Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Micro ion beam analysis for the erosion of beryllium marker tiles in a tokamak limiter
KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
Show others and affiliations
2019 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 450, p. 200-204Article in journal (Refereed) Published
Abstract [en]

Beryllium limiter marker tiles were exposed to plasma in the Joint European Torus to diagnose the erosion of main chamber wall materials. A limiter marker tile consists of a beryllium coating layer (7–9 μm) on the top of bulk beryllium, with a nickel interlayer (2–3 μm) between them. The thickness variation of the beryllium coating layer, after exposure to plasma, could indicate the erosion measured by ion beam analysis with backscattering spectrometry. However, interpretations from broad beam backscattering spectra were limited by the non-uniform surface structures. Therefore, micro-ion beam analysis (μ-IBA) with 3 MeV proton beam for Elastic backscattering spectrometry (EBS) and PIXE was used to scan samples. The spot size was in the range of 3–10 μm. Scanned areas were analysed with scanning electron microscopy (SEM) as well. Combining results from μ-IBA and SEM, we obtained local spectra from carefully chosen areas on which the surface structures were relatively uniform. Local spectra suggested that the scanned area (≈600 μm × 1200 μm) contained regions with serious erosion with only 2–3 μm coating beryllium left, regions with intact marker tile, and droplets with 90% beryllium. The nonuniform erosion, droplets mainly formed by beryllium, and the possible mixture of beryllium and nickel were the major reasons that confused interpretation from broad beam EBS.

Place, publisher, year, edition, pages
Elsevier, 2019. Vol. 450, p. 200-204
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-244028DOI: 10.1016/j.nimb.2018.08.028ISI: 000474501400041Scopus ID: 2-s2.0-85052728569OAI: oai:DiVA.org:kth-244028DiVA, id: diva2:1288575
Note

QC 20190218

Available from: 2019-02-13 Created: 2019-02-13 Last updated: 2019-07-30Bibliographically approved
In thesis
1. Impact of Surface Structures onDeposition and Erosion in a Tokamak
Open this publication in new window or tab >>Impact of Surface Structures onDeposition and Erosion in a Tokamak
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Fusion is a potentially unlimited and environmentally friendly energy source for human society in the future. However, along the way towards the application of fusion energy there are still unresolved complications. Among them, deposition and erosion are two critical issues. Deposition of fuel and impurities brings potential long-term fuel retention which may generate safety issues and limit the economic efficiency of fusion devices. Moreover, the erosion of the vacuum vessel wall in a fusion device generates impurities which contaminate core plasma and can restrict the life time of plasma facing component. The work in this thesis focuses on deposition and erosion on tiles in the JET-ILW project, which consist of tungsten (or tungsten coating carbon fibre composited) in the divertor and beryllium in limiters.

For the deposition issue, micro ion beam analysis (µ-IBA) was used for observing deuterium and beryllium distributions over tile surfaces. The surface topography was obtained from SEM, optical microscope and confocal laser scan microscope. Distribution maps from IBA were compared with surface topography. To explain experimental results, modelling of ion trajectories was applied on real and artificial surfaces. Micro IBA results show that deuterium and beryllium accumulated in depressed areas, e.g. pits, cracks or craters. Modelling implies that ion gyration, surface roughness and inclination of the magnetic field could to some extent explain this non-uniform distribution of deuterium and beryllium. The same kind of issue, although on different scale length, occurs also for penetration of impurities into artificial castellation grooves, also studied experimentally in the thesis.

For the erosion issue, the thesis includes analysis of a limiter marker tile which is designed for observing material erosion in JET. A new method to acquire erosion data from such marker tiles is proposed, by combining micro IBA and SEM image.  This method could separate the influence on IBA from roughness, a problem in applying IBA on rough surface. Similar Technique is applied to improve the interpretation of IBA measurements of deep penetration of deuterium into layered surface structures.

Abstract [sv]

Fusion är en potentiellt obegränsad och miljövänlig energikälla för det mänskliga samhället i framtiden. Det återstår emellertid vissa problem att lösa. Bland dem är deposition och erosion vid ytor som är i kontakt med plasmat kritiska. Deposition av bränsle och föroreningar ger potentiellt långsiktig ackumulation av bränsle (tritium) som kan ge upphov till säkerhetsproblem och försämra bränsleekonomin. Erosion av vakuumkärlets väggar i in fusionsanläggning alstrar förorenar plasmat och kan begränsa livstiden för väggkomponenter. Arbetet i denna avhandling fokuserar på deposition och erosion på ytor i JET-ILW-projektet, som består av volfram (eller volframbelagd kolfiberkomposit) i divertor och beryllium i limiter.

För depositionsfrågorna användes mikroanalys för att observera hur deuterium och beryllium fördelas över ytorna efter plasmaexponering. Yttopografi erhölls från SEM, optisk mikroskopi och konfokal laserskanmikroskopi. Distributionskartor från IBA jämfördes med yttopografin. För att förklara experimentella resultat användes modellering av jontrajektorior, dels på verklig experimentell topografi, dels på förenklade modellytor. Micro IBA-resultat visar att deuterium och beryllium ansamlas i mikroskopiskt nedsänkta områden, t.ex. gropar och sprickor. Modelleringen visar att joners gyratation delvis kan förklara denna ojämna fördelning av deuterium och beryllium.

För erosionsproblemet gjordes mätningar på markerplattor, konstruerade för att observera materialosion i JET. En ny metod införs för att erhålla erosionsdata, genom att kombinera mikro IBA och SEM-bild. Denna metod kan skilja på inflytande på IBA-resultat från skrovlighet, vilket är annars är ett problem IBA för på skrovlig yta. På samma sätt används mikroanalys för att förbättra tolkningen av analyser av deuterium som trängt in i en skiktad struktur.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. p. 65
Series
TRITA-EECS-AVL ; 2019:11
Keywords
Deposition, erosion, JET, micro ion beam analysis, Deposition, erosion, JET, mikrojonstråleanalys
National Category
Fusion, Plasma and Space Physics
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-244029 (URN)978-91-7873-080-3 (ISBN)
Public defence
2019-03-08, F3, Lindstedtsvägen 26, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20190214

Available from: 2019-02-14 Created: 2019-02-13 Last updated: 2019-02-14Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Zhou, YushanBergsåker, HenricBykov, IgorPetersson, Per
By organisation
Fusion Plasma Physics
In the same journal
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Fusion, Plasma and Space Physics

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 65 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf