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Analysis of deposited layers with deuterium and impurity elements on samples from the divertor of JET with ITER-like wall
KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics. (Plasma-Wall Interactions)ORCID iD: 0000-0001-9299-3262
KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.ORCID iD: 0000-0001-9901-6296
KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
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2019 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 516, p. 202-213Article in journal (Refereed) Published
Abstract [en]

Inconel-600 blocks and stainless steel covers for quartz microbalance crystals from remote corners in the JET-ILW divertor were studied with time-of-flight elastic recoil detection analysis and nuclear reaction analysis to obtain information about the areal densities and depth profiles of elements present in deposited material layers. Surface morphology and the composition of dust particles were examined with scanning electron microscopy and energy-dispersive X-ray spectroscopy. The analyzed components were present in JET during three ITER-like wall campaigns between 2010 and 2017. Deposited layers had a stratified structure, primarily made up of beryllium, carbon and oxygen with varying atomic fractions of deuterium, up to more than 20%. The range of carbon transport from the ribs of the divertor carrier was limited to a few centimeters, and carbon/deuterium co-deposition was indicated on the Inconel blocks. High atomic fractions of deuterium were also found in almost carbon-free layers on the quartz microbalance covers. Layer thicknesses up to more than 1 micrometer were indicated, but typical values were on the order of a few hundred nanometers. Chromium, iron and nickel fractions were less than or around 1% at layer surfaces while increasing close to the layer-substrate interface. The tungsten fraction depended on the proximity of the plasma strike point to the divertor corners. Particles of tungsten, molybdenum and copper with sizes less than or around 1 micrometer were found. Nitrogen, argon and neon were present after plasma edge cooling and disruption mitigation. Oxygen-18 was found on component surfaces after injection, indicating in-vessel oxidation. Compensation of elastic recoil detection data for detection efficiency and ion-induced release of deuterium during the measurement gave quantitative agreement with nuclear reaction analysis, which strengthens the validity of the results.

Place, publisher, year, edition, pages
2019. Vol. 516, p. 202-213
Keywords [en]
Fusion, Tokamak, Plasma-wall interactions, ToF-ERDA, NRA, SEM
National Category
Fusion, Plasma and Space Physics
Research subject
Physics
Identifiers
URN: urn:nbn:se:kth:diva-240616DOI: 10.1016/j.jnucmat.2018.11.027ISI: 000458897100020Scopus ID: 2-s2.0-85060313456OAI: oai:DiVA.org:kth-240616DiVA, id: diva2:1273304
Note

QC 20190125

Available from: 2018-12-20 Created: 2018-12-20 Last updated: 2019-08-08Bibliographically approved
In thesis
1. Material characterization for magnetically confined fusion: Surface analysis and method development
Open this publication in new window or tab >>Material characterization for magnetically confined fusion: Surface analysis and method development
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The dream of abundant clean energy has brought scientists and laypeople alike to ponder the possibilities of nuclear fusion since it was established as the energy source of the stars in 1939. Starting from the mid the 20th century, significant effort has been put into overcoming the technological challenges related to the construction of a power plant, but initial optimism has faded somewhat due to a notable absence of practical outcomes. Nevertheless, the research continues and progress is made slowly but surely.

The present work deals with a small part of the fusion puzzle, namely the materials to be used in the first wall surrounding a magnetically confined plasma. Carbon, which has historically been considered as the most viable element for this role, has been ruled out due to issues with plasma-induced erosion, hydrocarbon formation and a buildup of thick deposited material layers on wall components. The latter two lead to an unacceptable accumulation of radioactive tritium, both in the deposited layers and in dust particles. A metal wall, which would alleviate these particular problems but increase the severity of others, is therefore envisioned for a future demonstration reactor.

Three contributions to the overall research effort are made though this thesis. First, an increased understanding of plasma-induced erosion of so-called reduced activation ferritic-martensitic steels and preferential sputtering of light material components is provided. High-resolution ion beam analysis and microscopy methods are used to examine samples of such a steel after exposure to plasma under controlled circumstances. Model films consisting of a mixture of iron and tungsten deposited on silicon substrates are also studied as they constitute simpler systems where the effects of interest may be simulated. The knowledge obtained is necessary for an assessment of the possibility to use reduced activation steel as a plasma-facing material in specific regions of a reactor wall.

The second contribution consists of reports on the composition of deposited material layers on wall components retrieved from the plasma confinement experiments JET and TEXTOR. These provide limited conclusions on the range and rate of material erosion, transport and deposition in two cases.

Finally, a detection system for the ion beam technique elastic recoil detection analysis has been assembled, tested and put into operation. In addition to improving the quality of analyses performed on fusion-related materials, the system has become an established tool available for users of the 5 MV electrostatic pelletron accelerator at Uppsala University’s Tandem Laboratory.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. p. 189
Series
TRITA-EECS-AVL ; 2019:4
National Category
Fusion, Plasma and Space Physics
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-241093 (URN)978-91-7873-055-1 (ISBN)
Public defence
2019-02-13, F3, Lindstedtsvägen 26, Stockholm, 09:00 (English)
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Supervisors
Note

QC 20190110

Available from: 2019-01-16 Created: 2019-01-09 Last updated: 2019-01-18Bibliographically approved

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Ström, PetterPetersson, PerRubel, MarekBergsåker, HenricBykov, IgorFrassinetti, LorenzoGarcia Carrasco, AlvaroHellsten, TorbjörnMenmuir, SheenaTholerus, SimonWeckmann, ArminTolias, PanagiotisRatynskaia, Svetlana V.Rachlew, ElisabethVallejos, Pablo

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Ström, PetterPetersson, PerRubel, MarekBergsåker, HenricBykov, IgorFrassinetti, LorenzoGarcia Carrasco, AlvaroHellsten, TorbjörnMenmuir, SheenaTholerus, SimonWeckmann, ArminTolias, PanagiotisRatynskaia, Svetlana V.Rachlew, ElisabethVallejos, Pablo
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