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  • 1
    Publication Date: 2023-09-29
    Description: Magneto-impedance (MI) effect was discovered about 30 years ago and a micro-size magnetic sensor that utilizes this effect becomes commercially available. Nosé et al. (2022, doi: 10.1029/2022JA030809) made some modifications to the commercially available MI sensors to cover the dynamic range of the geomagnetic field. For the period of March 30 to April 27, 2018, they conducted experimental observations of geomagnetic field variations with the MI sensors at the Mineyama observatory in Japan. Data obtained with the MI sensors are compared with those from the fluxgate magnetometer (FGM) that has been working at the observatory. Results showed that the MI sensors can record geomagnetic field variations such as geomagnetic storms, Sq variations, low-latitude positive bays, SSC, and geomagnetic pulsations with a peak-to-peak amplitude of £ 1 nT that are also detected with the FGM. This study revealed that the MI sensor can measure the geomagnetic field variations in a period from a few tens of seconds to a few hours. Using MI sensors, Raspberry Pi, low-cost 24-bit A/D converters, and stable power supply circuits, we developed a magnetometer with approximately $4,000, which is named MIM-Pi (MI sensor Magnetometer with Raspberry Pi). Because of its low cost, MIM-Pi provides an opportunity to construct a dense observation network of geomagnetic field. We are now deploying MIM-Pi in Kanto-Tohoku area. When we apply the magnetoseismology method to the data from such dense observation network, it will be possible to monitor fine structures of the plasma mass density distribution in the inner magnetosphere.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5339-5342 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Normal and superconducting properties of PtSi films with thicknesses of d=2–20 nm have been investigated. The superconducting transition has been observed on the thin films down to d=4 nm. The systematic reduction of the transition temperature with decreasing d (increasing the sheet resistance) has been explained by the localization and Coulomb interaction effects on superconductivity. The temperature dependence of the upper critical field indicates that the PtSi films behave as homogeneous superconductors.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A 12-channel heterodyne radiometer system has been developed to obtain electron temperature with high time and spatial resolution from the electron cyclotron emission (ECE) in JT-60U. Resolutions of a single-sideband-type receiver are (1) Δt∼1 μs and (2) Δf=0.5 GHz. The second harmonic extraordinary mode of ECE is utilized for this system and the frequency band is 176–188 GHz. The noise level of the system is determined by unavoidable photon fluctuations, and the signal-to-noise ratio was measured to be about 50 with a video bandwidth of 100 kHz for a signal temperature above ∼200 eV. Details of the design, the obtained performance, and typical measurements are described. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 340-343 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs-AlGaAs quantum wires with various widths have been fabricated using electron beam lithography and Ar ion etching. Conductance was measured as a function of the etched depth and the wire width. The results indicate that defects diffuse at room temperature. Shubnikov–de Haas oscillations in GaAs-AlGaAs film and wires with different widths have been measured to investigate the effect of the surface damage on the electron transport characteristics. The analysis of the results shows that both electron density and scattering time decrease with decreasing the width of the channel. These are indicative of the side wall scattering and the damages induced during the sample preparation process.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 1165-1168 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A 20-channel electron cyclotron emission (ECE) detection system for the grating polychromator in JT-60U has been developed to measure electron temperature and its perturbations. Indium antimonide (InSb) detectors aligned in a row are cooled by liquid helium held by a 50 cm-diam cryostat, in which a hold time of the liquid helium reaches 7 weeks. Twenty-channel preamplifiers are dc-coupled ones, which enable to measure low-frequency ECE. From the comparison between the new system and the existing 20-channel detector system, where a refrigerator for cooling InSb detectors and ac-coupled preamplifiers are used, it is found that the signal-to-noise ratio is improved, and that small perturbations can be detected. By using this system, the electron temperature and its perturbations near the internal transport barrier in a reversed shear discharge are measured in detail. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Local steep pressure gradient generated near an internal transport barrier drives a radially localized magnetohydrodynamic (MHD) instability with low toroidal mode number (n) in the high-βp mode plasma in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) [Y. Koide et al., Phys. Plasmas 4, 1623 (1997)]. The instability occurs in the βp regime lower than that for the βp-collapse and its growth rate is of the order of the ideal MHD instability. By a linear analysis of ideal MHD stability, low n modes localized near the internal transport barrier are found to be destabilized in the situation that the bootstrap current driven by the steep pressure gradient reduces the local magnetic shear (s(approximately-less-than)0) where the safety factor is right close to an integer value. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A twenty-channel grating polychromator diagnostic system has been built to measure the temporal evolution of local electron temperatures in JT-60. A cross Czerny–Turner diffraction grating spectrometer is utilized for the measurement of second-harmonic electron cyclotron emission with extraordinary modes in the range 85–300 GHz, in which a grating plate grooved on both faces with different grating periods is applied effectively to yield a wide coverage for the toroidal fields. The grating angle is automatically set up by control of a stepping motor according to the relation of the grating equation. The diffracted light is detected by 20 indium-antimonide hot-electron bolometers cooled at 4.3 K in a modified Solvay cycle cryogenic refrigerator. A typical resolving power of the instrument was measured to be λ/Δλ∼130, providing a spatial resolution of 2.3 cm at the plasma center. The transmission line over ∼38 m long is composed of oversized S-band waveguides. The total transmissivity of this system is estimated to be ∼0.01.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1460-1462 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report emission from individual quantum dots excited by tunneling current injection using a scanning tunneling microscope (STM). By scanning the STM tip above the self-assembled InAs quantum dots, a spatially resolved scanning tunneling luminescence (STL) image was measured, which contained a fluorescent circular region with a diameter of 50 nm originating from a single InAs quantum dot. It was found that the spatial resolution of the STL system was about 40 nm, which is mainly due to lateral diffusion of holes injected into a GaAs capping layer grown at low temperature (480 °C). We also obtained STL spectra with a sharp single luminescent peak from a single InAs quantum dot. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 800-802 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose and demonstrate a seeded self-assembling growth technique for the fabrication of quantum dot structures by metal–organic chemical-vapor deposition. GaAs quantum dots were grown at the bottom of two-dimensional V-groove (2DVG) structures, which were composed of (111)A and (111)B facets on a GaAs(100) substrate. The 2DVG was grown by selective growth on a SiO2 patterned substrate. It was found that vertical GaAs quantum wires were also simultaneously formed in the 2DVGs. Using this technique, the stacking of GaAs quantum dots was realized. Photoluminescence and cathodoluminescence from each structure evidenced the formation of both the quantum wires and the quantum dots. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1421-1423 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the direct deposition of strained InGaAs-dot structures with a diameter of about 15 nm on GaAs surfaces by metalorganic chemical vapor deposition growth. High resolution scanning electron micrographs show highly uniform quantum-sized dots formed by the Stranski–Krastanow growth mode. The sharp photoluminescence emission band of buried dot structures indicates efficient carrier capture and a homogeneous heterointerface. The average dot size and area dot density can be controlled accurately by growth temperature, and InGaAs deposition thickness, respectively.
    Type of Medium: Electronic Resource
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