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  • 1995-1999  (1)
  • 1985-1989  (8)
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  • 1
    Electronic Resource
    Electronic Resource
    Conditional analysis of floating potential fluctuations at the edge of the Texas Experimental Tokamak Upgrade (TEXT-U) (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 839-845 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fluctuations in floating potential in the scrape-off layer and plasma edge were analyzed using a conditional statistical analysis technique. The floating potential fluctuations had a nearly Gaussian probability density function with the largest deviation from a Gaussian at the shear layer. The conditional averaging technique followed the statistical evolution of selected conditions in the floating potential signal. The decay rate of a conditional feature in time or space showed a small systematic variation with the amplitude of condition chosen. Either long-lived coherent structures are not present in statistically significant numbers, or the fluctuations are dominated by a large number of coherent structures with a nearly Gaussian distribution of fluctuation amplitudes, or conditional analysis using the amplitude of the floating potential as a condition is not a sensitive technique for identifying coherent structures. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871435
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Development of a plasma-fluctuation diagnostic software tool (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1938-1938 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This paper describes a software package that will ultimately be made available to the entire magnetic fusion energy community and which may be used to analyze and interpret linear and nonlinear fluctuation data generated by a wide variety of plasma diagnostics such as, for example, probes, scattering systems, and beams. The software tool is divided into two basic parts: mathematical/statistical programs and applications programs. The mathematical/statistical programs will be further subdivided into those suitable for stationary and nonstationary data. The stationary data package will include bispectral analysis, a very powerful tool in the analysis of nonlinear data. Application programs will include fluctuation-induced particle transport, two-point estimates of S(k, ω), three-wave coupling coefficients and energy cascading, and nonlinear digital filters. Both the prototype plasma-fluctuation diagnostic software tool and plans for the complete software package will be described. This work was supported by the U.S. DOE Contract No. DE-AC05-85ER80251.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138802
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Advanced plasma fluctuation analysis techniques and their impact on fusion research (invited) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1739-1744 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article reviews digital spectral analysis techniques that yield experimental insight into plasma turbulence. Methods to quantify the statistical properties of the fluctuations and to measure the particle and heat flux caused by electrostatic fluctuations are presented. Furthermore, analysis techniques to study the nonlinear coupling process of turbulence and the redistribution of energy among the different modes are discussed. The impact of the analysis techniques on fusion research is demonstrated with experimental results collected with Langmuir probes, heavy-ion beam probes, and laser scattering in the tokamak TEXT. Special emphasis is given to the characterization of the wavenumber distribution and the correlation lengths in all toroidal directions, including a first measurement of k(parallel) in a tokamak.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140098
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Plasma fluctuation signal analysis tool (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1751-1753 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A plasma fluctuation signal analysis software package is described that surmounts common difficulties by using an information-hiding method and a layered structure.This approach leads to portability and easy customization for experimentalists who are not necessarily experts in signal analysis. The software contents and examples of applications to actual experimental data will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140100
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Resolving the propagation direction of tokamak microturbulence via homodyne spectroscopy (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1977-1979 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new homodyne spectroscopy technique [T. Tsukishima and O. Asada, Jpn. J. Appl. Phys. 17, 2059 (1978)] has been applied to tokamak microturbulence measurements in order to resolve the frequency spectra and wave propagation direction of low-frequency density fluctuations. Application of this method provides a high-resolution, inexpensive, and easily implemented alternative to the more technically demanding heterodyne detection schemes typically available. Comparison of heterodyne and the new homodyne spectroscopy results will be made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138811
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Experimental measurement of three-wave coupling and energy cascading (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 153-163 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear coupling coefficient and the energy transfer associated with three-wave interactions are computed from measured data of the turbulent edge plasma of the Texas Experimental Tokamak(TEXT) [Nucl. Technol. Fusion 1, 479 (1981)]. The results show the presence of three-wave interactions. The interactions cause energy to cascade away from the dominant waves of the spectrum primarily toward lower, but also toward higher frequencies. The results are obtained with a new digital spectral analysis technique based on the estimation of higher-order cumulants. The method is discussed and tested on a simulation experiment. The same technique is useful for neutral fluids as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859082
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Temperature fluctuations and transport in a tokamak edge plasma (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 2027-2030 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using the technique first described by Robinson and Rusbridge [Plasma Phys. 11, 73 (1969)] electron temperature fluctuations have been measured in the scrape-off layer of the TEXT tokamak [Nucl. Technol. Fusion 1, 479 (1981)] to be T˜e/Te (approximately-equal-to)0.4ñe/ne. Particle and energy transport were estimated from 〈ñe E˜θ〉 and 〈T˜e E˜θ〉 correlations. The fluctuation-driven particle transport was consistent with earlier measurements and with measurements of global particle confinement. A high correlation of temperature and electric field fluctuations and a low but positive correlation between density and temperature fluctuations were observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859066
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  • 8
    Electronic Resource
    Electronic Resource
    Nonlinear spectral dynamics of a transitioning flow (1988)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 3577-3588 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear spectral dynamics of a transitioning flow in the wake of a flat plate is experimentally studied at different downstream positions with a two-point method. The measurement setup consists of two sensors, which are separated in the downstream direction. The quadratically nonlinear transfer function between the two points is then estimated from the digitized fluctuation data. Such transfer functions permit one to quantify the quadratically nonlinear spectral dynamics occurring between the two sensor points. The method used to estimate the transfer functions and local bicoherency for non-Gaussian input and output signals, by means of digital spectral analysis techniques, is briefly discussed. The measured quadratic transfer function of the experimental data changes gradually with downstream distance, but its main features are unchanged. The observed appearance of progressively higher harmonics of the fundamental mode and the filling in of the spectral valleys over short downstream distances are, thus, mainly caused by spectral redistribution of energy that is available in the interacting modes and not caused by abrupt changes in the coupling properties. This result is supported by the local bicoherency measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866875
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    The application of homodyne spectroscopy to the study of low-frequency microturbulence in the TEXT tokamak (1986)
    Springer
    International journal of infrared and millimeter waves 7 (1986), S. 447-457 
    Details
    ISSN: 1572-9559
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The wave propagation direction of microturbulence in a tokamak plasma has been accurately measured by application of a new homodyne spectroscopy technique. This method has been used in conjunction with a collective far-infrared laser scattering experiment on TEXT. The low-frequency density fluctuations are observed to propagate primarily in the electron diamagnetic drift direction, however, the broadband spectra also possess an appreciable level of fluctuations traveling in the ion drift direction. Application of the homodyne spectroscopy technique represents an inexpensive and easily implemented alternative to the more technically demanding heterodyne schemes available in the far-infrared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01010860
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    Paper (German National Licenses)
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