4/19/2010 Colloquium - Russ Doerner

Russ Doerner University of California, San Diego

Event Info

Title:  Multi-component Plasma Interactions with Elemental and Mixed-material Surfaces

Date: Apr 19, 2010
Location: 3105 Etcheverry Hall
Time: 4-5pm

Abstract

While significant advances in the understanding of PMI have occurred in recent years, much of this understanding concerns the interaction of a single-component plasma with an elemental material surface. This should be contrasted to ITER where material migration from the differing plasma-facing surfaces will lead to the formation of mixed-material surfaces interacting with the incident plasma. In addition, burning plasma will generate helium ash that will be included in the plasma reaching the surfaces surrounding the plasma. In present and proposed confinement devices, radiating species (such as argon, neon or nitrogen) are intentionally added to the divertor plasma and these radiating species will affect the PMI. This talk summarizes results from the PISCES steady-state plasma sources at UCSD showing that plasma-surface interactions (both erosion and retention properties) cannot easily be predicted by the superposition of results from pure, single-component plasma interacting with elemental surfaces. Small amounts of condensable impurities in the incident plasma can have dramatic consequences to the erosion behavior of the surface (for example, beryllium carbide surface layer formation on carbon samples exposed to beryllium containing plasma), whereas small amounts of non-condensable impurities (such as helium) have been observed to dramatically alter the retention of fuel species within the plasma-exposed material. The simulation plasma used to investigate plasma-material interactions, therefore, must be configured to conform as closely as possible to the conditions expected in confinement devices, both with respect to composition of materials in a surface, as well as constituents of the impinging plasma, to understand the evolution of surfaces and the feedback of the resultant surfaces to the incident plasma.

Speaker Biography

Dr. Doerner received degrees from Texas A&M University (B.S. in Physics, 1981) and the University of Wisconsin-Madison (M.S. in Materials Science, 1984 and Ph.D. in Electrical Engineering, 1988). Since that time he has performed experiments in the edge and scrape-off layer plasma of confinement machines throughout the world and has been involved in fundamental plasma-material interaction measurements. He presently leads the plasma-material interaction research program in the PISCES Laboratory at UCSD and was recently selected to lead the UCSD co-center of the Plasma-Surface Interaction Science Center, a collaborative effort with UC-Berkeley and MIT.