Browse Prior Art Database

Critical Current Measuring Method

IP.com Disclosure Number: IPCOM000045155D
Original Publication Date: 1983-Feb-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Arnett, PC: AUTHOR

Abstract

Establishing a standing wave in a circuit, and scanning the peak amplitude of the standing wave through the circuit by varying the frequency, makes it possible to identify a failing element in a superconducting circuit in its operating environment.

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Critical Current Measuring Method

Establishing a standing wave in a circuit, and scanning the peak amplitude of the standing wave through the circuit by varying the frequency, makes it possible to identify a failing element in a superconducting circuit in its operating environment.

Superconducting circuits that are intended to carry large currents may fail because some element in the circuit goes normal at a current below the operating level. Identification of the failing element normally involves placing each element of the circuit in its own test site which unnecessarily consumes test leads and, in some cases, creates an artificial electrical environment for the element.

This method is an AC critical current test in which a standing wave is established in the circuit and the peak amplitude of the standing wave is scanned through the circuit, by varying the frequency of the AC signal, to identify the element with the low critical current. Normally, this involves only minor modifications to the original circuit.

Fig. 1 shows a representative circuit that has line segments of two different materials M1 and M2 connected by an M1-M2 contact, and with the M2 crossing a high inductance ground plane hole and an insulation step into a capacitor. Even if the circuit was originally terminated in a short or a resistor in the test the termination becomes an open to create a current zero at the termination of the circuit. Indicated in Fig. 1 is the standing wave envelope of the current amplitude with an open termination. As the frequency increases, the peak amplitude moves...