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Ström, P., Petersson, P., Rubel, M., Bergsåker, H., Bykov, I., Frassinetti, L., . . . et al., . (2019). Analysis of deposited layers with deuterium and impurity elements on samples from the divertor of JET with ITER-like wall. Journal of Nuclear Materials, 516, 202-213
Open this publication in new window or tab >>Analysis of deposited layers with deuterium and impurity elements on samples from the divertor of JET with ITER-like wall
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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.

Keywords
Fusion, Tokamak, Plasma-wall interactions, ToF-ERDA, NRA, SEM
National Category
Fusion, Plasma and Space Physics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-240616 (URN)10.1016/j.jnucmat.2018.11.027 (DOI)000458897100020 ()2-s2.0-85060313456 (Scopus ID)
Note

QC 20190125

Available from: 2018-12-20 Created: 2018-12-20 Last updated: 2019-08-08Bibliographically approved
Jepu, I., Matthews, G. F., Widdowson, A., Rubel, M., Fortuna-Zalesna, E., Zdunek, J., . . . Lungu, C. P. (2019). Beryllium melting and erosion on the upper dump plates in JET during three ITER-like wall campaigns. Nuclear Fusion, 59(8), Article ID 086009.
Open this publication in new window or tab >>Beryllium melting and erosion on the upper dump plates in JET during three ITER-like wall campaigns
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 8, article id 086009Article in journal (Refereed) Published
Abstract [en]

Data on erosion and melting of beryllium upper limiter tiles, so-called dump plates (DP), are presented for all three campaigns in the JET tokamak with the ITER-like wall. High-resolution images of the upper wall of JET show clear signs of flash melting on the ridge of the roofshaped tiles. The melt layers move in the poloidal direction from the inboard to the outboard tile, ending on the last DP tile with an upward going waterfall-like melt structure. Melting was caused mainly by unmitigated plasma disruptions. During three ILW campaigns, around 15% of all 12376 plasma pulses were catalogued as disruptions. Thermocouple data from the upper dump plates tiles showed a reduction in energy delivered by disruptions with fewer extreme events in the third campaign, ILW-3, in comparison to ILW-1 and ILW-2. The total Be erosion assessed via precision weighing of tiles retrieved from JET during shutdowns indicated the increasing mass loss across campaigns of up to 0.6 g from a single tile. The mass of splashed melted Be on the upper walls was also estimated using the high-resolution images of wall components taken after each campaign. The results agree with the total material loss estimated by tile weighing (similar to 130 g). Morphological and structural analysis performed on Be melt layers revealed a multilayer structure of re-solidified material composed mainly of Be and BeO with some heavy metal impurities Ni, Fe, W. IBA analysis performed across the affected tile ridge in both poloidal and toroidal direction revealed a low D concentration, in the range 1-4 x 10(17) D atoms cm(-2).

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2019
Keywords
JET, ITER-like wall, beryllium, erosion, melt layer motion
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-255301 (URN)10.1088/1741-4326/ab2076 (DOI)000472804000005 ()
Note

QC 20190807

Available from: 2019-08-07 Created: 2019-08-07 Last updated: 2019-08-07Bibliographically approved
Litnovsky, A., Voitsenya, V. S., Reichle, R., Walsh, M., Razdobarin, A., Dmitriev, A., . . . Mertens, P. (2019). Diagnostic mirrors for ITER: research in the frame of International Tokamak Physics Activity. Nuclear Fusion, 59(6), Article ID 066029.
Open this publication in new window or tab >>Diagnostic mirrors for ITER: research in the frame of International Tokamak Physics Activity
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 6, article id 066029Article in journal (Refereed) Published
Abstract [en]

Mirrors will be used as first plasma-viewing elements in optical and laser-based diagnostics in ITER. Deterioration of the mirror performance due to e.g. sputtering of the mirror surface by plasma particles or deposition of impurities will hamper the entire performance of the affected diagnostic and thus affect ITER operation. The Specialists Working Group on First Mirrors (FM SWG) in the Topical Group on Diagnostics of the International Tokamak Physics Activity (ITPA) plays an important role in finding solutions for diagnostic first mirrors. Sound progress in research and development of diagnostic mirrors in ITER was achieved since the last overview in 2009. Single crystal (SC) rhodium (Rh) mirrors became available. SC rhodium and molybdenum (Mo) mirrors survived in conditions corresponding to similar to 200 cleaning cycles with a negligible degradation of reflectivity. These results are important for a mirror cleaning system which is presently under development. The cleaning system is based on sputtering of contaminants by plasma. Repetitive cleaning was tested on several mirror materials. Experiments comprised contamination/cleaning cycles. The reflectivity SC Mo and Rh mirrors has changed insignificantly after 80 cycles. First in situ cleaning using radiofrequency (RF) plasma was conducted in EAST tokamak with a mock-up plate of ITER edge Thomson Scattering (ETS) with five inserted mirrors. Contaminants from the mirrors were removed. Physics of cleaning discharge was studied both experimentally and by modeling. Mirror contamination can also be mitigated by protecting diagnostic ducts. A deposition mitigation (DeMi) duct system was exposed in KSTAR. The real-time measurement of deposition in the diagnostic duct was pioneered during this experiment. Results evidenced the dominating effect of the wall conditioning and baking on contamination inside the duct. A baffled cassette with mirrors was exposed at the main wall of JET for 23,6 plasma hours. No significant degradation of reflectivity was measured on mirrors located in the ducts. Predictive modeling was further advanced. A model for the particle transport, deposition and erosion at the port-plug was used in selecting an optical layout of several ITER diagnostics. These achievements contributed to the focusing of the first mirror research thus accelerating the diagnostic development. Modeling requires more efforts. Remaining crucial issues will be in a focus of the future work of the FM SWG.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
ITER, diagnostic mirrors, in situ mirror cleaning, recovery of reflectivity, single crystal mirrors, mirror protection, ITPA
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-252366 (URN)10.1088/1741-4326/ab1446 (DOI)000467461600008 ()2-s2.0-85067584703 (Scopus ID)
Note

QC 20190718

Available from: 2019-07-18 Created: 2019-07-18 Last updated: 2019-07-18Bibliographically approved
Moon, S., Petersson, P., Rubel, M., Fortuna-Zalesna, E., Widdowson, A., Jachmich, S., . . . Contributors, J. E. (2019). First mirror test in JET for ITER: Complete overview after three ILW campaigns. Nuclear Materials and Energy, 19, 59-66
Open this publication in new window or tab >>First mirror test in JET for ITER: Complete overview after three ILW campaigns
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2019 (English)In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 19, p. 59-66Article in journal (Refereed) Published
Abstract [en]

The First Mirror Test for ITER has been carried out in JET with mirrors exposed during: (i) the third ILW campaign (ILW-3, 2015–2016, 23.33 h plasma) and (ii) all three campaigns, i.e. ILW-1 to ILW-3: 2011–2016, 63,52 h in total. All mirrors from main chamber wall show no significant changes of the total reflectivity from the initial value and the diffuse reflectivity does not exceed 3% in the spectral range above 500 nm. The modified layer on surface has very small amount of impurities such as D, Be, C, N, O and Ni. All mirrors from the divertor (inner, outer, base under the bulk W tile) lost reflectivity by 20–80% due to the beryllium-rich deposition also containing D, C, N, O, Ni and W. In the inner divertor N reaches 5 × 10 17 cm −2 , W is up to 4.3 × 10 17 cm −2 , while the content of Ni is the greatest in the outer divertor: 3.8 × 10 17 cm −2 . Oxygen-18 used as the tracer in experiments at the end of ILW-3 has been detected at the level of 1.1 × 10 16 cm −2 . The thickness of deposited layer is in the range of 90 nm to 900 nm. The layer growth rate in the base (2.7 pm s − 1 ) and inner divertor is proportional to the exposure time when a single campaign and all three are compared. In a few cases, on mirrors located at the cassette mouth, flaking of deposits and erosion occurred.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
52.40 Hf, Diagnostic mirrors, Erosion-deposition, First Mirror Test, ITER-like Wall, JET
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-246438 (URN)10.1016/j.nme.2019.02.009 (DOI)2-s2.0-85061529095 (Scopus ID)
Note

QC 20190401

Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-04-01Bibliographically approved
Rubel, M. (2019). Fusion Neutrons: Tritium Breeding and Impact on Wall Materials and Components of Diagnostic Systems. Journal of fusion energy, 38(3-4), 315-329
Open this publication in new window or tab >>Fusion Neutrons: Tritium Breeding and Impact on Wall Materials and Components of Diagnostic Systems
2019 (English)In: Journal of fusion energy, ISSN 0164-0313, E-ISSN 1572-9591, Vol. 38, no 3-4, p. 315-329Article in journal (Refereed) Published
Abstract [en]

A concise overview is given on the impact of fusion neutrons on various classes of materials applied in reactor technology: plasma-facing, structural and functional tested for tritium production and for diagnostic systems. Tritium breeding in the reactor blanket, fuel cycle and separation of hydrogen isotopes are described together with issues related to primary (tritium) and induced radioactivity. Neutron-induced damage and degradation of material properties are addressed. Material testing under neutron fluxes and safety issues associated with handling components in the radioactive environment are described. A comprehensive list of references to monographs and research papers is included to help navigation in literature.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Controlled fusion, Tritium, Radiation damage, Transmutation, Fuel cycle
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-255727 (URN)10.1007/s10894-018-0182-1 (DOI)000476509600006 ()2-s2.0-85053238998 (Scopus ID)
Note

QC 20190813

Available from: 2019-08-13 Created: 2019-08-13 Last updated: 2019-08-13Bibliographically approved
Coad, J. P., Rubel, M., Likonen, J., Bekris, N., Brezinsek, S., Matthew, G. F., . . . Widdowson, A. M. (2019). Material migration and fuel retention studies during the JET carbon divertor campaigns. Fusion engineering and design, 138, 78-108
Open this publication in new window or tab >>Material migration and fuel retention studies during the JET carbon divertor campaigns
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2019 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 138, p. 78-108Article in journal (Refereed) Published
Abstract [en]

The first divertor was installed in the JET machine between 1992 and 1994 and was operated with carbon tiles and then beryllium tiles in 1994-5. Post-mortem studies after these first experiments demonstrated that most of the impurities deposited in the divertor originate in the main chamber, and that asymmetric deposition patterns generally favouring the inner divertor region result from drift in the scrape-off layer. A new monolithic divertor structure was installed in 1996 which produced heavy deposition at shadowed areas in the inner divertor corner, which is where the majority of the tritium was trapped by co-deposition during the deuterium-tritium experiment in 1997. Different divertor geometries have been tested since such as the Gas-Box and High-Delta divertors; a principle objective has been to predict plasma behaviour, transport and tritium retention in ITER. Transport modelling experiments were carried out at the end of four campaigns by puffing C-13-labelled methane, and a range of diagnostics such as quartz-microbalance and rotating collectors have been installed to add time resolution to the post-mortem analyses. The study of material migration after D-D and D-T campaigns clearly revealed important consequences of fuel retention in the presence of carbon walls. They gave a strong impulse to make a fundamental change of wall materials. In 2010 the carbon divertor and wall tiles were removed and replaced with tiles with Be or W surfaces for the ITER-Like Wall Project.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
Keywords
Fusion, JET, Divertor, Carbon, Plasma-facing components
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-244549 (URN)10.1016/j.fusengdes.2018.10.002 (DOI)000457663100013 ()2-s2.0-85056661344 (Scopus ID)
Note

QC 20190313

Available from: 2019-03-13 Created: 2019-03-13 Last updated: 2019-03-13Bibliographically approved
Oya, Y., Masuzaki, S., Tokitani, M., Azuma, K., Oyaidzu, M., Isobe, K., . . . Contributors, J. (2018). Correlation of surface chemical states with hydrogen isotope retention in divertor tiles of JET with ITER-Like Wall. Fusion engineering and design, 132, 24-28
Open this publication in new window or tab >>Correlation of surface chemical states with hydrogen isotope retention in divertor tiles of JET with ITER-Like Wall
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2018 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 132, p. 24-28Article in journal (Refereed) Published
Abstract [en]

To understand the fuel retention mechanism correlation of surface chemical states and hydrogen isotope retention behavior determined by XPS (X-ray photoelectron spectroscopy) and TDS (Thermal desorption spectroscopy), respectively, for JET ITER-Like Wall samples from operational period 2011–2012 were investigated. It was found that the deposition layer was formed on the upper part of the inner vertical divertor area. At the inner plasma strike point region, the original surface materials, W or Mo, were found, indicating to an erosion-dominated region, but deposition of impurities was also found. Higher heat load would induce the formation of metal carbide. At the outer horizontal divertor tile, mixed material layer was formed with iron as an impurity. TDS showed the H and D desorption behavior and the major D desorption temperature for the upper part of the inner vertical tile was located at 370 °C and 530 °C. At the strike point region, the D desorption temperature was clearly shifted toward higher release temperatures, indicating the stabilization of D trapping by higher heat load.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Hydrogen isotope behavior, JET-ILW, Plasma wall interactions
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-228730 (URN)10.1016/j.fusengdes.2018.04.124 (DOI)000436887700005 ()2-s2.0-85046629650 (Scopus ID)
Funder
EU, European Research Council
Note

QC 20180529

Available from: 2018-05-29 Created: 2018-05-29 Last updated: 2018-07-17Bibliographically approved
Rubel, M., Widdowson, A., Grzonka, J., Fortuna-Zalesna, E., Moon, S., Petersson, P., . . . Tokitani, M. (2018). Dust generation in tokamaks: Overview of beryllium and tungsten dust characterisation in JET with the ITER-like wall. Paper presented at 13th International Symposium on Fusion Nuclear Technology (ISFNT), SEP 25-29, 2017, Kyoto, Japan. Fusion engineering and design, 136, 579-586
Open this publication in new window or tab >>Dust generation in tokamaks: Overview of beryllium and tungsten dust characterisation in JET with the ITER-like wall
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2018 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 136, p. 579-586Article in journal (Refereed) Published
Abstract [en]

Operation of the JET tokamak with beryllium and tungsten ITER-like wall provides unique opportunity for detailed studies on dust generation: quantity, morphology, location, etc. The programme carried out in response to ITER needs for safety assessment comprises: (i) remotely controlled vacuum cleaning of the divertor; (ii) local sampling of loosely bound matter from plasma-facing components (PFC); (iii) collection of mobilized dust on various erosion-deposition probes located in the divertor and in the main chamber. Results of comprehensive analyses performed by a number of complementary techniques, e.g. a range of microscopy methods, electron and ion spectroscopy, liquid scintillography and thermal desorption, are summarized by following points: (a) Total amount of dust collected by vacuum cleaning after three campaigns is about 1-1.4 g per campaign (19.1-23.5 h plasma operation), i.e. over 100 times smaller than in JET operated with carbon walls (i.e. in JET-C). (b) Two major categories of Be dust are identified: flakes of co-deposits formed on PFC and droplets (2-10 mu m in diameter). Small quantifies, below 1 g, of Be droplets and splashes are associated mainly with melting of beryllium limiters.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
JET tokamak, ITER-like wall, Dust, Beryllium, Tungsten
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-240780 (URN)10.1016/j.fusengdes.2018.03.027 (DOI)000452583700110 ()2-s2.0-85044008512 (Scopus ID)
Conference
13th International Symposium on Fusion Nuclear Technology (ISFNT), SEP 25-29, 2017, Kyoto, Japan
Note

QC 20190109

Available from: 2019-01-09 Created: 2019-01-09 Last updated: 2019-01-09Bibliographically approved
Ström, P., Petersson, P., Rubel, M. & Possnert, G. (2018). Erratum: "A combined segmented anode gas ionization chamber and time-of-flight detector for heavy ion elastic recoil detection analysis" [Rev. Sci. Instrum. 87, 103303 (2016)]. Review of Scientific Instruments, 89(4), Article ID 049901.
Open this publication in new window or tab >>Erratum: "A combined segmented anode gas ionization chamber and time-of-flight detector for heavy ion elastic recoil detection analysis" [Rev. Sci. Instrum. 87, 103303 (2016)]
2018 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, no 4, article id 049901Article in journal (Refereed) Published
Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-227781 (URN)10.1063/1.5030502 (DOI)000431139400078 ()29716341 (PubMedID)2-s2.0-85045335587 (Scopus ID)
Note

QC 201805014

Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2019-01-09Bibliographically approved
Fazinic, S., Tadic, T., Vuksic, M., Rubel, M., Petersson, P., Fortuna-Zalesna, E. & Widdowson, A. (2018). Ion Microbeam Analyses of Dust Particles and Codeposits from JET with the ITER-Like Wall. Analytical Chemistry, 90(9), 5744-5752
Open this publication in new window or tab >>Ion Microbeam Analyses of Dust Particles and Codeposits from JET with the ITER-Like Wall
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2018 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 90, no 9, p. 5744-5752Article in journal (Refereed) Published
Abstract [en]

Generation of metal dust in the JET tokamak with the ITER-like wall (ILW) is a topic of vital interest to next-step fusion devices because of safety issues with plasma operation. Simultaneous Nuclear Reaction Analysis (NRA) and Particle Induced X-ray Emission (PIXE) with a focused four MeV He-3 microbeam was used to determine the composition of dust particles related to the JET operation with the ILW. The focus was on "Be-rich particles" collected from the deposition zone on the inner divertor tile. The particles found are composed of a mix of codeposited species up to 120 m in size with a thickness of 30-40 mu m, The main constituents are D from the fusion fuel, Be and W from the main plasma-facing components, and Ni and Cr from the Inconel grills of the antennas for auxiliary plasma heating. Elemental concentrations were estimated by iterative NRA-PIXE analysis. Two types of dust particles were found: (i) larger Be-rich particles with Be concentrations above 90 at% with a deuterium presence of up to 3.4 at% and containing Ni (1-3 at%), Cr (0.4-0.8 at%), W (0.2-0.9 at%), Fe (0.3-0.6 at%), and Cu and Ti in lower concentrations and (ii) small particles rich in Al and/or Si that were in some cases accompanied by other elements, such as Fe, Cu, or Ti or W and Mo.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-228440 (URN)10.1021/acs.analchem.8b00073 (DOI)000431464400032 ()29620878 (PubMedID)2-s2.0-85046455477 (Scopus ID)
Note

QC 20180529

Available from: 2018-05-29 Created: 2018-05-29 Last updated: 2018-10-16Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-9901-6296

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