Accession Number : ADA190879

Title :   Fluxons and Order in Long Josephson Junctions.

Descriptive Note : Annual rept. 15 Nov 86-15 Nov 87,

Corporate Author : UTAH UNIV SALT LAKE CITY DEPT OF PHYSICS

Personal Author(s) : Symko, Orest G

PDF Url : ADA190879

Report Date : 28 Dec 1987

Pagination or Media Count : 27

Abstract : This report presents the research that was conducted in the year 1987 and some of the results were achieved. Low frequency fluctuations were studied at metastable states of long Josephson junctions biased at Fiske steps in a magnetic field. The fluctuations exhibit telegraph type of noise whose origin in the thermal noise of the internal resistance of the junction. Temperature dependence of these fluctuations shows that a thermal activation process is responsible for the behavior. At lower temperatures, quantum mechanical tunneling is expected to contribute to the fluctuations and experiments are presently being prepared for such studies down to 10 mK in a 3He-4He dilution refrigerator. The I-V curves for our junctions show a regular step structure due to cavity resonances and they also show subharmonic generation of period three due to the strong non-linearities of the dissipative system. Such subharmonic voltage steps are important because they normally precede chaotic behavior. A study was also made of the effects of geometry on fluxon motion and the results show that the device characteristics depend strongly on the bias current distribution in the junction. Studies for the next period are presented; they consist of experiments on fluxon quantum tunneling down to temperatures of 10 mK and effects of dissipation on such tunneling; conductance fluctuations in the junction will also be investigated.

Descriptors :   *JOSEPHSON JUNCTIONS, *MAGNETIC FIELDS, *METASTABLE STATE, *NOISE, *QUANTUM ELECTRONICS, *TUNNELING, *VARIATIONS, ACTIVATION, BIAS, CAVITY RESONATORS, CONDUCTIVITY, DISSIPATION, DISTRIBUTION, HARMONICS, INTERNAL, LOW FREQUENCY, LOW TEMPERATURE, NOISE(ELECTRICAL AND ELECTROMAGNETIC), QUANTUM THEORY, RESISTANCE, TELEGRAPH SYSTEMS, TEMPERATURE, THERMAL PROPERTIES, THERMAL RESISTANCE, VOLTAGE

Subject Categories : Quantum Theory and Relativity
      Electrical and Electronic Equipment
      Cybernetics

Distribution Statement : APPROVED FOR PUBLIC RELEASE