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Hansen, Lene; Jørgensen, H.E.; Nørgaard-Nielsen, Hans Ulrik; Pedersen, Kenneth; Goudfrooij, P.; Linden-Vornle, M.J.D. |
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ISO far-infrared observations of rich galaxy clusters III. Abell 2029, Abell 2052, Abell 2142 |
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Journal Article |
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2000 |
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Astron. Astrophys. |
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A&A |
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362 |
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133-137 |
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A sample of five rich galaxy clusters has been mapped by ISO at 60 μm, 100 μm, 135 μm, and 200 μm using the PHT-C camera. In previous papers Abell 2670 and Sersic 159-03 were discussed. Here we present the results for Abell 2029, Abell 2052, and Abell 2142. The conclusion of the survey is that the relatively small fields (approximate to 60 square are minutes) are structured with filaments or superpositions of point sources. In some cases point sources (approximate to 0.1 Jy) can be identified with cluster galaxies. An attempt to demonstrate infrared emission from dust in the cooling flows (due to star formation) was inconclusive. |
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RPLAB @ s @ |
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456 |
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Wright, E. L.; Reese, E. D. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Detection of the cosmic infrared background at 2.2 and 3.5 microns using DIRBE observations |
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2000 |
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Astrophys. J. |
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545 |
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43-55 |
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IR applications |
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0004-637X |
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486 |
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Semenov, A. D.; Gol’tsman, G. N. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Nonthermal mixing mechanism in a diffusion-cooled hot-electron detector |
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Journal Article |
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2000 |
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J. Appl. Phys. |
Abbreviated Journal |
J. Appl. Phys. |
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87 |
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502-510 |
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NbN HEB mixers, nonthermal |
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We present an analysis of a diffusion-cooled hot-electron detector fabricated from clean superconducting material with low transition temperature. The distinctive feature of a clean material, i.e., material with large electron mean free path, is a relatively weak inelastic electron scattering that is not sufficient for the establishment of an elevated thermodynamic electron temperature when the detector is subjected to irradiation. We propose an athermal model of a diffusion-cooled detector that relies on suppression of the superconducting energy gap by the actual dynamic distribution of excess quasiparticles. The resistive state of the device is caused by the electric field penetrating into the superconducting bridge from metal contacts. The dependence of the penetration length on the energy gap delivers the detection mechanism. The sources of the electric noise are equilibrium fluctuations of the number of thermal quasiparticles and frequency dependent shot noise. Using material parameters typical for A1, we evaluate performance of the device in the heterodyne regime at terahertz frequencies. Estimates show that the mixer may have a noise temperature of a few quantum limits and a bandwidth of a few tens of GHz, while the required local oscillator power is in the μW range due to ineffective suppression of the energy gap by quasiparticles with high energies. |
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0021-8979 |
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1558 |
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Smirnov, K. V.; Ptitsina, N. G.; Vakhtomin, Y. B.; Verevkin, A. A.; Gol’tsman, G. N.; Gershenzon, E. M. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Energy relaxation of two-dimensional electrons in the quantum Hall effect regime |
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Journal Article |
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2000 |
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JETP Lett. |
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JETP Lett. |
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71 |
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31-34 |
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2DEG, GaAs/AlGaAs heterostructures |
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The mm-wave spectroscopy with high temporal resolution is used to measure the energy relaxation times τe of 2D electrons in GaAs/AlGaAs heterostructures in magnetic fields B=0–4 T under quasi-equilibrium conditions at T=4.2 K. With increasing B, a considerable increase in τe from 0.9 to 25 ns is observed. For high B and low values of the filling factor ν, the energy relaxation rate τ −1e oscillates. The depth of these oscillations and the positions of maxima depend on the filling factor ν. For ν>5, the relaxation rate τ −1e is maximum when the Fermi level lies in the region of the localized states between the Landau levels. For lower values of ν, the relaxation rate is maximum at half-integer values of τ −1e when the Fermi level is coincident with the Landau level. The characteristic features of the dependence τ −1e (B) are explained by different contributions of the intralevel and interlevel electron-phonon transitions to the process of the energy relaxation of 2D electrons. |
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0021-3640 |
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http://jetpletters.ru/ps/899/article_13838.shtml (“Энергетическая релаксация двумерных электронов в области квантового эффекта Холла”) |
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1559 |
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Semenov, A. D.; Hübers, H.-W.; Schubert, J.; Gol'tsman, G. N.; Elantiev, A. I.; Voronov, B. M.; Gershenzon, E. M. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Design and performance of the lattice-cooled hot-electron terahertz mixer |
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Journal Article |
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2000 |
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J. Appl. Phys. |
Abbreviated Journal |
J. Appl. Phys. |
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88 |
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11 |
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6758-6767 |
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HEB mixer, charge imbalance, HF current distribution |
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We present the measurements and the theoreticalmodel of the frequency-dependent noise temperature of a superconductor lattice-cooled hot-electron bolometer mixer in the terahertz frequency range. The increase of the noise temperature with frequency is a cumulative effect of the nonuniform distribution of the high-frequency current in the bolometer and the charge imbalance, which occurs at the edges of the normal domain and at the contacts with normal metal. We show that under optimal operation the fluctuation sensitivity of the mixer is determined by thermodynamic fluctuations of the noise power, whereas at small biases there appears additional noise, which is probably due to the flux flow. We propose the prescription of how to minimize the influence of the current distribution on the mixer performance. |
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0021-8979 |
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306 |
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Il'in, K. S.; Lindgren, M.; Currie, M. A.; Semenov, D.; Gol'tsman, G. N.; Sobolewski, Roman; Cherednichenko, S. I.; Gershenzon, E. M. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Picosecond hot-electron energy relaxation in NbN superconducting photodetectors |
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Journal Article |
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2000 |
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Appl. Phys. Lett. |
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Appl. Phys. Lett. |
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76 |
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19 |
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2752-2754 |
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NbN HEB detectors, two-temperature model, IF bandwidth |
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We report time-resolved characterization of superconducting NbN hot-electron photodetectors using an electro-optic sampling method. Our samples were patterned into micron-size microbridges from 3.5-nm-thick NbN films deposited on sapphire substrates. The devices were illuminated with 100 fs optical pulses, and the photoresponse was measured in the ambient temperature range between 2.15 and 10.6 K (superconducting temperature transition TC). The experimental data agreed very well with the nonequilibrium hot-electron, two-temperature model. The quasiparticle thermalization time was ambient temperature independent and was measured to be 6.5 ps. The inelastic electron–phonon scattering time Ï„e–ph tended to decrease with the temperature increase, although its change remained within the experimental error, while the phonon escape time Ï„es decreased almost by a factor of two when the sample was put in direct contact with superfluid helium. Specifically, Ï„e–ph and Ï„es, fitted by the two-temperature model, were equal to 11.6 and 21 ps at 2.15 K, and 10(±2) and 38 ps at 10.5 K, respectively. The obtained value of Ï„e–ph shows that the maximum intermediate frequency bandwidth of NbN hot-electron phonon-cooled mixers operating at TC can reach 16(+4/–3) GHz if one eliminates the bolometric phonon-heating effect. |
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0003-6951 |
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856 |
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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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Title |
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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Kawamura, Jonathan; Blundell, Raymond; Tong, C.-Y. Edward; Papa, D. Cosmo; Hunter, Todd R.; Paine, Scot.t. N.; Patt, Ferdinand; Gol'tsman, Gregory; Cherednichenko, Sergei; Voronov, Boris; Gershenzon, Eugene |
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Title |
Superconductive hot-electron bolometer mixer receiver for 800 GHz operation |
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Miscellaneous |
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2000 |
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IEEE Trans. Microwave Theory and Techniques |
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IEEE Trans. Microwave Theory and Techniques |
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48 |
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4 |
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683-689 |
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RPLAB @ s @ Kawamura_superconductivehot-electron |
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Kawamura, J.; Blundell, R.; Tong, C.-Y. E.; Papa, D. C.; Hunter, T. R.; Paine, S. N.; Patt, F.; Gol'tsman, G.; Cherednichenko, S.; Voronov, B.; Gershenzon, E. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Superconductive hot-electron-bolometer mixer receiver for 800-GHz operation |
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Journal Article |
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2000 |
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IEEE Trans. Microw. Theory Techn. |
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IEEE Trans. Microw. Theory Techn. |
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48 |
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4 |
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683-689 |
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NbN HEB mixers, LO power, local oscillator power, saturation, linearity, dynamic range |
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In this paper, we describe a superconductive hot-electron-bolometer mixer receiver designed to operate in the partially transmissive 350-μm atmospheric window. The receiver employs an NbN thin-film microbridge as the mixer element, in which the main cooling mechanism of the hot electrons is through electron-phonon interaction. At a local-oscillator frequency of 808 GHz, the measured double-sideband receiver noise temperature is TRX=970 K, across a 1-GHz intermediate-frequency bandwidth centered at 1.8 GHz. We have measured the linearity of the receiver and the amount of local-oscillator power incident on the mixer for optimal operation, which is PLO≈1 μW. This receiver was used in making observations as a facility instrument at the Heinrich Hertz Telescope, Mt. Graham, AZ, during the 1998-1999 winter observing season. |
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0018-9480 |
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RPLAB @ lobanovyury @ |
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573 |
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Sergeev, A.; Mitin, V. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Electron-phonon interaction in disordered conductors: Static and vibrating scattering potentials |
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2000 |
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Phys. Rev. B. |
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Phys. Rev. B. |
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61 |
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9 |
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6041-6047 |
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disordered conductors, scattering potential, electron-phonon interaction |
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Employing the Keldysh diagram technique, we calculate the electron-phonon energy relaxation rate in a conductor with the vibrating and static δ-correlated random electron-scattering potentials. If the scattering potential is completely dragged by phonons, this model yields the Schmid’s result for the inelastic electron-scattering rate τ−1e−ph. At low temperatures the effective interaction decreases due to disorder, and τ−1e−ph∝T4l (l is the electron mean-free path). In the presense of the static potential, quantum interference of numerous scattering processes drastically changes the effective electron-phonon interaction. In particular, at low temperatures the interaction increases, and τ−1e−ph∝T2/l. Along with an enhancement of the interaction, which is observed in disordered metallic films and semiconducting structures at low temperatures, the suggested model allows us to explain the strong sensitivity of the electron relaxation rate to the microscopic quality of a particular film. |
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