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Vortices in Long Josephson Junctions.

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Annual rept. 16 Nov 86-14 Nov 87,

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Research during the second year of this grant extended the studies begun during the first year on fabrication and modeling of long Josephson junction structures. The Nb-Pb technology, although reliable, is not versatile enough for proposed multilayer structures and considerable effort was expended in the development of an all Nb and a parallel all NbN technology. This effort is not over but recently we were able to demonstrate an all NbN vortex flow transistor possessing superior properties to the Nb-Pb version. New progress was made toward solution of the problems of high frequency testing of the very low impedance vortex flow transistor and towards determination of its potential for high frequency applications. It was demonstrated that the device exhibits active behavior in the form of a measurable transresistance out of frequencies of about 10 of the theoretical transit time cutoff frequency. Capability of higher frequency testing was developed with the design of novel new impedance matching structures. A new type of distributed amplifier was also proposed and modeled. Modeling of spatially nonuniform long junction structures resistance was necessary in order to obtain realistic simulations. The unusual magnetic field dependence we had seen in certain Nb-Pb VFT configurations is undergoing study with the design of new double junction NbN devices.

Subject Categories:

  • Electrical and Electronic Equipment
  • Quantum Theory and Relativity
  • Electricity and Magnetism

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