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BETA
Ratynskaia, Svetlana V.ORCID iD iconorcid.org/0000-0002-6712-3625
Alternative names
Publications (10 of 104) 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
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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
Labit, B., Frassinetti, L., Jonsson, T., Ratynskaia, S. V., Thorén, E., Tolias, P., . . . Zuin, M. (2019). Dependence on plasma shape and plasma fueling for small edge-localized mode regimes in TCV and ASDEX Upgrade. Nuclear Fusion, 59(8), Article ID 086020.
Open this publication in new window or tab >>Dependence on plasma shape and plasma fueling for small edge-localized mode regimes in TCV and ASDEX Upgrade
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 8, article id 086020Article in journal (Refereed) Published
Abstract [en]

Within the EUROfusion MST1 work package, a series of experiments has been conducted on AUG and TCV devices to disentangle the role of plasma fueling and plasma shape for the onset of small ELM regimes. On both devices, small ELM regimes with high confinement are achieved if and only if two conditions are fulfilled at the same time. Firstly, the plasma density at the separatrix must be large enough (n(e,sep)/n(G) similar to 0.3), leading to a pressure profile flattening at the separatrix, which stabilizes type-I ELMs. Secondly, the magnetic configuration has to be close to a double null (DN), leading to a reduction of the magnetic shear in the extreme vicinity of the separatrix. As a consequence, its stabilizing effect on ballooning modes is weakened.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2019
Keywords
H-mode, type-II ELMs, grassy ELMs, plasma triangularity, separatrix density, ballooning modes
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-255302 (URN)10.1088/1741-4326/ab2211 (DOI)000473079500003 ()
Note

QC 20190807

Available from: 2019-08-07 Created: 2019-08-07 Last updated: 2019-08-07Bibliographically approved
Trier, E., Frassinetti, L., Fridström, R., Garcia Carrasco, A., Hellsten, T., Johnson, T., . . . Zuin, M. (2019). ELM-induced cold pulse propagation in ASDEX Upgrade. Plasma Physics and Controlled Fusion, 61(4), Article ID 045003.
Open this publication in new window or tab >>ELM-induced cold pulse propagation in ASDEX Upgrade
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2019 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 4, article id 045003Article in journal (Refereed) Published
Abstract [en]

In ASDEX Upgrade, the propagation of cold pulses induced by type-I edge localized modes (ELMs) is studied using electron cyclotron emission measurements, in a dataset of plasmas with moderate triangularity. It is found that the edge safety factor or the plasma current are the main determining parameters for the inward penetration of the T-e perturbations. With increasing plasma current the ELM penetration is more shallow in spite of the stronger ELMs. Estimates of the heat pulse diffusivity show that the corresponding transport is too large to be representative of the inter-ELM phase. Ergodization of the plasma edge during ELMs is a possible explanation for the observed properties of the cold pulse propagation, which is qualitatively consistent with non-linear magneto-hydro-dynamic simulations.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
ELMs, MHD instabilities, stochastic field, magnetic islands, cold pulse
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-245121 (URN)10.1088/1361-6587/aaf9c3 (DOI)000458986000002 ()
Note

QC 20190315

Available from: 2019-03-15 Created: 2019-03-15 Last updated: 2019-05-20Bibliographically approved
Tolias, P., De Angeli, M., Riva, G., Ratynskaia, S. V., Daminelli, G., Laguardia, L., . . . Vassallo, E. (2019). The adhesion of tungsten dust on plasma-exposed tungsten surfaces. Nuclear Materials and Energy, 18, 18-22
Open this publication in new window or tab >>The adhesion of tungsten dust on plasma-exposed tungsten surfaces
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2019 (English)In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 18, p. 18-22Article in journal (Refereed) Published
Abstract [en]

The adhesion of tungsten dust is measured on plasma-exposed and non-exposed tungsten substrates with the electrostatic detachment method. Tungsten substrates of comparable surface roughness have been exposed to the deuterium plasmas of the GyM linear device and the argon plasmas of rf glow discharges under conditions which invariably modify the surface composition due to physical sputtering. The adhesion has been systematically characterized for different spherical nearly monodisperse dust populations. Independent of the dust size, an approximate 50% post-exposure reduction of the average and spread of the adhesive force has been consistently observed and attributed to surface chemistry modifications.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
Dust adhesion, Pull-off force, Dust remobilization, Electrostatic detachment, Adsorbates, Sputtering
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-247856 (URN)10.1016/j.nme.2018.12.002 (DOI)000460107500004 ()
Note

QC 20190326

Available from: 2019-03-26 Created: 2019-03-26 Last updated: 2019-03-26Bibliographically approved
Tierens, W., Frassinetti, L., Hellsten, T., Petersson, P., Fridström, R., Garcia Carrasco, A., . . . et al., . (2019). Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments. Nuclear Fusion, 59(4), Article ID 046001.
Open this publication in new window or tab >>Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 4, article id 046001Article in journal (Refereed) Published
Abstract [en]

In this paper we validate the finite element code RAPLICASOL, which models radiofrequency wave propagation in edge plasmas near ICRF antennas, against calculations with the TOPICA code. We compare the output of both codes for the ASDEX Upgrade 2-strap antenna, and for a 4-strap WEST-like antenna. Although RAPLICASOL requires considerably fewer computational resources than TOPICA, we find that the predicted quantities of experimental interest (including reflection coefficients, coupling resistances, S- and Z-matrix entries, optimal matching settings, and even radiofrequency electric fields) are in good agreement provided we are careful to use the same geometry in both codes.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
ICRF, finite elements, simulation
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-243928 (URN)10.1088/1741-4326/aaf455 (DOI)000456197200001 ()
Note

QC 20190212

Available from: 2019-02-12 Created: 2019-02-12 Last updated: 2019-02-12Bibliographically approved
Tolias, P., Riva, G., De Angeli, M., Ratynskaia, S. V., Daminelli, G., Lungu, C. P. & Porosnicu, C. (2018). Adhesive force distributions for tungsten dust deposited on bulk tungsten and beryllium-coated tungsten surfaces. Nuclear Materials and Energy, 15, 55-63
Open this publication in new window or tab >>Adhesive force distributions for tungsten dust deposited on bulk tungsten and beryllium-coated tungsten surfaces
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2018 (English)In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 15, p. 55-63Article in journal (Refereed) Published
Abstract [en]

Comprehensive measurements of the adhesive force for tungsten dust adhered to tungsten surfaces have been performed with the electrostatic detachment method. Monodisperse spherical dust has been deposited with gas dynamics techniques or with gravity mimicking adhesion as it naturally occurs in tokamaks. The adhesive force is confirmed to follow the log-normal distribution and empirical correlations are proposed for the size-dependence of its mean and standard deviation. Systematic differences are observed between the two deposition methods and attributed to plastic deformation during sticking impacts. The presence of thin beryllium coatings on tungsten surfaces is demonstrated to barely affect adhesion.

Place, publisher, year, edition, pages
Elsevier Ltd, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-238239 (URN)10.1016/j.nme.2018.05.013 (DOI)000435611400009 ()2-s2.0-85048178222 (Scopus ID)
Note

QC 20181031

Available from: 2018-10-31 Created: 2018-10-31 Last updated: 2019-05-23Bibliographically approved
Vignitchouk, L., Delzanno, G. L., Tolias, P. & Ratynskaia, S. V. (2018). Electron reflection effects on particle and heat fluxes to positively charged dust subject to strong electron emission. Physics of Plasmas, 25(6), Article ID 063702.
Open this publication in new window or tab >>Electron reflection effects on particle and heat fluxes to positively charged dust subject to strong electron emission
2018 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, no 6, article id 063702Article in journal (Refereed) Published
Abstract [en]

A new model describing dust charging and heating in unmagnetized plasmas in the presence of large electron emission currents is presented. By accounting for the formation of a potential well due to trapped emitted electrons when the dust is positively charged, this model extends the so-called OML+ approach, thus far limited to thermionic emission, by including electron-induced emission processes, and in particular low-energy quasi-elastic electron reflection. Revised semi-analytical formulas for the current and heat fluxes associated with emitted electrons are successfully validated against particle-in-cell simulations and predict an overall reduction of dust heating by up to a factor of 2. When applied to tungsten dust heating in divertor-like plasmas, the new model predicts that the dust lifetime increases by up to 80%, as compared with standard orbital-motion-limited estimates.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2018
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-232414 (URN)10.1063/1.5026384 (DOI)000437193700127 ()2-s2.0-85048606159 (Scopus ID)
Funder
EU, Horizon 2020, 633053Swedish Research CouncilLars Hierta Memorial Foundation
Note

QC 20180726

Available from: 2018-07-26 Created: 2018-07-26 Last updated: 2018-07-26Bibliographically approved
Ratynskaia, S. V., Tolias, P., De Angeli, M., Ripamonti, D., Riva, G., Aussems, D. & Morgan, T. W. (2018). Interaction of adhered beryllium proxy dust with transient and stationary plasmas. Nuclear Materials and Energy, 17, 222-227
Open this publication in new window or tab >>Interaction of adhered beryllium proxy dust with transient and stationary plasmas
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2018 (English)In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 17, p. 222-227Article in journal (Refereed) Published
Abstract [en]

Tungsten (W) substrates with adhered beryllium (Be) proxy dust-copper, chromium, aluminium -have been exposed in the Magnum-PSI linear device. Their interaction with transient and stationary plasmas has been systematically studied under varying heat fluxes and magnetic field topologies. The dust remobilization activities, macro-morphological changes and chemical modifications induced by the plasma incidence are documented. Aluminium is identified to be the most suitable surrogate material due to the similar binary phase diagram and nearly identical evaporation rates. Extrapolation suggests that Be dust cannot survive on hot W surfaces but it can trigger mixed Be/W effects prior to its plasma removal.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
Keywords
Transient heat loads, Dust remobilization, Dust survivability, Dust adhesion, Mixed material effects
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-241225 (URN)10.1016/j.nme.2018.11.007 (DOI)000454165000031 ()2-s2.0-85056451086 (Scopus ID)
Note

QC 20190117

Available from: 2019-01-17 Created: 2019-01-17 Last updated: 2019-01-17Bibliographically approved
Thorén, E., Ratynskaia, S. V., Tolias, P., Pitts, R. A., Krieger, K., Komm, M. & Baken, M. (2018). MEMOS 3D modelling of ELM-induced transient melt damage on an inclined tungsten surface in the ASDEX Upgrade outer divertor. Nuclear Materials and Energy, 17, 194-199
Open this publication in new window or tab >>MEMOS 3D modelling of ELM-induced transient melt damage on an inclined tungsten surface in the ASDEX Upgrade outer divertor
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2018 (English)In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 17, p. 194-199Article in journal (Refereed) Published
Abstract [en]

The first MEMOS 3D simulations of liquid metal motion on an inclined bulk tungsten sample transiently molten by edge-localized modes (ELMs) are reported. The exposures took place at the outer ASDEX-Upgrade divertor with the tungsten surface tangent intersecting the magnetic field at similar to 18 degrees. Simulations confirm that the observed poloidal melt motion is caused by the volumetric J x B force with J the bulk replacement current triggered by thermionic emission. The final erosion profile and total melt build up are reproduced by employing the escaping thermionic current dependence on the incident heat flux derived from dedicated particle-in-cell simulations. Modelling reveals that melt dynamics is governed by the volumetric Lorentz force, capillary flows due to thermal surface tension gradients and viscous deceleration. The effect of the evolving surface deformation, that locally alters the field-line inclination modifying the absorbed power flux and the escaping thermionic current, in the final surface morphology is demonstrated to be significant.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
Keywords
Melting, Tungsten, Divertor, Melt layer motion, MEMOS, Thermionic emission
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-241221 (URN)10.1016/j.nme.2018.11.006 (DOI)000454165000026 ()2-s2.0-85056610668 (Scopus ID)
Note

QC 20190118

Available from: 2019-01-18 Created: 2019-01-18 Last updated: 2019-01-18Bibliographically approved
Panarese, A., Bruno, D., Tolias, P., Ratynskaia, S. V., Longo, S. & de Angelis, U. (2018). Molecular dynamics calculation of the spectral densities of plasma fluctuations. Journal of Plasma Physics, 84(3), Article ID 905840308.
Open this publication in new window or tab >>Molecular dynamics calculation of the spectral densities of plasma fluctuations
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2018 (English)In: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 84, no 3, article id 905840308Article in journal (Refereed) Published
Abstract [en]

Spectral densities of plasma fluctuations are calculated for the thermal case using classical molecular dynamics (MD) assuming Coulomb interactions and a short-range cutoff radius. The aim of the calculation is to verify limits and performances of such calculations in the light of possible generalizations, e.g. collisional or non-ideal plasmas. Results are presented for ideal, collisionless, fully ionized thermal plasmas. Comparison with the analytical theory reveals a generally satisfactory agreement with possibility for improvement when more strict numerical parameters are used albeit with a strong increase in computational cost. The largest deviations have been observed in the vicinity of the weakly damped eigenmodes. The agreement is strong in other parts of the spectrum, where Landau damping is prominent, and overcomes the effects stemming from the excess collisionality and coupling as well as from the exclusion of short-range collisions.

Place, publisher, year, edition, pages
CAMBRIDGE UNIV PRESS, 2018
Keywords
plasma properties, plasma simulation
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-240044 (URN)10.1017/S0022377818000491 (DOI)000450962300009 ()
Funder
Swedish Research Council
Note

QC 20181210

Available from: 2018-12-10 Created: 2018-12-10 Last updated: 2018-12-10Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6712-3625

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