axial strain of superconducting multi-filamentary Bi2Sr2Ca2Cu3Ox (Bi-2223) AgMg sheathed tapes. For the bending strain measurement the tape is sandwiched between a curved base and cover plate. Six sets of bending plates introduce bending strains ranging from 0% to 1.0%. The measurements show a slight decrease in Ic after the first bending step after which the degradation becomes more pronounced. The Ic in a bent conductor is calculated assuming a linear axial strain profile inside the conductor. For this calculation the Ic degradation determined in an axial compression and elongation experiment is used. The model predicts an immediate decrease of Ic, caused by the compressive strain dependence. There is a good agreement (within 5%) between the measured data and the calculated values. Based on this good agreement it can be concluded that a possible shift in the neutral line or the formation of additional cracks due to bending has no significant influence on the Ic degradation. It is concluded that the influence of thermal contraction is crucial for a good calculation.
Abstra&Electricfield effect devices and quasiparticle injection effect devices are good candidates for the realization of three terminal devices from high-T, materials, since they take explicit advantage of the low carrier concentration in these compounds. We describe the fabrication and operation of both types of devices, and discuss their performance as transistor-like elements.
The sensitivity of an overlapped tube cryogenic current comparator (CCC), coupled to a SQUID by means of a flux transformer, is calculated and compared with measurements. Conditions for optimal coupling between the CCC and the SQUID are derived. Based on these, an optimal CCC for precision measurements of very small currents in the nanoampere range has been designed. The paper describes the construction and testing of some parts of the system. An essential element is a home-made dc SQUID with low current noise and low inductance input coil equal to that of the CCC overlapped shield, which we use as sensing coil.
Abstract-The magnetic field dependence of the critical current in (Bi Pb) 2 Sr 2 Ca 2 Cu 3 O 10+ tapes is compared with the magnetization response of isolated grains extracted from the tapes. Special attention is paid to the low-field behavior. The goal of the experiment is to test the widely-used hypothesis that current paths in these tapes contain both weak-and strong-linked branches, which in low field act in parallel. The data agree with this hypothesis; at temperatures above 50 K the powder magnetization drops off exponentially from the self-field to the irreversibility field, while the transport and magnetization currents in the intact tapes show an extra low-field component. Below 50 K the powder behavior becomes less straightforward, but the parallel-path picture in the tapes still holds.
Dc SQUIDS with an optimal input coil inductance have been developed for a Cryogenic Current Comparator (CCC) that is used for the calibration of electrical standards. We studied a series of SQUIDS with input inductances in the range from 20-160 nH. The electrical properties like input current noise and flux-to-voltage transfer have been investigated. The CCC is an overlapping tube configuration and the tube itself is used as the pick-up coil of the flux transformer circuit of the SQUID. The coupling between CCC and flux transformer is in this case ideal and should have an optimal value when the effective overlapping tube inductance, typically in the range from 10-100 nH, equals that of the SQUID input coil (flux transformer theory). To compare with theory, sensitivity measurements on the SQUID-CCC have been performed in a special set-up where the effective overlapping tube inductance can be modified placing the CCC in a superconducting shield at various distances.
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.