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  • 1990-1994  (27)
  • 1900-1904  (2)
  • 1860-1869  (4)
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2925-2938 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Conventional rf SQUIDs (superconducting quantum interference devices) consist of a superconducting loop interrupted by one weak link, and when read out via a tank circuit they produce output signals in the order of a few tens of microvolts. When the single weak link is replaced by a dc SQUID (a superconducting loop with two junctions) a so-called double quantization loop SQUID is formed. In this paper it is shown theoretically, and supported experimentally with thin-film devices of three different designs, that the general behaviour can be explained by a simplified picture of the fixed critical current of the single junction of the rf SQUID being replaced by an effective critical current of a dc SQUID loop that is varied by the applied magnetic flux (i.e., we have a rf SQUID with a variable β parameter). A more detailed analysis of the experimental data and the theory of this novel device reveals its interesting nonlinear character and shows the deviations from this simple picture. It is demonstrated experimentally that output signals in the order of ≥1 mV can be obtained with a suitable read-out mode for the tank circuit, a clear advantage when compared to conventional rf SQUIDs. With respect to dc SQUIDs, the coupling to integrated planar input coils will be unproblematic since no microwave resonances should occur in the structures.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1000-1006 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The radio frequency (rf) properties of a dc superconducting quantum interference device (SQUID) coupled to a multiturn input coil have been studied both experimentally and theoretically using an expanded model of the coupled SQUID. The input coil and washer resonances observed in the measured impedance of the expanded model are shown to be in quantitative agreement with the theory presented previously. When the input coil resonances are suppressed by resistive damping, it is shown that the impedance of the coupled SQUID at low frequencies is determined solely by an effective inductance that is much lower than the SQUID inductance. A simple equivalent circuit of the coupled SQUID for this case is proposed. The rf properties of SQUIDs with gradiometric washer configurations are also discussed. It is shown that the rf properties of these devices can be predicted from the properties of the individual washers.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2338-2346 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A complete circuit model of a dc superconducting quantum interference device (SQUID) coupled to a multiturn input coil has been developed. With this model, it is shown that the rf properties of the coupled SQUID can be calculated using only the given parameters of the SQUID. There are no adjustable parameters. The resonant structures in the SQUID characteristics caused by the presence of the input coil have been quantitatively studied. Methods to suppress the resonant structures have also been investigated. It is shown that the present circuit model explains well the experimentally observed rf properties of coupled SQUIDs. The present circuit model is therefore useful for the design of highly sensitive SQUIDs.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3005-3011 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A picovoltmeter working at 4.2 K and based on a direct current superconducting quantum interference device (dc SQUID) with additional passive positive feedback for investigating the properties of superconducting thin films, Josephson junctions, and SQUIDs has been developed. It has a large small-signal bandwidth fm(approximately-equal-to)800 kHz, a slew rate of (approximately-equal-to)38 mV/s, a dynamic range of 146 dB, and a voltage resolution of 5 pV/Hz1/2 for a signal source impedance Rs=0 Ω. The noise temperature is (approximately-equal-to)0.6 K for Rs=1 Ω. In this article the dynamics and noise properties of the instrument are discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4737-4740 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simplified theoretical analysis and experimental investigations of a partially resistive superconducting quantum interference device with two quantization loops have been performed. The advantage of this device is an extremely large output signal. It is shown that the output signal oscillates with a period determined by the nonstationary Josephson relation. This device was experimentally compared to the dc resistive superconducting quantum interference device used as a test structure.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 406-408 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A dc superconducting quantum interference device (SQUID) magnetometer has been integrated on a 9×9 mm2 chip with eight pick-up loops in parallel to directly form a SQUID inductance of about 0.5 nH. Very simple feedback electronics have been developed which do not require liquid-helium temperature impedance matching circuits or flux modulation techniques. The magnetometer has a typical white noise of 8 fT/(Hz)1/2 and a 1/f corner frequency below 3.5 Hz. With an additional positive feedback circuit at 4.2 K the white noise level has been further reduced to 4.5 fT/(Hz)1/2. Using a two-pole integrator, a 3 dB bandwidth around 0.5 MHz and a maximum slew rate of 3 mT/s at 1.3 kHz have been attained with a ±0.4 μT feedback range.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 279-281 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of the noble metals Ag and Au are prospective candidates for application as electrical contacts in high temperature superconductor (HTSC) thin film devices. We present first results on intrinsic stress in Ag and Au films measured during and after their UHV deposition onto YBa2Cu3O7−x thin film substrates. At 110 K film growth proceeds by columnar grain growth with tensile stresses as huge as the tensile strength of the bulk phase. At room temperature and up to 600 K the films grow via island growth developing much smaller film stress. At temperatures above 550 K a compressive stress contribution due to interdiffusion of oxygen from the HTSC substrates into the contact films is observed.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 228-230 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have designed and fabricated a low-noise dc superconducting quantum interference device (SQUID) magnetometer that is integrated on a 4×4 mm2 chip. The white flux noise of the magnetometer measured in a flux-locked-loop mode using simple, direct-coupled electronics with additional positive feedback (APF) is 6.4×10−7 Φ0/(square root of)Hz. The corresponding white flux density noise is 3.9 fT/(square root of)Hz. The SQUID flux-to-voltage transfer function with APF is enhanced to 4.7 mV/Φ0 at the optimal working point, thereby significantly reducing the preamplifier contribution to the total noise. A maximum feedback field of 65 nT for frequencies up to 300 Hz and a maximum slew rate of 120 μT/s at 300 Hz have been attained using a two-pole integrator.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Contact dermatitis 24 (1991), S. 0 
    ISSN: 1600-0536
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 3851 consecutive patients patch tested between January 1985 and March 1990 have been analysed for rubber allergies. The incidence of rubber allergy was 3.8% (n=145) In 80/145 patients (55%). the source of rubber sensitization was occupational, 67 of whom (84%) had acquired allergy from wearing rubber gloves a work. Most of them (36%) were employed in the health services. The most commonly positive rubber-mix in this group was thiuram-mix (72%) Followed by carba-mix (25%.) 13/80 patients (16%) had occupational rubber allergy from industrial rubber products other than gloves. Patch tests revealed thiuram-mix (62%) as the most commonly positive rubber-mix but, in contrast to the group with glove-induced rubber allergy, black-rubber-mix came second (38%) In 47/145 patients (32%) the source of rubber sensitization W8S non-occupational; in 18/145 (13%) the origin remained unknown.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 3038-3042 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A process for the fabrication of high-quality, all-refractory Josephson junctions of the type Nb/Six Ny /Nb is described in detail. The junctions have been fabricated using the selective niobium anodization process with a tunnel barrier consisting of an amorphous Si film converted to its nitride by the application of a rf plasma of nitrogen. An attractive feature of these junctions is their comparably low specific capacitance C/A=3.9±0.1 μF/cm2 (for Jc =6 A/cm2 ). Junctions of this type having critical current densities up to Jc =2000 A/cm2 and Vm =16 mV have been fabricated. Excellent magnetic field threshold curves have also been observed for these junctions, indicating that the critical current density is very uniform.
    Type of Medium: Electronic Resource
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