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Quasiparticle Injector/Extractor Pulse Generator

IP.com Disclosure Number: IPCOM000052449D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Faris, SM: AUTHOR

Abstract

This article relates generally to Josephson junction switching circuits and more specifically to a circuit incorporating Josephson junctions which injects and extracts energetic quasiparticles into a superconducting sample under investigation in the transient state on a picosecond time scale.

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Quasiparticle Injector/Extractor Pulse Generator

This article relates generally to Josephson junction switching circuits and more specifically to a circuit incorporating Josephson junctions which injects and extracts energetic quasiparticles into a superconducting sample under investigation in the transient state on a picosecond time scale.

A recently published josephson junction sampling technique [*] permits the measurement of waveforms in the cryogenic environment with picosecond resolution and high sensitivity. It was immediately recognized that such a technique is indispensible for the investigation of superconductivity in the transient state. The need for a versatile circuit which is capable of injecting quasiparticles into a sample under investigation in the picosecond time scale was also recognized. Such quasiparticles (electrons) have to be energetic enough to break pairs in the sample under investigation to be able to drive it far from equilibrium. Rapid changes in the system are then monitored by the above- mentioned sampling unit, making it possible to measure many dynamic parameters of the sample.

The circuit of the above figure is capable of injecting and extracting energetic quasiparticles at high speed. The waveform applied to a sample can be varied in shape and duration. The circuit can be triggered by room temperature control lines which have slow rise times (a few nanoseconds). The circuit shown includes a source which provides gate current Ig2 which flows initially through two serially disposed Josephson devices Q2. Devices Q2 are shunted by Josephson junction devices Q3 which are in series with a load L. Load L may be a thin film or other device under investigation. The voltage across...