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| Author |
Samsonova, A. S.; Zolotov, P. I.; Baeva, E. M.; Lomakin, A. I.; Titova, N. A.; Kardakova, A. I.; Goltsman, G. N. |
Title  |
Signatures of surface magnetic disorder in niobium films |
Type |
Journal Article |
| Year |
2021 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
| Volume |
31 |
Issue |
5 |
Pages |
1-5 |
| Keywords |
Nb films |
| Abstract |
We present our studies on the evolution of the normal and superconducting properties with thickness of thin Nb films with a low level of non-magnetic disorder ( kFl≈150 for the thickest film in the set). The analysis of the superconducting behavior points to the presence of magnetic moments, hidden in the native oxide on the surface of Nb films. Using the Abrikosov-Gorkov theory, we obtain the density of surface magnetic moments of 1013 cm −2 , which is in agreement with the previously reported data for Nb films. |
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1051-8223 |
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1792 |
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| Author |
Czerny, Carl; Germer, Heinrich |
| Title |
Selected pianoforte-studies. Edition nr. 300 |
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Book Whole |
| Year |
1900 |
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children, music, piano, learning, school |
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Hansen |
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1845 |
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Semenov, Alexei; Hübers, Heinz.-Wilhelm; Richter, Heiko; Birk, Manfred; Krocka, Michael; Mair, Ulrich; Smirnov, Konstantin; Gol'tsman, Grigory; Voronov, Boris |
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Performance of terahertz heterodyne receiver with a superconducting hot-electron mixer |
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Conference Article |
| Year |
2002 |
Publication |
Proc. 13th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 13th Int. Symp. Space Terahertz Technol. |
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Pages |
229-234 |
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During the past decade major advances have been made regarding low noise mixers for terahertz heterodyne receivers. State of the art hot-electron-bolometer (HEB) mixers have noise temperatures close to the quantum limit and require less than a microwatt power from the local oscillator (L0). The technology is now at a point where the performance of a practical receiver employing such mixer, rather than the figures of merit of the mixer itself, is of major concern. We have incorporated a phonon-cooled NbN HEB mixer in a 2.5 THz heterodyne receiver and investigated its performance. This yields important information for future development of heterodyne receivers such as GREAT (German receiver for astronomy at THz frequencies aboard SOFIA) [1] and TELIS (Terahertz limb sounder), a balloon borne heterodyne receiver for atmospheric research [2]. Both are currently under development at DLR. |
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1529 |
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Schroeder, E.; Mauskopf, P.; Pilyavsky, G.; Sinclair, A.; Smith, N.; Bryan, S.; Mani, H.; Morozov, D.; Berggren, K.; Zhu, D.; Smirnov, K.; Vakhtomin, Y. |
| Title |
On the measurement of intensity correlations from laboratory and astronomical sources with SPADs and SNSPDs |
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Conference Article |
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2016 |
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Proc. SPIE |
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Proc. SPIE |
| Volume |
9907 |
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99070P (1 to 13) |
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SPAD, NbN SSPD applications, SNSPD |
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We describe the performance of detector modules containing silicon single photon avalanche photodiodes (SPADs) and superconducting nanowire single photon detectors (SNSPDs) to be used for intensity interferometry. The SPADs are mounted in fiber-coupled and free-space coupled packages. The SNSPDs are mounted in a small liquid helium cryostat coupled to single mode fiber optic cables which pass through a hermetic feed-through. The detectors are read out with microwave amplifiers and FPGA-based coincidence electronics. We present progress on measurements of intensity correlations from incoherent sources including gas-discharge lamps and stars with these detectors. From the measured laboratory performance of the correlation system, we estimate the sensitivity to intensity correlations from stars using commercial telescopes and larger existing research telescopes. |
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SPIE |
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Malbet, F.; Creech-Eakman, M.J.; Tuthill, P.G. |
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Optical and Infrared Interferometry and Imaging V |
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1809 |
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Gol'tsman, G. N.; Karasik, B. S.; Svechnikov, S. I.; Gershenzon, E. M.; Ekström, H.; Kollberg E. |
| Title |
Noise temperature of NbN hot—electron quasioptical superconducting mixer in 200-700 GHz range |
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Abstract |
| Year |
1995 |
Publication |
Proc. 6th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 6th Int. Symp. Space Terahertz Technol. |
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268 |
| Keywords |
NbN HEB mixers, noise temperature |
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The electron heating effect in superconducting films is becoming very attractive for the development of THz range mixers because of the absence of frequency limitations inherent in the bolometric mechanism. However, the evidence for the spectral dependence of the position of optimal operating point has been found recently for NbN thin film devices 1.2 • The effect is presumably attributed to the variation in the absorption of radiation depending on the frequency. Since the resistive state is not spatially uniform the coupling efficiency of the mixer device with radiation can be different for frequencies larger than Zeilh and those smaller than 2Alh (d is the effective superconducting gap in the resistive state). To study the effect more thoroughly we have investigated the noise temperature of quasioptical NbN mixer device with broken hue tapered slot antenna in the frequency range 200-700 GHz. The device consists of several (5-10) parallel strips 1 jim wide and 6-7 tun thick made from NbN film on Si0 2 -Si 3 N 4 -Si membrane. The strips are connected with the gold contacts of the slot-line antenna which serves both as bias and IF leads. We used backward wave oscillators as LO sources and a standard hot/cold load technique for noise temperature measurements. The frequency dependence of noise temperature is mainly determined by two factors: frequency properties of the antenna and frequency dependence of the NbN film impedance. To separate both factors we monitored the frequency dependence of the device responsivity in the detector mode at a higher temperature within the superconducting transition where the impedance of NbN film is close to its normal resistance. In this case the impedance of the device itself is frequency independent. The experimental results will be reported at the Symposium. 1. G. Gollsman, S. Jacobsson, H. EkstrOm, B. Karasik, E. Kollberg, and E. Gershenzon, “Slot-line tapered antenna with NbN hot electron mixer for 300-360 GHz operation,” Proc of the 5th Int. Symp. on Space Terahertz Technology, pp. 209-213a, May 10-12,1994. 2. B.S. Karasik, G.N. Gol i tsman, B.M. Voronov, S.I. Svechnikov, E.M. Gershenzon, H. Ekstrom, S. Jacobsson, E. Kollberg, and K.S. Yngvesson, “Hot electron quasioptical NbN superconducting mixer,” presented at the ASC94, submitted to IEEE Trans. on Appl. Superconductivity. |
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1627 |
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