Events in Physics
On the physics of the first wall in fusion devices
Title: On the physics of the first wall in fusion devices
By: Sergei Krasheninnikov (University California San Diego)
Date: Wednesday 19th June 2013
Where: PLT
Time: 16.30pm
Abstract:
Over the years, and in particular with the beginning of the ITER era, it became clear that the fusion has, at least, two major issues: core plasma confinement and the performance of the first wall. Different aspects of the plasma confinement were the subjects of intense theoretical and experimental studies for a long time and the main plasma physics issues are rather familiar to the theoretical part of fusion community. On the contrary, the studies of the physics of the first wall in fusion devices, in particular some puzzling experimental observations and theoretical issues, approaches, models, etc., are not very familiar to fusion plasma theorists. Meanwhile, already existing experimental observations and theoretical models show that the irradiation of the first wall by fusion relevant plasmas results in interesting and rich physics of i) first wall material evolution, and ii) behavior of hydrogen/helium gas absorbed by the wall. Both these issues often exhibit strong synergistic effects and have direct and important implications for all future fusion reactors.
In this talk we start with reviewing main issues of the first wall in fusion devices, experimental technique, and the most interesting and, in many cases, puzzling experimental observations, including the formation of “swamp” of helium nano-bubbles, “fuzz”, hydrogen outgassing, etc. Then, we outline the main theoretical approaches used to study the physics of the first wall, including Molecular Dynamic (MD) simulation, continuum Reaction-Diffusion (RD) models, etc. We illustrate the outcomes of these approaches with some particular examples, trying to link them to the experimental data. We will also emphasize some common features of the models that describe transport processes in the wall, magnetized plasmas and beyond. In the conclusions, we will discuss the existing gaps of our understanding of the physics of the first wall.