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Impact of helium implantation and ion-induced damage on reflectivity of molybdenum mirrors
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
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2016 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584Article in journal (Refereed) PublishedText
Abstract [en]

Molybdenum mirrors were irradiated with Mo and He ions to simulate the effect of neutron irradiation on diagnostic first mirrors in next-generation fusion devices. Up to 30 dpa were produced under molybdenum irradiation leading to a slight decrease of reflectivity in the near infrared range. After 3×1017 cm-2 of helium irradiation, reflectivity decreased by up to 20%. Combined irradiation by helium and molybdenum led to similar effects on reflectivity as irradiation with helium alone. Ion beam analysis showed that only 7% of the implanted helium was retained in the first 40nm layer of the mirror. The structure of the near-surface layer after irradiation was studied with scanning transmission electron microscopy and the extent and size distribution of helium bubbles was documented. The consequences of ion-induced damage on the performance of diagnostic components are discussed.

Place, publisher, year, edition, pages
Elsevier, 2016.
Keyword [en]
Diagnostic mirrors, Fusion, Helium, Ion-induced damage, Molybdenum, Fusion reactions, High resolution transmission electron microscopy, Infrared devices, Ion beams, Ions, Irradiation, Mirrors, Radiation, Reflection, Scanning electron microscopy, Transmission electron microscopy, Helium implantation, Helium irradiation, Implanted helium, Ion beam analysis, Near-infrared range, Near-surface layers, Scanning transmission electron microscopy, Neutron irradiation
National Category
Accelerator Physics and Instrumentation Fusion, Plasma and Space Physics Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:kth:diva-188336DOI: 10.1016/j.nimb.2016.02.065ISI: 000382413500018ScopusID: 2-s2.0-84960914771OAI: oai:DiVA.org:kth-188336DiVA: diva2:934785
Note

QC 20160609

Available from: 2016-06-09 Created: 2016-06-09 Last updated: 2016-09-23Bibliographically approved
In thesis
1. Impact of material migration on plasma-facing components in tokamaks
Open this publication in new window or tab >>Impact of material migration on plasma-facing components in tokamaks
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Plasma-wall interaction plays an essential role in the performance and safety of a fusion reactor. This thesis focuses on the impact of material migration on plasma-facing components. It is based on experiments performed in tokamaks: JET, TEXTOR and ASDEX Upgrade. The objectives of the experiments were to assess fuel and impurity removal under ion cyclotron wall conditioning (ICWC) and plasma impact on diagnostic mirrors.

In wall conditioning studies, tracer techniques based on the injection of rare isotopes (15N, 18O) were used to determine conclusively the impact of the respective gases. For the first time, probe surfaces and wall components exposed to ICWC were examined by surface analysis methods. Discharges in hydrogen were the most efficient to erode carbon co-deposits, resulting in a reduction of the initial deuterium content by a factor of two. It was also found that impurities desorbed under ICWC are partly re-deposited on the wall.

Plasma impact on diagnostic mirrors was determined by surface analysis of test mirrors exposed at JET. Reflectivity of mirrors from the divertor region was severely decreased due to deposits of beryllium, deuterium, carbon and other impurities. This result points out the need to develop mirror maintenance procedures. Neutron damage on mirrors was simulated by ion irradiation in an ion implanter. It was shown that damage levels similar to those expected in the first wall of a fusion reactor do not produce a significant change in reflectivity.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 54 p.
Series
TRITA-EE, ISSN 1653-5146
Keyword
Fusion, material migration, wall conditioning, diagnostic mirrors, plasma-facing materials
National Category
Fusion, Plasma and Space Physics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-190903 (URN)978-91-7729-046-9 (ISBN)
Public defence
2016-09-15, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160819

Available from: 2016-08-19 Created: 2016-08-18 Last updated: 2016-08-19Bibliographically approved

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Garcia-Carrasco, AlvaroPetersson, PerHallén, AndersRubel, Marek
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Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Accelerator Physics and InstrumentationFusion, Plasma and Space PhysicsAtom and Molecular Physics and Optics

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