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BETA
Ratynskaia, Svetlana V.ORCID iD iconorcid.org/0000-0002-6712-3625
Alternative names
Publications (10 of 106) 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 ()2-s2.0-85070909412 (Scopus ID)
Note

QC 20190807

Available from: 2019-08-07 Created: 2019-08-07 Last updated: 2019-10-04Bibliographically 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
Joffrin, E., Bergsåker, H., Bykov, I., Frassinetti, L., Fridström, R., Garcia Carrasco, A., . . . et al., . (2019). Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall. Nuclear Fusion, 59(11), Article ID 112021.
Open this publication in new window or tab >>Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 11, article id 112021Article in journal (Refereed) Published
Abstract [en]

For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des. 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D-T mixtures since 1997 and the first ever D-T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D-T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D-T preparation. This intense preparation includes the review of the physics basis for the D-T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D-T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfven eigenmode antennas, neutral gauges, radiation hard imaging systems...) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D-T campaign provides an incomparable source of information and a basis for the future D-T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
fusion power, JET, tritium, isotope
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-260157 (URN)10.1088/1741-4326/ab2276 (DOI)000484122200001 ()2-s2.0-85070875113 (Scopus ID)
Note

QC 20190926

Available from: 2019-09-26 Created: 2019-09-26 Last updated: 2019-10-04Bibliographically approved
De Angeli, M., Lazzaro, E., Tolias, P., Ratynskaia, S. V., Vignitchouk, L., Castaldo, C., . . . Uccello, A. (2019). Pre-plasma remobilization of ferromagnetic dust in FTU and possible interference with tokamak operations. Nuclear Fusion, 59(10), Article ID 106033.
Open this publication in new window or tab >>Pre-plasma remobilization of ferromagnetic dust in FTU and possible interference with tokamak operations
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 10, article id 106033Article in journal (Refereed) Published
Abstract [en]

Experimental evidence of the pre-plasma remobilization of ferromagnetic dust in FTU is presented. Thomson scattering data and IR camera observations document the occurrence of intrinsic dust remobilization prior to discharge start-up and allow for a rough calculation of the average mobilized dust density. Exposures of calibrated extrinsic non-magnetic and ferromagnetic dust to sole magnetic field discharges reveal that the magnetic moment force is the main mobilizing force, as confirmed by theoretical estimates. Pre-plasma remobilization probabilities are computed for varying dust sizes. The impact of prematurely remobilized dust on the breakdown and burn-through start-up phases is investigated together with the discharge termination induced once the plasma plateau is established.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
magnetic dust, dust mobilization, discharge start-up, discharge breakdown, dust in tokamaks
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-261002 (URN)10.1088/1741-4326/ab369f (DOI)000484508000003 ()2-s2.0-85072714767 (Scopus ID)
Note

QC 20191010

Available from: 2019-10-10 Created: 2019-10-10 Last updated: 2019-10-10Bibliographically 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
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ORCID iD: ORCID iD iconorcid.org/0000-0002-6712-3625

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