Computations of Intermittent Transport in Scrape-Off Layer Plasmas

Abstract

Two-dimensional fluid simulations of interchange turbulence for geometry and parameters relevant for the scrape-off layer of magnetized plasmas are presented. The computations, which have distinct plasma production and loss regions, reveal bursty ejection of particles and heat from the bulk plasma in the form of blobs. These structures propagate far into the scrape-off layer where they are dissipated due to transport along open magnetic field lines. From single-point recordings it is shown that the blobs have asymmetric conditional wave forms and lead to positively skewed and flattened probability distribution functions. The radial propagation velocity may reach one-tenth of the sound speed. These results are in excellent agreement with recent experimental measurements.

Impact of large island perturbations on turbulent blob transport in tokamaks

“…It is found that these ergodized magnetic structures cause a strong suppression of blob transport in the SOL and that edge localized modes ͑ELM's͒ are reduced or even disappear. A number of numerical investigations of SOL turbulence and blob transport have been performed on the basis of 2D fluid models [6][7][8][9] and 3D gyrofluid models. 10 Simulations of 3D drift turbulence in ergodized magnetic configurations without SOL effects have been reported in Refs.…”

Stochastic Modeling of Intermittent Scrape-Off Layer Plasma Fluctuations

“…This results in singlepoint recordings dominated by large-amplitude bursts, which have an asymmetric wave form with a fast rise and a slow decay, and positively skewed and flattened amplitude probability density functions [7][8][9][10][11][12][13][14]. Measurements on a number of tokamak experiments have demonstrated that as the empirical discharge density is approached, the radial SOL particle density profile becomes broader and plasma-wall interactions increase [11][12][13][14][15].…”

“…This is the typical wave form found from probe and gas puff imaging measurements in the far SOL [7][8][9][10][11][12][13]. The integral given in Eq.…”

Turbulence and bias-induced flows in simple magnetized toroidal plasmas

“…Away from the walls of the plasma chamber, the spatial structures at these parameters are approximately periodic over a vertical distance L v /N and have toroidal wavelengths 2πR, consistent with the k 0 nature of the interchange modes noted earlier [4]. The evolution of turbulence driven by the interchange instability displays an intermittent (bursty) character [14]. During the burst shown in Fig.…”

“…In the unbiased case, the interchange instability in the SMT was initially simulated with the electrostatic twodimensional (2D) fluid model [5,12,13] that includes plasma sources and parallel losses. Similar fluid models are also used to study the interchange instability in the SOL of tokamaks [14,15]. In the 2D simulations of the SMT configuration, the vertical extent of the simulation domain is controlled by the pitch of the field lines: assuming k = 0, all quantities must be periodic in the vertical direction on the length scale L v /N .…”