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Pineda, J. L.; Langer, W. D.; Velusamy, T.; Goldsmith, P. F. |
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A Herschel [C ii] Galactic plane survey. I. The global distribution of ISM gas components |
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2013 |
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Astron. Astrophys. |
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554 |
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A103 |
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HEB mixer applications, HIFI, Herschel, ISM: general / stars: formation / evolution / ISM: clouds / ISM: structure / submillimeter: ISM |
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Abstract |
Context. The [C ii] 158 μm line is an important tool for understanding the life cycle of interstellar matter. Ionized carbon is present in a variety of phases of the interstellar medium (ISM), including the diffuse ionized medium, warm and cold atomic clouds, clouds in transition from atomic to molecular, and dense and warm photon dominated regions.
Aims. Velocity-resolved observations of [C ii] are the most powerful technique available to disentangle the emission produced by these components. These observations can also be used to trace CO-dark H2 gas and determine the total mass of the ISM.
Methods. The Galactic Observations of Terahertz C+ (GOT C+) project surveys the [C ii] 158 μm line over the entire Galactic disk with velocity-resolved observations using the Herschel/HIFI instrument. We present the first longitude-velocity maps of the [C ii] emission for Galactic latitudes b = 0°, ±0.5°, and ±1.0°. We combine these maps with those of H i, 12CO, and 13CO to separate the different phases of the ISM and study their properties and distribution in the Galactic plane.
Results. [C ii] emission is mostly associated with spiral arms, mainly emerging from Galactocentric distances between 4 and 10 kpc. It traces the envelopes of evolved clouds as well as clouds that are in the transition between atomic and molecular. We estimate that most of the observed [C ii] emission is produced by dense photon dominated regions (~47%), with smaller contributions from CO-dark H2 gas (~28%), cold atomic gas (~21%), and ionized gas (~4%). Atomic gas inside the Solar radius is mostly in the form of cold neutral medium (CNM), while the warm neutral medium gas dominates the outer galaxy. The average fraction of CNM relative to total atomic gas is ~43%. We find that the warm and diffuse CO-dark H2 is distributed over a larger range of Galactocentric distances (4–11 kpc) than the cold and dense H2 gas traced by 12CO and 13CO (4–8 kpc). The fraction of CO-dark H2 to total H2 increases with Galactocentric distance, ranging from ~20% at 4 kpc to ~80% at 10 kpc. On average, CO-dark H2 accounts for ~30% of the molecular mass of the Milky Way. When the CO-dark H2 component is included, the radial distribution of the CO-to-H2 conversion factor is steeper than that when only molecular gas traced by CO is considered. Most of the observed [C ii] emission emerging from dense photon dominated regions is associated with modest far-ultraviolet fields in the range χ0 â‰<192> 1 – 30. |
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Омельянук, А. Н.; Ильичев, Е. В.; Шевченко, С. Н. |
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Title |
Квантовые когерентные явления в джозефсоновских кубитах |
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Book Whole |
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2013 |
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Наукова думка |
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Josephson qubit, quantum computer, Rabi cycle, Landau-Zener effect, multiphoton transitions, single qubits |
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Монография посвящена актуальным проблемам физики сверхпроводниковых джозефсоновских кубитов — макроскопических квантовых структур, перспективных элементов квантовых компьютеров. Приведены элементы квантовой механики кубитов, фундаментальные свойства сверхпроводников, физика классических и квантовых джозефсоновских структур. Рассмотрены основные типы сверхпроводниковых кубитов. Изложены результаты экспериментальных и теоретических исследований квантовых когерентных явлений в джозефсоновских кубитах. Рассмотрены спектроскопия энергетичеÂских состояний, осцилляции Раби, эффект Ландау-Зинера, многофотонные переходы в одиночних кубитах и в системах связанных кубитов. Изучено влияние шумов на потоковый кубит и на его классический аналог.
Для специалистов в области теоретической и прикладной физики, сверхпроводниковой микроэлектроники, а также аспирантов и студентов физико-технических специальностей. |
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ФТИНТ им. Б. И. Верника НАН Украины |
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Киев |
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Russian |
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978-966-00-1260-8 |
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Ссылку прислал Саша Семенов в [RpL 755]. |
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933 |
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Zhang, W.; Miao, W.; Li, S. L.; Zhou, K. M.; Shi, S. C.; Gao, J. R.; Goltsman, G. N. |
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Measurement of the spectral response of spiral-antenna coupled superconducting hot electron bolometers |
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2013 |
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IEEE Trans. Appl. Supercond. |
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IEEE Trans. Appl. Supercond. |
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23 |
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3 |
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2300804-2300804 |
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NbN HEB detector |
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Measured spectral response of spiral-antenna coupled superconducting hot electron bolometers (HEBs) often drops dramatically at frequencies that are still within the frequency range of interest (e.g., ~ 5 THz). This is inconsistent with the implied low receiver noise temperatures from the same measurements. To understand this discrepancy, we exhaustively test and calibrate the thermal sources used in Fourier transform spectrometer measurements. We first investigate the absolute emission spectrum of high-pressure Hg arc lamp, then measure the spectral response of two spiral-antenna coupled NbN HEBs with a Martin-Puplett interferometer as spectrometer and 77 K blackbody as broadband signal source. The measured absolute emission spectrum of Hg arc lamp is proportional to frequency, corresponding to an equivalent blackbody temperature of 4000 K at 1 THz, 1500 K at 3 THz, and 800 K at 5 THz, respectively. Measured spectral response of spiral-antenna coupled NbN HEBs, corrected for air absorption, is nearly flat in the frequency range of 0.5-4 THz, consistent with simulated coupling efficiency between HEB and spiral-antenna. These results explain the discrepancy, and prove that spiral-antenna coupled superconducting NbN HEBs work well in a wide frequency range. In addition, this calibration method and these results are broadly applicable to other quasi-optical THz receivers. |
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1051-8223 |
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1371 |
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Shurakov, A.; Tong, C.-Y. E.; Blundell, R.; Kaurova, N.; Voronov, B.; Gol'tsman, G. |
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Microwave stabilization of a HEB mixer in a pulse-tube cryocooler |
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2013 |
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IEEE Trans. Appl. Supercond. |
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IEEE Trans. Appl. Supercond. |
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23 |
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3 |
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1501504-1501504 |
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NbN HEB mixers |
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We report the results of our study of the stability of an 800 GHz hot electron bolometer (HEB) mixer cooled with a pulse-tube cryocooler. Pulse-tube cryocoolers introduce temperature fluctuations as well as mechanical vibrations at a frequency of ~1 Hz, both of which can cause receiver gain fluctuations at that frequency. In our system, the motor of the cryocooler was separated from the cryostat to minimize mechanical vibrations, leaving thermal effects as the dominant source of the receiver gain fluctuations. We measured root mean square temperature variations of the 4 K stage of ~7 mK. The HEB mixer was pumped by a solid state local oscillator at 810 GHz. The root mean square current fluctuations at the low noise operating point (1.50 mV, 56.5 μA) were ~0.12 μA, and were predominantly due to thermal fluctuations. To stabilize the bias current, microwave radiation was injected to the HEB mixer. The injected power level was set by a proportional-integral-derivative controller, which completely compensates for the bias current oscillations induced by the pulse-tube cryocooler. Significant improvement in the Allan variance of the receiver output power was obtained, and an Allan time of 5 s was measured. |
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1051-8223 |
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1372 |
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Peltonen, J. T.; Astafiev, O. V.; Korneeva, Y. P.; Voronov, B. M.; Korneev, A. A.; Charaev, I. M.; Semenov, A. V.; Golt'sman, G. N.; Ioffe, L. B.; Klapwijk, T. M.; Tsai, J. S. |
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Coherent flux tunneling through NbN nanowires |
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2013 |
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Phys. Rev. B |
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Phys. Rev. B |
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88 |
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22 |
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220506 (1 to 5) |
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NbN nanowires |
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We demonstrate evidence of coherent magnetic flux tunneling through superconducting nanowires patterned in a thin highly disordered NbN film. The phenomenon is revealed as a superposition of flux states in a fully metallic superconducting loop with the nanowire acting as an effective tunnel barrier for the magnetic flux, and reproducibly observed in different wires. The flux superposition achieved in the fully metallic NbN rings proves the universality of the phenomenon previously reported for InOx. We perform microwave spectroscopy and study the tunneling amplitude as a function of the wire width, compare the experimental results with theories, and estimate the parameters for existing theoretical models. |
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1098-0121 |
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