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Strained Superconducting Switch

IP.com Disclosure Number: IPCOM000043395D
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Brady, MJ: AUTHOR [+2]

Abstract

This article relates generally to switchable superconducting devices and more particularly to superconducting alloys the critical currents of which change when subjected to strain. Nb3Sn, a Type II superconducting alloy, is affected by "in-situ" stress/strain. The parameters most sensitive to stress strain are the critical current Ic, the critical field Hc2, and the transition temperature 1,2 . The critical current (Ic) change in Nb3Sn as a function of strain provides a unique way of modulating the current, and has applications as (a) a new switching device and (b) as an acoustic detector. Films of Nb3Sn can be deposited in a pre-biased strain state utilizing ion beam deposition [3]. A small amount of induced strain will then cause a large change in critical current, allowing a reasonable current modulation.

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Strained Superconducting Switch

This article relates generally to switchable superconducting devices and more particularly to superconducting alloys the critical currents of which change when subjected to strain. Nb3Sn, a Type II superconducting alloy, is affected by "in-situ" stress/strain. The parameters most sensitive to stress strain are the critical current Ic, the critical field Hc2, and the transition temperature 1,2 . The critical current (Ic) change in Nb3Sn as a function of strain provides a unique way of modulating the current, and has applications as (a) a new switching device and (b) as an acoustic detector. Films of Nb3Sn can be deposited in a pre-biased strain state utilizing ion beam deposition [3]. A small amount of induced strain will then cause a large change in critical current, allowing a reasonable current modulation. This induced strain can be applied to the pre- strained film of Nb3Sn by coupling a surface acoustic wave (SAW), propagating on a piezoelectric substrate, into a deposited layer of Nb3Sn. Utilization of lithium niobate at cryogenic temperatures has been demonstrated [4]. Interdigital fingers deposited on the piezo- electric substrate act as the source of the surface acoustic wave.

This is depicted in Fig. 1. The modulation of the critical current is schematically shown in Fig. 2. The IV characteristics for weak link bridges is depicted in Fig. 3, with similar modulation possible with a tunnel junction (not shown) also shown in...