The latest BOUTþþ studies show an emerging understanding of dynamics of edge localized mode (ELM) crashes and the consistent collisionality scaling of ELM energy losses with the world multitokamak database. A series of BOUTþþ simulations are conducted to investigate the scaling characteristics of the ELM energy losses vs collisionality via a density scan. Linear results demonstrate that as the pedestal collisionality decreases, the growth rate of the peeling-ballooning modes decreases for high n but increases for low n (1 < n < 5), therefore the width of the growth rate spectrum c(n) becomes narrower and the peak growth shifts to lower n. Nonlinear BOUTþþ simulations show a two-stage process of ELM crash evolution of (i) initial bursts of pressure blob and void creation and (ii) inward void propagation. The inward void propagation stirs the top of pedestal plasma and yields an increasing ELM size with decreasing collisionality after a series of microbursts. The pedestal plasma density plays a major role in determining the ELM energy loss through its effect on the edge bootstrap current and ion diamagnetic stabilization. The critical trend emerges as a transition (1) linearly from ballooning-dominated states at high collisionality to peelingdominated states at low collisionality with decreasing density and (2) nonlinearly from turbulence spreading dynamics at high collisionality into avalanche-like dynamics at low collisionality. V C 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4905070]The phenomena of nonlocal transport, such as avalanches or turbulence spreading, are well-known in diverse systems. Examples include, but are not limited to: piles of granular matter, discrete energy dissipating events in earthquakes and solar flares, and turbulent overshoot and penetration in fluid turbulence. Nonlocal dynamics of turbulence, transport, and zonal flows are often observed in plasma turbulence simulations and experiments, such as Edge Localized Modes (ELMs) in tokamaks. ELMs are a common characteristic feature of the tokamak H-mode plasma regime, where the high frequency ELM instability repeats periodically throughout the high confinement mode (H-mode) phase of the discharge. 1 The instability causes quasi-periodic relaxations of the edge pedestal, resulting in a series of hot plasma eruptions on a fast MHD timescale and leading to large energy fluxes to the plasma facing components (PFCs), which will suffer from excessive ablation, fast erosion, or melting. The concern about the survival of PFCs in ITER has sparked intense interest in ELM dynamics and in the parameter scaling of ELM energy loss. Numerous experiments in divertor tokamaks have shown a decrease in the relative type I ELM energy loss with increasing pedestal density (collisionality) over a decade ago. 2 There are attempts to provide an explanation for the dependence of ELM energy loss on collisionality. 3 However, there is as yet no common accepted explanation of the observed scaling neither from analytical theory nor numerical simulations. 4He...
This Letter presents an extension of a recently developed technique for speeding up the iterative solution of MOM linear equations—referred to in the literature [4,5] as the MNM method—when sweeping the frequency in the content of RCS computation. It is shown that extended MNM is useful for efficient iterative solution of the multiple right‐hand‐side situations arising in the angular sweep problem. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 273–276, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10436
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.