A Numerical Treatment of the Rf SQUID: II. Noise Temperature

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We investigate rf SQUIDs (Superconducting QUantum Interference Devices), coupled to a resonant input circuit, a readout tank circuit and a preamplifier, by numerically solving the corresponding Langevin equations and optimizing model parameters with respect to noise temperature. We also give approximate analytic solutions for the noise temperature, which we reduce to parameters of the SQUID and the tank circuit in the absence of the input circuit. The analytic solutions agree with numerical simulations of the full circuit to within 10%, and are similar to expressions used to calculate the noise temperature of dc SQUIDs. The best device performance is obtained ... continued below

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Kleiner, Reinhold; Koelle, Dieter & Clarke, John January 15, 2007.

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We investigate rf SQUIDs (Superconducting QUantum Interference Devices), coupled to a resonant input circuit, a readout tank circuit and a preamplifier, by numerically solving the corresponding Langevin equations and optimizing model parameters with respect to noise temperature. We also give approximate analytic solutions for the noise temperature, which we reduce to parameters of the SQUID and the tank circuit in the absence of the input circuit. The analytic solutions agree with numerical simulations of the full circuit to within 10%, and are similar to expressions used to calculate the noise temperature of dc SQUIDs. The best device performance is obtained when {beta}{sub L}{prime} {triple_bond} 2{pi}LI{sub 0}/{Phi}{sub 0} is 0.6-0.8; L is the SQUID inductance, I{sub 0} the junction critical current and F{sub 0} the flux quantum. For a tuned input circuit we find an optimal noise temperature T{sub N,opt} {approx} 3Tf/f{sub c}, where T, f and f{sub c} denote temperature, signal frequency and junction characteristic frequency, respectively. This value is only a factor of 2 larger than the optimal noise temperatures obtained by approximate analytic theories carried out previously in the limit {beta}{sub L}{prime} << 1. We study the dependence of the noise temperature on various model parameters, and give examples using realistic device parameters of the extent to which the intrinsic noise temperature can be realized experimentally.

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  • Journal Name: Journal of Low Temperature Physics; Journal Volume: 149; Journal Issue: 5-6; Related Information: Journal Publication Date: 12/2007

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  • Report No.: LBNL--62298-(II)
  • Grant Number: DE-AC02-05CH11231
  • DOI: 10.1007/s10909-007-9512-9 | External Link
  • Office of Scientific & Technical Information Report Number: 928721
  • Archival Resource Key: ark:/67531/metadc893820

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  • January 15, 2007

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  • Sept. 27, 2016, 1:39 a.m.

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Kleiner, Reinhold; Koelle, Dieter & Clarke, John. A Numerical Treatment of the Rf SQUID: II. Noise Temperature, article, January 15, 2007; United States. (digital.library.unt.edu/ark:/67531/metadc893820/: accessed August 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.