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  • 1
    Electronic Resource
    Electronic Resource
    The role of energetic electrons in self-oscillations of a discharge plasma (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 5006-5012 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The role of energetic electrons in periodic self-oscillations of a discharge plasma has been studied by measuring the spatiotemporal evolution of plasma potential, electron density, and electron velocity distribution function. It is found that the self-oscillation involves the instabilities of sheaths, propagation of a double layer and competition between the ionization, thermalization, and diffusion. The energetic electrons are the key factor which links these processes to form the oscillation cycle. The time interval of each phase in the cycle is estimated according to the physical process and the calculations are in agreement with experimental measurements. The study of the probe perturbation effect on the oscillations indicates that the length of the oscillation period is related to the amount of energetic electrons; the more energetic electrons, the shorter the period. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1406134
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  • 2
    Electronic Resource
    Electronic Resource
    Enhanced electron attachment to Rydberg states in molecular hydrogen volume discharges (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7064-7069 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We review recent studies on negative ion formation and studies in other areas that are relevant to the role of high-Rydberg states of H2 and H3 in hydrogen negative ion sources. Possible mechanisms for the formation of these excited states are discussed, including the formation of long-lived superexcited (core-excited) Rydberg states. Experimental evidence for negative ion formation via electron attachment to core-excited Rydberg states in a glow discharge apparatus is presented. An expression for the dissociative electron attachment rate constant for Rydberg molecules is derived based on electron capture by a Rydberg molecule due to polarization interaction. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370513
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  • 3
    Electronic Resource
    Electronic Resource
    Multichannel far-infrared polarimeter-interferometer system on the MST reversed field pinch : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 1077-1080 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The multichannel far-infrared (FIR) heterodyne polarimeter-interferometer system on the Madison Symmetric Torus (MST) is now operational. The combined system consists of 11 channels with variable radial and toroidal spacing. Poloidal magnetic field is determined by measuring the Faraday rotation of the FIR laser beam after propagation through the plasma by use of a phase technique. The polarimeter has 3 mrad rms noise level and 1 ms temporal resolution while the interferometer resolution is nedl=1×1012 cm−2 with time response of 1 μs. Absolute calibration of the polarimeter system is achieved by use of a rotating quartz half-wave plate. The first 11-channel polarimeter measurements from MST indicate a Faraday rotation profile in good agreement with expectations from the MSTFIT equilibrium code. Future plans to reduce the polarimeter time response from 1 ms to 10 μs will allow direct measurement of magnetic fluctuations associated with global resistive tearing modes on MST. The effect of these modes on density is already clearly resolved and provides insight into the dynamics of these structures. Improving the time response will also result in lower phase noise for both the polarimeter and interferometer. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1321744
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  • 4
    Electronic Resource
    Electronic Resource
    Multichannel interferometer system for the helically symmetric experiment : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 1081-1084 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A multichannel millimeter-wave interferometer system has been designed, fabricated and installed on the helically symmetric experiment (HSX), located at the University of Wisconsin, Madison. The interferometer system will view the plasma cross section along nine adjacent chords with 1.5 cm spacing. With this arrangement, coverage will span from the low-field side plasma scrape-off layer to well past the magnetic axis. For the plasma densities anticipated on HSX, a solid-state source operating at 288 GHz will be utilized. At this frequency refraction will be manageable, being less than the channel spacing. The source will be bias-tuned and modulated with a sawtooth wave form at 750 kHz in order to generate the intermediate frequency necessary for the heterodyne detection scheme. The signals will be measured using Schottky-diode corner-cube mixers. The interferometer will have sensitivity nedl(approximate)8×1011 cm−2, being able to measure density changes 〈1%. Initially, the phase will be evaluated using analog electronics with bandwidth 〈10 kHz providing real-time line-integrated output. A digital phase comparator scheme will also be implemented whereby the measured wave forms are directly digitized and the phase evaluated using a software-based algorithm. This will increase the time response up to the modulation frequency of 750 kHz. Improved time response will permit measurement of high-frequency density fluctuations along with "fast changes in" the equilibrium profile. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1319366
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  • 5
    Electronic Resource
    Electronic Resource
    Layered defective lanthanum titanate thin films prepared by pulsed laser ablation of potassium lanthanum titanate ceramics (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 191-193 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of Lanthanum titanate have been prepared on SiO2 coated Si and fused silica substrates by excimer ultraviolet laser ablation of potassium lanthanum titanate ceramics (K2La2Ti3O10). X-ray θ–2θ scans revealed that the films as-grown at a substrate temperature of 750–850 °C were single phase defective perovskite, and exhibited superstructure line in addition to the lines expected for the foundamenal perovskite structure. The films can be produced by escaping of potassium from K2La2Ti3O10 and the superstructure line observed was considered to arise from the ordered arrangement of the A-site vacancies. The chemical compositions of the films were determined by x-ray photoelectron spectroscopy (XPS). Optical waveguiding properties were demonstrated by m-line measurement using a rutile prism coupling method. The as grown films are colorless and transparent, and have the effective refractive index of 1.917 for TE modes at 632.8 nm. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117368
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  • 6
    Electronic Resource
    Electronic Resource
    Large magnetic entropy change in La0.75Ca0.25MnO3 (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 904-905 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic entropy change of La0.75Ca0.25MnO3 with different particle size has been investigated. Magnetic entropy change ∼4.7 J/kg K larger than that of Gd has been observed at 224 K under a magnetic field of 1.5 T in comparatively big particles. This phenomenon of large magnetic entropy change indicates that the perovskite-type manganese oxides have potential applications for magnetic refrigerants in high temperature.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118309
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  • 7
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    Observations of zonal flows in electrode biasing experiments on the Joint Texas Experimental tokamak (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-04-12
    Description: Zonal flows (ZFs) are observed during the electrode biasing (EB) high confinement mode (H-mode) using Langmuir probe arrays on the edge of J-TEXT tokamak. The long-distance correlation characteristics of floating potentials and interactions with turbulence are studied. During positive biasing H-mode, either the geodesic acoustic mode or low frequency ZF increases. Strong suppression of radial transport by ZFs is found in the low frequency region. The components of the radial particle flux without and with EB are compared in the frequency domain. The interaction between ZFs and ambient turbulence is also discussed. The results show that the rate of ZFs' shear is comparable with that of E × B shear, suggesting that ZFs could be the trigger of the biasing H-mode.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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