Investigations of the Dynamics of Turbulent Transport: Implications for Self Consistent Transport Models, Transport Barrier Formation and Transport Evolution
- Univ. of Alaska, Fairbanks, AK (United States)
Turbulent transport is the mechanism by which turbulence moves “stuff”. This “stuff” can be anything from heat, moisture and pollution in neutral fluids to heat particles waste and momentum in plasmas. Understanding and controlling this turbulent transport is fundamental in many areas and is a crucial element on the path to the generation of usable fusion energy and the success of devices such as the International Thermonuclear Experimental Reactor (ITER). Our understanding of turbulent transport can improve our ability to trigger, sustain and control enhanced confinement regimes (regimes where the turbulent transport is reduced or controlled). The formation of an edge transport barrier is a central element of the H-mode, while internal transport barriers (ITB) open the path to advanced confinement regimes. Underlying this critical element is the need to understand the fundamental transport dynamics including those that lead to changes in the confinement regimes that creates these barriers including the new promising I-mode. The first part of this research was to further develop our already existing self-consistent model for the formation and evolution of transport barriers so that it can be applied to the investigation of transport dynamics in burning plasma conditions. The actual full simulation of the dynamics of barriers in these plasmas is a multi-scale problem that is still beyond current computational capabilities, however, we have shown in the past that simpler heuristic models can be constructed that exploit the universal characteristics of these regimes (which have been found in various regions of the confined plasma, from the edge to the core, and in various device types) and qualitatively capture the basic dynamics to a large extent. In the current project, we will exercise the model further using these new additions which will allow us to develop new schemes that can be tested experimentally for triggering and control of barriers in these enhanced confinement regimes in which a reasonable amount of power is provided by the α-particles produced as fusion by-products, as well as validating the physics of the models in burning plasma conditions. A possible mechanism for understanding the I-mode is explored in an extension to the model which, if successful, would have great promise for understanding and control. This mechanism also could be of great importance in many other areas ranging from chemical mixing to space and galactic plasmas. The second concurrent objective of the project is central to the successful modeling of transport in next-step devices. It is fundamentally understanding the underlying nature of self-consistent global transport in a gradient driven turbulent transport system. In addition to the physics value, this is essential to the goal of being able to produce reliable estimates of the global energy and α-particle confinement time in burning plasma conditions. It has been shown that many aspects of turbulent transport in confined plasmas behave in ways that are simply not consistent with the standard “diffusive” model of turbulent transport. We have shown in the past that a general paradigm for turbulent transport in magnetically confined plasmas, based on non-diffusive transport, can be successful in providing a reasonable explanation for some of the apparent discrepancies between most theoretical models of turbulent transport and experimental observations of the transport in these plasmas. These studies have opened up entire new types of behavior and have even made specific predictions of the needed elements for the large turbulence simulations to capture the correct transport physics. In this project, we have validated and extended these results with more complete, self-consistent primitive equation systems. A variety of codes have been used, with profile evolution, full transport diagnostics and in conjunction with the lessons learnt from the previous work with simple models, to investigate scalings, regimes of universal behavior and the effect of isotropy and homogeneity breaking mechanisms such as flows, phase shifts and edge effects. This project has led to an improved basic understanding of the fundamentals of turbulent transport and its control that in turn will improve the modeling of burning plasma devices and can then lead to an increase in the likelihood of the successful utilization of fusion energy.
- Research Organization:
- Univ. of Alaska, Fairbanks, AK (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- DOE Contract Number:
- FG02-04ER54741
- OSTI ID:
- 1485313
- Report Number(s):
- DOE-UAF-54741-1
- Country of Publication:
- United States
- Language:
- English
Similar Records
U.S. Transport Task Force Meeting - April 2014 Final Report
EMAPS: An Efficient Multiscale Approach to Plasma Systems with Non-MHD Scale Effects