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Impact of ion cyclotron wall conditioning on fuel removal from plasma-facing components at TEXTOR
KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
Vise andre og tillknytning
2014 (engelsk)Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T159, s. 014017-Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Ion cyclotron wall conditioning (ICWC) is based on low temperature and low density plasmas produced and sustained by ion cyclotron resonance (ICR) pulses in reactive or noble gases. The technique is being developed for ITER. It is tested in tokamaks in the presence of toroidal magnetic field (0.2-3.8 T) and heating power of the order of 10(5) W. ICWC with hydrogen, deuterium and oxygen-helium mixture was studied in the TEXTOR tokamak. The exposed samples were pre-characterized limiter tiles mounted on specially designed probes. The objectives were to assess the reduction of deuterium content, the uniformity of the reduction and the retention of seeded oxygen. For the last objective oxygen-18 was used as a marker. ICWC in hydrogen caused a drop of deuterium content in the tile by a factor of more than 2: from 4.5x10(18) to 1.9x10(18) D cm(-2). A decrease of the fuel content by approximately 25% was achieved by the ICWC in oxygen, while no reduction of the fuel content was measured after exposure to discharges in deuterium. These are the first data ever obtained showing quantitatively the local decrease of deuterium in wall components treated by ICWC in a tokamak. The oxygen retention in the tiles exposed to ICWC with oxygen-helium was analyzed for different orientations and radial positions with respect to plasma. An average retention of 1.38x10(16) O-18 cm(-2) was measured. A maximum of the retention, 4.4x10(16) O-18 cm(-2), was identified on a sample surface near the plasma edge. The correlation with the gas inlet and antennae location has been studied.

sted, utgiver, år, opplag, sider
2014. Vol. T159, s. 014017-
Emneord [en]
ion cyclotron wall conditioning, plasma-facing components, fuel retention, fuel removal, TEXTOR
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-145840DOI: 10.1088/0031-8949/2014/T159/014017ISI: 000334847800018Scopus ID: 2-s2.0-84902191459OAI: oai:DiVA.org:kth-145840DiVA, id: diva2:720649
Konferanse
14th International Conference on Plasma-Facing Materials and Components for Fusion Applications, PFMC 2013; Julich; Germany; 13 May 2013 through 17 May 2013
Forskningsfinansiär
Swedish Research Council, 621-2009-4138 621-2012-4148
Merknad

QC 20140602

Tilgjengelig fra: 2014-06-02 Laget: 2014-06-02 Sist oppdatert: 2017-12-05bibliografisk kontrollert
Inngår i avhandling
1. Plasma-Facing Components in Tokamaks: Studies of Wall Conditioning Processes and Plasma Impact on Diagnostic Mirrors
Åpne denne publikasjonen i ny fane eller vindu >>Plasma-Facing Components in Tokamaks: Studies of Wall Conditioning Processes and Plasma Impact on Diagnostic Mirrors
2014 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Understanding of material migration and its impact on the formation of co-deposited mixed material layers on plasma-facing components is essential for the development of fusion reactors. This thesis focuses on this topic. It is based on experiments performed at JET and TEXTOR tokamaks. The major objectives were to determine: (i) fuel and impurity removal from plasma-facing components by ICWC in different gas mixtures, (ii) fuel and impurity transport connected to ICWC operation, (iii) plasma impact on diagnostic mirrors. All these issues are in line with the ITER needs: mitigation of co-deposition and fuel inventory, and the performance of first mirrors in long-term operation. The novelty in research is demonstrated by several elements. In wall conditioning studies, tracer techniques based on injection of rare isotopes (N-15, O-18) were used to determine conclusively the impact of respective gases. Also, a new approach to ICWC was developed by combining global gas balance studies based on mass spectrometry and the use of multiple surface probes exposed to discharges and then studied ex-situ with accelerator-based techniques. Impact of plasma on diagnostic mirrors was determined after exposure to the entire first experimental campaign in JET-ILW.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2014. s. xiv, 44
Serie
TRITA-EE, ISSN 1653-5146 ; 2014:060
Emneord
Plasa-wall interactions, wall conditioning, tracers, diagnostic mirrors, ICWC
HSV kategori
Forskningsprogram
Fysik
Identifikatorer
urn:nbn:se:kth:diva-154621 (URN)978-91-7595-309-0 (ISBN)
Presentation
2014-11-07, Seminar room, Teknikringen 31, KTH- Royal Institute of Technology, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Merknad

QC 20141103

Tilgjengelig fra: 2014-11-03 Laget: 2014-10-26 Sist oppdatert: 2014-11-03bibliografisk kontrollert
2. Impact of material migration on plasma-facing components in tokamaks
Åpne denne publikasjonen i ny fane eller vindu >>Impact of material migration on plasma-facing components in tokamaks
2016 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2016. s. 54
Serie
TRITA-EE, ISSN 1653-5146
Emneord
Fusion, material migration, wall conditioning, diagnostic mirrors, plasma-facing materials
HSV kategori
Forskningsprogram
Fysik
Identifikatorer
urn:nbn:se:kth:diva-190903 (URN)978-91-7729-046-9 (ISBN)
Disputas
2016-09-15, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Merknad

QC 20160819

Tilgjengelig fra: 2016-08-19 Laget: 2016-08-18 Sist oppdatert: 2016-08-19bibliografisk kontrollert

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