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  • 1
    Electronic Resource
    Electronic Resource
    Positive holes in magnesium oxide. Correlation between magnetic, electric, and dielectric anomalies : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6031-6033 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic susceptibility measurements of high purity MgO single crystals (〈50-wt. ppm transition metals) by means of a vibrating-sample magnetometer shows an anomaly at 800 K. At the same temperature the electric conductivity increases anomalously, the static dielectric constant (large-closed-square) increases from 9 to ≈150, a pronounced positive surface charge appears, and Fe2+ in the MgO matrix oxidizes to Fe3+. The data are consistent with O2−2 (peroxy) defects, representing self-trapped, spin-paired positive holes at Mg2+ vacancy sites. Diamagnetic at low temperatures, the holes start to decouple their spins (approximately-greater-than)600 K, probably forming at first V0 centers (two O− at an Mg2+ vacancy), then V− centers (single O− at an Mg2+ vacancy), and releasing mobile O− states. These O− represent itinerant charge carriers on acceptor levels near the O 2p-dominated valence band and conduct by O−/O2− valency fluctuations. The O− concentration is of the order of 8 × 1019 cm−3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347807
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  • 2
    Electronic Resource
    Electronic Resource
    Compact low-pass electrical filters for cryogenic detectors (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2638-2640 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe the design and performance of compact, low-pass electrical filters, suitable for operation at cryogenic temperatures. The filters are two pole LC filters with a cutoff at ≈100 kHz, an attenuation of −24 dB/octave, and a stop band rejection of −80 dB between 5 and 20 MHz. Their function is to suppress rf voltage noise to sensitive cryogenic detectors. The low-pass filters are realized using surface mounted devices on thin PC boards which can be stacked for maximum packing density. Compact modules containing 14 and 35 filters have been developed and installed in the Infrared Telescope in Space. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145601
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  • 3
    Electronic Resource
    Electronic Resource
    Multiplexed Readout of Superconducting Bolometers (2000)
    Springer
    International journal of infrared and millimeter waves 21 (2000), S. 1909-1916 
    Details
    ISSN: 1572-9559
    Keywords: bolometers ; SQUIDS ; multiplexing ; transition edge sensors ; far infrared ; submillimeter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Studies of emission in the far-infrared and submillimeter from astrophysical sources require large arrays of detectors containing hundreds to thousands of elements. A multiplexed readout is necessary for practical implementation of such arrays, and can be developed using SQUIDS, such that, e.g., a 32 × 32 array of bolometers can be read out using ≈100 wires rather than the 〉2000 needed with a brute force expansion of existing arrays. These bolometer arrays are made by micromachining techniques, using superconducting transition edge sensors as the thermistors. We describe the development of this multiplexed superconducting bolometer array architecture as a step toward bringing about the first astronomically useful arrays of this design. This technology will be used in the SAFIRE instrument on SOFIA, and is a candidate for a wide variety of other spectroscopic and photometric instruments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006752416612
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