A tutorial course with contributions from experts in the fields covered by the meeting will be held on Sunday, 17 June, 2018 from 1:00 PM – 5:30 PM in Richardson Auditorium.
These introductory lectures are open to all the participants and are particularly dedicated to PhD students, PostDocs, and newcomers in the field. The talks and speakers will be:
- 1:00 PM Physics of Linear Devices – Greg deTemmerman, Coordinating scientist Edge plasma and Plasma Wall Interactions, ITER Organisation (abstract below).
- 2:00 PM Chemistry at the edge: Surface science probes of plasma-materials interactions – Professor Bruce E. Koel, Department of Chemical and Biological Engineering, Princeton University (abstract below).
- 3:30 PM 3D Stellarator Edge Physics – Yuhe Feng, Senior Scientist. Stellarator Theory Division, Max-Planck Institute for Plasma Physics, Greifswald (abstract below).
- 4:30 PM SOL physics + heat dissipation – Robert Goldston, Professor of Astrophysical Sciences, Princeton University (abstract below).
The conference will open on Monday morning with an introductory talk by Prof. R. Socolow ‘In a low-carbon future, where does fusion fit in?’ (abstract below).
Speakers, please refer to important instructions for uploading your presentations.
Understanding plasma-material interactions in fusion devices using linear plasma devices
G. De Temmerman, ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex France
In a fusion device, power from the core plasma has to be exhausted by the surrounding plasma-facing components (PFC) which are thus exposed to high heat (up to >10MW.m-2) and particle fluxes (up to 10^24 m-2 s-1). In ITER, materials will be exposed to unprecedented fluences of low energy particles and regular thermal shocking from transient events. Understanding plasma-material interactions (PMI) is therefore a high priority topic to ensure successful operations of ITER and allow the development of advanced materials/PFCs.
The intrinsic complexity of fusion devices, means that PMI studies are either campaign integrated, with samples recovered during machine openings, or rely on the use of dedicated probe systems allowing samples to be exposed and retracted without the need for a vessel vent.
Linear plasma devices, sometimes called divertor simulators, provide a cost-effective access to fusion-relevant conditions and offer the opportunity to investigate the synergistic and coupled effects taking place at the plasma-material interface. They also offer a good control over the plasma and surface conditions allowing parameters to be varied in a systematic manner.
This contribution will introduce PMI in fusion devices, discuss the design principles behind modern LPDs and highlight some of their key contributions to fusion research.
Chemistry at the edge: Surface science probes of plasma-materials interactions
B.E. Koel, Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08540, USA
The chemical composition of surface and near-surface layers of materials in tokamaks has a powerful influence on plasma performance, however it is typically hidden from view. Insights into processes and properties of plasma facing surfaces can be obtained via surface analytical and imaging techniques. These include electron spectroscopies, ion scattering, and electron microscopy that can offer finely detailed atomistic-scale information. In addition, temperature programmed desorption (TPD) mass spectrometry can probe thermal stability, reactivity, and measure deuterium uptake and retention. We will review the fundamentals of these techniques and illustrate their application in investigations of boronization, erosion and deposition, and hydrogen retention in lithium-coated PFCs. Finally, we will discuss lab-based studies, in which quantitative measurements are obtained under controlled conditions on well-defined surfaces in order to provide a fundamental framework for understanding reaction mechanisms at the plasma-materials interface. These can provide direct comparisons to and validation of theoretical calculations and simulations.
3D Stellarator Edge Physics
Y. Feng Max-Planck-Institute fuer Plasmaphysik, Greifswald/Garching Germany
Divertor concepts presently explored on stellarators utilize resonant helical field components inherently existing in the field spectrum of 3D-shaped coils. Typical examples are the island divertor for the advanced low-shear stellarators W7-AS and W7-X and the helical divertor for the high-shear, large helical device LHD. Because of resonance effects even a small low-order resonant field component in the orders of 10-4-10-3 can cause a significant departure of field lines from their original rational surface to form magnetic islands. Depending on the field spectrum and the rotational transform profile at the edge, the scrape-off layers in stellarators usually exhibit complex 3D field structures in which closed, open and even stochastic field-lines co-exist. As plasma transport is closely bound with magnetic fields, an interesting question emerges as to how a divertor works with such complex magnetic fields. This topic has been investigated over more than one decade both experimentally on W7-AS and LHD, and theoretically using the EMC3-Eirene code and simple models. Using the island divertor as example, the present paper gives a brief overview on what we think we have understood about this complex topic, what are the uncertain and open issues, and what is expected for W7-X, which recently went into operation.
SOL physics + heat dissipation – Robert Goldston, Professor of Astrophysical Sciences, Princeton University.
The scrape-off layer (SOL) forms the plasma side of the plasma-material interface. As a result, understanding the SOL is a key element in solving the problems that arise at this interface: high heat flux, material erosion, and impurity influx to the main plasma. We will review the basic theory of the SOL, including the elementary two-point model and the transformation from heat flux crossing the last-closed flux surface to heat flux arriving at a divertor or limiter target. Next we will survey the stunning experimental results of the last seven years, indicating that the SOL power scrape-off width scales roughly with the poloidal gyro-radius, rather than with the system size, as previously assumed. Then we will explore the implications of a very narrow SOL: the very high projected heat flux on limiters and divertors in attached plasmas, the problem of detachment with such a small scrape-off layer volume to radiate power, and the potential role of the SOL in setting the density limit of H-mode operation. Finally we will review the range of theoretical treatments that are consistent with these results, and their predictions for the future.
In a low-carbon future, where does fusion fit in?
Prof. Robert Socolow, Princeton University
In this talk, I will tell a linear and a non-linear story. The linear story is of ever-greater global determination to slow the arrival of dangerous climate change. The non-linear story is of the competitions among low-carbon alternatives for the global energy system.
The glamor of fusion energy emerged into a 1950s world where time horizons were much longer than they are today: the finitude of fossil-fuel and even uranium resources led to a search for an energy system that could last at least thousands of years. The dire consequences of the greenhouse effect on much shorter time scales were not recognized then, but they have gained prominence monotonically, and the time frame of energy conversations is now decades, Low-carbon technology is arriving; what is uncertain is how quickly and how disruptively. The new vocabulary of carbon management includes stabilization wedges, carbon budgets, temperature ceilings, overshoots, and negative carbon.
Within this evolving conversation, many low-carbon energy options are competing for the public’s favor. The competition is often contentious, with advocates of one option often genuinely dismayed that some other option is being taken seriously. The latest news is not favorable to fusion. Costs have plunged for power harvested by the photovoltaic panel and the wind turbine, as both have benefited from modularity. Meanwhile, construction costs have soared for commercial nuclear fission power plants and demonstration coal plants that capture CO2. The idea that “baseload” power is essential is being undermined. The fusion community must recognize a new question: how effectively can fusion power complement wind and solar, given their inherent deficiencies of intermittency and unpredictability? Fusion competes here with load-following natural gas and fission power plants, with load-following on the demand side (demand-side management), and with energy storage. Can the magnificent plasma science that many of you are currently pursuing reveal hitherto unappreciated opportunities for the burning plasma in such a competition?
I can’t require any reading, but I hope some of you will read the “fusion distillate”:
Co-authors and I explain the technology and policy dimensions of magnetic confinement fusion power to readers with technological appetite but no previous specialized background. I believe we have written a uniquely balanced and accessible introduction to your field. I welcome your reactions.