Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 11) Show all publications
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
Show others...
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
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
Weckmann, A., Petersson, P., Rubel, M., Ström, P., Kurki-Suonio, T., Sarkimaki, K., . . . Airila, M. (2018). Review on global migration, fuel retention and modelling after TEXTOR decommission. NUCLEAR MATERIALS AND ENERGY, 17, 83-112
Open this publication in new window or tab >>Review on global migration, fuel retention and modelling after TEXTOR decommission
Show others...
2018 (English)In: NUCLEAR MATERIALS AND ENERGY, Vol. 17, p. 83-112Article, review/survey (Refereed) Published
Abstract [en]

Before decommissioning of the TEXTOR tokamak in 2013, the machine was conditioned with a comprehensive migration experiment where MoF6 and N-15(2) were injected on the very last operation day. Thereafter, all plasmafacing components (PFCs) were available for extensive studies of both local and global migration of impurities - Mo, W, Inconel alloy constituents, 15 N, F - and fuel retention studies. Measurements were performed on 140 limiter tiles out of 864 throughout the whole machine to map global transport. One fifth of the introduced molybdenum could be found. Wherever possible, the findings are compared to results obtained previously in other machines. This review incorporates both published and unpublished results from this TEXTOR study and combines findings with analytical methods as well as modelling results from two codes, ERO and ASCOT. The main findings are: Both local and global molybdenum transport can be explained by toroidal plasma flow and (sic) x (sic) drift. The suggested transport scheme for molybdenum holds also for other analysed species, namely tungsten from previous experiments and medium-Z metals (Cr-Cu) introduced on various occasions. Analytical interpretation of several deposition profile features is possible with basic geometrical and plasma physics considerations. These are deposition profiles on the collector probe, the lower part of the inner bumper limiter, the poloidal cross-section of the inner bumper limiter, and the poloidal limiter. Any deposition pattern found in this TEXTOR study, including fuel retention, has neither poloidal nor toroidal symmetry, which is often assumed when determining deposition profiles on global scale. Fuel retention is highly inhomogeneous due to local variation of plasma parameters - by auxiliary heating systems and impurity injection - and PFC temperature. Local modelling with ERO yields good qualitative agreement but too high local deposition efficiency. Global modelling with ASCOT shows that the radial electric field and source form have a high impact on global deposition patterns, while toroidal flow has little influence. Some of the experimental findings could be reproduced. Still, qualitative differences between simulated and experimental global deposition patterns remain. The review closes with lessons learnt during this extensive TEXTOR study which might be helpful for future scientific exploitation of other tokamaks to be decommissioned.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
Keywords
Global migration, Tokamak, high-Z material, Molybdenum, Modelling, ASCOT, ERO, Fuel retention, Deposition
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-241223 (URN)10.1016/j.nme.2018.09.003 (DOI)000454165000013 ()2-s2.0-85054327579 (Scopus ID)
Note

QC 20190115

Available from: 2019-01-15 Created: 2019-01-15 Last updated: 2019-01-15Bibliographically approved
Ström, P., Petersson, P., Arredondo Parra, R., Oberkofler, M., Schwarz-Selinger, T. & Primetzhofer, D. (2018). Sputtering of polished EUROFER97 steel: Surface structure modification and enrichment with tungsten and tantalum. Journal of Nuclear Materials, 508, 139-146
Open this publication in new window or tab >>Sputtering of polished EUROFER97 steel: Surface structure modification and enrichment with tungsten and tantalum
Show others...
2018 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 508, p. 139-146Article in journal (Refereed) Published
Abstract [en]

Surface structure modification and enrichment with tungsten and tantalum were measured for polished EUROFER97 samples after exposure to a deuterium ion beam. Time-of-flight medium energy ion scattering and time-of-flight elastic recoil detection analysis were implemented for measuring atomic composition profiles. Atomic force microscopy and optical microscopy were used to investigate surface morphology. The deuterium particle fluence was varied between 1021 D/m2 and 1024 D/m2, projectile energy was 200 eV/D and exposure temperatures up to 1050 K were applied. The average fraction of tungsten plus tantalum to total metal content in the 2 nm closest to the sample surface was increased from an initial 0.0046 to 0.12 for the sample exposed to the highest fluence at room temperature. The enrichment was accompanied by an increase in surface roughness of one order of magnitude and grain dependent erosion of the material. The appearance of protrusions with heights up to approximately 40 nm after ion beam exposure at room temperature was observed on individual grains. Samples exposed to 1023 D/m2 at temperatures of 900 K and 1050 K displayed recrystallization and cracking while changes to the total surface fraction of tungsten and tantalum were limited to less than a factor of two compared to the sample exposed to the same fluence at room temperature.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
AFM, Erosion, EUROFER, Sputtering, ToF-ERDA, ToF-MEIS
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-229259 (URN)10.1016/j.jnucmat.2018.05.031 (DOI)000439134500016 ()2-s2.0-85047329344 (Scopus ID)
Funder
Swedish Research Council, 821-2012-5144Swedish Foundation for Strategic Research , RIF14-0053EU, European Research Council
Note

QC 20180601

Available from: 2018-06-01 Created: 2018-06-01 Last updated: 2019-01-09Bibliographically approved
Koslowski, H., Bhattacharyya, S., Hansen, P., Linsmeier, C., Rasinski, M. & Ström, P. (2018). Temperature-dependent in-situ LEIS measurement of W surface enrichment by 250 eV D sputtering of EUROFER. Nuclear Materials and Energy, 16, 181-190
Open this publication in new window or tab >>Temperature-dependent in-situ LEIS measurement of W surface enrichment by 250 eV D sputtering of EUROFER
Show others...
2018 (English)In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 16, p. 181-190Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Low energy ion scattering (LEIS); EUROFER; Plasma-surface interaction; Preferential sputtering; W diffusion in Fe; Diffusion activation energy
National Category
Fusion, Plasma and Space Physics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-232439 (URN)10.1016/j.nme.2018.07.001 (DOI)000442226800028 ()2-s2.0-85049915542 (Scopus ID)
Note

QC 20180821

Available from: 2018-07-23 Created: 2018-07-23 Last updated: 2018-09-07Bibliographically approved
Fortuna-Zalesna, E., Weckmann, A., Grozonka, J., Rubel, M., Esser, H. G., Freisinger, M., . . . Ström, P. (2016). Dust Survey Following the Final Shutdown of TEXTOR: Metal Particles and Fuel Retention. Physica Scripta, T167, Article ID 014059.
Open this publication in new window or tab >>Dust Survey Following the Final Shutdown of TEXTOR: Metal Particles and Fuel Retention
Show others...
2016 (English)In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, article id 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
Keywords
TEXTOR, dust, fuel retention, high-Z metals
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-178047 (URN)10.1088/0031-8949/T167/1/014059 (DOI)000383504700060 ()2-s2.0-84959896914 (Scopus ID)
Note

QC 20160127

Available from: 2015-12-03 Created: 2015-12-03 Last updated: 2017-06-30Bibliographically approved
Ström, P., Petersson, P., Rubel, M., Primetzhofer, D., Brezinsek, S., Kreter, A., . . . Sugiyama, K. (2016). Ion beam analysis of tungsten layers in EUROFER model systems and carbon plasma facing components. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 371, 355-359
Open this publication in new window or tab >>Ion beam analysis of tungsten layers in EUROFER model systems and carbon plasma facing components
Show others...
2016 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 371, p. 355-359Article in journal (Refereed) Published
Abstract [en]

The tungsten enriched surface layers in two fusion-relevant EUROFER steel model samples, consisting of an iron-tungsten mixture exposed to sputtering by deuterium ions, were studied by Rutherford backscattering spectrometry and medium energy ion scattering. Exposure conditions were the same for the two samples and the total amount of tungsten atoms per unit area in the enriched layers were similar (2e15 and 2.4e15 atoms/cm2 respectively), despite slightly different initial atomic compositions. A depth profile featuring exponential decrease in tungsten content towards higher depths with 10-20 atomic percent of tungsten at the surface and a decay constant between 0.05 and 0.08 Å-1 was indicated in one sample, whereas only the total areal density of tungsten atoms was measured in the other. In addition, two different beams, iodine and chlorine, were employed for elastic recoil detection analysis of the deposited layer on a polished graphite plate from a test limiter in the TEXTOR tokamak following experiments with tungsten hexafluoride injection. The chlorine beam was preferred for tungsten analysis, mainly because it (as opposed to the iodine beam) does not give rise to problems with overlap of forward scattered beam particles and recoiled tungsten in the spectrum.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
ERDA, EUROFER, Fusion, MEIS, Tungsten, Atoms, Carbon, Chlorine, Forward scattering, Fusion reactions, Iodine, Ion beams, Ions, Magnetoplasma, Rutherford backscattering spectroscopy, Elastic recoil detection analysis, Exposure parameters, Medium energy ion scattering, Orders of magnitude, Rutherford back-scattering spectrometry
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-177225 (URN)10.1016/j.nimb.2015.09.024 (DOI)000373412000071 ()2-s2.0-84960241915 (Scopus ID)
Note

QC 20171027

Available from: 2015-11-25 Created: 2015-11-17 Last updated: 2019-01-09Bibliographically approved
Ström, P., Petersson, P., Rubel, M., Weckmann, A., Brezinsek, S., Kreter, A., . . . Rozniatowski, K. (2015). Characterisation of surface layers formed on plasma-facing components in controlled fusion devices: Role of heavy ion elastic recoil detection. Vacuum, 122, 260-267
Open this publication in new window or tab >>Characterisation of surface layers formed on plasma-facing components in controlled fusion devices: Role of heavy ion elastic recoil detection
Show others...
2015 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 122, p. 260-267Article in journal (Refereed) Published
Abstract [en]

Wall components retrieved from the TEXTOR tokamak after tracer experiments with nitrogen-15 and molybdenum hexafluoride (MoF6) injection were studied to determine deposition patterns and, by this, to conclude on material migration. Toroidal limiter tiles made of carbon fibre composites and fine grain graphite were examined using time-of-flight heavy ion elastic recoil detection analysis. Molybdenum deposition patterns indicated migration based on erosion and prompt re-deposition. Nitrogen-15 was trapped together with the deposited molybdenum. Some information on the depth distribution of species in the top 400 nm layer of the limiters was obtained; however surface roughness of the samples strongly limited resolution. In the case of molybdenum, the largest concentration was found in the 100 nm outermost layer, whereas fluorine and nitrogen-15 displayed more irregular profiles. Other species, besides deuterium fuel and carbon-12, were also identified: boron-10 and boron-11 originating from boronisations, carbon-13 from earlier tracer experiments, nitrogen-14 from plasma edge cooling and metals eroded from the Inconel wall.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-178042 (URN)10.1016/j.vacuum.2015.04.019 (DOI)2-s2.0-84945489472 (Scopus ID)
Note

QC 20150203

Available from: 2015-12-03 Created: 2015-12-03 Last updated: 2019-01-09Bibliographically approved
Cherigier-Kovacic, L., Ström, P., Lejeune, A. & Doveil, F. (2015). Electric field induced Lyman-alpha emission of a hydrogen beam for electric field measurements. Review of Scientific Instruments, 86(6), Article ID 063504.
Open this publication in new window or tab >>Electric field induced Lyman-alpha emission of a hydrogen beam for electric field measurements
2015 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 86, no 6, article id 063504Article in journal (Refereed) Published
Abstract [en]

Electric field induced Lyman-alpha emission is a new way of measuring weak electric fields in vacuum and in a plasma. It is based on the emission of Lyman-alpha radiation (121.6 nm) by a low-energy metastable H atom beam due to Stark-quenching of the 2s level induced by the field. In this paper, we describe the technique in detail. Test measurements have been performed in vacuum between two plates polarized at a controlled voltage. The intensity of emitted radiation, proportional to the square of the field modulus, has been recorded by a lock-in technique, which gives an excellent signal to noise ratio. These measurements provide an in situ calibration that can be used to obtain the absolute value of the electric field. A diagnostic of this type can help to address a long standing challenge in plasma physics, namely, the problem of measuring electric fields without disturbing the equilibrium of the system that is being studied.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-172502 (URN)10.1063/1.4922856 (DOI)000357690300015 ()26133836 (PubMedID)2-s2.0-84933575644 (Scopus ID)
Note

QC 20150825

Available from: 2015-08-25 Created: 2015-08-25 Last updated: 2017-12-04Bibliographically approved
Rubel, M., Weckmann, A., Ström, P., Petersson, P., Garcia Carrasco, A., Brezinsek, S., . . . Fortuna-Zalesna, E. (2015). Tracer techniques for the assessment of material migration and surface modification of plasma-facing components. Journal of Nuclear Materials, 463, 280-284
Open this publication in new window or tab >>Tracer techniques for the assessment of material migration and surface modification of plasma-facing components
Show others...
2015 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, p. 280-284Article in journal (Refereed) Published
Abstract [en]

Tracer techniques were used in the TEXTOR tokamak to determine high-Z metal migration and the deposition of species used for plasma edge cooling or wall conditioning under different types of operation conditions. Volatile molybdenum hexa-fluoride, nitrogen-15 and oxygen-18 were used as markers in tokamak or ion cyclotron wall conditioning discharges (ICWC). The objective was to obtain qualitative and quantitative of a global and local deposition pattern and material mixing effects. The deposition and retention was studied on plasma-facing components, collector probes and test limiters. Optical spectroscopy and ex-situ analysis techniques were used to determine the plasma response to tracer injection and the modification of surface composition. Molybdenum and light isotopes were detected on all types of limiters and short-term probes retrieved from the vessel showing that both helium and nitrogen are trapped following wall conditioning and edge cooling. Only small amounts below 1 x 10(19) m(-2) of O-18 were detected on surfaces treated by oxygen-assisted ICWC.

Place, publisher, year, edition, pages
Elsevier, 2015
National Category
Materials Engineering Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-172689 (URN)10.1016/j.jnucmat.2014.11.074 (DOI)000358467200052 ()2-s2.0-84937517699 (Scopus ID)
Funder
Swedish Research Council, 621-2009-4138
Note

QC 20150901

Available from: 2015-09-01 Created: 2015-08-27 Last updated: 2017-06-30Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9299-3262

Search in DiVA

Show all publications