Study of temperature dependence of hydrogen retention in lithium coatings on stainless steel with the Materials Analysis Particle Probe (MAPP)

Bedoya Arroyave, Carlos Felipe

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Description

Title

Study of temperature dependence of hydrogen retention in lithium coatings on stainless steel with the Materials Analysis Particle Probe (MAPP)

Author(s)

Bedoya Arroyave, Carlos Felipe

Issue Date

2015-12-09

Director of Research (if dissertation) or Advisor (if thesis)

Allain, Jean Paul

Department of Study

Nuclear, Plasma, & Radiological Engineering

Discipline

Nuclear, Plasma, & Radiological Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Plasma Materials Interactions (PMI)
• Nuclear fusion
• X ray Photoelectron Spectroscopy (XPS)
• tokamak
• National Spherical Torus eXperiment - Updated (NSTX-U)
• Lithium Tokamak eXperiment (LTX)
• Materials Analysis Particle Probe (MAPP)

Abstract

Plasma materials interactions (PMI) in tokamak machines play a crucial role in the overall plasma performance. For this reason PMI research has gained great interest during the last couple of decades. Proper conditioning of Plasma Facing Components (PFCs) has shown to have dramatic effects in important plasma parameters as plasma current and density. Several conditioning approaches have been developed and investigated e.g. plasma glows and vessel bake outs. Furthermore, conditioning via the deposition of thin films of low Z metals such as Li has also been explored. The positive effects of Li on fusion plasmas have been reported in several studies. One important conclusion of those, is the fact that all the improvements associated with Li coatings on PFCs vary dramatically during the course of a campaign, being depended on numerous factors, such as time, residual gases composition and plasma exposures. This illustrates the complicated and symbiotic relationship between the state of the plasma facing materials and the plasma itself. As a consequence, the need for detailed and quantitative results documenting that relationship increased. Controlled experiments in laboratories have been performed in combination with post- mortem analysis of divertors tiles. However, both method have key shortcomings that limit the depth of their results. This work is dedicated to the development, upgrade and implementation of an alternative analysis technique. The Materials Analysis Particle Probe (MAPP) is an in-vacuo characterization facility, designed to analyze samples exposed to tokamak plasmas. MAPP was engineered to be attached to tokamak machines and expose a set of samples to a little as a single shot, the samples can then be retracted to a chamber for chemical analysis. MAPP is equipped to perform X ray Photoelectron Spectroscopy (XPS), Ion Scattering Spectroscopy (ISS), Direct Recoil Spectroscopy (DRS) and Thermal Desorption Spectroscopy (TDS). The hardware used to execute these tech- niques is controlled via a set of LabView® virtual instruments (VIs). Additional VIs were also developed for safety interlocks and control of vacuum hardware on the chamber. MAPP was initially designed to be deployed in the National Spherical Tokamak eXperiment (NSTX), however, given its versatility it can also be used in other machines. As such, this work includes a chapter detailing the experience and results gathered while MAPP was installed on the Lithium Tokamak eXperiment (LTX). Finally, a summary of the installation activities to connect MAPP to NSTX-U and a list of possible experiments to be performed with the machine will be given.

Graduation Semester

2015-12

Type of Resource

text

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Copyright and License Information

Copyright 2015 by Carlos Felipe Bedoya Arroyave

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