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Publikasjoner (10 av 13) 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: 2019-10-29bibliografisk kontrollert
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.
Åpne denne publikasjonen i ny fane eller vindu >>Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
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2019 (engelsk)Inngår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, nr 11, artikkel-id 112021Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
IOP PUBLISHING LTD, 2019
Emneord
fusion power, JET, tritium, isotope
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-260157 (URN)10.1088/1741-4326/ab2276 (DOI)000484122200001 ()2-s2.0-85070875113 (Scopus ID)
Merknad

QC 20190926

Tilgjengelig fra: 2019-09-26 Laget: 2019-09-26 Sist oppdatert: 2019-10-04bibliografisk kontrollert
Weckmann, A., Kurki-Suonio, T., Särkimäki, K., Romazanov, J., Kirschner, A., Hakola, A., . . . Brezinsek, S. (2019). Physics affecting heavy impurity migration in tokamaks: Benchmarking test-ion code ASCOT against TEXTOR tracer experiment. Nuclear Materials and Energy, 19, 307-315
Åpne denne publikasjonen i ny fane eller vindu >>Physics affecting heavy impurity migration in tokamaks: Benchmarking test-ion code ASCOT against TEXTOR tracer experiment
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2019 (engelsk)Inngår i: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 19, s. 307-315Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Erosion, transport and deposition of wall impurities are major concerns in future magnetic fusion devices, both from the perspective of the fusion plasma and the machine wall. An extensive study on molybdenum transport and deposition performed in the TEXTOR tokamak yielded a detailed deposition map that is ideal for benchmark deposition studies. A qualitative benchmark is attempted in this article with the ASCOT code. We set up a full 3D model of the TEXTOR tokamak and studied the influence of different physical mechanisms and their strengths on molybdenum deposition patterns on the simulated plasma-facing components: atomic processes, Coulomb collisions, scrape-off layer (SOL) profiles, source distribution, marker starting energy, radial electric field strength, SOL flow and toroidal plasma rotation. The outcome comprises 13 simulations, each with 100,000 markers. The findings are: • Toroidal plasma movement, either within the LCFS or as SOL flow, is negligible. • SOL profile and marker starting energy have modest impact on deposition. • Source distribution has a large impact in combination with radial electric field profiles. • The E⇀×B⇀ drift has the highest impact on the deposition profiles. © 2019 The Authors

sted, utgiver, år, opplag, sider
Elsevier Ltd, 2019
Emneord
3D modeling, Deposition, Electric field effects, Plasma simulation, Sols, Tokamak devices, Deposition patterns, Deposition profiles, Magnetic fusion devices, Physical mechanism, Plasma-facing components, Radial electric field, Source distribution, Toroidal plasma rotation, Magnetoplasma
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-252513 (URN)10.1016/j.nme.2019.02.033 (DOI)000470746100049 ()2-s2.0-85062721466 (Scopus ID)
Merknad

QC 20190710

Tilgjengelig fra: 2019-07-10 Laget: 2019-07-10 Sist oppdatert: 2019-07-10bibliografisk kontrollert
Garzotti, L., Frassinetti, L., Stefániková, E., Bergsåker, H., Bykov, I., Garcia Carrasco, A., . . . Zychor, I. (2019). Scenario development for D-T operation at JET. Nuclear Fusion, 59(7), Article ID 076037.
Åpne denne publikasjonen i ny fane eller vindu >>Scenario development for D-T operation at JET
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2019 (engelsk)Inngår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, nr 7, artikkel-id 076037Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The JET exploitation plan foresees D-T operations in 2020 (DTE2). With respect to the first D-T campaign in 1997 (DTE1), when JET was equipped with a carbon wall, the experiments will be conducted in presence of a beryllium-tungsten ITER-like wall and will benefit from an extended and improved set of diagnostics and higher additional heating power (32 MW neutral beam injection + 8 MW ion cyclotron resonance heating). There are several challenges presented by operations with the new wall: a general deterioration of the pedestal confinement; the risk of heavy impurity accumulation in the core, which, if not controlled, can cause the radiative collapse of the discharge; the requirement to protect the divertor from excessive heat loads, which may damage it permanently. Therefore, an intense activity of scenario development has been undertaken at JET during the last three years to overcome these difficulties and prepare the plasmas needed to demonstrate stationary high fusion performance and clear alpha particle effects. The paper describes the status and main achievements of this scenario development activity, both from an operational and plasma physics point of view.

sted, utgiver, år, opplag, sider
IOP PUBLISHING LTD, 2019
Emneord
tokamaks, magnetic confinement fusion, nuclear fusion power
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-262997 (URN)10.1088/1741-4326/ab1cca (DOI)000471317000001 ()2-s2.0-85069038696 (Scopus ID)
Merknad

QC 20191025

Tilgjengelig fra: 2019-10-25 Laget: 2019-10-25 Sist oppdatert: 2019-10-25bibliografisk kontrollert
Grigore, E., Gherendi, M., Baiasu, F., Firdaouss, M., Hernandez, C., Weckmann, A., . . . Hakola, A. (2019). The influence of N on the D retention within W coatings for fusion applications. Fusion engineering and design, 146, 1959-1962
Åpne denne publikasjonen i ny fane eller vindu >>The influence of N on the D retention within W coatings for fusion applications
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2019 (engelsk)Inngår i: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 146, s. 1959-1962Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Plasma facing components (PFC) in a fusion device are subjected to a harsh operating environment involving high heat fluxes and exposure to high fluxes of hydrogen isotopes. This exposure can lead to high fuel retention that can raise serious concern from the safety point of view. One of the reasons for the use of W as a material for the construction of the first wall is to reduce fuel retention compared to carbon wall. Nitrogen seeding, used during the operation of fusion reactors, represents a method to cool the divertor plasma and to reduce the W source in the divertor due to ELMS. However an exposure of the PFC to a combination of hydrogen isotopes and nitrogen can lead to changes in properties of exposed surfaces or to unexpected material behavior. In this work, the influence of nitrogen on the deuterium content within tungsten coatings produced by reactive high power impulse magnetron sputtering (HIPIMS) was investigated. The deposition process of W coatings in a nitrogen deuterium environment leads to a significant retention of deuterium. Coatings with a deuterium content up to 54 at% were obtained in the presence of nitrogen compared with a deuterium content of 25 at% measured for the coatings produced in absence of nitrogen from the deposition atmosphere.

sted, utgiver, år, opplag, sider
ELSEVIER SCIENCE SA, 2019
Emneord
Deuterium containing coatings, HIPIMS, Tungsten nitride, Nitrogen seeding
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-262985 (URN)10.1016/j.fusengdes.2019.03.075 (DOI)000488313700122 ()2-s2.0-85063037874 (Scopus ID)
Merknad

QC 20191029

Tilgjengelig fra: 2019-10-29 Laget: 2019-10-29 Sist oppdatert: 2019-10-29bibliografisk 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
Sergienko, G., Esser, H. G., Kirschner, A., Huber, A., Freisinger, M., Brezinsek, S., . . . Heinola, K. (2017). Quartz micro-balance results of pulse-resolved erosion/deposition in the JET-ILW divertor. NUCLEAR MATERIALS AND ENERGY, 12, 478-482
Åpne denne publikasjonen i ny fane eller vindu >>Quartz micro-balance results of pulse-resolved erosion/deposition in the JET-ILW divertor
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2017 (engelsk)Inngår i: NUCLEAR MATERIALS AND ENERGY, ISSN 2352-1791, Vol. 12, s. 478-482Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

A set of quartz crystal microbalances (QMB) was used at JET with full carbon wall to monitor mass erosion/ deposition rates in the remote areas of the divertor. After introduction of the ITER-like wall (ILW) in JET with beryllium main wall and tungsten divertor, strong reduction of the material deposition and accompanied fuel retention was observed. Therefore the existing QMB electronics have been modified to improve the accuracy of frequency measurements by a factor of ten down to 0.1 Hz which corresponds to 1.4 ng cm(-2). The averaged deposition rates of 1.2-3 ng cm(-2) s(-1) and erosion rates of 5.6-8.1 ng cm(-2) s(-1) were observed in the inner divertor of JET-ILW with the inner strike point positions close to the bottom edge of vertical tile 3 and at the horizontal tile 4 respectively. The erosion with averaged rates of approximate to 2.1 ng cm(-2) s(-1) and approximate to 120 ng cm(-2) s(-1) were observed in the outer divertor for the outer strike point positions at tile 5 and tile 6 respectively.

HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-220635 (URN)10.1016/j.nme.2017.03.007 (DOI)000417293300074 ()2-s2.0-85015777449 (Scopus ID)
Merknad

QC 20180112

Tilgjengelig fra: 2018-01-12 Laget: 2018-01-12 Sist oppdatert: 2018-01-12bibliografisk kontrollert
Weckmann, A., Petersson, P., Kirschner, A., Wienhold, P., Brezinsek, S., Kreter, A., . . . Rubel, M. (2017). Whole-machine material migration studies in the TEXTOR tokamak with molybdenum. NUCLEAR MATERIALS AND ENERGY, 12, 518-523
Åpne denne publikasjonen i ny fane eller vindu >>Whole-machine material migration studies in the TEXTOR tokamak with molybdenum
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2017 (engelsk)Inngår i: NUCLEAR MATERIALS AND ENERGY, ISSN 2352-1791, Vol. 12, s. 518-523Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

MoF6 injection from a localised source into plasma edge in the TEXTOR tokamak was the last experiment before the final shut-down of the TEXTOR machine. During decommissioning all plasma-facing components (PFCs) became available for surface studies. Detailed mapping of Mo deposition was performed in order to determine its migration on global scale. The concentration of Mo on PFC decays exponentially with distance from the source. The decay length is of the order of 0.1 m on the main PFC and 1 m on the receded components. Also the decay lengths modelled with the ERO code are between 0.15-1.3 m, depending on the anomalous cross-field diffusion coefficient. The inner bumper limiter is found to be the major repository for Mo. Material balance measurements show that only up to 22% of the injected Mo was detected on all the PFCs thus indicating that a large fraction of injected Mo may have been pumped out before being deposited.

sted, utgiver, år, opplag, sider
Elsevier, 2017
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-220638 (URN)10.1016/j.nme.2016.12.011 (DOI)000417293300081 ()2-s2.0-85009253075 (Scopus ID)
Merknad

QC 20180112

Tilgjengelig fra: 2018-01-12 Laget: 2018-01-12 Sist oppdatert: 2018-02-20bibliografisk kontrollert
Fortuna-Zalesna, E., Weckmann, A., Grozonka, J., Rubel, M., Esser, H. G., Freisinger, M., . . . Ström, P. (2016). Dust Survey Following the Final Shutdown of TEXTOR: Metal Particles and Fuel Retention. Physica Scripta, T167, Article ID 014059.
Åpne denne publikasjonen i ny fane eller vindu >>Dust Survey Following the Final Shutdown of TEXTOR: Metal Particles and Fuel Retention
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2016 (engelsk)Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, artikkel-id 014059Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The work presents results of a broad TEXTOR dust survey in terms of its composition, structure, distribution and fuel content. The dust particles were collected after final shutdown of TEXTOR in December 2013. Fuel retention, as determined by thermal desorption, varied significantly, even by two orders of magnitude, dependent on the dust location in the machine. Dust structure was examined by means of scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, focused ion beam and scanning transmission electron microscopy. Several categories of dust have been identified. Carbon-based stratified and granular deposits were dominating, but the emphasis in studies was on metal dust. They were found in the form of small particles, small spheres, flakes and splashes which formed “comet”-like structures clearly indicating directional effects in the impact on surfaces of plasma-facing components. Nickel-rich alloys from the Inconel liner and iron-based ones from various diagnostic holders were the main components of metal-containing dust, but also molybdenum and tungsten debris were detected. Their origin is discussed.

sted, utgiver, år, opplag, sider
Institute of Physics Publishing (IOPP), 2016
Emneord
TEXTOR, dust, fuel retention, high-Z metals
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-178047 (URN)10.1088/0031-8949/T167/1/014059 (DOI)000383504700060 ()2-s2.0-84959896914 (Scopus ID)
Merknad

QC 20160127

Tilgjengelig fra: 2015-12-03 Laget: 2015-12-03 Sist oppdatert: 2017-06-30bibliografisk kontrollert
Weckmann, A., Petersson, P., Rubel, M., Wienhold, P., Brezinsek, S., Coenen, J. W., . . . Pospieszczyk, A. (2016). Local Migration Studies of High-Z Metals in the TEXTOR Tokamak. Physica Scripta, T167, Article ID 014058.
Åpne denne publikasjonen i ny fane eller vindu >>Local Migration Studies of High-Z Metals in the TEXTOR Tokamak
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2016 (engelsk)Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, artikkel-id 014058Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Volatile compounds of tungsten (WF6) and molybdenum (MoF6) were used as tracers of high-Z metal migration in the TEXTOR tokamak in several gas injection experiments when puffing was done through a test limiter. The experiments with W were performed prior major shut-downs, while the MoF6 was followed by the final shutdown in connection with TEXTOR decommissioning. In all cases a set of various surface probes and limiter tiles were retrieved and analysed with electron and ion beam techniques. The focus was on the local deposition in the vicinity of the gas inlet and in the inlet system. Depth profiles in the deposits and metal distribution maps clearly shown that only near the gas inlet significant amounts of Mo are deposited along the scrape-off layer flow and E×B drift directions, which could be reproduced by ERO-code modelling. Correlation between the plasma operation scenario and the deposition patterns is presented.

sted, utgiver, år, opplag, sider
Institute of Physics Publishing (IOPP), 2016
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-178044 (URN)10.1088/0031-8949/T167/1/014058 (DOI)000383504700059 ()2-s2.0-84959870422 (Scopus ID)
Merknad

QC 20170630

Tilgjengelig fra: 2015-12-03 Laget: 2015-12-03 Sist oppdatert: 2017-11-29bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0003-1062-8101