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Author Shcherbatenko, M.; Tretyakov, I.; Lobanov, Yu.; Maslennikov, S. N.; Kaurova, N.; Finkel, M.; Voronov, B.; Goltsman, G.; Klapwijk, T. M. doi  openurl
  Title Nonequilibrium interpretation of DC properties of NbN superconducting hot electron bolometers Type Journal Article
  Year 2016 Publication Appl. Phys. Lett. Abbreviated Journal  
  Volume 109 Issue 13 Pages 132602  
  Keywords HEB mixer, contacts  
  Abstract We present a physically consistent interpretation of the dc electrical properties of niobiumnitride (NbN)-based superconducting hot-electron bolometer mixers, using concepts of nonequilibrium superconductivity. Through this, we clarify what physical information can be extracted from the resistive transition and the dc current-voltage characteristics, measured at suitably chosen temperatures, and relevant for device characterization and optimization. We point out that the intrinsic spatial variation of the electronic properties of disordered superconductors, such as NbN, leads to a variation from device to device.  
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  Call Number Serial 1107  
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Author Tretyakov, Ivan; Ryabchun, Sergey; Finkel, Matvey; Maslennikova, Anna; Kaurova, Natalia; Lobastova, Anastasia; Voronov, Boris; Gol'tsman, Gregory doi  openurl
  Title Low noise and wide bandwidth of NbN hot-electron bolometer mixers Type Journal Article
  Year 2011 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.  
  Volume 98 Issue Pages 033507 (1 to 3)  
  Keywords NbN HEB mixer  
  Abstract We report a record double sideband noise temperature of 600 K (5hν/kB) offered by a NbN hot-electron bolometer receiver at 2.5 THz. Allowing for standing wave effects, this value was found to be constant in the intermediate frequency range 1–7 GHz, which indicates that the mixer has an unprecedentedly large noise bandwidth in excess of 7 GHz. The insight into this is provided by gain bandwidth measurements performed at the superconducting transition. They show that the dependence of the bandwidth on the mixer length follows the model for an HEB mixer with diffusion and phonon cooling of the hot electrons.  
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  Notes Approved no  
  Call Number RPLAB @ gujma @ Serial 638  
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Author Phillips, T. G.; Jefferts, K. B. doi  openurl
  Title A low temperature bolometer heterodyne receiver for Millimeter wave astronomy Type Journal Article
  Year 1973 Publication Rev. Sci. Instrum. Abbreviated Journal Rev. Sci. Instrum.  
  Volume 44 Issue 8 Pages 1009-1014  
  Keywords InSb HEB mixer  
  Abstract Liquid helium cooled InSb hot electronbolometers are used in a balanced mixer configuration as detectors for an imagelessmicrowave receiver. The system is designed for mounting at the prime focus of the National Radio Astronomy Observatory (NRAO) 11 m antenna at Kitt Peak, Arizona, and is suitable for the study of rotational line spectra of interstellar gas molecules. Currently the operating frequency is in the 90–140 GHz band where the double sideband system noise temperature is 250 K.  
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  Notes Recommended by Klapwijk Approved no  
  Call Number Serial 927  
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Author Baselmans, J. J. A.; Hajenius, M.; Gao, J. R.; Klapwijk, T. M.; de Korte, P. A. J.; Voronov, B.; Gol'tsman, G. doi  openurl
  Title Doubling of sensitivity and bandwidth in phonon cooled hot electron bolometer mixers Type Journal Article
  Year 2004 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.  
  Volume 84 Issue 11 Pages 1958-1960  
  Keywords NbN HEB mixers  
  Abstract We demonstrate that the performance of NbN lattice cooled hot electron bolometer mixers depends strongly on the interface quality between the bolometer and the contact structure. We show experimentally that both the receiver noise temperature and the gain bandwidth can be improved by more than a factor of 2 by cleaning the interface and adding an additional superconducting interlayer to the contact pad. Using this we obtain a double sideband receiver noise temperature TN,DSB=950 K

at 2.5 THz and 4.3 K, uncorrected for losses in the optics. At the same bias point, we obtain an IF gain bandwidth of 6 GHz.
 
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  Notes Approved no  
  Call Number Serial 352  
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Author Pineda, J. L.; Langer, W. D.; Velusamy, T.; Goldsmith, P. F. doi  openurl
  Title A Herschel [C ii] Galactic plane survey. I. The global distribution of ISM gas components Type Journal Article
  Year 2013 Publication Astron. Astrophys. Abbreviated Journal  
  Volume 554 Issue Pages A103  
  Keywords HEB mixer applications, HIFI, Herschel, ISM: general / stars: formation / evolution / ISM: clouds / ISM: structure / submillimeter: ISM  
  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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  Notes Approved no  
  Call Number Serial 1100  
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