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  • 1
    Electronic Resource
    Electronic Resource
    A novel technique for measuring resistance fluctuations independently of background noise (1989)
    Springer
    Applied physics 48 (1989), S. 233-236 
    Details
    ISSN: 1432-0630
    Keywords: 06 ; 07 ; 61.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A novel method is presented for measuring the spectral density of resistance fluctuations without the explicit determination of the voltage background noise (Johnson noise, pre-amplifier noise). The output of a standard ac bridge excited by a single-frequency alternating current is demodulated by two phase-sensitive detectors which operate in quadrature. When the phase difference between excitation and detection is properly set, the real part of the cross-spectral density of the two demodulators shows only the spectral density of the resistance fluctuations and not the disturbing background noise. The feasibility of our new method is demonstrated by measurements of 1/f noise of a thin-film A1 sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00619390
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic background noise cancellation in real-world environments (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 1529-1533 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Measurements of the magnetic field noise and the spatial correlation of the noise were made in a typical laboratory environment using two three-axis fluxgate magnetometers. The magnitude of the magnetic field noise was found to be approximately 100 pT/Hz at 10 Hz with a correlation of 90% at a separation of 1 m between the two sensors. The correlation was significantly reduced from noise induced eddy currents near large metallic surfaces. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150490
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  • 3
    Electronic Resource
    Electronic Resource
    Extremely low-noise potentiometry with a scanning tunneling microscope (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 301-305 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Novel ac biasing and detection techniques have been developed to allow a scanning tunneling microscope (STM) to measure spatial variations in electric potential on metallic surfaces with sub-μV sensitivity. When implemented with a room-temperature STM operating with minimal electrical shielding and no vibration isolation, the voltage sensitivity was limited by the thermal (Johnson) noise of the tunneling resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140428
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  • 4
    Electronic Resource
    Electronic Resource
    Performance of dc SQUIDs with resistively shunted inductance (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1451-1453 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated and characterized the noise performance of well-coupled Nb-Pb alloy edge junction dc superconducting quantum interference devices (SQUIDs) with a resistively shunted inductance. The extra damping resistor removes the resonances in the current-voltage characteristics resulting in a very low value of the extrinsic energy sensitivity in flux-locked-loop operation. Numerical simulations, with the junction capacitance included, indicate that the damping resistance does not degrade noise performance until it is significantly less than the junction-shunting resistance. We also tested different SQUID designs and demonstrated that a large SQUID inductance, proposed earlier to be desirable when resistively shunted, can seriously affect the low-frequency flux noise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101583
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  • 5
    Electronic Resource
    Electronic Resource
    Noise and hysteresis in flux-locked TlBaCaCuO SQUIDs (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2259-2261 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of TlBaCaCuO-based dc superconducting quantum interference devices (SQUIDs) performed using a practical feedback circuit gave a flat frequency response and an energy sensitivity of 6×10−30 J/Hz at 5 kHz and 77 K with an 80 pH SQUID. Flux-locked loop operation was demonstrated to be strongly effective in eliminating the magnetic field hysteresis of the SQUID. The SQUIDs were operated in the flux-locked loop at temperatures over 90 K and the 1/f noise was found to decrease with increasing temperature near 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101141
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of radio frequency radiation on the dc SQUID (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 100-102 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of radio frequency radiation on the dc SQUID are examined. Simulations show how the shape of the SQUID transfer characteristic is distorted by radio frequency interference (RFI). How this affects three commonly used SQUID modulation methods is discussed, and the results explain why we experimentally observe the bias current reversing readout method to be the least susceptible to RFI. The commonly seen increase in the low frequency flux noise power spectrum of dc SQUIDs in unshielded environments is also explained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113046
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  • 7
    Electronic Resource
    Electronic Resource
    Characterizing, modeling, and optimizing high-Tc superconducting quantum interference devices (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 378-381 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the current-voltage, flux-voltage, and noise characteristics of 77 K superconducting quantum interference devices made with step edge junctions and multilevel edge junctions on SrTiO3 substrates and with step edge junctions on LaAlO3. We find in each case that the I-V curves can have excess currents of up to 50%–80%, that the responsivity, ∂V/∂Φ, can be substantially smaller than expected from the resistively shunted junction (RSJ) model, but that the white noise voltage spectral density is about as expected. We discuss the extent to which the reduction of the responsivity is correlated with the excess current. We note that the observed unchanged magnitude of the voltage noise and the reduced responsivity would both be expected if we based the RSJ predictions on a model in which the excess current is not considered part of the Josephson current. Finally and perhaps fundamentally, we find that simulations made assuming a nonsinusoidal current-phase relationship give rise to an excess current, a reduction of the responsivity, and little change in the voltage noise spectral density, at least qualitatively as is observed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359333
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  • 8
    Electronic Resource
    Electronic Resource
    Reliable single-target sputtering process for high-temperature superconducting films and devices (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 444-446 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a simple, single-target magnetron sputtering process for films of high-temperature superconductors involving an off-axis sputtering geometry. The process lends itself both to film growth with high-temperature post-anneals and to low-temperature in situ film growth. The post-anneal process routinely yields YBa2Cu3O7−x films on SrTiO3 substrates that are fully superconducting at 86–89 K. Current densities at 77 K range from 104 to 8×105 A/cm2. A single-level superconducting quantum interference device (dc SQUID), made by photolithographically patterning a low current density film, has a flux noise level at 77 K of 3×10−4 Φ0/(Hz)1/2 at 20 Hz, dominated by low-frequency noise associated with flux motion in the film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100615
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  • 9
    Electronic Resource
    Electronic Resource
    Low-noise thin-film TlBaCaCuO dc SQUIDs operated at 77 K (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 951-953 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have made a series of single-level dc superconducting quantum interference devices (SQUIDs) from 4-μm-thick TlBaCaCuO films with large grain sizes and operated them in liquid nitrogen. Although device characteristics could not be precisely controlled, some devices had white-noise levels that approached thermally limited noise above ∼1000 Hz. In addition, devices with 5 and 80 pH loop inductances had 1/ f noise levels at 10 Hz of 2×10−29 and 5×10−29 J/Hz, respectively. The noise levels at these frequencies are comparable to commercial rf SQUIDs operating in liquid helium, but the hysteresis of the voltage-flux characteristic of the high Tc SQUIDs remains large.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100817
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  • 10
    Electronic Resource
    Electronic Resource
    REMOTE-REFERENCE MAGNETOTELLURICS: EQUIPMENT AND PROCEDURES (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 31 (1983), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: During the past 3 years, major advances in the magnetotelluric technique have improved the quality of magnetotelluric data to the point where random errors in the impedance tensor and tipper are generally smaller than the uncertainty in their interpretation. The major factor in this improvement has been the introduction of the remote-reference technique, although the use of ultrasensitive magnetometers and minicomputers for in-field data processing has also been important. After a review of the remote-reference technique, this paper describes the equipment and procedures used for remote-reference magnetotellurics by the authors. Magnetometers using d.c. Superconducting Quantum Interference Devices typically have a sensitivity of 10−14 T Hz−1/2, a dynamic range of 107 in a 1 Hz bandwidth, and a slewing rate of 3 × 10−5.T s−1 at 10 kHz. The electric field measurements use conventional Cu-CuSO4 electrodes. The remote magnetic reference signals are transmitted to the base station using FM analog telemetry. The data are collected and processed by a minicomputer based on an LSI-11 microprocessor; the essential results—for example, the apparent resistivities and the tipper components, with their probable errors—are available in the field. Practical details are given of the handling of superconducting devices, low temperature cryostats and liquid helium in the field. Various spurious noise sources are mentioned, and techniques for minimizing their effects are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1983.tb01047.x
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