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BETA
Ratynskaia, Svetlana V.ORCID iD iconorcid.org/0000-0002-6712-3625
Alternative names
Publications (10 of 117) Show all publications
Sias, G., Frassinetti, L., Hellsten, T., Petersson, P., Rubel, M., Fridström, R., . . . Zychor, I. (2019). A locked mode indicator for disruption prediction on JET and ASDEX upgrade. Fusion engineering and design, 138, 254-266
Open this publication in new window or tab >>A locked mode indicator for disruption prediction on JET and ASDEX upgrade
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2019 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 138, p. 254-266Article in journal (Refereed) Published
Abstract [en]

The aim of this paper is to present a signal processing algorithm that, applied to the raw Locked Mode signal, allows us to obtain a disruption indicator in principle exploitable on different tokamaks. A common definition of such an indicator for different machines would facilitate the development of portable systems for disruption prediction, which is becoming of increasingly importance for the next tokamak generations. Moreover, the indicator allows us to overcome some intrinsic problems in the diagnostic system such as drift and offset. The behavior of the proposed indicator as disruption predictor, based on crossing optimized thresholds of the signal amplitude, has been analyzed using data of both JET and ASDEX Upgrade experiments. A thorough analysis of the disruption prediction performance shows how the indicator is able to recover some missed and tardy detections of the raw signal. Moreover, it intervenes and corrects premature or even wrong alarms due to, e.g., drifts and/or offsets.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
Keywords
Tokamak, Disruption prediction, Locked mode signal, Disruption indicators, Feature extraction
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-269602 (URN)10.1016/j.fusengdes.2018.11.021 (DOI)000457663100032 ()2-s2.0-85057571211 (Scopus ID)
Note

QC 20200407

Available from: 2020-04-07 Created: 2020-04-07 Last updated: 2020-04-07Bibliographically approved
Vignitchouk, L., Ratynskaia, S. V., Tolias, P., Pitts, R. A., De Temmerman, G., Lehnen, M. & Kiramov, D. (2019). Accumulation of beryllium dust in ITER diagnostic ports after off-normal events. Paper presented at 23rd International Conference on Plasma-Surface Interactions in Controlled Fusion Devices (PSI), JUN 18-22, 2018, Princeton Univ, Princeton, NJ. Nuclear Materials and Energy, 20, Article ID UNSP 100684.
Open this publication in new window or tab >>Accumulation of beryllium dust in ITER diagnostic ports after off-normal events
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2019 (English)In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 20, article id UNSP 100684Article in journal (Refereed) Published
Abstract [en]

Dust transport simulations are used to predict the effect of diagnostic ports on the in-vessel inventory of solid beryllium particles produced during mitigated disruptions in ITER. Beryllium dust is assumed to originate from the re-solidification of liquid droplets, which are initially ejected during transient first-wall melting events and subsequently interact with the disrupting plasma. The trajectories of droplets launched with various initial conditions, as well as the time evolution of their temperature and mass, are simulated until either complete vaporization or immobilization upon undergoing a sticking or splashing impact with the wall is realized. The results indicate that approximately 10% of the dust mass in the vessel can be expected to reside inside ports, in particular those located in the equatorial plane or in the lower outboard first wall.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Beryllium, Dust, Droplets, Disruptions
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-266196 (URN)10.1016/j.nme.2019.100684 (DOI)000500930800002 ()2-s2.0-85065446827 (Scopus ID)
Conference
23rd International Conference on Plasma-Surface Interactions in Controlled Fusion Devices (PSI), JUN 18-22, 2018, Princeton Univ, Princeton, NJ
Note

QC 20200110

Available from: 2020-01-10 Created: 2020-01-10 Last updated: 2020-01-10Bibliographically approved
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: 2019-10-29Bibliographically approved
Drenik, A., Bergsaker, H., Bykov, I., Frassinetti, L., Garcia Carrasco, A., Hellsten, T., . . . Zychor, I. (2019). Analysis of the outer divertor hot spot activity in the protection video camera recordings at JET. Fusion engineering and design, 139, 115-123
Open this publication in new window or tab >>Analysis of the outer divertor hot spot activity in the protection video camera recordings at JET
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2019 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 139, p. 115-123Article in journal (Refereed) Published
Abstract [en]

Hot spots on the divertor tiles at JET result in overestimation of the tile surface temperature which causes unnecessary termination of pulses. However, the appearance of hot spots can also indicate the condition of the divertor tile surfaces. To analyse the behaviour of the hot spots in the outer divertor tiles of JET, a simple image processing algorithm is developed. The algorithm isolates areas of bright pixels in the camera image and compares them to previously identified hot spots. The activity of the hot spots is then linked to values of other signals and parameters in the same time intervals. The operation of the detection algorithm was studied in a limited pulse range with high hot spot activity on the divertor tiles 5, 6 and 7. This allowed us to optimise the values of the controlling parameters. Then, the wider applicability of the method has been demonstrated by the analysis of the hot spot behaviour in a whole experimental campaign.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
Keywords
JET, ITER-like wall, Plasma-wall interaction, Image analysis
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-269599 (URN)10.1016/j.fusengdes.2018.12.079 (DOI)000458939100016 ()2-s2.0-85059687937 (Scopus ID)
Note

QC 20200407

Available from: 2020-04-07 Created: 2020-04-07 Last updated: 2020-04-07Bibliographically 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 ()2-s2.0-85064405933 (Scopus ID)
Note

QC 20190315

Available from: 2019-03-15 Created: 2019-03-15 Last updated: 2020-05-11Bibliographically approved
Vasilopoulou, T., Bergsåker, H., Bykov, I., Frassinetti, L., Garcia Carrasco, A., Hellsten, T., . . . Zychor, I. (2019). Improved neutron activation dosimetry for fusion. Fusion engineering and design, 139, 109-114
Open this publication in new window or tab >>Improved neutron activation dosimetry for fusion
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2019 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 139, p. 109-114Article in journal (Refereed) Published
Abstract [en]

Neutron activation technique has been widely used for the monitoring of neutron fluence at the Joint European Torus (JET) whereas it is foreseen to be employed at future fusion plants, such as ITER and DEMO. Neutron activation provides a robust tool for the measurement of neutron fluence in the complex environment encountered in a tokamak. However, activation experiments previously performed at JET showed that the activation foils used need to be calibrated in a real fusion environment in order to provide accurate neutron fluence data. Triggered by this challenge, an improved neutron activation method for the evaluation of neutron fluence at fusion devices has been developed. Activation assemblies similar to those used at JET were irradiated under 14 MeV neutrons at the Frascati Neutron Generator (FNG) reference neutron field. The data obtained from the calibration experiment were applied for the analysis of activation foil measurements performed during the implemented JET Deuterium-Deuterium (D-D) campaign. The activation results were compared against thermoluminescence measurements and a satisfactory agreement was observed. The proposed method provides confidence on the use of activation technique for the precise estimation of neutron fluence at fusion devices and enables its successful implementation in the forthcoming JET Deuterium-Tritium (D-T) campaign.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
Keywords
Neutron activation, Neutron dosimetry, JET, Fusion
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-269598 (URN)10.1016/j.fusengdes.2019.01.002 (DOI)000458939100015 ()2-s2.0-85059692263 (Scopus ID)
Note

QC 20200401

Available from: 2020-04-01 Created: 2020-04-01 Last updated: 2020-04-01Bibliographically approved
Meyer, H., Frassinetti, L., Garcia Carrasco, A., Ratynskaia, S. V., Rubel, M., Thorén, E., . . . et al., . (2019). Overview of physics studies on ASDEX Upgrade. Nuclear Fusion, 59(11), Article ID 112014.
Open this publication in new window or tab >>Overview of physics studies on ASDEX Upgrade
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 11, article id 112014Article in journal (Refereed) Published
Abstract [en]

The ASDEX Upgrade (AUG) programme, jointly run with the EUROfusion MST1 task force, continues to significantly enhance the physics base of ITER and DEMO. Here, the full tungsten wall is a key asset for extrapolating to future devices. The high overall heating power, flexible heating mix and comprehensive diagnostic set allows studies ranging from mimicking the scrape-off-layer and divertor conditions of ITER and DEMO at high density to fully non-inductive operation (q(95) = 5.5, beta(N) <= 2.8) at low density. Higher installed electron cyclotron resonance heating power <= 6 MW, new diagnostics and improved analysis techniques have further enhanced the capabilities of AUG. Stable high-density H-modes with P-sep/R <= 11 MW m(-1) with fully detached strike-points have been demonstrated. The ballooning instability close to the separatrix has been identified as a potential cause leading to the H-mode density limit and is also found to play an important role for the access to small edge-localized modes (ELMs). Density limit disruptions have been successfully avoided using a path-oriented approach to disruption handling and progress has been made in understanding the dissipation and avoidance of runaway electron beams. ELM suppression with resonant magnetic perturbations is now routinely achieved reaching transiently H-H98(y,H-2) <= 1.1. This gives new insight into the field penetration physics, in particular with respect to plasma flows. Modelling agrees well with plasma response measurements and a helically localised ballooning structure observed prior to the ELM is evidence for the changed edge stability due to the magnetic perturbations. The impact of 3D perturbations on heat load patterns and fast-ion losses have been further elaborated. Progress has also been made in understanding the ELM cycle itself. Here, new fast measurements of T-i and E-r allow for inter ELM transport analysis confirming that E-r is dominated by the diamagnetic term even for fast timescales. New analysis techniques allow detailed comparison of the ELM crash and are in good agreement with nonlinear MHD modelling. The observation of accelerated ions during the ELM crash can be seen as evidence for the reconnection during the ELM. As type-I ELMs (even mitigated) are likely not a viable operational regime in DEMO studies of 'natural' no ELM regimes have been extended. Stable I-modes up to n/n(GW) <= 0.7 have been characterised using beta-feedback. Core physics has been advanced by more detailed characterisation of the turbulence with new measurements such as the eddy tilt angle-measured for the first time-or the cross-phase angle of T-e and n(e) fluctuations. These new data put strong constraints on gyro-kinetic turbulence modelling. In addition, carefully executed studies in different main species (H, D and He) and with different heating mixes highlight the importance of the collisional energy exchange for interpreting energy confinement. A new regime with a hollow T-e profile now gives access to regimes mimicking aspects of burning plasma conditions and lead to nonlinear interactions of energetic particle modes despite the sub-Alfvenic beam energy. This will help to validate the fast-ion codes for predicting ITER and DEMO.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
nuclear fusion, magnetic confinement, tokamak physics, ITER, DEMO
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-263334 (URN)10.1088/1741-4326/ab18b8 (DOI)000490603100002 ()2-s2.0-85072124840 (Scopus ID)
Note

QC 20191106

Available from: 2019-11-06 Created: 2019-11-06 Last updated: 2019-11-06Bibliographically approved
Pucella, G., Ratynskaia, S. V., Tolias, P., Zito, P. & et al., . (2019). Overview of the FTU results. Nuclear Fusion, 59(11), Article ID 112015.
Open this publication in new window or tab >>Overview of the FTU results
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 11, article id 112015Article in journal (Refereed) Published
Abstract [en]

Since the 2016 IAEA Fusion Energy Conference, FTU operations have been mainly devoted to experiments on runaway electrons and investigations into a tin liquid limiter; other experiments have involved studies of elongated plasmas and dust. The tearing mode onset in the high density regime has been studied by means of the linear resistive code MARS, and the highly collisional regimes have been investigated. New diagnostics, such as a runaway electron imaging spectroscopy system for in-flight runaway studies and a triple Cherenkov probe for the measurement of escaping electrons, have been successfully installed and tested, and new capabilities of the collective Thomson scattering and the laser induced breakdown spectroscopy diagnostics have been explored.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
tokamak, overview, FTU
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-263333 (URN)10.1088/1741-4326/ab19ef (DOI)000490603100003 ()2-s2.0-85072733362 (Scopus ID)
Note

QC 20191107

Available from: 2019-11-07 Created: 2019-11-07 Last updated: 2019-11-07Bibliographically 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
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ORCID iD: ORCID iD iconorcid.org/0000-0002-6712-3625

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