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Dust Survey Following the Final Shutdown of TEXTOR: Metal Particles and Fuel Retention
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.ORCID iD: 0000-0003-1062-8101
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.ORCID iD: 0000-0001-9901-6296
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2016 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, 014059Article in journal (Refereed) Published
Abstract [en]

The work presents results of a broad TEXTOR dust survey in terms of its composition, structure, distribution and fuel content. The dust particles were collected after final shutdown of TEXTOR in December 2013. Fuel retention, as determined by thermal desorption, varied significantly, even by two orders of magnitude, dependent on the dust location in the machine. Dust structure was examined by means of scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, focused ion beam and scanning transmission electron microscopy. Several categories of dust have been identified. Carbon-based stratified and granular deposits were dominating, but the emphasis in studies was on metal dust. They were found in the form of small particles, small spheres, flakes and splashes which formed “comet”-like structures clearly indicating directional effects in the impact on surfaces of plasma-facing components. Nickel-rich alloys from the Inconel liner and iron-based ones from various diagnostic holders were the main components of metal-containing dust, but also molybdenum and tungsten debris were detected. Their origin is discussed.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2016. Vol. T167, 014059
Keyword [en]
TEXTOR, dust, fuel retention, high-Z metals
National Category
Fusion, Plasma and Space Physics
URN: urn:nbn:se:kth:diva-178047DOI: 10.1088/0031-8949/T167/1/014059ISI: 000383504700060ScopusID: 2-s2.0-84959896914OAI: diva2:876343

QC 20160127

Available from: 2015-12-03 Created: 2015-12-03 Last updated: 2016-10-20Bibliographically approved
In thesis
1. Material migration in tokamaks: Studies of deposition processes and characterisation of dust particles
Open this publication in new window or tab >>Material migration in tokamaks: Studies of deposition processes and characterisation of dust particles
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Thermonuclear fusion may become an attractive future power source. The most promising of all fusion machine concepts is the tokamak. Despite decades of active research, still huge tasks remain before a fusion power plant can go online. One of these important tasks deals with the interaction between the fusion plasma and the reactor wall. This work focuses on how eroded wall materials of different origin and mass are transported in a tokamak device. Element transport can be examined by injection of certain species of unique and predetermined origin, so called tracers. Tracer experiments were conducted at the TEXTOR tokamak before its final shutdown. This offered an unique opportunity for studies of the wall and other internal components: For the first time it was possible to completely dismantle such a machine and analyse every single part of reactor wall, obtaining a detailed pattern of material migration. Main focus of this work is on the high-Z metals tungsten and molybdenum, which were introduced by WF6 and MoF6 injection into the TEXTOR tokamak in several material migration experiments. It is shown that Mo and W migrate in a similar way around the tokamak and that Mo can be used as tracer for W transport. It is further shown how other materials - medium-Z (Ni), low-Z (N-15 and F), fuel species (D) - migrate and get deposited. Finally, the outcome of dust sampling studies is discussed. It is shown that dust appearance and composition depends on origin, formation conditions and that it can originate even from remote systems like the NBI system. Furthermore, metal splashes and droplets have been found, some of them clearly indicating boiling processes.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. 80 p.
TRITA-EE, ISSN 1653-5146 ; 2015:102
tokamak, fusion, plasma, material migration, particle transport, TEXTOR, PWI, plasma-wall interaction, plasma facing components, PFC, PFM, plasma facing materials, ALT limiter, MoF6, tracer experiment, molybdenum hexafluoride, future energy source, fuel retention, deuterium retention
National Category
Fusion, Plasma and Space Physics
urn:nbn:se:kth:diva-178026 (URN)978-91-7595-766-1 (ISBN)
2015-12-15, Seminarierummet på plan 3, Teknikringen 31, KTH, Stockholm, 10:15 (English)

QC 20151203

Available from: 2015-12-03 Created: 2015-12-02 Last updated: 2015-12-03Bibliographically approved

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