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Author |
Encrenaz, Thérèse |
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Title |
Neutral Atmospheres of the Giant Planets: An Overview of Composition Measurements |
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2005 |
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Space Science Reviews |
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Space Sci Rev |
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116 |
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1-2 |
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99-119 |
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0038-6308 |
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RPLAB @ s @ |
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443 |
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Morozov, D. V.; Smirnov, K. V.; Smirnov, A. V.; Lyakhov, V. A.; Goltsman, G. N. |
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Title |
A millimeter-submillimeter phonon-cooled hot-electron bolometer mixer based on two-dimensional electron gas in an AlGaAs/GaAs heterostructure |
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Journal Article |
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Year |
2005 |
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Semicond. |
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Semicond. |
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Volume |
39 |
Issue |
9 |
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1082-1086 |
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Keywords |
2D electron gas, AlGaAs/GaAs heterostructures, mixers |
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Experimental results obtained by studying the main characteristics of a millimeter-submillimeter wave mixer based on the hot-electron effect in a two-dimensional electron gas in a AlGaAs/GaAs heterostructure with a phonon-scattering cooling mechanism for charge carriers are reported. The gain bandwidth of the mixer is 4 GHz, the internal conversion losses are 13 dB, and the optimum local-oscillator power is 0.5 μW (for a mixer area of 1 μm2). It is shown that a millimeter-submillimeter-wave receiver with a noise temperature of 1900 K can be developed on the basis of a AlGaAs/GaAs mixer. This mixer also appears to be promising for use in array receiver elements. |
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1063-7826 |
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1463 |
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Tol, J. van; Brunel, L.-C.; Wylde, R. J. |
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A quasioptical transient electron spin resonance spectrometer operating at 120 and 240 GHz |
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Journal Article |
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2005 |
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Rev. Sci. Instrum. |
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Rev. Sci. Instrum. |
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76 |
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7 |
Pages |
074101 (1 to 8) |
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Schottky, noise temperature |
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A new multifrequency quasioptical electron paramagnetic resonance (EPR) spectrometer is described. The superheterodyne design with Schottky diode mixer/detectors enables fast detection with subnanosecond time resolution. Optical access makes it suitable for transient EPR (TR-EPR) at 120 and 240 GHz. These high frequencies allow for an accurate determination of small g-tensor anisotropies as are encountered in excited triplet states of organic molecules like porphyrins and fullerenes. The measured concentration sensitivity for continuous-wave (cw) EPR at 240 GHz and at room temperature without cavity is 1013 spins/cm3 (15 nM) for a 1 mT linewidth and a 1 Hz bandwidth. With a Fabry-Perot cavity and a sample volume of 30 nl, the sensitivity at 240 GHz corresponds to [approximate]3×109 spins for a 1 mT linewidth. The spectrometer's performance is illustrated with applications of transient EPR of excited triplet states of organic molecules, as well as cw EPR of nitroxide reference systems and a thin film of a colossal magnetoresistance material. |
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Actually, noise spectral density is given (3e-19 W/Hz) |
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588 |
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Finkel, M. I.; Maslennikov, S. N.; Gol'tsman, G. N. |
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Title |
Terahertz heterodyne receivers based on superconductive hot-electron bolometer mixers |
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Journal Article |
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2005 |
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Radiophys. Quant. Electron. |
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Radiophys. Quant. Electron. |
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48 |
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10-11 |
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859-864 |
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HEB, applications |
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We consider recent results in development of hot-electron bolometer mixers. Special attention is paid to optimization of the contacts between the antenna and the active area of a superconducting film. An important result in the study of the parasitic effect of direct detection is obtained during the measurement of the noise temperatures by the hot/cold load method. The latest results of studies of the waveguide hot-electron bolometer mixers and their successful practical applications are considered. Progress in development of high-frequency (over 1.3 THz) heterodyne receivers for several important international projects is discussed and new submillimeter radio astronomy projects ESPRIT and SAFIR are described. |
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0033-8443 |
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381 |
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Gol'tsman, Gregory N.; Vachtomin, Yuriy B.; Antipov, Sergey V.; Finkel, Matvey I.; Maslennikov, Sergey N.; Smirnov, Konstantin V.; Polyakov, Stanislav L.; Svechnikov, Sergey I.; Kaurova, Natalia S.; Grishina, Elisaveta V.; Voronov, Boris M. |
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Title |
NbN phonon-cooled hot-electron bolometer mixer for terahertz heterodyne receivers |
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Conference Article |
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Year |
2005 |
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Proc. SPIE |
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Proc. SPIE |
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5727 |
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95-106 |
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NbN HEB mixers |
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We present the results of our studies of NbN phonon-cooled HEB mixers at terahertz frequencies. The mixers were fabricated from NbN film deposited on a high-resistivity Si substrate with an MgO buffer layer. The mixer element was integrated with a log-periodic spiral antenna. The noise temperature measurements were performed at 2.5 THz and at 3.8 THz local oscillator frequencies for the 3 x 0.2 μm2 active area devices. The best uncorrected receiver noise temperatures found for these frequencies are 1300 K and 3100 K, respectively. A water vapour discharge laser was used as the LO source. The largest gain bandwidth of 5.2 GHz was achieved for a mixer based on 2 nm thick NbN film deposited on MgO layer over Si substrate. The gain bandwidth of the mixer based on 3.5 nm NbN film deposited on Si with MgO is 4.2 GHz and the noise bandwidth for the same device amounts to 5 GHz. We also present the results of our research into decrease of the direct detection contribution to the measured Y-factor and a possible error of noise temperature calculation. The use of a square nickel cell mesh as an IR-filter enabled us to avoid the effect of direct detection and measure apparent value of the noise temperature which was 16% less than that obtained using conventional black polyethylene IR-filter. |
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Terahertz and Gigahertz Electronics and Photonics IV |
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