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| Author |
Ожегов, Р.В.; Окунев, О.В.; Гольцман, Г.Н. |
| Title |
Флуктуационная чувствительность сверхпроводящего болометрического смесителя на эффекте разогрева электронного газа |
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Journal Article |
| Year |
2009 |
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Радиотехника |
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3 |
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120-124 |
| Keywords |
смеситель на горячих электронах; флуктуационная чувствительность; тепловизор терагерцевого диапазона частот; hot-electron bolometer mixer; Imaging system; Noise equivalent temperature difference; Heterodyne receiver; Terahertz range |
| Abstract |
Interest in research in the terahertz range is driven by a great number of various applications, where terahertz instruments may play a leading role. To name just a few, such applications include study of the cosmic microwave background radiation and the distribution of the dark matter, medicine, navigation, fire alarm, security systems and environmental monitoring. The paper discusses the possibility of using a receiver based on the hot-electron effect in superconducting films as an imaging system. We present the results of the noise equivalent temperature difference (NETD) measurements performed with a hot-electron bolometer mixer made from a thin superconducting film. The receiver with a noise temperature of ~ 3800 K at a local oscillator frequency of 300 GHz a bandwidth of 500 MHz and an integration time of 1 s has offered an NETD of 0.5 K. We have also developed a technique that enabled us to reduce the contribution of the mixer gain fluctuations to the overall system instability. As of this writing, the above value of the NETD is the lowest value offered for this type of receiver, which indicates the possibility to use such receivers in real-time imaging systems. The technique offered in the paper for achieving the limiting value of the NETD offers an alternative to the phase-locking scheme.
Представены результаты измерения флуктуационной чувствительности (NETD – noise equivalent temperature difference) болометрического смесителя на эффекте разогрева электронного газа в тонких сверхпроводящих пленках. Получено предельное значение NETD, равное 0,5 К, при шумовой температуре приемника 3800 К, ширине полосы преобразования 500 МГц, постоянной времени 1 с и частоте гетеродина 300 ГГц. Разработана методика достижения предельной флуктуационной чувствительности, позволяющая избежать влияния нестабильности коэффициента преобразования смесителя. |
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RPLAB @ gujma @ |
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728 |
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Deang, Jennifer; Du, Qiang; Gunzburger, Max D. |
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Modeling and computation of random thermal fluctuations and material defects in the Ginzburg–Landau model for superconductivity |
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Journal Article |
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2002 |
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J. Comp. Phys. |
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181 |
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1 |
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45-67 |
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noise; superconductivity; finite element methods; fluctuations. |
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It is well known that thermal fluctuations and material impurities affect the motion of vortices in superconductors. These effects are modeled by variants of a time-dependent Ginzburg-Landau model containing either additive or multiplicative noise. Numerical computations are presented that illustrate the effects that noise has on the dynamics of vortex nucleation and vortex motion. For an additive noise model with relatively low variances, it is found that the vortices form a quasi-steady-state lattice in which the vortex core sizes remain roughly fixed but their positions vibrate. Two multiplicative noise models are considered. For one model having relatively long-range order, the sizes of the vortex cores vary in time and from one vortex to another. Finally, for the additive noise case, we show that as the variance of the noise tends to zero, solutions of the stochastic time-dependent Ginzburg-Landau equations converge to solutions of the corresponding equations with no noise. |
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758 |
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Hoevers, H. F. C.; Bento, A. C.; Bruijn, M. P.; Gottardi, L.; Korevaar, M. A. N.; Mels, W. A.; de Korte, P. A. J. |
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Thermal fluctuation noise in a voltage biased superconducting transition edge thermometer |
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Journal Article |
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2000 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
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77 |
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26 |
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4421-4424 |
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TES; bolometer; thermal fluctuation noise; TFN |
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The current noise at the output of a microcalorimeter with a voltage biased superconducting transition edge thermometer is studied in detail. In addition to the two well-known noise sources: thermal fluctuation noise from the heat link to the bath and Johnson noise from the resistive thermometer, a third noise source strongly correlated with the steepness of the thermometer is required to fit the measured noise spectra. Thermal fluctuation noise, originating in the thermometer itself, fully explains the additional noise. A simple model provides quantitative agreement between the observed and calculated noise spectra for all bias points in the superconducting transition. |
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RPLAB @ gujma @ |
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759 |
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Burke, P. J.; Schoelkopf, R. J.; Prober, D. E.; Skalare, A.; Karasik, B. S.; Gaidis, M. C.; McGrath, W. R.; Bumble, B.; Leduc, H. G. |
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Spectrum of thermal fluctuation noise in diffusion and phonon cooled hot-electron mixers |
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Journal Article |
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1998 |
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Applied Physics Letters |
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Appl. Phys. Lett. |
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72 |
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12 |
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1516-1518 |
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HEB mixer; thermal fluctuation noise; TFN |
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A systematic study of the intermediate frequency noise bandwidth of Nb thin-film superconducting hot-electron bolometers is presented. We have measured the spectrum of the output noise as well as the conversion efficiency over a very broad intermediate frequency range (from 0.1 to 7.5 GHz) for devices varying in length from 0.08 μm to 3 μm. Local oscillator and rf signals from 8 to 40 GHz were used. For a device of a given length, the spectrum of the output noise and the conversion efficiency behave similarly for intermediate frequencies less than the gain bandwidth, in accordance with a simple thermal model for both the mixing and thermal fluctuation noise. For higher intermediate frequencies the conversion efficiency decreases; in contrast, the noise decreases but has a second contribution which dominates at higher frequency. The noise bandwidth is larger than the gain bandwidth, and the mixer noise is low, between 120 and 530 K (double side band). |
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RPLAB @ gujma @ |
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760 |
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Kooi, Jacob Willem |
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Advanced receivers for submillimeter and far infrared astronomy |
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Book Whole |
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2008 |
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University of Groningen |
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RUG |
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HEB, SIS, TES, NEP, noise temperature, IF bandwidth, waveguide, impedance, conversion gain, FTS, integrated array, stability, Allan variance, multi-layer antireflection coating |
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Doctoral thesis |
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978-90-367-3653-4 |
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881 |
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