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Petersson, Per
Publikasjoner (10 av 27) Visa alla publikasjoner
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
Åpne denne publikasjonen i ny fane eller vindu >>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 (engelsk)Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 516, s. 202-213Artikkel i tidsskrift (Fagfellevurdert) 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.

Emneord
Fusion, Tokamak, Plasma-wall interactions, ToF-ERDA, NRA, SEM
HSV kategori
Forskningsprogram
Fysik
Identifikatorer
urn:nbn:se:kth:diva-240616 (URN)10.1016/j.jnucmat.2018.11.027 (DOI)000458897100020 ()2-s2.0-85060313456 (Scopus ID)
Merknad

QC 20190125

Tilgjengelig fra: 2018-12-20 Laget: 2018-12-20 Sist oppdatert: 2019-08-08bibliografisk kontrollert
Jepu, I., Matthews, G. F., Widdowson, A., Rubel, M., Fortuna-Zalesna, E., Zdunek, J., . . . Lungu, C. P. (2019). Beryllium melting and erosion on the upper dump plates in JET during three ITER-like wall campaigns. Nuclear Fusion, 59(8), Article ID 086009.
Åpne denne publikasjonen i ny fane eller vindu >>Beryllium melting and erosion on the upper dump plates in JET during three ITER-like wall campaigns
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2019 (engelsk)Inngår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, nr 8, artikkel-id 086009Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Data on erosion and melting of beryllium upper limiter tiles, so-called dump plates (DP), are presented for all three campaigns in the JET tokamak with the ITER-like wall. High-resolution images of the upper wall of JET show clear signs of flash melting on the ridge of the roofshaped tiles. The melt layers move in the poloidal direction from the inboard to the outboard tile, ending on the last DP tile with an upward going waterfall-like melt structure. Melting was caused mainly by unmitigated plasma disruptions. During three ILW campaigns, around 15% of all 12376 plasma pulses were catalogued as disruptions. Thermocouple data from the upper dump plates tiles showed a reduction in energy delivered by disruptions with fewer extreme events in the third campaign, ILW-3, in comparison to ILW-1 and ILW-2. The total Be erosion assessed via precision weighing of tiles retrieved from JET during shutdowns indicated the increasing mass loss across campaigns of up to 0.6 g from a single tile. The mass of splashed melted Be on the upper walls was also estimated using the high-resolution images of wall components taken after each campaign. The results agree with the total material loss estimated by tile weighing (similar to 130 g). Morphological and structural analysis performed on Be melt layers revealed a multilayer structure of re-solidified material composed mainly of Be and BeO with some heavy metal impurities Ni, Fe, W. IBA analysis performed across the affected tile ridge in both poloidal and toroidal direction revealed a low D concentration, in the range 1-4 x 10(17) D atoms cm(-2).

sted, utgiver, år, opplag, sider
Institute of Physics (IOP), 2019
Emneord
JET, ITER-like wall, beryllium, erosion, melt layer motion
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-255301 (URN)10.1088/1741-4326/ab2076 (DOI)000472804000005 ()
Merknad

QC 20190807

Tilgjengelig fra: 2019-08-07 Laget: 2019-08-07 Sist oppdatert: 2019-08-07bibliografisk kontrollert
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.
Åpne denne publikasjonen i ny fane eller vindu >>ELM-induced cold pulse propagation in ASDEX Upgrade
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2019 (engelsk)Inngår i: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, nr 4, artikkel-id 045003Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
IOP PUBLISHING LTD, 2019
Emneord
ELMs, MHD instabilities, stochastic field, magnetic islands, cold pulse
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-245121 (URN)10.1088/1361-6587/aaf9c3 (DOI)000458986000002 ()
Merknad

QC 20190315

Tilgjengelig fra: 2019-03-15 Laget: 2019-03-15 Sist oppdatert: 2019-05-20bibliografisk kontrollert
Moon, S., Petersson, P., Rubel, M., Fortuna-Zalesna, E., Widdowson, A., Jachmich, S., . . . Contributors, J. E. (2019). First mirror test in JET for ITER: Complete overview after three ILW campaigns. Nuclear Materials and Energy, 19, 59-66
Åpne denne publikasjonen i ny fane eller vindu >>First mirror test in JET for ITER: Complete overview after three ILW campaigns
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2019 (engelsk)Inngår i: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 19, s. 59-66Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The First Mirror Test for ITER has been carried out in JET with mirrors exposed during: (i) the third ILW campaign (ILW-3, 2015–2016, 23.33 h plasma) and (ii) all three campaigns, i.e. ILW-1 to ILW-3: 2011–2016, 63,52 h in total. All mirrors from main chamber wall show no significant changes of the total reflectivity from the initial value and the diffuse reflectivity does not exceed 3% in the spectral range above 500 nm. The modified layer on surface has very small amount of impurities such as D, Be, C, N, O and Ni. All mirrors from the divertor (inner, outer, base under the bulk W tile) lost reflectivity by 20–80% due to the beryllium-rich deposition also containing D, C, N, O, Ni and W. In the inner divertor N reaches 5 × 10 17 cm −2 , W is up to 4.3 × 10 17 cm −2 , while the content of Ni is the greatest in the outer divertor: 3.8 × 10 17 cm −2 . Oxygen-18 used as the tracer in experiments at the end of ILW-3 has been detected at the level of 1.1 × 10 16 cm −2 . The thickness of deposited layer is in the range of 90 nm to 900 nm. The layer growth rate in the base (2.7 pm s − 1 ) and inner divertor is proportional to the exposure time when a single campaign and all three are compared. In a few cases, on mirrors located at the cassette mouth, flaking of deposits and erosion occurred.

sted, utgiver, år, opplag, sider
Elsevier, 2019
Emneord
52.40 Hf, Diagnostic mirrors, Erosion-deposition, First Mirror Test, ITER-like Wall, JET
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-246438 (URN)10.1016/j.nme.2019.02.009 (DOI)2-s2.0-85061529095 (Scopus ID)
Merknad

QC 20190401

Tilgjengelig fra: 2019-04-01 Laget: 2019-04-01 Sist oppdatert: 2019-04-01bibliografisk kontrollert
Blanken, T. C., Frassinetti, L., Fridström, R., Garcia-Carrasco, A., Hellsten, T., Jonsson, T., . . . Dori, V. (2019). Real-time plasma state monitoring and supervisory control on TCV. Nuclear Fusion, 59(2), Article ID 026017.
Åpne denne publikasjonen i ny fane eller vindu >>Real-time plasma state monitoring and supervisory control on TCV
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2019 (engelsk)Inngår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, nr 2, artikkel-id 026017Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In ITER and DEMO, various control objectives related to plasma control must be simultaneously achieved by the plasma control system (PCS), in both normal operation as well as off-normal conditions. The PCS must act on off-normal events and deviations from the target scenario, since certain sequences (chains) of events can precede disruptions. It is important that these decisions are made while maintaining a coherent prioritization between the real-time control tasks to ensure high-performance operation. In this paper, a generic architecture for task-based integrated plasma control is proposed. The architecture is characterized by the separation of state estimation, event detection, decisions and task execution among different algorithms, with standardized signal interfaces. Central to the architecture are a plasma state monitor and supervisory controller. In the plasma state monitor, discrete events in the continuous-valued plasma state arc modeled using finite state machines. This provides a high-level representation of the plasma state. The supervisory controller coordinates the execution of multiple plasma control tasks by assigning task priorities, based on the finite states of the plasma and the pulse schedule. These algorithms were implemented on the TCV digital control system and integrated with actuator resource management and existing state estimation algorithms and controllers. The plasma state monitor on TCV can track a multitude of plasma events, related to plasma current, rotating and locked neoclassical tearing modes, and position displacements. In TCV experiments on simultaneous control of plasma pressure, safety factor profile and NTMs using electron cyclotron heating (ECI I) and current drive (ECCD), the supervisory controller assigns priorities to the relevant control tasks. The tasks are then executed by feedback controllers and actuator allocation management. This work forms a significant step forward in the ongoing integration of control capabilities in experiments on TCV, in support of tokamak reactor operation.

sted, utgiver, år, opplag, sider
Institute of Physics (IOP), 2019
Emneord
real-time control, supervisory control, control of tokamak plasmas
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-242971 (URN)10.1088/1741-4326/aaf451 (DOI)000455823900003 ()
Merknad

QC 20190212

Tilgjengelig fra: 2019-02-12 Laget: 2019-02-12 Sist oppdatert: 2019-02-12bibliografisk kontrollert
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.
Åpne denne publikasjonen i ny fane eller vindu >>Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments
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2019 (engelsk)Inngår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, nr 4, artikkel-id 046001Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
IOP PUBLISHING LTD, 2019
Emneord
ICRF, finite elements, simulation
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-243928 (URN)10.1088/1741-4326/aaf455 (DOI)000456197200001 ()
Merknad

QC 20190212

Tilgjengelig fra: 2019-02-12 Laget: 2019-02-12 Sist oppdatert: 2019-02-12bibliografisk kontrollert
Rubel, M., Widdowson, A., Grzonka, J., Fortuna-Zalesna, E., Moon, S., Petersson, P., . . . Tokitani, M. (2018). Dust generation in tokamaks: Overview of beryllium and tungsten dust characterisation in JET with the ITER-like wall. Paper presented at 13th International Symposium on Fusion Nuclear Technology (ISFNT), SEP 25-29, 2017, Kyoto, Japan. Fusion engineering and design, 136, 579-586
Åpne denne publikasjonen i ny fane eller vindu >>Dust generation in tokamaks: Overview of beryllium and tungsten dust characterisation in JET with the ITER-like wall
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2018 (engelsk)Inngår i: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 136, s. 579-586Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Operation of the JET tokamak with beryllium and tungsten ITER-like wall provides unique opportunity for detailed studies on dust generation: quantity, morphology, location, etc. The programme carried out in response to ITER needs for safety assessment comprises: (i) remotely controlled vacuum cleaning of the divertor; (ii) local sampling of loosely bound matter from plasma-facing components (PFC); (iii) collection of mobilized dust on various erosion-deposition probes located in the divertor and in the main chamber. Results of comprehensive analyses performed by a number of complementary techniques, e.g. a range of microscopy methods, electron and ion spectroscopy, liquid scintillography and thermal desorption, are summarized by following points: (a) Total amount of dust collected by vacuum cleaning after three campaigns is about 1-1.4 g per campaign (19.1-23.5 h plasma operation), i.e. over 100 times smaller than in JET operated with carbon walls (i.e. in JET-C). (b) Two major categories of Be dust are identified: flakes of co-deposits formed on PFC and droplets (2-10 mu m in diameter). Small quantifies, below 1 g, of Be droplets and splashes are associated mainly with melting of beryllium limiters.

sted, utgiver, år, opplag, sider
Elsevier, 2018
Emneord
JET tokamak, ITER-like wall, Dust, Beryllium, Tungsten
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-240780 (URN)10.1016/j.fusengdes.2018.03.027 (DOI)000452583700110 ()2-s2.0-85044008512 (Scopus ID)
Konferanse
13th International Symposium on Fusion Nuclear Technology (ISFNT), SEP 25-29, 2017, Kyoto, Japan
Merknad

QC 20190109

Tilgjengelig fra: 2019-01-09 Laget: 2019-01-09 Sist oppdatert: 2019-01-09bibliografisk kontrollert
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.
Åpne denne publikasjonen i ny fane eller vindu >>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 (engelsk)Inngår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, nr 4, artikkel-id 049901Artikkel i tidsskrift (Fagfellevurdert) Published
sted, utgiver, år, opplag, sider
American Institute of Physics (AIP), 2018
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-227781 (URN)10.1063/1.5030502 (DOI)000431139400078 ()29716341 (PubMedID)2-s2.0-85045335587 (Scopus ID)
Merknad

QC 201805014

Tilgjengelig fra: 2018-05-14 Laget: 2018-05-14 Sist oppdatert: 2019-01-09bibliografisk kontrollert
Fazinic, S., Tadic, T., Vuksic, M., Rubel, M., Petersson, P., Fortuna-Zalesna, E. & Widdowson, A. (2018). Ion Microbeam Analyses of Dust Particles and Codeposits from JET with the ITER-Like Wall. Analytical Chemistry, 90(9), 5744-5752
Åpne denne publikasjonen i ny fane eller vindu >>Ion Microbeam Analyses of Dust Particles and Codeposits from JET with the ITER-Like Wall
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2018 (engelsk)Inngår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 90, nr 9, s. 5744-5752Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Generation of metal dust in the JET tokamak with the ITER-like wall (ILW) is a topic of vital interest to next-step fusion devices because of safety issues with plasma operation. Simultaneous Nuclear Reaction Analysis (NRA) and Particle Induced X-ray Emission (PIXE) with a focused four MeV He-3 microbeam was used to determine the composition of dust particles related to the JET operation with the ILW. The focus was on "Be-rich particles" collected from the deposition zone on the inner divertor tile. The particles found are composed of a mix of codeposited species up to 120 m in size with a thickness of 30-40 mu m, The main constituents are D from the fusion fuel, Be and W from the main plasma-facing components, and Ni and Cr from the Inconel grills of the antennas for auxiliary plasma heating. Elemental concentrations were estimated by iterative NRA-PIXE analysis. Two types of dust particles were found: (i) larger Be-rich particles with Be concentrations above 90 at% with a deuterium presence of up to 3.4 at% and containing Ni (1-3 at%), Cr (0.4-0.8 at%), W (0.2-0.9 at%), Fe (0.3-0.6 at%), and Cu and Ti in lower concentrations and (ii) small particles rich in Al and/or Si that were in some cases accompanied by other elements, such as Fe, Cu, or Ti or W and Mo.

sted, utgiver, år, opplag, sider
AMER CHEMICAL SOC, 2018
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-228440 (URN)10.1021/acs.analchem.8b00073 (DOI)000431464400032 ()29620878 (PubMedID)2-s2.0-85046455477 (Scopus ID)
Merknad

QC 20180529

Tilgjengelig fra: 2018-05-29 Laget: 2018-05-29 Sist oppdatert: 2018-10-16bibliografisk kontrollert
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
Åpne denne publikasjonen i ny fane eller vindu >>Review on global migration, fuel retention and modelling after TEXTOR decommission
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2018 (engelsk)Inngår i: NUCLEAR MATERIALS AND ENERGY, Vol. 17, s. 83-112Artikkel, forskningsoversikt (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
ELSEVIER SCIENCE BV, 2018
Emneord
Global migration, Tokamak, high-Z material, Molybdenum, Modelling, ASCOT, ERO, Fuel retention, Deposition
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-241223 (URN)10.1016/j.nme.2018.09.003 (DOI)000454165000013 ()2-s2.0-85054327579 (Scopus ID)
Merknad

QC 20190115

Tilgjengelig fra: 2019-01-15 Laget: 2019-01-15 Sist oppdatert: 2019-01-15bibliografisk kontrollert
Organisasjoner