59th Annual Meeting of the APS Division of Plasma Physics
Volume 62, Number 12
Monday–Friday, October 23–27, 2017;
Milwaukee, Wisconsin
Session YI2: SOL and Divertor
9:30 AM–12:30 PM,
Friday, October 27, 2017
Room: 102ABC
Chair: John Canik, Oak Ridge National Laboratory
Abstract ID: BAPS.2017.DPP.YI2.4
Abstract: YI2.00004 : Density profiles in the Scrape-Off Layer interpreted through filament dynamics
11:00 AM–11:30 AM
Preview Abstract
View Presentation
Abstract
Author:
Fulvio Militello
(Culham Centre for Fusion Energy)
We developed a new theoretical framework to clarify the relation between
radial Scrape-Off Layer density profiles and the fluctuations that generate
them. The framework provides an interpretation of the experimental features
of the profiles and of the turbulence statistics on the basis of simple
properties of the filaments, such as their radial motion and their draining
towards the divertor. L-mode and inter-ELM filaments are described as a
Poisson process in which each event is independent and modelled with a wave
function of amplitude and width statistically distributed according to
experimental observations and evolving according to fluid equations. We will
rigorously show that radially accelerating filaments, less efficient
parallel exhaust and also a statistical distribution of their radial
velocity can contribute to induce flatter profiles in the far SOL and
therefore enhance plasma-wall interactions. A quite general result of our
analysis is the resiliency of this non-exponential nature of the profiles
and the increase of the relative fluctuation amplitude towards the wall, as
experimentally observed. According to the framework, profile broadening at
high fueling rates can be caused by interactions with neutrals (e.g. charge
exchange) in the divertor or by a significant radial acceleration of the
filaments. The framework assumptions were tested with 3D numerical
simulations of seeded SOL filaments based on a two fluid model. In
particular, filaments interact through the electrostatic field they generate
only when they are in close proximity (separation comparable to their width
in the drift plane), thus justifying our independence hypothesis. In
addition, we will discuss how isolated filament motion responds to
variations in the plasma conditions, and specifically divertor conditions.
Finally, using the theoretical framework we will reproduce and interpret
experimental results obtained on JET, MAST and HL-2A.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2017.DPP.YI2.4