Blar i forfatter "Kube, Ralph"

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    • Scrape-off layer turbulence in TCV: Evidence in support of stochastic modelling. 

      Theodorsen, Audun; Garcia, Odd Erik; Horacek, Jan; Kube, Ralph; Pitts, RA (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-28)
      Intermittent fluctuations in the TCV scrape-off layer have been investigated by analysing long Langmuir probe data time series under stationary conditions, allowing calculation of fluctuation statistics with high accuracy. The ion saturation current signal is dominated by the frequent occurrence of large-amplitude bursts attributed to filament structures moving through the scrape-off layer. The ...

    • Statistical properties of fluctuation driven flows in the outboard mid-plane SOL of Alcator C-Mod 

      Kube, Ralph; Garcia, Odd Erik; Theodorsen, Audun; Kuang, Adam; Brunner, Dan; LaBombard, Brian; Terry, Jim L. (Conference object; Konferansebidrag, 2018)
      The scale length of the radial density profile in scrape-off layer plasmas has been shown to depend on the line-averaged plasma density. While first reported on AlcatorC-Mod, recent work verifies this phenomena in JET and ASDEX Upgrade. In low density plasmas with a sheath-limited SOL, the density profiles present a two-scale structure which allows the separation of the SOL into two distinct regions. ...

    • Statistical properties of the plasma fluctuations and turbulent cross-field fluxes in the outboard mid-plane scrape-off layer of Alcator C-Mod 

      Kube, Ralph; Garcia, Odd Erik; Theodorsen, Audun; Kuang, Adam; LaBombard, Brian; Terry, Jim L.; Brunner, Dan (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-29)
      The Alcator C-Mod mirror Langmuir probe diagnostic is used to characterize plasma fluctuations in the outboard mid-plane scrape-off layer (SOL). Ohmically heated L-mode plasmas with Greenwald fractions from 0.1 to 0.45 are analyzed. In plasmas with a low line-averaged core density, the radial profiles of the average electron density and temperature feature a two-scale structure with a strong gradient ...

    • Stochastic modeling of scrape-off layer fluctuations 

      Kube, Ralph; Theodorsen, Audun; Garcia, Odd Erik; Brunner, Daniel; Kuang, Adam; LaBombard, Brian; Terry, James L. (Conference object; Konferansebidrag, 2017-08-24)
      1. Stochastic model of data time series <br> 2. Comparison to experimental measurements

    • Stochastic modelling of intermittent fluctuations in the scrape-off layer: Correlations, distributions, level crossings, and moment estimation 

      Garcia, Odd Erik; Kube, Ralph; Theodorsen, Audun; Pecseli, Hans (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05)
      A stochastic model is presented for intermittent fluctuations in the scrape-off layer of magnetically confined plasmas. The fluctuations in the plasma density are modeled by a super-position of uncorrelated pulses with fixed shape and duration, describing radial motion of blob-like structures. In the case of an exponential pulse shape and exponentially distributed pulse amplitudes, predictions are ...

    • Unified transport scaling laws for plasma blobs and depletions 

      Wiesenberger, Matthias; Held, Markus; Kube, Ralph; Garcia, Odd Erik (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-14)
      We study the dynamics of seeded plasma blobs and depletions in an (effective) gravitational field. For incompressible flows, the radial center of mass velocity of blobs and depletions is proportional to the square root of their initial cross-field size and amplitude. If the flows are compressible, this scaling holds only for ratios of amplitude to size larger than a critical value. Otherwise, the ...

    • Universality of intermittent fluctuations in the Alcator C-Mod scrape-off layer 

      Kube, Ralph; Garcia, Odd Erik; Theodorsen, Audun; Brunner, Dan; Kuang, Adam; LaBombard, Brian; Terry, Jim L. (Conference object; Konferansebidrag, 2017)

    • Universality of Poisson-driven plasma fluctuations in the Alcator C-Mod scrape-off layer 

      Theodorsen, Audun; Garcia, Odd Erik; Kube, Ralph; LaBombard, Brian; Terry, James L. (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-18)
      Large-amplitude, intermittent fluctuations are ubiquitous in the boundary region of magnetically confined plasmas and lead to detrimental plasma-wall interactions in the nextgeneration, high duty cycle fusion power experiments. Using gas puff imaging data time series from the scrape-off layer in the Alcator C-Mod device, it is here demonstrated that the large-amplitude fluctuations can be described ...

    • Velocity scaling for filament motion in scrape-off layer plasmas 

      Kube, Ralph; Garcia, Odd Erik (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)