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Vignitchouk, LadislasORCID iD iconorcid.org/0000-0001-7796-1887
Alternative names
Publications (10 of 16) Show all publications
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
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
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
Vignitchouk, L., Ratynskaia, S., Kantor, M., Tolias, P., De Angeli, M., van der Meiden, H., . . . Banon, J.-P. (2018). Validating heat balance models for tungsten dust in cold dense plasmas. Plasma Physics and Controlled Fusion, 60(11), Article ID 115002.
Open this publication in new window or tab >>Validating heat balance models for tungsten dust in cold dense plasmas
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2018 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 60, no 11, article id 115002Article in journal (Refereed) Published
Abstract [en]

The first comparison of dust radius and surface temperature estimates, obtained from spectroscopic measurements of thermal radiation, with simulations of dust heating and vaporization by the MIGRAINe dust dynamics code is reported. The measurements were performed during controlled tungsten dust injection experiments in the cold and dense plasmas of Pilot-PSI, reproducing ITER divertor conditions. The comparison has allowed us to single out the dominating role of the work function contribution to the dust heating budget. However, in the plasmas of interest, dust was found to enter the strong vaporization regime, in which its temperature is practically insensitive to plasma properties and the various uncertainties in modeling. This makes the dust temperature a poor figure of merit for model validation purposes. On the other hand, simple numerical scalings obtained from orbital-motion-limited estimates were found to be remarkably robust and sufficient to understand the main physics at play in such cold and dense plasmas.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2018
Keywords
tungsten, dust, orbital-motion-limited, Pilot-PSI
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-235552 (URN)10.1088/1361-6587/aadbcb (DOI)000444743500002 ()2-s2.0-85055574326 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20181002

Available from: 2018-10-02 Created: 2018-10-02 Last updated: 2019-08-20Bibliographically approved
Vignitchouk, L., Ratynskaia, S. V. & Tolias, P. (2017). Analytical model of particle and heat flux collection by dust immersed in dense magnetized plasmas. Plasma Physics and Controlled Fusion, 59(10), Article ID 104002.
Open this publication in new window or tab >>Analytical model of particle and heat flux collection by dust immersed in dense magnetized plasmas
2017 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 59, no 10, article id 104002Article in journal (Refereed) Published
Abstract [en]

A comprehensive analytical description is presented for the particle and heat fluxes collected by dust in dense magnetized plasmas. Compared to the widely used orbital motion limited theory, the suppression of cross-field transport leads to a strong reduction of the electron fluxes, while ion collection is inhibited by thin-sheath effects and the formation of a potential overshoot along the field lines. As a result, the incoming heat flux loses its sensitivity to the floating potential, thereby diminishing the importance of electron emission processes in dust survivability. Numerical simulations implementing the new model for ITER-like detached divertor plasmas predict a drastic enhancement of the dust lifetime.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2017
Keywords
dust, droplets, dust heating, magnetized electron collection, thin-sheath ions
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-213756 (URN)10.1088/1361-6587/aa7c44 (DOI)000407750200001 ()2-s2.0-85029917782 (Scopus ID)
Note

QC 20170911

Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2017-09-11Bibliographically approved
Tolias, P., Ratynskaia, S. V., Shalpegin, A., Vignitchouk, L., Brochard, F., De Angeli, M. & van der Meiden, H. (2017). Experimental validation of the analytical model for tungsten dust - wall mechanical impacts incorporated in the MIGRAINe dust dynamics code. NUCLEAR MATERIALS AND ENERGY, 12, 524-529
Open this publication in new window or tab >>Experimental validation of the analytical model for tungsten dust - wall mechanical impacts incorporated in the MIGRAINe dust dynamics code
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2017 (English)In: NUCLEAR MATERIALS AND ENERGY, ISSN 2352-1791, Vol. 12, p. 524-529Article in journal (Refereed) Published
Abstract [en]

Mechanical dust-wall collisions are unavoidable in fusion devices and their accurate modeling is essential for the understanding of dust transport. The MIGRAINe dust dynamics code features analytical models addressing all facets of dust-surface impacts, some aspects of which have not been experimentally validated thus far. Dedicated dust injection experiments have been carried out in Pilot-PSI resulting to the visualization of in-plasma tungsten dust-surface impacts with an unprecedented resolution. They allowed for a calibration of key quantities of the MIGRAINe impact model.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-220639 (URN)10.1016/j.nme.2017.01.007 (DOI)000417293300082 ()2-s2.0-85015661567 (Scopus ID)
Note

QC 20180112

Available from: 2018-01-12 Created: 2018-01-12 Last updated: 2018-01-12Bibliographically approved
Ratynskaia, S. V., Tolias, P., De Angeli, M., Weinzettl, V., Matejicek, J., Bykov, I., . . . De Temmerman, G. (2017). Tungsten dust remobilization under steady-state and transient plasma conditions. NUCLEAR MATERIALS AND ENERGY, 12, 569-574
Open this publication in new window or tab >>Tungsten dust remobilization under steady-state and transient plasma conditions
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2017 (English)In: NUCLEAR MATERIALS AND ENERGY, ISSN 2352-1791, Vol. 12, p. 569-574Article in journal (Refereed) Published
Abstract [en]

Remobilization is one of the most prominent unresolved fusion dust-relevant issues, strongly related to the lifetime of dust in plasma-wetted regions, the survivability of dust on hot plasma-facing surfaces and the formation of dust accumulation sites. A systematic cross-machine study has been initiated to investigate the remobilization of tungsten micron-size dust from tungsten surfaces implementing a newly developed technique based on controlled pre-adhesion by gas dynamics methods. It has been utilized in a number of devices and has provided new insights on remobilization under steady-state and transient conditions. The experiments are interpreted with contact mechanics theory and heat conduction models.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-220643 (URN)10.1016/j.nme.2016.10.021 (DOI)000417293300090 ()2-s2.0-85006994117 (Scopus ID)
Note

QC 20180111

Available from: 2018-01-11 Created: 2018-01-11 Last updated: 2018-05-23Bibliographically approved
Tolias, P., Ratynskaia, S., De Angeli, M., De Temmerman, G., Ripamonti, D., Riva, G., . . . Litnovsky, A. (2016). Dust remobilization in fusion plasmas under steady state conditions. Plasma Physics and Controlled Fusion, 58(2), Article ID 025009.
Open this publication in new window or tab >>Dust remobilization in fusion plasmas under steady state conditions
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2016 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 58, no 2, article id 025009Article in journal (Refereed) Published
Abstract [en]

The first combined experimental and theoretical studies of dust remobilization by plasma forces are reported. The main theoretical aspects of remobilization in fusion devices under steady state conditions are analyzed. In particular, the dominant role of adhesive forces is highlighted and generic remobilization conditions-direct lift-up, sliding, rolling-are formulated. A novel experimental technique is proposed, based on controlled adhesion of dust grains on tungsten samples combined with detailed mapping of the dust deposition profile prior and post plasma exposure. Proof-of-principle experiments in the TEXTOR tokamak and the EXTRAP-T2R reversed-field pinch are presented. The versatile environment of the linear device Pilot-PSI allowed for experiments with different magnetic field topologies and varying plasma conditions that were complemented with camera observations.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2016
Keywords
dust adhesion, dust remobilization, PFC
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-184561 (URN)10.1088/0741-3335/58/2/025009 (DOI)000371570900010 ()2-s2.0-84955304982 (Scopus ID)
Note

QC 20160405

Available from: 2016-04-05 Created: 2016-04-01 Last updated: 2017-11-30Bibliographically approved
Vignitchouk, L. (2016). Modelling the multifaceted physics of metallic dust and droplets in fusion plasmas. (Doctoral dissertation). KTH Royal Institute of Technology
Open this publication in new window or tab >>Modelling the multifaceted physics of metallic dust and droplets in fusion plasmas
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Plasma-material interaction constitutes one of the major scientific and technological issues affecting the development of thermonuclear fusion power plants. In particular, the release of metallic dust and droplets from plasmafacing components is a crucial aspect of reactor operation. By penetrating into the burning plasma, these micrometric particles act as a source of impurities which tend to radiate away the plasma energy, cooling it down below the threshold temperatures for sustainable fusion reactions. By accumulating in the reactor chamber, dust particles tend to retain fuel elements, lowering the reactor efficiency and increasing its radioactivity content. Dust accumulation also increases the risk of explosive hydrogen production upon accidental air or water ingress in the vacuum chamber. Numerical dust transport codes provide the essential framework to guide theoretical and experimental dust studies by simulating the intricate couplings between the many physical processes driving dust dynamics in fusion plasmas. This thesis reports on the development and validation of the MIGRAINe code, which specifically targets plasma-surface interaction processes and the physics of dust particles impinging on plasma-facing components to address long-term dust migration and accumulation in fusion devices.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. p. 80
Series
TRITA-EE, ISSN 1653-5146 ; 2016:084
National Category
Fusion, Plasma and Space Physics
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-187638 (URN)978-91-7729-041-4 (ISBN)
Public defence
2016-06-13, E3, Osquars backe 14, Stockholm, 13:30 (English)
Opponent
Supervisors
Note

QC 20160525

Available from: 2016-05-25 Created: 2016-05-25 Last updated: 2016-05-26Bibliographically approved
Ratynskaia, S., Tolias, P., Shalpegin, A., Vignitchouk, L. T., De Angell, M., Bykov, I., . . . De Temmerman, G. (2015). Elastic-plastic adhesive impacts of tungsten dust with metal surfaces in plasma environments. Journal of Nuclear Materials, 463, 877-880
Open this publication in new window or tab >>Elastic-plastic adhesive impacts of tungsten dust with metal surfaces in plasma environments
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2015 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, p. 877-880Article in journal (Refereed) Published
Abstract [en]

Dust-surface collisions impose size selectivity on the ability of dust grains to migrate in scrape-off layer and divertor plasmas and to adhere to plasma-facing components. Here, we report first experimental evidence of dust impact phenomena in plasma environments concerning low-speed collisions of tungsten dust with tungsten surfaces: re-bouncing, adhesion, sliding and rolling. The results comply with the predictions of the model of elastic-perfectly plastic adhesive spheres employed in the dust dynamics code MIGRAINe for sub- to several meters per second impacts of micrometer-range metal dust.

National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-172698 (URN)10.1016/j.jnucmat.2014.09.064 (DOI)000358467200187 ()2-s2.0-84937636637 (Scopus ID)
Note

QC 20150901

Available from: 2015-09-01 Created: 2015-08-27 Last updated: 2017-12-04Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7796-1887

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