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Ström, Petter
Publications (10 of 20) Show all publications
Gupta, R., Behera, N., Venugopal, V., Basu, S., Puri, A., Ström, P., . . . Kumar, A. (2020). Engineering of spin mixing conductance at Ru/FeCo/Ru interfaces: Effect of Re doping. Physical Review B, 101, Article ID 024401.
Open this publication in new window or tab >>Engineering of spin mixing conductance at Ru/FeCo/Ru interfaces: Effect of Re doping
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2020 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 101, article id 024401Article in journal (Refereed) Published
National Category
Materials Engineering
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-402512 (URN)10.1103/PhysRevB.101.024401 (DOI)
Available from: 2020-01-16 Created: 2020-01-16 Last updated: 2020-01-16
Ström, P., Petersson, P., Rubel, M. J., Fortuna-Zaleśna, E., Widdowson, A. & Sergienko, G. (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 analysed 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 mu m were indicated, but typical values were on the order of a few hundred nm. 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 mu m 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
Identifiers
urn:nbn:se:uu:diva-379019 (URN)10.1016/j.jnucmat.2018.11.027 (DOI)000458897100020 ()
Funder
Swedish Foundation for Strategic Research , RIF14-0053Swedish Research Council, 821-2012-5144Swedish Research Council, 2015-04884Swedish Research Council, 2017-00643
Note

Authors listed as Contributor / bidragsgivare above are part of EUROfusion Consortium, JET, Culham Science Centre, UK.

Available from: 2019-03-12 Created: 2019-03-12 Last updated: 2019-04-24Bibliographically approved
Huber, A., Brezinsek, S., Kirschner, A., Ström, P., Sergienko, G., Huber, V., . . . Mertens, P. (2019). Determination of tungsten sources in the JET-ILW divertor by spectroscopic imaging in the presence of a strong plasma continuum. Paper presented at 23rd Int. Conference on Plasma Surface Interactions in Controlled Fusion Devices. Nuclear Materials and Energy, 18, 118-124
Open this publication in new window or tab >>Determination of tungsten sources in the JET-ILW divertor by spectroscopic imaging in the presence of a strong plasma continuum
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2019 (English)In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 18, p. 118-124Article in journal (Refereed) Published
Abstract [en]

The identification of the sources of atomic tungsten and the measurement of their radiation distribution in front of all plasma-facing components has been performed in JET with the help of two digital cameras with the same two-dimensional view, equipped with interference filters of different bandwidths centred on the W I (400.88 nm) emission line. A new algorithm for the subtraction of the continuum radiation was successfully developed and is now used to evaluate the W erosion even in the inner divertor region where the strong recombination emission is dominating over the tungsten emission. Analysis of W sputtering and W redistribution in the divertor by video imaging spectroscopy with high spatial resolution for three different magnetic configurations was performed. A strong variation of the emission of the neutral tungsten in toroidal direction and corresponding W erosion has been observed. It correlates strongly with the wetted area with a maximal W erosion at the edge of the divertor tile.

National Category
Fusion, Plasma and Space Physics
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-382284 (URN)10.1016/j.nme.2018.12.009 (DOI)000460107500022 ()2-s2.0-85058552880 (Scopus ID)
Conference
23rd Int. Conference on Plasma Surface Interactions in Controlled Fusion Devices
Note

QC 20190128

Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-04-24
Ström, P. (2019). Material characterization for magnetically confined fusion: Surface analysis and method development. (Doctoral dissertation). KTH Royal Institute of Technology
Open this publication in new window or tab >>Material characterization for magnetically confined fusion: Surface analysis and method development
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The dream of abundant clean energy has brought scientists and laypeople alike to ponder the possibilities of nuclear fusion since it was established as the energy source of the stars in 1939. Starting from the mid the 20th century, significant effort has been put into overcoming the technological challenges related to the construction of a power plant, but initial optimism has faded somewhat due to a notable absence of practical outcomes. Nevertheless, the research continues and progress is made slowly but surely.

The present work deals with a small part of the fusion puzzle, namely the materials to be used in the first wall surrounding a magnetically confined plasma. Carbon, which has historically been considered as the most viable element for this role, has been ruled out due to issues with plasma-induced erosion, hydrocarbon formation and a buildup of thick deposited material layers on wall components. The latter two lead to an unacceptable accumulation of radioactive tritium, both in the deposited layers and in dust particles. A metal wall, which would alleviate these particular problems but increase the severity of others, is therefore envisioned for a future demonstration reactor.

Three contributions to the overall research effort are made though this thesis. First, an increased understanding of plasma-induced erosion of so-called reduced activation ferritic-martensitic steels and preferential sputtering of light material components is provided. High-resolution ion beam analysis and microscopy methods are used to examine samples of such a steel after exposure to plasma under controlled circumstances. Model films consisting of a mixture of iron and tungsten deposited on silicon substrates are also studied as they constitute simpler systems where the effects of interest may be simulated. The knowledge obtained is necessary for an assessment of the possibility to use reduced activation steel as a plasma-facing material in specific regions of a reactor wall.

The second contribution consists of reports on the composition of deposited material layers on wall components retrieved from the plasma confinement experiments JET and TEXTOR. These provide limited conclusions on the range and rate of material erosion, transport and deposition in two cases.

Finally, a detection system for the ion beam technique elastic recoil detection analysis has been assembled, tested and put into operation. In addition to improving the quality of analyses performed on fusion-related materials, the system has become an established tool available for users of the 5 MV electrostatic pelletron accelerator at Uppsala University’s Tandem Laboratory.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. p. 189
National Category
Fusion, Plasma and Space Physics
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:uu:diva-382310 (URN)978-91-7873-055-1 (ISBN)
Public defence
2019-02-13, F3, Lindstedtsvägen 26, Stockholm, 09:00 (English)
Opponent
Supervisors
Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-04-24Bibliographically 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:uu:diva-382292 (URN)10.1063/1.5030502 (DOI)000431139400078 ()29716341 (PubMedID)2-s2.0-85045335587 (Scopus ID)
Note

QC 201805014

Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-04-24
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
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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:uu:diva-382298 (URN)10.1016/j.nme.2018.09.003 (DOI)000454165000013 ()2-s2.0-85054327579 (Scopus ID)
Note

QC 20190115

Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-04-24
Ström, P., Petersson, P., Parra, R. A., 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
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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 10(21) D/m(2) and 10(24) D/m(2), 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 10(23) D/m(2) 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 SCIENCE BV, 2018
Keywords
EUROFER, Sputtering, Erosion, ToF-MEIS, AFM, ToF-ERDA
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-361484 (URN)10.1016/j.jnucmat.2018.05.031 (DOI)000439134500016 ()
Funder
Swedish Foundation for Strategic Research , RIF14-0053Swedish Research Council, 821-2012-5144
Available from: 2018-09-27 Created: 2018-09-27 Last updated: 2019-04-24
Ström, P., Petersson, P. & Hamberg, M. (2018). Surface oxide and roughness on test samples for the Ultra High Vacuum section of the Laser Heater for the European XFEL. Vacuum, 149, 83-86
Open this publication in new window or tab >>Surface oxide and roughness on test samples for the Ultra High Vacuum section of the Laser Heater for the European XFEL
2018 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 149, p. 83-86Article in journal (Refereed) Published
Abstract [en]

The European X-ray Free Electron Laser has recently started with operation for users. An approximately 3 m long ultra high vacuum laser heater section is implemented to overcome possible electron bunch instabilities. We describe the process of determining the oxide layer thickness and surface roughness on test samples of the internal surface material in the laser heater vacuum chambers using elastic recoil detection analysis and optical surface profiling. The results are compared to specified values and show that surface roughness on the samples is larger than the requested maximum, with RMS deviations from a mean plane of up to 1.76 mu m for 0.60 x 0.45 square millimeter scans. The maximum oxide layer thickness is 5.5 nm on non-electropolished surfaces assuming cuprous oxide with density 6.0 g per cubic centimeter and 4.0 nm on electropolished surfaces.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keywords
European XFEL, Laser Heater, Vacuum chambers, Surface roughness, Oxide
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-348837 (URN)10.1016/j.vacuum.2017.12.014 (DOI)000425576100014 ()
Funder
Swedish Foundation for Strategic Research , RIF14-0053Swedish Research Council, 821-2012-5144, 828-2008-1093Stiftelsen Olle Engkvist Byggmästare, 2013/689
Available from: 2018-04-23 Created: 2018-04-23 Last updated: 2019-04-24
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
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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:uu:diva-382285 (URN)10.1016/j.nme.2018.07.001 (DOI)000442226800028 ()2-s2.0-85049915542 (Scopus ID)
Note

QC 20180821

Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-04-24
Ström, P., Primetzhofer, D., Schwarz-Selinger, T. & Sugiyama, K. (2017). Compositional and morphological analysis of FeW films modified by sputtering and heating. Nuclear Materials and Energy, 472-477
Open this publication in new window or tab >>Compositional and morphological analysis of FeW films modified by sputtering and heating
2017 (English)In: Nuclear Materials and Energy, E-ISSN 2352-1791, p. 472-477Article in journal (Refereed) Published
Abstract [en]

Surface compositional changes of iron-tungsten films by deuterium (D) ion bombardment were studied by means of medium energy ion scattering, elastic recoil detection analysis and Rutherford backscattering spectrometry. The energy of the bombarding ions was 200 eV/D and the fluence was varied from 1021 D/m2 to 1024 D/m2. A significant increase of the tungsten concentration within the 20 nm closest to the sample surface, caused by preferential sputtering of iron, was seen for the films exposed 1023 D/m2 or more. In the sample exposed to the highest fluence, 1024 D/m2, the concentration of tungsten was increased from an initial 1.7 at. % up to approximately 24 at. % averaged over the 5 nm closest to the surface. The analysis was complicated by the presence of oxygen on the sample surfaces. In order to study the thermal stability of the tungsten enriched layer, the sample initially exposed to 1023 D/m2 at room temperature was heated to 400 °C in the measurement chamber for medium energy ion scattering and several spectra were recorded at intermediate temperatures. The obtained data showed that the layer was relatively stable below 200 °C whereas a drastic change in the film composition occurred between 200 °C and 250 °C due to interdiffusion of iron and silicon, the latter of which was the substrate material. The surface morphologies of the films were probed with atomic force microscopy showing that protrusions of 10–100 nm width appeared after deuterium bombardment at fluences higher than 1022 D/m2.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-382323 (URN)10.1016/j.nme.2017.03.002 (DOI)
Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-04-24
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