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| Author | Barends, R.; Hajenius, M.; Gao, J. R.; Klapwijk, T. M. | ||||
| Title | Current-induced vortex unbinding in bolometer mixers | Type | Journal Article | ||
| Year | 2005 | Publication | Applied Physics Letters | Abbreviated Journal | Appl. Phys. Lett. |
| Volume | 87 | Issue | Pages | 263506 (1 to 3) | |
Keywords  |
HEB mixer numerical model, HEB model, IV-curves, vortex-antivortex, Berezinskii–Kosterlitz–Thouless theory, diffusion cooling channel, diffusion channel, distributed HEB model, distributed model, self-heating effect, temperature profile | ||||
| Abstract | We present a description of the current-voltage characteristics of hot electron bolometers in terms of the current-dependent intrinsic resistive transition of NbN films. We find that, by including this current dependence, we can correctly predict the complete current-voltage characteristics, showing excellent agreement with measurements for both low and high bias and for small as well as large devices. It is assumed that the current dependence is due to vortex-antivortex unbinding as described in the Berezinskii–Kosterlitz–Thouless theory. The presented approach will be useful in guiding device optimization for noise and bandwidth. | ||||
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| Notes | Approved | no | |||
| Call Number | Serial | 604 | |||
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| Author | Khosropanah, P.; Merkel, H.; Yngvesson, S.; Adam, A.; Cherednichenko, S.; Kollberg, E. | ||||
| Title | A distributed device model for phonon-cooled HEB mixers predicting IV characteristics, gain, noise and IF bandwidth | Type | Conference Article | ||
| Year | 2000 | Publication | Proc. 11th Int. Symp. Space Terahertz Technol. | Abbreviated Journal | |
| Volume | Issue | Pages | 474-488 | ||
| Keywords |
HEB mixer numerical model, diffusion cooling channel, diffusion channel, distributed HEB model, distributed model | ||||
| Abstract | A distributed model for phonon-cooled superconductor hot electron bolometer (HEB) mixers is given, which is based on solving the one-dimensional heat balance equation for the electron temperature profile along the superconductor strip. In this model it is assumed that the LO power is absorbed uniformly along the bridge but the DC power absorption depends on the local resistivity and is thus not uniform. The electron temperature dependence of the resistivity is assumed to be continuous and has a Fermi form. These assumptions are used in setting up the non-linear heat balance equation, which is solved numerically for the electron temperature profile along the bolometer strip. Based on this profile the resistance of the device and the IV curves are calculated. The IV curves are in excellent agreement with measurement results. Using a small signal model the conversion gain of the mixer is obtained. The expressions for Johnson noise and thermal fluctuation noise are derived. The calculated results are in close agreement with measurements, provided that one of the parameters used is adjusted. | ||||
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| Publisher | Place of Publication | University of Michigan, Ann Arbor, MI USA | Editor | ||
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| Notes | Approved | no | |||
| Call Number | Serial | 893 | |||
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| Author | Karasik, B. S.; Elantiev, A. I. | ||||
| Title | Noise temperature limit of a superconducting hot-electron bolometer mixer | Type | Journal Article | ||
| Year | 1996 | Publication | Applied Physics Letters | Abbreviated Journal | Appl. Phys. Lett. |
| Volume | 68 | Issue | 6 | Pages | 853-855 |
| Keywords |
HEB mixer noise temperature, Johnson noise, thermal fluctuation noise, noise bandwidth | ||||
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| Series Volume | Series Issue | Edition | |||
| ISSN | 0003-6951 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 260 | |||
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| Author | Ynvesson, K. Sigfrid; Kollberg, Erik L. | ||||
| Title | Optimum receiver noise temperature for NbN HEB mixers according to standard model | Type | Conference Article | ||
| Year | 1999 | Publication | Proc. 10th Int. Symp. Space Terahertz Technol. | Abbreviated Journal | |
| Volume | Issue | Pages | 566-582 | ||
| Keywords |
HEB mixer model, standard model, electro-thermal feedback, self-heating parameter, heating efficiency | ||||
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| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 895 | |||
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| Author | Klapwijk, T. M.; Barends, R.; Gao, J. R.; Hajenius, M.; Baselmans, J. J. A. | ||||
| Title | Improved superconducting hot-electron bolometer devices for the THz range | Type | Conference Article | ||
| Year | 2004 | Publication | Proc. SPIE | Abbreviated Journal | Proc. SPIE |
| Volume | 5498 | Issue | Pages | 129-139 | |
| Keywords |
HEB mixer distributed model, numerical model | ||||
| Abstract | Improved and reproducible heterodyne mixing (noise temperatures of 950 K at 2.5 THz) has been realized with NbN based hot-electron superconducting devices with low contact resistances. A distributed temperature numerical model of the NbN bridge, based on a local electron and a phonon temperature, has been used to understand the physical conditions during the mixing process. We find that the mixing is predominantly due to the exponential rise of the local resistivity as a function of electron temperature. | ||||
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| Notes | Invited talk, Recommended by Klapwijk | Approved | no | ||
| Call Number | Serial | 912 | |||
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| Author | Hajenius, M.; Barends, R.; Gao, J. R.; Klapwijk, T. M.; Baselmans, J. J. A.; Baryshev, A.; Voronov, B.; Gol'tsman, G. | ||||
| Title | Local resistivity and the current-voltage characteristics of hot electron bolometer mixers | Type | Journal Article | ||
| Year | 2005 | Publication | IEEE Trans. Appl. Supercond. | Abbreviated Journal | IEEE Trans. Appl. Supercond. |
| Volume | 15 | Issue | 2 | Pages | 495-498 |
| Keywords |
HEB mixer distributed model, HEB distributed model, distributed HEB model | ||||
| Abstract | Hot-electron bolometer devices, used successfully in low noise heterodyne mixing at frequencies up to 2.5 THz, have been analyzed. A distributed temperature numerical model of the NbN bridge, based on a local electron and a phonon temperature, is used to model pumped IV curves and understand the physical conditions during the mixing process. We argue that the mixing is predominantly due to the strongly temperature dependent local resistivity of the NbN. Experimentally we identify the origins of different transition temperatures in a real HEB device, suggesting the importance of the intrinsic resistive transition of the superconducting bridge in the modeling. | ||||
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| Series Volume | Series Issue | Edition | |||
| ISSN | 1051-8223 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 980 | |||
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| Author | Chavarr'ıa, L.; Herpin, F.; Jacq, T.; Braine, J.; Bontemps, S.; Baudry, A.; Marseille, M.; van der Tak, F.; Pietropaoli, B.; Wyrowski, F.; Shipman, R.; Frieswijk, W.; van Dishoeck, E. F.; Cernicharo, J.; Bachiller, R.; Benedettini, M.; Benz, A. O.; Bergin, E.; Bjerkeli, P.; Blake, G. A.; Bruderer, S.; Caselli, P.; Codella, C.; Daniel, F.; di Giorgio, A. M.; Dominik, C.; Doty, S. D.; Encrenaz, P.; Fich, M.; Fuente, A.; Giannini, T.; Goicoechea, J. R.; de Graauw, T.; Hartogh, P.; Helmich, F.; Herczeg, G. J.; Hogerheijde, M. R.; Johnstone, D.; Jørgensen, J. K.; Kristensen, L. E.; Larsson, B.; Lis, D.; Liseau, R.; McCoey, C.; Melnick, G.; Nisini, B.; Olberg, M.; Parise, B.; Pearson, J. C.; Plume, R.; Risacher, C.; Santiago-Garc'ıa, J.; Saraceno, P.; Stutzki, J.; Szczerba, R.; Tafalla, M.; Tielens, A.; van Kempen, T. A.; Visser, R.; Wampfler, S. F.; Willem, J.; Yıldız, U. A. | ||||
| Title | Water in massive star-forming regions: HIFI observations of W3 IRS5 | Type | Journal Article | ||
| Year | 2010 | Publication | Astron. Astrophys. | Abbreviated Journal | |
| Volume | 521 | Issue | Pages | L37 (1 to 5) | |
| Keywords |
HEB mixer applications, HIFI, Herschel, stars: formation, stars: massive, ISM: molecules, ISM: abundances, dust, extinction, radio lines: ISM | ||||
| Abstract | We present Herschel observations of the water molecule in the massive star-forming region W3 IRS5. The o-H217O 110-101, p-H218O 111-000, p-H2O 202-111, p-H2O 111-000, o-H2O 221-212, and o-H2O 212-101 lines, covering a frequency range from 552 up to 1669 GHz, have been detected at high spectral resolution with HIFI. The water lines in W3 IRS5 show well-defined high-velocity wings that indicate a clear contribution by outflows. Moreover, the systematically blue-shifted absorption in the H2O lines suggests expansion, presumably driven by the outflow. No infall signatures are detected. The p-H2O 111-000 and o-H2O 212-101 lines show absorption from the cold material (T ~ 10 K) in which the high-mass protostellar envelope is embedded. One-dimensional radiative transfer models are used to estimate water abundances and to further study the kinematics of the region. We show that the emission in the rare isotopologues comes directly from the inner parts of the envelope (T â‰<b3> 100 K) where water ices in the dust mantles evaporate and the gas-phase abundance increases. The resulting jump in the water abundance (with a constant inner abundance of 10-4) is needed to reproduce the o-H217O 110-101 and p-H218O 111-000 spectra in our models. We estimate water abundances of 10-8 to 10-9 in the outer parts of the envelope (T â‰<b2> 100 K). The possibility of two protostellar objects contributing to the emission is discussed. | ||||
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| Notes | Approved | no | |||
| Call Number | Chav13HEBapplHIFIb | Serial | 1086 | ||
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| Author | Justtanont, K.; Decin, L.; Schöier, F. L.; Maercker, M.; Olofsson, H.; Bujarrabal, V.; Marston, A. P.; Teyssier, D.; Alcolea, J.; Cernicharo, J.; Dominik, C.; de Koter, A.; Melnick, G.; Menten, K.; Neufeld, D.; Planesas, P.; Schmidt, M.; Szczerba, R.; Waters, R.; de Graauw, Th.; Whyborn, N.; Finn, T.; Helmich, F.; Siebertz, O.; Schmülling, F.; Ossenkopf, V.; Lai, R. | ||||
| Title | A HIFI preview of warm molecular gas around χ Cygni: first detection of H2O emission toward an S-type AGB star | Type | Journal Article | ||
| Year | 2010 | Publication | Astron. Astrophys. | Abbreviated Journal | |
| Volume | 521 | Issue | Pages | L6 | |
| Keywords |
HEB mixer applications, HIFI, Herschel, stars: AGB and post-AGB / circumstellar matter / stars: kinematics and dynamics / stars: individual: χ Cyg / stars: late-type / stars: mass-loss | ||||
| Abstract | Aims. A set of new, sensitive, and spectrally resolved, sub-millimeter line observations are used to probe the warm circumstellar gas around the S-type AGB star χ Cyg. The observed lines involve high rotational quantum numbers, which, combined with previously obtained lower-frequency data, make it possible to study in detail the chemical and physical properties of, essentially, the entire circumstellar envelope of χ Cyg. Methods. The data were obtained using the HIFI instrument aboard Herschel, whose high spectral resolution provides valuable information about the line profiles. Detailed, non-LTE, radiative transfer modelling, including dust radiative transfer coupled with a dynamical model, has been performed to derive the temperature, density, and velocity structure of the circumstellar envelope. Results. We report the first detection of circumstellar H2O rotational emission lines in an S-star. Using the high-J CO lines to derive the parameters for the circumstellar envelope, we modelled both the ortho- and para-H2O lines. Our modelling results are consistent with the velocity structure expected for a dust-driven wind. The derived total H2O abundance (relative to H2) is (1.1±0.2) × 10-5, much lower than that in O-rich stars. The derived ortho-to-para ratio of 2.1±0.6 is close to the high-temperature equilibrium limit, consistent with H2O being formed in the photosphere. |
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| Notes | Approved | no | |||
| Call Number | Serial | 1096 | |||
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| Author | Hartogh, P.; Jarchow, C.; Lellouch, E.; de Val-Borro, M.; Rengel, M.; Moreno, R.; Medvedev, A. S.; Sagawa, H.; Swinyard, B. M.; Cavalié, T.; Lis, D. C.; BłÄ™cka, M. I.; Banaszkiewicz, M.; Bockelée-Morvan, D.; Crovisier, J.; Encrenaz, T.; Küppers, M.; Lara, L.-M.; Szutowicz, S.; Vandenbussche, B.; Bensch, F.; Bergin, E. A.; Billebaud, F.; Biver, N.; Blake, G. A.; Blommaert, J. A. D. L.; Cernicharo, J.; Decin, L.; Encrenaz, P.; Feuchtgruber, H.; Fulton, T.; de Graauw, T.; Jehin, E.; Kidger, M.; Lorente, R.; Naylor, D. A.; Portyankina, G.; Sánchez-Portal, M.; Schieder, R.; Sidher, S.; Thomas, N.; Verdugo, E.; Waelkens, C.; Whyborn, N.; Teyssier, D.; Helmich, F.; Roelfsema, P.; Stutzki, J.; LeDuc, H. G.; Stern, J. A. | ||||
| Title | Herschel/HIFI observations of Mars: First detection of O2 at submillimetre wavelengths and upper limits on HCl and H2O2 | Type | Journal Article | ||
| Year | 2010 | Publication | Astron. Astrophys. | Abbreviated Journal | |
| Volume | 521 | Issue | Pages | L49 | |
| Keywords |
HEB mixer applications, HIFI, Herschel, planets and satellites: atmospheres / radiative transfer / submillimeter: general / molecular processes | ||||
| Abstract | We report on an initial analysis of Herschel/HIFI observations of hydrogen chloride (HCl), hydrogen peroxide (H2O2), and molecular oxygen (O2) in the Martian atmosphere performed on 13 and 16 April 2010 (Ls ~ 77°). We derived a constant volume mixing ratio of 1400 ± 120 ppm for O2 and determined upper limits of 200 ppt for HCl and 2 ppb for H2O2. Radiative transfer model calculations indicate that the vertical profile of O2 may not be constant. Photochemical models determine the lowest values of H2O2 to be around Ls ~ 75° but overestimate the volume mixing ratio compared to our measurements. | ||||
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| Notes | Approved | no | |||
| Call Number | Serial | 1093 | |||
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| Author | Pineda, J. L.; Velusamy, T.; Langer, W. D.; Goldsmith, P. F.; Li, D.; Yorke, H. W. | ||||
| Title | A sample of [C II] clouds tracing dense clouds in weak FUV fields observed by Herschel | Type | Journal Article | ||
| Year | 2010 | Publication | Astron. Astrophys. | Abbreviated Journal | |
| Volume | 521 | Issue | Pages | L19 | |
| Keywords |
HEB mixer applications, HIFI, Herschel, ISM: structure / photon-dominated region / ISM: supernova remnants / evolution | ||||
| Abstract | The [C ii] fine-structure line at 158 μm is an excellent tracer of the warm diffuse gas in the ISM and the interfaces between molecular clouds and their surrounding atomic and ionized envelopes. Here we present the initial results from Galactic observations of terahertz C+ (GOT C+), a Herschel key project devoted to studying the [C ii] emission in the Galactic plane using the HIFI instrument. We used the [C ii] emission, together with observations of CO, as a probe to understand the effects of newly formed stars on their interstellar environment and characterize the physical and chemical state of the star-forming gas. We collected data along 16 lines-of-sight passing near star-forming regions in the inner Galaxy near longitudes 330° and 20°. We identified fifty-eight [C ii] components that are associated with high-column density molecular clouds as traced by 13CO emission. We combined [C ii], 12CO, and 13CO observations to derive the physical conditions of the [C ii]-emitting regions in our sample of high-column density clouds based on comparing results from a grid of photon dominated region (PDR) models. From this unbiased sample, our results suggest that most of the [C ii] emission originates in clouds with H2 volume densities between 103.5 and 105.5 cm-3 and weak FUV strength (χ0 = 1–10). We find two regions where our analysis suggest high densities >105 cm-3 and strong FUV fields (χ0 = 104–106), likely associated with massive star formation. We suggest that [C ii] emission in conjunction with CO isotopes is a good tool for differentiating regions of massive star formation (high densities/strong FUV fields) and regions that are distant from massive stars (lower densities/weaker FUV fields) along the line-of-sight. | ||||
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| Notes | Approved | no | |||
| Call Number | Serial | 1101 | |||
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