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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 4582-4591 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: S-Cam is a cryogenic optical camera for ground-based astronomy designed around a 6×6 array of superconducting tunnel junctions. It has been conceived as a technology demonstrator, aimed at proving the potential of a new generation of single photon counting detectors for ground-based telescopes and as a possible precursor to a future space-based instrumentation. The camera is based on a 6×6 array of Ta–Al Josephson junctions, operating at about 350 mK and individually read out. For each detected photon, the absorption position, the arrival time, and the corresponding energy are measured. This allows for recording an image and simultaneously obtaining spectrophotometric information from the observed objects. In this article we provide an overview of the latest cryogenic detector performance, an up-to-date description of the S-Cam system, and a summary of the results obtained both during testing at ESTEC and during actual observations at the William Herschel Telescope in La Palma (Canary Islands, Spain). An example of the novel astronomical data obtained during the latest observation campaigns (December 1999 and April 2000) is also described. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 7641-7646 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report the detection of individual optical and ultraviolet photons using a different approach to photon detection based on a superconducting tunnel junction. A 20×20 μm2 junction, employing a 100 nm niobium film and operated at a temperature of ∼0.4 K, has been used to detect individual photons with inherently high quantum efficiency (〉45%) over a broad wavelength range (between 200 and 500 nm), yielding high temporal (sub-ms) resolution, spatial resolution determined by the junction size, under conditions of minimal dark current, and in the absence of read noise. The quantum efficiency is limited by surface reflection, and could be improved by the deposition of antireflection coatings. The theoretical wavelength response range continues into the far UV and soft x-ray region, and is presently limited beyond 500 nm largely by the available signal processing electronics. The device intrinsically functions at very high incident photon rates—with count rates of order ∼10 kHz or higher being feasible and again currently limited primarily by the signal processing electronics—thus providing a correspondingly enhanced dynamic range by several orders of magnitude compared with previous panoramic photon counting detectors. The measured charge output from the device is highly linear with photon energy resulting in an optical photon detection system with intrinsic spectral resolution, related to the critical temperature of the junction material and, in the current device, providing a limiting spectral resolution of about 50 nm. It is realistic in the future to envisage that these devices could be packaged into arrays, with the resulting system characteristics offering advantages over detectors based on semiconductors. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 269 (1977), S. 223-224 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Our observing frequency was 2.7 GHz, as used by Gearhart and Pacht1, and the beam size (FWHP) 3.7 x 3.7 cosec 5 arc s; in one case, OS210, the source had previously been mapped at 5 GHz (ref. 2) with a beam size 2 x 4.1 arc s. Figure 1 shows the 2.7-GHz maps in which the declination scales have ...
    Materialart: Digitale Medien
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  • 4
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] FIG.1 A diagram of the 20 x 20 m device (not to scale). It was fabricated from a 'sandwich' of Nb/AI/ACVAI/Nb multilayer deposited on polished sapphire. The base and top niobium films have a thickness of 100 nm; both the aluminium films are 120 nm thick. The insulating tunnel barrier of the device ...
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Astrophysics and space science 241 (1996), S. 89-104 
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The proposed baseline GAIA mission will be able to detect the astrometric signature of Jupiter-size planets around of the order of a million stars, using either global or narrow-angle astrometry. If the mission can realize the higher astrometric accuracy that photon statistics allows for bright stars, lower-mass planets (from Earth size to ten times larger) can be found around ten to a few hundred stars.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 340 (1989), S. 111-116 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] The Hipparcos satellite, due to be launched aboard Ariane on 27 July, aims to provide an enormous advance in the quality and quantity of stellar astrometric ...
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of low temperature physics 93 (1993), S. 659-664 
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Superconducting Tunnel Junctions have been investigated in the past as particle and X-ray detectors. We report here on results obtained illuminating Nb-Al-AlOx-Nb junctions with radiation covering the UV to IR (250 – 1100 nm) at 0.30 K. In the presence of continuous illumination, an increase of the subgap current is observed, while the change is found to be consistent with the amount of energy supplied to the junction. Several measurements have been performed in a pulsed mode, showing the detection of pulses containing about 100 photons each, at λ=850 nm. These results have allowed a determination of the mean energy required to create a single charge carrier in Nb, which agrees well with theoretical predictions. Such results open new possibilities for the fabrication of optical photon counting cameras based on Josephson junctions.
    Materialart: Digitale Medien
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