Methods for the analysis of low-Z plasma facing surfaces in magnetic fusion applications
type: CreativeWork
description: A number of advances in the design and operating performance of magnetic fusion devices have been made in recent decades. While the optimization of reactor components and magnetic topologies have led to considerable improvements in plasma density, temperature, and confinement time, research also suggests that materials selection in plasma-facing components (PFCs) can also have a substantial impact on plasma performance. Within the plasma-material interaction (PMI) community, the application of low-Z materials on wall components is of particular interest. In order to better understand the behavior of various low-Z systems, two PFC studies are described herein. The goals of these studies were to: (1) better understand material migration in boronized graphite wall tiles via the ex-vessel characterization of the B-O-C layer in exposed graphite samples, and (2) explore issues relating to the impacts of handling and processing on a liquid phase Sn-Li binary alloy. The National Spherical Torus Experiment Upgrade (NSTX-U) has been used to investigate the effect of wall tile surface conditioning on plasma performance during operation. Previous campaigns have demonstrated the enhanced suppression of edge-localized modes (ELMs) and reduced divertor recycling when wall tile conditioning via boronization was performed, and high confinement (H-mode) operating conditions were routinely achieved during operation after conditioning. In order to better understand the impact of surface conditioning and subsequent plasma exposure on wall materials, cored sample of the exposed NSTX-U wall tiles were obtained and their surface chemistry was analyzed. The boronized NSTX-U samples were analyzed using X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and Rutherford backscattering spectrometry (RBS). In addition, variations in surface morphology in each tile were mapped using a 3D laser scanning confocal microscope. Similar to the pure low-Z c…
abstract: A number of advances in the design and operating performance of magnetic fusion devices have been made in recent decades. While the optimization of reactor components and magnetic topologies have led to considerable improvements in plasma density, temperature, and confinement time, research also suggests that materials selection in plasma-facing components (PFCs) can also have a substantial impact on plasma performance. Within the plasma-material interaction (PMI) community, the application of low-Z materials on wall components is of particular interest. In order to better understand the behavior of various low-Z systems, two PFC studies are described herein. The goals of these studies were to: (1) better understand material migration in boronized graphite wall tiles via the ex-vessel characterization of the B-O-C layer in exposed graphite samples, and (2) explore issues relating to the impacts of handling and processing on a liquid phase Sn-Li binary alloy. The National Spherical Torus Experiment Upgrade (NSTX-U) has been used to investigate the effect of wall tile surface conditioning on plasma performance during operation. Previous campaigns have demonstrated the enhanced suppression of edge-localized modes (ELMs) and reduced divertor recycling when wall tile conditioning via boronization was performed, and high confinement (H-mode) operating conditions were routinely achieved during operation after conditioning. In order to better understand the impact of surface conditioning and subsequent plasma exposure on wall materials, cored sample of the exposed NSTX-U wall tiles were obtained and their surface chemistry was analyzed. The boronized NSTX-U samples were analyzed using X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and Rutherford backscattering spectrometry (RBS). In addition, variations in surface morphology in each tile were mapped using a 3D laser scanning confocal microscope. Similar to the pure low-Z c…
author: Sandefur, Heather Nicole
language: en
keywords: Nuclear fusion, plasma-material interactions
date published: 2020-03-02T22:15:17Z
date modified: 2026-07-22T22:24:45Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois at Urbana-Champaign

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2142/106388