Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Characterization of avalanche-like events in a confined plasma : Review,Tutorial and Invited Papers from the 43rd Annual Meeting of the APS Division of Plasma Physics (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 1962-1969 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: One mechanism for transport of energy and particles in a plasma is by discrete, intermittent, uncorrelated events, often called avalanches. This paper reports observations and quantitative characterization of avalanche events in a magnetically confined plasma. The observations are primarily of electron temperature fluctuations. Avalanches are identified by their large spatial scale, up to the system size, by self-similar behavior in the frequency spectrum and the autocorrelation function and by propagation. The two-point cross-correlation function allows determination of a characteristic velocity, which typically varies from several hundred meters per second in the outer part of the plasma to zero or even inward near the axis. This can be interpreted as resulting from the prevalence of negative avalanches (i.e., holes) near the axis. The presence of a long-tailed probability distribution is indicated by a Hurst parameter (H) in the range 0.80 to 0.95, which becomes smaller in the outer quarter of the plasma radius. Density fluctuation spectra from the plasma core also show self-similar behavior. Power transport estimates show that about half of the heat flux is carried by the avalanche events under conditions with no magnetohydrodynamic activity. These observations are qualitatively similar to results of modeling calculations based on drift wave turbulence. It is reasonable to infer that avalanches are the macroscopic manifestation of turbulence which inherently has a small spatial scale and, thus, allow a local, gyro-Bohm scaling process to show global Bohm-type behavior. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1452730
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Effects of non-Maxwellian (super-Gaussian) electron velocity distribution on the spectrum of Thomson scattering (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2736-2740 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamic form factor for Thomson scattering with a non-Maxwellian (super-Gaussian) electron velocity distribution is analytically and numerically studied for the first time. Both the ion and electron features of the spectra for α〉1 are found to be affected strongly. For the ion feature, the use of the usual theoretical spectra with the assumption of a Maxwellian distribution for fitting the measured Thomson scattering spectra may have resulted in some errors in calculating the plasma parameters in high-Z plasmas irradiated with high intensity light. However, it is impossible to use the ion feature of the measured spectra alone to deduce the form of the electron distribution. For the electron feature, the spectral shape (in particular the peak amplitude) changes sensitively with the distribution index. It would be possible to detect the super-Gaussian distribution by simultaneously measuring the ion and electron features of the spectra. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872141
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Fluctuation measurements in the DIII-D and TEXT tokamaks via collective scattering and reflectometry (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3509-3519 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Anomalous transport in fusion plasmas remains an enigma requiring explanation. A predictive capability is highly desirable if confinement enhancement regimes such as H mode or super shots are to be extrapolated to the next phase in development of the International Fusion program, epitomized, for example in ITER. Therefore, identification of the role that electrostatic turbulence plays in confinement is a critical issue requiring detailed experimental data capable of testing and challenging existing theoretical models. This article presents microturbulence measurements obtained on the DIII-D and TEXT tokamaks utilizing heterodyne, far-infrared collective scattering, and reflectometry techniques. The experimental systems are described on both machines and emphasis placed on results obtained during the L-H transition, ELM activity, and saturated ohmic operation where ion temperature gradient driven (ITGD) turbulence is theoretically predicted to exist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141560
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    UCLA FIR diagnostic systems on TEXT and developments for TEXT Upgrade (abstract) : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3071-3071 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A multipurpose multiview far-infrared diagnostic system is being designed and constructed for the TEXT Upgrade. The system's capabilities, designed to enhance the applications of the present FIR system on TEXT, will include two-view interferometry, polarimetry, and collective scattering in order to measure the plasma density profile, current profile, and density fluctuation distribution. The interferometer/polarimeter system will possess high spatial (Δx=1.5 cm) and high-density (≤5×1010 cm−3) resolution. Tomographic reconstruction techniques will be employed to investigate both the equilibrium and perturbed profiles of plasma density. This represents an extension of the present work on TEXT where MHD effects such as sawteeth, Mirnov oscillations, and disruptions have been studied. Two-view multichannel collective scattering (1≤k⊥≤20 cm−1) will allow the kr and kθ spectra to be measured simultaneously. Heterodyne detection permits the wave propagation direction and multiple modes to be resolved unambiguously. Cross correlation of signals from each view may produce significant improvement in the scattering system spatial resolution. A reflectometry system will also be installed to study fluctuations and provide more localized measurement. This work was supported by U.S. DOE contract No. DE-FG03-86ER-53225 and DE-FG03-88ER-53267.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141733
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Effects of super-Gaussian electron velocity distributions on the ion feature of Thomson scattering off two-ion plasmas (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 1073-1078 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of super-Gaussian velocity distributions on the ion feature of Thomson scattering off two-ion plasmas is studied. The analytical solution to the dispersion equation shows that although both the frequencies of the two (fast and slow) ion-acoustic waves increase with the index of the super-Gaussian, the slow wave is more weakly dependent on the index due to the screening of the light ions. In the case that plasma can sustain two lightly damped ion-acoustic waves, the inferred plasma parameters such as electron temperature and plasma temperature ratio may suffer some errors without consideration of super-Gaussian electron velocity distributions. Since the relative intensity between the resonant peaks of the fast and slow waves is sensitive to the super-Gaussian index, the super-Gaussian velocity distributions may be measurable with Thomson scattering off laser-heated two species ion plasmas. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1454121
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Thomson scattering measurement of gold plasmas produced with 0.351 μm laser light (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 4144-4148 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Detailed measurements of gold plasmas produced with 0.351 μm laser light are reported. The temporal and spatial variations of Z¯Te are obtained in the case that pump intensities are 6.5×1013 and 1.4×1014 W/cm2. The experimental results are qualitatively consistent with two nonlocalized absorption models. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1391445
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Modification of electron transport due to dynamic screening of the Coulomb interaction (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 5259-5262 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dynamic screening of the Coulomb interaction is included to calculate electron transport coefficient (electron thermal conductivity) in the fluid limit for an unmagnetized plasma. Calculated results show that the dynamic screening effect can reduce electron thermal conductivity and may be important for low-Z plasma with very large electron–ion temperature ratio (Te/Ti(approximately-greater-than)103). © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1322559
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Influence of Rayleigh scattering on the ion feature of Thomson scattering spectrum from a partially stripped plasma (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2980-2982 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Studied in this paper is the influence of Rayleigh scattering on the ion feature of the Thomson scattering spectrum from a partially stripped plasma. The result shows that the profile of the scattering spectrum is nearly the same as that of Thomson scattering with inclusion of Rayleigh scattering, but the intensity of the scattering signal may be remarkably different from that of Thomson scattering. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1366617
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Experimental observation of ion-acoustic waves in an inhomogeneous dusty plasma (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 1459-1462 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The propagation of a dust-ion-acoustic wave (DIAW) wave down the steep density gradient in an inhomogeneous diffusive dusty plasma is experimentally studied. It is observed that the presence of the dust enhances the plasma inhomogeneity. The phase velocity of the DIAW increases rapidly with distance and becomes supersonic. The interplay between the effects of the density nonuniformity and collisional damping results in the continuous transition of the relative amplitude of the DIAW from damping to growth. The experimental data are in agreement with theoretical prediction and confirm the importance of density-dependent ion–dust collisions. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1362530
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...