Browse Prior Art Database

Power Dwell Using Vortex Flow of Long Josephson Junctions

IP.com Disclosure Number: IPCOM000045348D
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 3 page(s) / 50K

Publishing Venue

IBM

Related People

Kaplan, SB: AUTHOR

Abstract

Vortex flow in a long Josephson junction may be used to provide power dwell, needed to minimize the punchthrough problem, without the need for auxiliary circuits.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Power Dwell Using Vortex Flow of Long Josephson Junctions

Vortex flow in a long Josephson junction may be used to provide power dwell, needed to minimize the punchthrough problem, without the need for auxiliary circuits.

One method of reducing punchthrough in latching Josephson circuits is to synthesize a power supply waveform with a dwell near zero voltage. Previous proposals for providing this dwell make use of auxiliary circuitry which decreases circuit density and tends to increase power consumption. This method takes advantage of the properties of the long Josephson junction to achieve the same effect without any auxiliary circuitry.

A Josephson junction of length 1 > 2 Pi Lambda(j) (2 pi times the Josephson penetration depth) may support the continuous motion of Josephson vortices when a control current I(c) places at least one vortex in the junction and the supply current I(s) is large enough to overcome the dissipative forces which slow down the vortices. This results in a non-linear "vortex-flow" branch in the currentvoltage characteristic of the junction. The voltage position of this branch increases with I(c) as more vortices are placed in the junction. The dynamic resistance is a sharply decreasing function of the supply current. When I(s) increases to the point where the vortices travel with the maximum velocity allowed in the junction cavity, the operating point switches to the quasi-particle tunneling characteristic.

First, consider a single regulator junction with the structure shown in Figs. 1A and 1B. The base electrode 1 and counterelectrode 3 are separated by the tunnel barrier 2. A control line 4 is deposited atop the structure and is electrically isolated by an insulating layer (not shown). When a sinusoidal I(s) and constant I(c) are applied as shown, the current-voltage characteristic shown in Fig. 2 is traced. The initial voltage across the load is zero until the zero voltage Josephson current 5 is exceeded by I(s). If I(c) is large enough to provide a vortex-flow branch, the operating point then switches to the branch 6 shown in Fig. 2. The voltage across the load remains small until the maximum current of this branch is exceeded. This is the mechanism that causes a...