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| Author | Zhang, W.; Miao, W.; Li, S. L.; Zhou, K. M.; Shi, S. C.; Gao, J. R.; Goltsman, G. N. | ||||
| Title | Measurement of the spectral response of spiral-antenna coupled superconducting hot electron bolometers | Type | Journal Article | ||
| Year | 2013 | Publication  |
IEEE Trans. Appl. Supercond. | Abbreviated Journal | IEEE Trans. Appl. Supercond. |
| Volume | 23 | Issue | 3 | Pages | 2300804-2300804 |
| Keywords | NbN HEB detector | ||||
| Abstract | 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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| Series Volume | Series Issue | Edition | |||
| ISSN | 1051-8223 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 1371 | |||
| Permanent link to this record | |||||
| Author | Shurakov, A.; Tong, C.-Y. E.; Blundell, R.; Kaurova, N.; Voronov, B.; Gol'tsman, G. | ||||
| Title | Microwave stabilization of a HEB mixer in a pulse-tube cryocooler | Type | Journal Article | ||
| Year | 2013 | Publication |
IEEE Trans. Appl. Supercond. | Abbreviated Journal | IEEE Trans. Appl. Supercond. |
| Volume | 23 | Issue | 3 | Pages | 1501504-1501504 |
| Keywords | NbN HEB mixers | ||||
| Abstract | 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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| Series Volume | Series Issue | Edition | |||
| ISSN | 1051-8223 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 1372 | |||
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| Author | Lusche, R.; Semenov, A.; Il'in, K.; Korneeva, Y.; Trifonov, A.; Korneev, A.; Hubers, H.; Siegel, M.; Gol'tsman, G. | ||||
| Title | Effect of the wire width and magnetic field on the intrinsic detection efficiency of superconducting nanowire single-photon detectors | Type | Journal Article | ||
| Year | 2013 | Publication |
IEEE Trans. Appl. Supercond. | Abbreviated Journal | IEEE Trans. Appl. Supercond. |
| Volume | 23 | Issue | 3 | Pages | 2200205-2200205 |
| Keywords | SSPD, SNSPD | ||||
| Abstract | We present thorough measurements of the intrinsic detection efficiency in the wavelength range from 350 to 2500 nm for meander-type TaN and NbN superconducting nanowire single-photon detectors with different widths of the nanowire. The width varied from 70 nm to 130 nm. The open-beam configuration allowed us to accurately normalize measured spectra and to extract the intrinsic detection efficiency. For detectors from both materials the intrinsic detection efficiency at short wavelengths amounts at 100% and gradually decreases at wavelengths larger than the specific cut-off wavelengths, which decreases with the width of the nanowire. Furthermore, we show that applying weak magnetic fields perpendicular to the meander plane decreases the smallest detectable photon flux. | ||||
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| ISSN | 1051-8223 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 1376 | |||
| Permanent link to this record | |||||
| Author | Cavalié, T.; Feuchtgruber, H.; Lellouch, E.; de Val-Borro, M.; Jarchow, C.; Moreno, R.; Hartogh, P.; Orton, G.; Greathouse, T. K.; Billebaud, F.; Dobrijevic, M.; Lara, L. M.; González, A.; Sagawa, H. | ||||
| Title | Spatial distribution of water in the stratosphere of Jupiter from Herschel HIFI and PACS observations | Type | Journal Article | ||
| Year | 2013 | Publication |
Astron. Astrophys. | Abbreviated Journal | |
| Volume | 553 | Issue | Pages | A21 (1 to 16) | |
| Keywords | HEB mixer applications, HIFI, Herschel | ||||
| Abstract | Context. In the past 15 years, several studies suggested that water in the stratosphere of Jupiter originated from the Shoemaker-Levy 9 (SL9) comet impacts in July 1994, but a direct proof was missing. Only a very sensitive instrument observing with high spectral/spatial resolution can help to solve this problem. This is the case of the Herschel Space Observatory, which is the first telescope capable of mapping water in Jupiter's stratosphere. Aims. We observed the spatial distribution of the water emission in Jupiter's stratosphere with the Heterodyne Instrument for the Far Infrared (HIFI) and the Photodetector Array Camera and Spectrometer (PACS) onboard Herschel to constrain its origin. In parallel, we monitored Jupiter's stratospheric temperature with the NASA Infrared Telescope Facility (IRTF) to separate temperature from water variability. Methods. We obtained a 25-point map of the 1669.9 GHz water line with HIFI in July 2010 and several maps with PACS in October 2009 and December 2010. The 2010 PACS map is a 400-point raster of the water 66.4 μm emission. Additionally, we mapped the methane ν4 band emission to constrain the stratospheric temperature in Jupiter in the same periods with the IRTF. Results. Water is found to be restricted to pressures lower than 2 mbar. Its column density decreases by a factor of 2–3 between southern and northern latitudes, consistently between the HIFI and the PACS 66.4 μm maps. We infer that an emission maximum seen around 15 °S is caused by a warm stratospheric belt detected in the IRTF data. Conclusions. Latitudinal temperature variability cannot explain the global north-south asymmetry in the water maps. From the latitudinal and vertical distributions of water in Jupiter's stratosphere, we rule out interplanetary dust particles as its main source. Furthermore, we demonstrate that Jupiter's stratospheric water was delivered by the SL9 comet and that more than 95% of the observed water comes from the comet according to our models. |
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| Notes | Approved | no | |||
| Call Number | Serial | 1085 | |||
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| Author | Pineda, J. L.; Langer, W. D.; Velusamy, T.; Goldsmith, P. F. | ||||
| 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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