Convective transport in the scrape-off layer of tokamaks

Aydemir, A. Y.

doi:10.1063/1.1927539

Cited by 62 publications

(86 citation statements)

References 20 publications

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“…[3]. In controlled fusion, this effect is studied in association with the formation of coherent structures (blobs) in the scrape-off layer of tokamak plasmas [4] In geophysics, the observed rocking of the floating bubbles in the equatorial ionospheric F-region is attributed to this effect [5]. Similarly, a zigzag path of magnetic flux tubes emerging in the solar interior, caused by vortex shedding, has been found in numerical simulations [6].…”

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confidence: 95%

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Phenomenon of Alfvénic Vortex Shedding

et al. 2010

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“…However, the results obtained can be easily applied to other relevant plasma systems by straightforward renormalisation. Equations (1)(2)(3)(4)(5) are numerically solved with the use of the Lagrangian-remap code Lare2d [15]. In our studies we simulate the plasma dynamics in a domain …”

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confidence: 99%

Phenomenon of Alfvénic Vortex Shedding

et al. 2010

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“…[22][23][24][25][26][27][28][29][30][31][32][33][34][35] During their radial propagation, the blob-like structures develop a steep front and a trailing wake, which can also be observed in numerical simulations of isolated blob structures [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] and simulations of scrape-off layer turbulence. [51][52][53][54][55][56][57][58][59][60][61] Conditional averaging of experimental measurement data have shown that large-amplitude fluctuations are well described by an exponential wave form.…”

Section: Introductionmentioning

confidence: 99%

“…(38) and (43), respectively. In order to demonstrate this, the frequency spectra for two elementary pulse functions will be reviewed.…”

Section: A Derivatives and Discontinuitiesmentioning

confidence: 99%

Auto-correlation function and frequency spectrum due to a super-position of uncorrelated exponential pulses

Garcia

Theodorsen

2017

Physics of Plasmas

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The auto-correlation function and the frequency power spectral density due to a super-position of uncorrelated exponential pulses are considered. These are shown to be independent of the degree of pulse overlap and thereby the intermittency of the stochastic process. For constant pulse duration and a one-sided exponential pulse shape, the power spectral density has a Lorentzian shape which is flat for low frequencies and a power law at high frequencies. The algebraic tail is demonstrated to result from the discontinuity in the pulse function. For a strongly asymmetric two-sided exponential pulse shape, the frequency spectrum is a broken power law with two scaling regions. In the case of a symmetric pulse shape, the power spectral density is the square of a Lorentzian function. The steep algebraic tail at high frequencies in these cases is demonstrated to follow from the discontinuity in the derivative of the pulse function. A random distribution of pulse durations is shown to result in apparently longer correlation times but has no influence on the asymptotic power law tail of the frequency spectrum. The effect of additional random noise is also discussed, leading to a flat spectrum for high frequencies. The probability density function for the fluctuations is shown to be independent of the distribution of pulse durations. The predictions of this model describe the variety of auto-correlation functions and power spectral densities reported from experimental measurements in the scrape-off layer of magnetically confined plasmas.

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“…Following [9], we introduce here the typical blob size [34] and velocity [35]: The linear size of each blob in the radial and poloidal direction, a r and a q , are computed as the HWHM of the density fluctuation n r t n r t n r , , , , ,…”

Section: Characterization Of the Blob Size And Shapementioning

confidence: 99%

Blob properties in full-turbulence simulations of the TCV scrape-off layer

Nespoli

Furno

Labit

et al. 2017

Plasma Phys. Control. Fusion

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To investigate blob properties in the tokamak scrape-off layer (SOL), we perform dedicated numerical nonlinear simulations of plasma turbulence in the SOL of a TCV discharge using the Global Braginskii Solver code. A blob detection technique is used for the first time in a threedimensional (3D) full-turbulence simulation to track the motion of the filaments in the SOL. The specific size, density amplitude and radial velocity of the blobs are computed, with the typical values being 7.4 s r , n 0.33 e and c 0.016 s , respectively. The analysis of blob structure in the parallel direction shows that the blobs are partially detached from the limiter. The cross correlation analysis shows how the blobs are born all along the entire field line, not being generated primarily on the low field side SOL and expanding towards the limiter. The blob radial velocity agrees well with the inertial branch of the existing scaling law. The radial particle and heat fluxes given by blobs are shown to be responsible of up to 100% and 70% of the turbulent particle and heat flux in the far SOL, respectively. The results of a second simulation with a 40 times higher resistivity are also discussed.

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Convective transport in the scrape-off layer of tokamaks

Cited by 62 publications

References 20 publications

Phenomenon of Alfvénic Vortex Shedding

Phenomenon of Alfvénic Vortex Shedding

Auto-correlation function and frequency spectrum due to a super-position of uncorrelated exponential pulses

Blob properties in full-turbulence simulations of the TCV scrape-off layer

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