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  • 1.
    Ben Yaala, M.
    et al.
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Moser, L.
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Steiner, R.
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Butoi, B.
    Natl Inst Laser Plasma & Radiat Phys, 409 Atomistilor St, Magurele 077125, Romania..
    Dinca, P.
    Natl Inst Laser Plasma & Radiat Phys, 409 Atomistilor St, Magurele 077125, Romania..
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Marot, L.
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Meyer, E.
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Deuterium as a cleaning gas for ITER first mirrors: experimental study on beryllium deposits from laboratory and JET-ILW2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 9, article id 096027Article in journal (Refereed)
    Abstract [en]

    Cleaning techniques for metallic first mirrors are needed in more than 20 optical diagnostic systems from ITER to avoid reflectivity losses. Plasma sputtering is considered as one of the most promising techniques to remove deposits coming from the main wall (mainly beryllium and tungsten). Previous plasma cleaning studies were conducted on mirrors contaminated with beryllium and tungsten where argon and/or helium were employed as process gas, demonstrating removal of contamination and recovery of optical properties. Still, both abovementioned process gases have a non-negligible sputtering yield on mirrors. In this work, we explored the possibility to use a sputter gas having a small impact on mirrors while being efficient on Be deposits, e.g. deuterium. Two sputtering regimes were studied, on laboratory deposits as well as on mirrors exposed in .TET-ILW, namely physical sputtering (220eV ion energy) and chemically assisted physical sputtering (60 eV ion energy) using capacitively coupled plasma with radio frequency. The removal of Be and mixed Be/W contaminants, as well as the recovery of reflectivity, was achieved when deuterium was employed at 220eV while cleaning at 60eV was only fully efficient on laboratory beryllium deposits. On mirrors exposed in JET-ILW, the situation is more complex due to the presence of tungsten in the contaminant film, leading to the formation of a tungsten enriched surface that is not easily sputtered, especially at 60eV.

  • 2.
    Bergsåker, Henric
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Bykov, Igor
    Zhou, Yushan
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Possnert, G
    Likonen, J
    Pettersson, J
    Koivuranta, S
    Widdowson, A.M.
    contributors, JET
    Deep deuterium retention and Be/W mixingat tungsten coated surfaces in the JETdivertor2016In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896Article in journal (Refereed)
    Abstract [en]

    Surface samples from a full poloidal set of divertor tiles exposed in JET through operations2010–2012 with ITER-like wall have been investigated using SEM, SIMS, ICP-AES analysisand micro beam nuclear reaction analysis (μ-NRA). Deposition of Be and retention of D ismicroscopically inhomogeneous. With careful overlaying of μ-NRA elemental maps with SEMimages, it is possible to separate surface roughness effects from depth profiles at microscopicallyflat surface regions, without pits. With (3He, p) μ-NRA at 3–5 MeV beam energy the accessibledepth for D analysis in W is about 9 μm, sufficient to access the W/Mo and Mo/W interfaces inthe coatings and beyond, while for Be in W it is about 6 μm. In these conditions, at all plasmawetted surfaces, D was found throughout the whole accessible depth at concentrations in therange 0.2–0.7 at% in W. Deuterium was found to be preferentially trapped at the W/Mo andMo/W interfaces. Comparison is made with SIMS profiling, which also shows significant Dtrapping at the W/Mo interface. Mixing of Be and W occurs mainly in deposited layers.

  • 3.
    Bhatti, Muhammad Khurram
    et al.
    Informat Technol Univ, Embedded Comp Lab, 346-B Ferozpur Rd, Lahore, Pakistan..
    Oz, Isil
    Izmir Inst Technol, Comp Engn Dept, Izmir, Turkey..
    Amin, Sarah
    Informat Technol Univ, Embedded Comp Lab, 346-B Ferozpur Rd, Lahore, Pakistan..
    Mushtaq, Maria
    Informat Technol Univ, Embedded Comp Lab, 346-B Ferozpur Rd, Lahore, Pakistan..
    Farooq, Umer
    Dhofar Univ, Dept Elect & Comp Engn, Salalah 211, Oman..
    Popov, Konstantin
    SICS, Isafjordsgatan 22, S-16429 Kista, Sweden..
    Brorsson, Mats
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics. , S-16429 Kista, Sweden..
    Locality-aware task scheduling for homogeneous parallel computing systems2018In: Computing, ISSN 0010-485X, E-ISSN 1436-5057, Vol. 100, no 6, p. 557-595Article in journal (Refereed)
    Abstract [en]

    In systems with complex many-core cache hierarchy, exploiting data locality can significantly reduce execution time and energy consumption of parallel applications. Locality can be exploited at various hardware and software layers. For instance, by implementing private and shared caches in a multi-level fashion, recent hardware designs are already optimised for locality. However, this would all be useless if the software scheduling does not cast the execution in a manner that promotes locality available in the programs themselves. Since programs for parallel systems consist of tasks executed simultaneously, task scheduling becomes crucial for the performance in multi-level cache architectures. This paper presents a heuristic algorithm for homogeneous multi-core systems called locality-aware task scheduling (LeTS). The LeTS heuristic is a work-conserving algorithm that takes into account both locality and load balancing in order to reduce the execution time of target applications. The working principle of LeTS is based on two distinctive phases, namely; working task group formation phase (WTG-FP) and working task group ordering phase (WTG-OP). The WTG-FP forms groups of tasks in order to capture data reuse across tasks while the WTG-OP determines an optimal order of execution for task groups that minimizes the reuse distance of shared data between tasks. We have performed experiments using randomly generated task graphs by varying three major performance parameters, namely: (1) communication to computation ratio (CCR) between 0.1 and 1.0, (2) application size, i.e., task graphs comprising of 50-, 100-, and 300-tasks per graph, and (3) number of cores with 2-, 4-, 8-, and 16-cores execution scenarios. We have also performed experiments using selected real-world applications. The LeTS heuristic reduces overall execution time of applications by exploiting inter-task data locality. Results show that LeTS outperforms state-of-the-art algorithms in amortizing inter-task communication cost.

  • 4.
    Blanken, T. C.
    et al.
    Eindhoven Univ Technol, Control Syst Technol Grp, Dept Mech Engn, POB 513, NL-5600 MB Eindhoven, Netherlands.;Eindhoven Univ Technol, POB 513, NL-5600 MB Eindhoven, Netherlands..
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Fridström, Richard
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Jonsson, T.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vignitchouk, Ladislas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Dori, V
    Univ Split, Fac Elect Engn Mech Engn & Naval Architecture, R Boskovica 32, Split 21000, Croatia..
    Real-time plasma state monitoring and supervisory control on TCV2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 2, article id 026017Article in journal (Refereed)
    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.

  • 5.
    Brunsell, Per R.
    et al.
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Bergsåker, Henric
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Brzozowski, Jerzy
    Cecconello, Marco
    Drake, James R.
    Malmberg, Jenny-Ann
    Scheffel, Jan
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Schnack, Dalton
    Mode Dynamics and Confinement in the Reversed-field Pinch2000In: 18th IAEA Fusion Energy Conference in Sorrento, Italy, 4-10 Oct. 2000. Paper IAEA-CN-77/EXP3/14, 2000Conference paper (Refereed)
    Abstract [en]

    Tearing mode dynamics and toroidal plasma flow in the RFP has been experimentally studied in the Extrap T2 device. A toroidally localised, stationary magnetic field perturbation, the ``slinky mode'' is formed in nearly all discharges. There is a tendency of increased phase alignment of different toroidal Fourier modes, resulting in higher localised mode amplitudes, with higher magnetic fluctuation level. The fluctuation level increases slightly with increasing plasma current and plasma density. The toroidal plasma flow velocity and the ion temperature has been measured with Doppler spectroscopy. Both the toroidal plasma velocity and the ion temperature clearly increase with I/N. Initial, preliminary experimental results obtained very recently after a complete change of the Extrap T2 front-end system (first wall, shell, TF coil), show that an operational window with mode rotation most likely exists in the rebuilt device, in contrast to the earlier case discussed above. A numerical code DEBSP has been developed to simulate the behaviour of RFP confinement in realistic geometry, including essential transport physics. Resulting scaling laws are presented and compared with results from Extrap T2 and other RFP experiments.

  • 6. Bílková, P.
    et al.
    Böhm, P.
    Komm, M.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Peterka, M.
    Šos, M.
    Seidl, J.
    Grover, O.
    Havlíček, J.
    Mitošinková, K.
    Varju, J.
    Vondráček, P.
    Urban, J.
    Imríšek, M.
    Markovič, T.
    Weinzettl, V.
    Hron, M.
    Pánek, R.
    Relative shift in position of temperature and density pedestals at the COMPASS tokamak2017In: 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS) , 2017Conference paper (Refereed)
  • 7.
    Coad, J. P.
    et al.
    Culham Sci Ctr, Culham Ctr Fus Energy, Abingdon OX14 3DB, Oxon, England..
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Likonen, J.
    VTT Tech Res Ctr Finland, POB 1000, FIN-02044 Espoo, Finland..
    Bekris, N.
    Karlsruhe Inst Technol, D-76021 Karlsruhe, Germany..
    Brezinsek, S.
    Forschungszentrum Juelich, Inst Energieforsch Plasmaphys, D-52425 Julich, Germany..
    Matthew, G. F.
    Culham Sci Ctr, Culham Ctr Fus Energy, Abingdon OX14 3DB, Oxon, England..
    Mayer, M.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Widdowson, A. M.
    Culham Sci Ctr, Culham Ctr Fus Energy, Abingdon OX14 3DB, Oxon, England..
    Material migration and fuel retention studies during the JET carbon divertor campaigns2019In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 138, p. 78-108Article in journal (Refereed)
    Abstract [en]

    The first divertor was installed in the JET machine between 1992 and 1994 and was operated with carbon tiles and then beryllium tiles in 1994-5. Post-mortem studies after these first experiments demonstrated that most of the impurities deposited in the divertor originate in the main chamber, and that asymmetric deposition patterns generally favouring the inner divertor region result from drift in the scrape-off layer. A new monolithic divertor structure was installed in 1996 which produced heavy deposition at shadowed areas in the inner divertor corner, which is where the majority of the tritium was trapped by co-deposition during the deuterium-tritium experiment in 1997. Different divertor geometries have been tested since such as the Gas-Box and High-Delta divertors; a principle objective has been to predict plasma behaviour, transport and tritium retention in ITER. Transport modelling experiments were carried out at the end of four campaigns by puffing C-13-labelled methane, and a range of diagnostics such as quartz-microbalance and rotating collectors have been installed to add time resolution to the post-mortem analyses. The study of material migration after D-D and D-T campaigns clearly revealed important consequences of fuel retention in the presence of carbon walls. They gave a strong impulse to make a fundamental change of wall materials. In 2010 the carbon divertor and wall tiles were removed and replaced with tiles with Be or W surfaces for the ITER-Like Wall Project.

  • 8.
    Coda, S.
    et al.
    Ecole Polytech Fed Lausanne, Swiss Plasma Ctr, CH-1015 Lausanne, Switzerland..
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Zuin, M.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    et al.,
    Physics research on the TCV tokamak facility: from conventional to alternative scenarios and beyond2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 11, article id 112023Article in journal (Refereed)
    Abstract [en]

    The research program of the TCV tokamak ranges from conventional to advanced-tokamak scenarios and alternative divertor configurations, to exploratory plasmas driven by theoretical insight, exploiting the device's unique shaping capabilities. Disruption avoidance by real-time locked mode prevention or unlocking with electron-cyclotron resonance heating (ECRH) was thoroughly documented, using magnetic and radiation triggers. Runaway generation with high-Z noble-gas injection and runaway dissipation by subsequent Ne or Ar injection were studied for model validation. The new 1 MW neutral beam injector has expanded the parameter range, now encompassing ELMy H-modes in an ITER-like shape and nearly noninductive II-mode discharges sustained by electron cyclotron and neutral beam current drive. In the H-mode, the pedestal pressure increases modestly with nitrogen seeding while fueling moves the density pedestal outwards, but the plasma stored energy is largely uncorrelated to either seeding or fueling. High fueling at high triangularity is key to accessing the attractive small edge-localized mode (type-II) regime. Turbulence is reduced in the core at negative triangularity, consistent with increased confinement and in accord with global gyrokinetic simulations. The geodesic acoustic mode, possibly coupled with avalanche events, has been linked with particle flow to the wall in diverted plasmas. Detachment, scrape-off layer transport, and turbulence were studied in L- and H-modes in both standard and alternative configurations (snowflake, super-X, and beyond). The detachment process is caused by power `starvation' reducing the ionization source, with volume recombination playing only a minor role. Partial detachment in the H-mode is obtained with impurity seeding and has shown little dependence on flux expansion in standard single-null geometry. In the attached 1,-mode phase, increasing the outer connection length reduces the in-out heat-flow asymmetry. A doublet plasma, featuring an internal X-point, was achieved successfully, and a transport barrier was observed in the mantle just outside the internal separatrix. In the near future variableconfiguration baffles and possibly divertor ptunping will be introduced to investigate the effect of divertor closure on exhaust and performance, and 3.5 MW ECR and 1 MW neutral beam injection heating will be added.

  • 9. Di Siena, A.
    et al.
    Görler, T.
    Doerk, H.
    Bilato, R.
    Citrin, J.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Schneider, M.
    Poli, E.
    Impact of realistic fast ion distribution function in gyrokinetic GENE simulations2017In: 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS) , 2017Conference paper (Refereed)
    Abstract [en]

    Understanding the stabilising mechanism of fast particles on plasma turbulence is an essential task for a fusion reactor, where the energetic particles can constitute a significant fraction of the main ions. While the consideration of equivalent Maxwellian distributed fast ions in the simulations has greatly improved the agreement with experiments, fast ion electromagnetic stabilization seems to be somewhat over-estimated. Power balance is usually reached only with increased plasma gradients. However, it is well known that to rigorously model highly non thermalised particles, a non-Maxwellian background distribution function is needed. To this aim, a previous study on a particular JET plasma has been revised and analysed with the gyrokinetic code GENE. Fast particles have been modelled with a number of different analytic and numerical distributions. The latter have been imported from the modelling tools NEMO/SPOT and SELFO. 

  • 10.
    Dumont, R. J.
    et al.
    CEA, IRFM, F-13108 St Paul Les Durance, France..
    Mailloux, J.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Aslanyan, V
    MIT, PSFC, 175 Albany St, Cambridge, MA 02039 USA..
    Baruzzo, M.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Challis, C. D.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Coffey, I
    Queens Univ, Dept Pure & Appl Phys, Belfast BT7 1NN, Antrim, North Ireland..
    Czarnecka, A.
    Inst Plasma Phys & Laser Microfus, Hery St 23, PL-00908 Warsaw, Poland..
    Delabie, E.
    Oak Ridge Natl Lab, Oak Ridge, TN USA..
    Eriksson, J.
    Uppsala Univ, Dept Phys & Astron, SE-75119 Uppsala, Sweden..
    Faustin, J.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Ferreira, J.
    Univ Lisbon, IST, Inst Plasmas & Fusao Nucl, Lisbon, Portugal..
    Fitzgerald, M.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Garcia, J.
    CEA, IRFM, F-13108 St Paul Les Durance, France..
    Giacomelli, L.
    Univ Milano Bicocca, Piazza Sci 3, I-20126 Milan, Italy..
    Giroud, C.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Hawkes, N.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Jacquet, Ph
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Joffrin, E.
    CEA, IRFM, F-13108 St Paul Les Durance, France..
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Keeling, D.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    King, D.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Kiptily, V
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Lomanowski, B.
    Aalto Univ, POB 14100, FIN-00076 Aalto, Finland..
    Lerche, E.
    Ass EUROFUS Belgian State, LPP ERM KMS, TEC Partner, Brussels, Belgium..
    Mantsinen, M.
    Barcelona Supercomp Ctr, Barcelona, Spain.;ICREA, Barcelona, Spain..
    Meneses, L.
    Univ Lisbon, IST, Inst Plasmas & Fusao Nucl, Lisbon, Portugal..
    Menmuir, S.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    McClements, K.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Moradi, S.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Nabais, F.
    Univ Lisbon, IST, Inst Plasmas & Fusao Nucl, Lisbon, Portugal..
    Nocente, M.
    Univ Milano Bicocca, Piazza Sci 3, I-20126 Milan, Italy..
    Patel, A.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Patten, H.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Puglia, P.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Scannell, R.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Sharapov, S.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Solano, E. R.
    CIEMAT, Lab Nacl Fus, Madrid, Spain..
    Tsalas, M.
    FOM Inst DIFFER, NL-3430 BE Nieuwegein, Netherlands.;ITER Org, Route Vinon Sur Verdon, F-13067 St Paul Les Durance, France..
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Weisen, H.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Scenario development for the observation of alpha-driven instabilities in JET DT plasmas2018In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 58, no 8, article id 082005Article in journal (Refereed)
    Abstract [en]

    In DT plasmas, toroidal Alfven eigenmodes (TAEs) can be made unstable by the alpha particles resulting from fusion reactions, and may induce a significant redistribution of fast ions. Recent experiments have been conducted in JET deuterium plasmas in order to prepare scenarios aimed at observing alpha-driven TAEs in a future JET DT campaign. Discharges at low density, large core temperatures associated with the presence of internal transport barriers and characterised by good energetic ion confinement have been performed. ICRH has been used in the hydrogen minority heating regime to probe the TAE stability. The consequent presence of MeV ions has resulted in the observation of TAEs in many instances. The impact of several key parameters on TAE stability could therefore be studied experimentally. Modeling taking into account NBI and ICRH fast ions shows good agreement with the measured neutron rates, and has allowed predictions for DT plasmas to be performed.

  • 11.
    Fazinic, Stjepko
    et al.
    Rudjer Boskovic Inst, Bijenicka 54, Zagreb 10000, Croatia..
    Tadic, Tonic
    Rudjer Boskovic Inst, Bijenicka 54, Zagreb 10000, Croatia..
    Vuksic, Marin
    Rudjer Boskovic Inst, Bijenicka 54, Zagreb 10000, Croatia..
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Fortuna-Zalesna, Elibieta
    Warsaw Univ Technol, Fac Mat Sci & Technol, Woloska 141, PL-02507 Warsaw, Poland..
    Widdowson, Anna
    Culham Sci Ctr, Culham Ctr Fus Energy, Abingdon OX14 3DB, Oxon, England..
    Ion Microbeam Analyses of Dust Particles and Codeposits from JET with the ITER-Like Wall2018In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 90, no 9, p. 5744-5752Article in journal (Refereed)
    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.

  • 12. Field, A. R.
    et al.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Maggi, C.
    Saarelma, S.
    Inter-ELM power losses and their dependence on pedestal parameters in JET C-And ITER-like wall H-mode plasmas2018In: 45th EPS Conference on Plasma Physics, EPS 2018, European Physical Society (EPS) , 2018, p. 1636-1639Conference paper (Refereed)
  • 13.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Dunne, M. G.
    Sheikh, U.
    Orain, F.
    Bernert, M.
    Birkenmeier, G.
    Blanchard, P.
    Carralero, D.
    Cavedon, M.
    Coda, S.
    Fischer, R.
    Hoelzl, M.
    Laggner, F.
    McDermott, R. M.
    Meyer, H.
    Merle, A.
    Theiler, C.
    Verhaegh, K.
    Viezzer, E.
    Wolfrum, E.
    Role of the scrape-off layer in the type I ELM dynamics in AUG and TCV2017In: 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS) , 2017Conference paper (Refereed)
  • 14.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Saarelma, S.
    Imbeaux, F.
    Verdoolaege, G.
    Bilkova, P.
    Bohm, P.
    Fridström, R.
    Giovannozzi, E.
    Owsiak, M.
    Dunne, M.
    Labit, B.
    Scannell, R.
    Hillesheim, J. C.
    The EUROfusion JET-ILW pedestal database2018In: 45th EPS Conference on Plasma Physics, EPS 2018, European Physical Society (EPS) , 2018, p. 1056-1059Conference paper (Refereed)
  • 15.
    Frassinetti, Lorenzo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Scheffel, Jan
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vektoranalys2019 (ed. 1)Book (Refereed)
    Abstract [sv]

    Läroböcker i vektoranalys är ofta kortfattade. Denna bok, som kan användas för såväl grundläggande som mer avancerade kurser, behandlar ämnet mer utförligt.

    Bokens pedagogiska idé skiljer sig markant från liknande böcker. Återkommande inslag är tydligt formulerade problem som fångar det centrala i vektoranalysen. Syftet med problemen är dels att väcka intresse för den teori och de metoder som behandlas, dels att stimulera till aktivt lärande. 

    Boken innehåller genomarbetade och lättillgängliga teoriavsnitt - som börjar med grundläggande vektoralgebra och slutar med kartesiska tensorer och en härledning av vektoranalysens huvudsats. Dessutom ingår ett stort antal konkreta exempel och många tillämpningar. Sist i varje kapitel finns en sammanfattning av den viktigaste teorin och övningsuppgifter med svar. Ledningar och fullständiga lösningar finns på Libers webbplats. Där finns även ett Appendix med tillämpningar.

  • 16.
    Garcia Carrasco, Alvaro
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Widdowson, A.
    Fortuna-Zalesna, E.
    Jachmich, S.
    Brix, M.
    Marot, L.
    Plasma impact on diagnostic mirrors in JET2017In: NUCLEAR MATERIALS AND ENERGY, ISSN 2352-1791, Vol. 12, p. 506-512Article in journal (Refereed)
    Abstract [en]

    Metallic mirrors will be essential components of all optical systems for plasma diagnosis in ITER. This contribution provides a comprehensive account on plasma impact on diagnostic mirrors in JET with the ITER-Like Wall. Specimens from the First Mirror Test and the lithium-beam diagnostic have been studied by spectrophotometry, ion beam analysis and electron microscopy. Test mirrors made of molybdenum were retrieved from the main chamber and the divertor after exposure to the 2013-2014 experimental campaign. In the main chamber, only mirrors located at the entrance of the carrier lost reflectivity (Be deposition), while those located deeper in the carrier were only slightly affected. The performance of mirrors in the JET divertor was strongly degraded by deposition of beryllium, tungsten and other species. Mirrors from the lithium-beam diagnostic have been studied for the first time. Gold coatings were severely damaged by intense arcing. As a consequence, material mixing of the gold layer with the stainless steel substrate occurred. Total reflectivity dropped from over 90% to less than 60%, i.e. to the level typical for stainless steel.

  • 17.
    Garcia Carrasco, Alvaro
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Schwarz-Selinger, T.
    Wauters, T.
    Douai, D.
    Bobkov, V.
    Cavazzana, R.
    Krieger, K.
    Lyssoivan, A.
    Moeller, S.
    Spolaore, M.
    Rohde, V.
    Rubel, M.
    Investigation of probe surfaces after ion cyclotron wall conditioning in ASDEX upgrade2017In: NUCLEAR MATERIALS AND ENERGY, ISSN 2352-1791, Vol. 12, p. 733-735Article in journal (Refereed)
    Abstract [en]

    For the first time, material analysis techniques have been applied to study the effect of ion cyclotron wall conditioning (ICWC) on probe surfaces in a metal-wall machine. ICWC is a technique envisaged to contribute to the removal of fuel and impurities from the first wall of ITER. The objective of this work was to assess impurity migration under ICWC operation. Tungsten probes were exposed in ASDEX Upgrade to discharges in helium. After wall conditioning, the probes were covered with a co-deposited layer containing D, B, C, N, O and relatively high amount of He. The concentration ratio He/C+B was 0.7. The formation of the co-deposited layer indicates that a fraction of the impurities desorbed from the wall under ICWC operation are transported by plasma and deposited away from their original location.

  • 18.
    Garcia-Munoz, M.
    et al.
    Univ Seville, Dept Atom Mol & Nucl Phys, Seville, Spain..
    Sharapov, S. E.
    Culham Sci Ctr, Abingdon, Oxon, England..
    Van Zeeland, M. A.
    Gen Atom, San Diego, CA USA..
    Ascasibar, E.
    CIEMAT, Madrid, Spain..
    Cappa, A.
    CIEMAT, Madrid, Spain..
    Chen, L.
    Zhejiang Univ, IFTS, Hangzhou, Zhejiang, Peoples R China.;Zhejiang Univ, Dept Phys, Hangzhou, Zhejiang, Peoples R China.;Univ Calif Irvine, Dept Phys & Astron, Irvine, CA USA..
    Ferreira, J.
    IST, Lisbon, Portugal..
    Galdon-Quiroga, J.
    Univ Seville, Dept Atom Mol & Nucl Phys, Seville, Spain..
    Geiger, B.
    Max Planck Inst Plasma Phys, Garching, Germany..
    Gonzalez-Martin, J.
    Univ Seville, Dept Atom Mol & Nucl Phys, Seville, Spain..
    Heidbrink, W. W.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA USA..
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Lauber, Ph
    Max Planck Inst Plasma Phys, Garching, Germany..
    Mantsinen, M.
    Barcelona Supercomp Ctr, Barcelona, Spain.;ICREA, Pg Lluis Companys 23, Barcelona, Spain..
    Melnikov, A. , V
    Nabais, F.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA USA..
    Rivero-Rodriguez, J. F.
    Univ Seville, Dept Atom Mol & Nucl Phys, Seville, Spain..
    Sanchis-Sanchez, L.
    Univ Seville, Dept Atom Mol & Nucl Phys, Seville, Spain..
    Schneider, P.
    Max Planck Inst Plasma Phys, Garching, Germany..
    Stober, J.
    Max Planck Inst Plasma Phys, Garching, Germany..
    Suttrop, W.
    Max Planck Inst Plasma Phys, Garching, Germany..
    Todo, Y.
    Natl Inst Fus Sci, Toki, Gifu, Japan..
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Zonca, F.
    Zhejiang Univ, IFTS, Hangzhou, Zhejiang, Peoples R China.;Zhejiang Univ, Dept Phys, Hangzhou, Zhejiang, Peoples R China.;ENEA, Fus & Nucl Safety Dept, CR Frascati, Rome, Italy..
    Meyer, H.
    Active control of Alfven eigenmodes in magnetically confined toroidal plasmas2019In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 5, article id 054007Article in journal (Refereed)
    Abstract [en]

    Alfven waves are electromagnetic perturbations inherent to magnetized plasmas that can be driven unstable by a free energy associated with gradients in the energetic particles' distribution function. The energetic particles with velocities comparable to the Alfven velocity may excite Alfven instabilities via resonant wave-particle energy and momentum exchange. Burning plasmas with large population of fusion born super-Alfvenic alpha particles in magnetically confined fusion devices are prone to excite weakly-damped Alfven eigenmodes (AEs) that, if allowed to grow unabated, can cause a degradation of fusion performance and loss of energetic ions through a secular radial transport. In order to control the fast-ion distribution and associated Alfvenic activity, the fusion community is currently searching for external actuators that can control AEs and energetic ions in the harsh environment of a fusion reactor. Most promising control techniques are based on (i) variable fast-ion sources to modify gradients in the energetic particles' distribution, (ii) localized electron cyclotron resonance heating to affect the fast-ion slowing-down distribution, (iii) localized electron cyclotron current drive to modify the equilibrium magnetic helicity and thus the AE existence criteria and damping mechanisms, and (iv) externally applied 3D perturbative fields to manipulate the fast-ion distribution and thus the wave drive. Advanced simulations help to identify the key physics mechanisms underlying the observed AE mitigation and suppression and thus to develop robust control techniques towards future burning plasmas.

  • 19.
    Hoelzl, M.
    et al.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Huijsmans, G. T. A.
    CEA, IRFM, St Paul Les Durance, France.;Eindhoven Univ Technol, Eindhoven, Netherlands..
    Orain, F.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Artola, F. J.
    Aix Marseille Univ, CNRS, Marseille 20, France..
    Pamela, S.
    Culham Sci Ctr, CCFE, Abingdon, Oxon, England..
    Becoulet, M.
    CEA, IRFM, St Paul Les Durance, France..
    van Vugt, D.
    Eindhoven Univ Technol, Eindhoven, Netherlands..
    Liu, F.
    CEA, IRFM, St Paul Les Durance, France.;Univ Cote dAzur, Lab JA Dieudonne, CNRS, UMR 7351,UNS, Nice 02, France..
    Futatani, S.
    Barcelona Supercomp Ctr, Barcelona, Spain..
    Lessig, A.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Wolfrum, E.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Mink, F.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Trier, E.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Dunne, M.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Viezzer, E.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Eich, T.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Vanovac, B.
    Dutch Inst Fundamental Energy Res, DIFFER, Eindhoven, Netherlands..
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Guenter, S.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Lackner, K.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Krebs, I.
    Princeton Plasma Phys Lab, POB 451, Princeton, NJ 08543 USA..
    Insights into type-I edge localized modes and edge localized mode control from JOREK non-linear magneto-hydrodynamic simulations2018In: Contributions to Plasma Physics, ISSN 0863-1042, E-ISSN 1521-3986, Vol. 58, no 6-8, p. 518-528Article in journal (Refereed)
    Abstract [en]

    Edge localized modes (ELMs) are repetitive instabilities driven by the large pressure gradients and current densities in the edge of H-mode plasmas. Type-I ELMs lead to a fast collapse of the H-mode pedestal within several hundred microseconds to a few milliseconds. Localized transient heat fluxes to divertor targets are expected to exceed tolerable limits for ITER, requiring advanced insights into ELM physics and applicable mitigation methods. This paper describes how non-linear magneto-hydrodynamic (MHD) simulations can contribute to this effort. The JOREK code is introduced, which allows the study of large-scale plasma instabilities in tokamak X-point plasmas covering the main plasma, the scrape-off layer, and the divertor region with its finite element grid. We review key physics relevant for type-I ELMs and show to what extent JOREK simulations agree with experiments and help reveal the underlying mechanisms. Simulations and experimental findings are compared in many respects for type-I ELMs in ASDEX Upgrade. The role of plasma flows and non-linear mode coupling for the spatial and temporal structure of ELMs is emphasized, and the loss mechanisms are discussed. An overview of recent ELM-related research using JOREK is given, including ELM crashes, ELM-free regimes, ELM pacing by pellets and magnetic kicks, and mitigation or suppression by resonant magnetic perturbation coils (RMPs). Simulations of ELMs and ELM control methods agree in many respects with experimental observations from various tokamak experiments. On this basis, predictive simulations become more and more feasible. A brief outlook is given, showing the main priorities for further research in the field of ELM physics and further developments necessary.

  • 20. Horvath, L.
    et al.
    Maggi, C. F.
    Belonohy, E.
    Delabie, E. G.
    Flanagan, J.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Giroud, C.
    Keeling, D.
    King, D.
    Maslov, M.
    Matthews, G. F.
    Menmuir, S.
    Saarelma, S.
    Silburn, S. A.
    Sips, A. C. C.
    Weisen, H.
    Gibson, K. J.
    Pedestal structure and stability in H and D isotope experiments on JET-ILW2017In: 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS) , 2017Conference paper (Refereed)
  • 21. Huber, A.
    et al.
    Brezinsek, S.
    Kirschner, A.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Sergienko, G.
    Huber, V.
    Borodkina, I.
    Douai, D.
    Jachmich, S.
    Linsmeier, Ch.
    Lomanowski, B.
    Matthews, G.F
    Mertens, P.h
    Determination of tungsten sources in the JET-ILW divertor by spectroscopic imaging in the presence of a strong plasma continuum2019In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 18, p. 118-124Article in journal (Refereed)
    Abstract [en]

    The identification of the sources of atomic tungsten and the measurement of their radiation distribution in front of all plasma-facing components has been performed in JET with the help of two digital cameras with the same two-dimensional view, equipped with interference filters of different bandwidths centred on the W I (400.88 nm) emission line. A new algorithm for the subtraction of the continuum radiation was successfully developed and is now used to evaluate the W erosion even in the inner divertor region where the strong recombination emission is dominating over the tungsten emission. Analysis of W sputtering and W redistribution in the divertor by video imaging spectroscopy with high spatial resolution for three different magnetic configurations was performed. A strong variation of the emission of the neutral tungsten in toroidal direction and corresponding W erosion has been observed. It correlates strongly with the wetted area with a maximal W erosion at the edge of the divertor tile.

  • 22.
    Jepu, I
    et al.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Magurele 077125, Romania.;Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Matthews, G. F.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Widdowson, A.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics. EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.
    Fortuna-Zalesna, E.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Warsaw Univ Technol, PL-02507 Warsaw, Poland..
    Zdunek, J.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Magurele 077125, Romania..
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics. EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.
    Thompson, V
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Dinca, P.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Magurele 077125, Romania..
    Porosnicu, C.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Magurele 077125, Romania..
    Coad, P.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Heinola, K.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Univ Helsinki, POB 64, Helsinki 00560, Finland..
    Catarino, N.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Univ Lisbon, Inst Super Tecn, IPFN, Av Rovisco Pais, P-1049001 Lisbon, Portugal..
    Pompilian, O. G.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Magurele 077125, Romania..
    Lungu, C. P.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Magurele 077125, Romania..
    Beryllium melting and erosion on the upper dump plates in JET during three ITER-like wall campaigns2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 8, article id 086009Article in journal (Refereed)
    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).

  • 23. Joffrin, E.
    et al.
    Bergsåker, Henric
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Fridström, Richard
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Moon, Sunwoo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Zhou, Yushan
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Zychor, I
    et al.,
    Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 11, article id 112021Article in journal (Refereed)
    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.

  • 24. Joly, J.
    et al.
    Garcia, J.
    Imbeaux, F.
    Dumont, R.
    Schneider, M.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Artaud, J. F.
    Self-consistent modelling of heating synergy between NBI and ICRH in JET deuterium plasmas2019In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 7, article id 075017Article in journal (Refereed)
    Abstract [en]

    Auxiliary heating is essential to initiate fusion in future tokamaks. In particular, ion heating tends to maximise the alpha power generation by increasing the thermal ion temperature. In order to simulate the plasma heating by ion cyclotron radio frequency waves, the EVE code, a full wave code for IC wave propagation, and SPOT, an orbit following Monte Carlo code combined with the RFOF library which calculates the absorption of wave by ions, have been coupled together. This new package is used for simulating JET plasmas with strong interplay between ion cyclotron resonant heating and neutral beam injection. Simulations shows that up to 20% of the neutron rate generated in recent JET D plasmas is due to the synergy between both heating mechanisms. However, the H concentration plays a critical role on such interplay, because the synergy efficiency weakens with the H concentration. Therefore, the control of the H concentration is mandatory for optimising the fusion reaction rate generation at JET.

  • 25. Kappatou, A.
    et al.
    Angioni, C.
    Sips, A. C. C.
    Lerche, E.
    Pütterich, T.
    Dunne, M.
    Neu, R.
    Giroud, C.
    Challis, C.
    Hobirk, J.
    Kim, H. -T
    Nunes, I.
    Tsalas, M.
    Cave-Ayland, K.
    Valcarcel, D. F.
    Menmuir, S.
    Lebschy, A.
    Viezzer, E.
    McDermott, R. M.
    Potzel, S.
    Ryter, F.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Delabie, E.
    Saarelma, S.
    Bernert, M.
    The effect of helium on plasma performance at ASDEX Upgrade and JET2017In: 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS) , 2017Conference paper (Refereed)
  • 26. Koslowski, H.R.
    et al.
    Bhattacharyya, S.R.
    Hansen, P.
    Linsmeier, Ch.
    Rasinski, M.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Temperature-dependent in-situ LEIS measurement of W surface enrichment by 250 eV D sputtering of EUROFER2018In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 16, p. 181-190Article in journal (Refereed)
  • 27.
    Labit, B.
    et al.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Thorén, Emil
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Vallejos Olivares, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Zuin, M.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Dependence on plasma shape and plasma fueling for small edge-localized mode regimes in TCV and ASDEX Upgrade2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 8, article id 086020Article in journal (Refereed)
    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.

  • 28.
    Lindvall, Kristoffer
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Scheffel, Jan
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    A time-spectral method for initial-value problems using a novel spatial subdomain scheme2018In: COGENT MATHEMATICS, ISSN 2331-1835, Vol. 5, no 1, article id 1529280Article in journal (Refereed)
    Abstract [en]

    We analyse a novel subdomain scheme for time-spectral solution of initial-value partial differential equations. In numerical modelling spectral methods are commonplace for spatially dependent systems, whereas finite difference schemes are typically applied for the temporal domain. The Generalized Weighted Residual Method (GWRM) is a fully spectral method that spectrally decomposes all specified domains, including the temporal domain, using multivariate Chebyshev polynomials. The Common Boundary-Condition method (CBC) here proposed is a spatial subdomain scheme for the GWRM. It solves the physical equations independently from the global connection of subdomains in order to reduce the total number of modes. Thus, it is a condensation procedure in the spatial domain that allows for a simultaneous global temporal solution. It is here evaluated against the finite difference methods of Crank-Nicolson and Lax-Wendroff for two example linear PDEs. The CBC-GWRM is also applied to the linearised ideal magnetohydrodynamic (MHD) equations for a screw pinch equilibrium. The growth rate of the most unstable mode was efficiently computed with an error <0.1%.

  • 29.
    Lindvall, Kristoffer
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Scheffel, Jan
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Can the Time-Spectral Method GWRM Advance Fusion Transport Modelling?2017In: 59th Annual Meeting of the APS Division of Plasma Physics, 2017Conference paper (Refereed)
    Abstract [en]

    Transport phenomena in fusion plasma pose a daunting task for both real-time experiments and numerical modelling. The transport is driven by micro-instabilities caused by a host of unstable modes, for example ion temperature gradient and trapped electron modes. These modes can be modelled using fluid or gyrokinetic equations. However, the equations are characterised by high degrees of freedom and high temporal and spatial numerical requirements. Thus, a time-spectral method GWRM has been developed in order to efficiently solve these multiple time scale equations. The GWRM assumes a multivariate Chebyshev expansion ansatz in time, space, and parameter domain. Advantages are that time constraining CFL criteria no longer apply and that the solution accurately averages over small time-scale dynamics. For benchmarking, a two-fluid 2D drift wave turbulence model has been solved in order to study toroidal ion temperature gradient growth rates and nonlinear behaviour.

  • 30.
    Lindvall, Kristoffer
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Scheffel, Jan
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Spectral Representation of Time and Physical Parameters in Numerical Weather Prediction2018In: Understanding of Atmospheric Systems with Efficient Numerical Methods for Observation and Prediction, IntechOpen , 2018Chapter in book (Refereed)
    Abstract [en]

    Numerical weather prediction (NWP) is a difficult task in chaotic dynamical regimes because of the strong sensitivity to initial conditions and physical parameters. As a result, high numerical accuracy is usually necessary. In this chapter, an accurate and efficient alternative to the traditional time stepping solution methods is presented; the time-spectral method. The generalized weighted residual method (GWRM) solves systems of nonlinear ODEs and PDEs using a spectral representation of time. Not being subject to CFL-like criteria, the GWRM typically employs time intervals two orders of magnitude larger than those of time-stepping methods. As an example, efficient solution of the chaotic Lorenz 1984 equations is demonstrated. The results indicate that the method has strong potential for NWP. Furthermore, employing spectral representations of physical parameters and initial values, families of solutions are obtained in a single computation. Thus, the GWRM is conveniently used for studies of system parameter dependency and initial condition error growth in NWP.

  • 31.
    Litnovsky, A.
    et al.
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, D-52425 Julich, Germany..
    Voitsenya, V. S.
    NSC Kharkov Inst Phys & Technol, IPP, UA-61008 Kharkov, Ukraine..
    Reichle, R.
    ITER Org, Route Vinon Sur Verdon,CS 90 046, F-13067 Saint Paul Lez Durance, France..
    Walsh, M.
    ITER Org, Route Vinon Sur Verdon,CS 90 046, F-13067 Saint Paul Lez Durance, France..
    Razdobarin, A.
    Ioffe Physictech Inst, Polytech Skaya 26, St Petersburg 194021, Russia..
    Dmitriev, A.
    Ioffe Physictech Inst, Polytech Skaya 26, St Petersburg 194021, Russia..
    Babinov, N.
    Ioffe Physictech Inst, Polytech Skaya 26, St Petersburg 194021, Russia..
    Marot, L.
    Univ Basel, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Moser, L.
    Univ Basel, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Yan, R.
    Chinese Acad Sci, Inst Plasma Phys, Hefei 230031, Anhui, Peoples R China..
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Widdowson, A.
    CCFE EURATOM Fus Assoc, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England..
    Moon, Sunwoo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Oh, S. G.
    Ajou Univ, Suwon 16499, South Korea..
    An, Y.
    Natl Fus Res Inst, Daejeon 34133, South Korea..
    Shigin, P.
    ITER Org, Route Vinon Sur Verdon,CS 90 046, F-13067 Saint Paul Lez Durance, France..
    Orlovskiy, I
    Natl Res Ctr Kurchatov Inst, Moscow 123098, Russia..
    Vukolov, K. Yu
    Natl Res Ctr Kurchatov Inst, Moscow 123098, Russia..
    Andreenko, E.
    Natl Res Ctr Kurchatov Inst, Moscow 123098, Russia..
    Krimmer, A.
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, D-52425 Julich, Germany..
    Kotov, V
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, D-52425 Julich, Germany..
    Mertens, Ph
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, D-52425 Julich, Germany..
    Diagnostic mirrors for ITER: research in the frame of International Tokamak Physics Activity2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 6, article id 066029Article in journal (Refereed)
    Abstract [en]

    Mirrors will be used as first plasma-viewing elements in optical and laser-based diagnostics in ITER. Deterioration of the mirror performance due to e.g. sputtering of the mirror surface by plasma particles or deposition of impurities will hamper the entire performance of the affected diagnostic and thus affect ITER operation. The Specialists Working Group on First Mirrors (FM SWG) in the Topical Group on Diagnostics of the International Tokamak Physics Activity (ITPA) plays an important role in finding solutions for diagnostic first mirrors. Sound progress in research and development of diagnostic mirrors in ITER was achieved since the last overview in 2009. Single crystal (SC) rhodium (Rh) mirrors became available. SC rhodium and molybdenum (Mo) mirrors survived in conditions corresponding to similar to 200 cleaning cycles with a negligible degradation of reflectivity. These results are important for a mirror cleaning system which is presently under development. The cleaning system is based on sputtering of contaminants by plasma. Repetitive cleaning was tested on several mirror materials. Experiments comprised contamination/cleaning cycles. The reflectivity SC Mo and Rh mirrors has changed insignificantly after 80 cycles. First in situ cleaning using radiofrequency (RF) plasma was conducted in EAST tokamak with a mock-up plate of ITER edge Thomson Scattering (ETS) with five inserted mirrors. Contaminants from the mirrors were removed. Physics of cleaning discharge was studied both experimentally and by modeling. Mirror contamination can also be mitigated by protecting diagnostic ducts. A deposition mitigation (DeMi) duct system was exposed in KSTAR. The real-time measurement of deposition in the diagnostic duct was pioneered during this experiment. Results evidenced the dominating effect of the wall conditioning and baking on contamination inside the duct. A baffled cassette with mirrors was exposed at the main wall of JET for 23,6 plasma hours. No significant degradation of reflectivity was measured on mirrors located in the ducts. Predictive modeling was further advanced. A model for the particle transport, deposition and erosion at the port-plug was used in selecting an optical layout of several ITER diagnostics. These achievements contributed to the focusing of the first mirror research thus accelerating the diagnostic development. Modeling requires more efforts. Remaining crucial issues will be in a focus of the future work of the FM SWG.

  • 32. Louche, F.
    et al.
    Wauters, T.
    Ragona, R.
    Moeller, S.
    Durodie, F.
    Litnovsky, A.
    Lyssoivan, A.
    Messiaen, A.
    Ongena, J.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brezinsek, S.
    Linsmeier, Ch.
    Van Schoor, M.
    Design of an ICRF system for plasma-wall interactions and RF plasma production studies on TOMAS2017In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 123, p. 317-320Article in journal (Refereed)
    Abstract [en]

    Ion cyclotron wall conditioning (ICWC) is being developed for ITER and W7-X as a baseline conditioning technique in which the ion cyclotron heating and current drive system will be employed to produce and sustain the currentless conditioning plasma. The TOMAS project (TOroidal MAgnetized System, operated at the FZ-juelich, Germany) proposes to explore several key aspects of ICWC. For this purpose we have designed an ICRF system made of a single strap antenna within a metallic box, connected to a feeding port and a pre-matching system. We discuss the design work of the antenna system with the help of the commercial electromagnetic software CST Microwave Studio (R). The simulation results for a given geometry provide input impedance matrices for the two-port system. These matrices are afterwards inserted into various circuit models to assess the accessibility of the required frequency range. The sensitivity of the matching system to uncertainties on plasma loading and capacitance values is notably addressed. With a choice of three variable capacitors we show that the system can cope with such uncertainties. We also demonstrate that the system can cope as well with the high reflected power levels during the short breakdown phase of the RF discharge, but at the cost of a significantly reduced coupled power.

  • 33.
    Marco, Aitor
    et al.
    IDOM, Adv Design & Anal Dept, Bilbao, Spain..
    Garrido, Aitor J.
    Univ Basque Country, UPV EHU, Inst Res & Dev Proc, ACG,IIDP,Automat Control & Syst Engn Dept, Bilbao, Spain..
    Coda, Stefano
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Garrido, Izaskun
    Univ Basque Country, UPV EHU, Inst Res & Dev Proc, ACG,IIDP,Automat Control & Syst Engn Dept, Bilbao, Spain..
    Ahn, J.
    Albanese, R.
    Alberti, S.
    Alessi, E.
    CNR, IFP, Via R Cozzi 53, I-20125 Milan, Italy..
    Allan, S.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Anand, H.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Anastassiou, G.
    Natl Tech Univ Athens, Athens, Greece..
    Andrebe, Y.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Angioni, C.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Ariola, M.
    Univ Napoli Parthenope, Consorzio CREATE, Via Claudio 21, I-80125 Naples, Italy..
    Bernert, M.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Beurskens, M.
    Max Planck Inst Plasma Phys, Teilinst Greifswald, D-17491 Greifswald, Germany..
    Bin, W.
    CNR, IFP, Via R Cozzi 53, I-20125 Milan, Italy..
    Blanchard, P.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Blanken, T. C.
    Eindhoven Univ Technol, POB 513, NL-5600 MB Eindhoven, Netherlands..
    Boedo, J. A.
    Univ Calif San Diego, Energy Res Ctr, La Jolla, CA 92093 USA..
    Bolzonella, T.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Bouquey, F.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Braunmueller, F. H.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Bufferand, H.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Buratti, P.
    ENEA CR Frascati, Unita Tecn Fus, Via E Fermi 45, I-00044 Rome, Italy..
    Calabro, G.
    ENEA CR Frascati, Unita Tecn Fus, Via E Fermi 45, I-00044 Rome, Italy..
    Camenen, Y.
    Aix Marseille Univ, CNRS, PIIM, F-13013 Marseille, France..
    Carnevale, D.
    Univ Roma Tor Vergata, Via Politecn 1, I-00133 Rome, Italy..
    Carpanese, F.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Causa, F.
    ENEA CR Frascati, Unita Tecn Fus, Via E Fermi 45, I-00044 Rome, Italy..
    Cesario, R.
    ENEA CR Frascati, Unita Tecn Fus, Via E Fermi 45, I-00044 Rome, Italy..
    Chapman, I. T.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Chellai, O.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Choi, D.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Cianfarani, C.
    ENEA CR Frascati, Unita Tecn Fus, Via E Fermi 45, I-00044 Rome, Italy..
    Ciraolo, G.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Citrin, J.
    FOM Inst DIFFER Dutch Inst Fundamental Energy Res, Eindhoven, Netherlands..
    Costea, S.
    Univ Innsbruck, Inst Ionen & Angew Phys, Tech Str 25, A-6020 Innsbruck, Austria..
    Crisanti, F.
    ENEA CR Frascati, Unita Tecn Fus, Via E Fermi 45, I-00044 Rome, Italy..
    Cruz, N.
    Univ Lisbon, Inst Super Tecn, Inst Plasmas & Fusao Nucl, Lisbon, Portugal..
    Czarnecka, A.
    Inst Plasma Phys & Laser Microfus, Hery 23, PL-01497 Warsaw, Poland..
    Decker, J.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    De Masi, G.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    De Tommasi, G.
    Univ Napoli Federico II, Consorzio CREATE, Via Claudio 21, I-80125 Naples, Italy..
    Douai, D.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Dunne, M.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Duval, B. P.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Eich, T.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Elmore, S.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Esposito, B.
    ENEA CR Frascati, Unita Tecn Fus, Via E Fermi 45, I-00044 Rome, Italy..
    Faitsch, M.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Fasoli, A.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Fedorczak, N.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Felici, F.
    Eindhoven Univ Technol, POB 513, NL-5600 MB Eindhoven, Netherlands..
    Fevrier, O.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Ficker, O.
    Inst Plasma Phys AS CR, Za Slovankou 1782-3, Prague 18200, Czech Republic..
    Fietz, S.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Fontana, M.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Furno, I.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Galeani, S.
    Univ Roma Tor Vergata, Via Politecn 1, I-00133 Rome, Italy..
    Gallo, A.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Galperti, C.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Garavaglia, S.
    CNR, IFP, Via R Cozzi 53, I-20125 Milan, Italy..
    Garrido, I.
    Univ Basque Country, UPV EHU, Fac Engn, Paseo RafaelMoreno 3, Bilbao 48013, Spain..
    Geiger, B.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany.;Max Planck Inst Plasma Phys, Teilinst Greifswald, D-17491 Greifswald, Germany..
    Giovannozzi, E.
    ENEA CR Frascati, Unita Tecn Fus, Via E Fermi 45, I-00044 Rome, Italy..
    Gobbin, M.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Goodman, T. P.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Gorini, G.
    Univ Milano Bicocca, Dept Phys G Occhialini, Piazza Sci 3, I-20126 Milan, Italy..
    Gospodarczyk, M.
    Univ Roma Tor Vergata, Via Politecn 1, I-00133 Rome, Italy..
    Granucci, G.
    CNR, IFP, Via R Cozzi 53, I-20125 Milan, Italy..
    Graves, J. P.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Guirlet, R.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Hakola, A.
    VTT Tech Res Ctr Finland Ltd, POB 1000, FI-02044 Espoo, Finland..
    Ham, C.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Harrison, J.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Hawke, J.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Hennequin, P.
    Ecole Polytech, CNRS, UMR7648, Lab Phys Plasmas, F-91128 Palaiseau, France..
    Hnat, B.
    Univ Oxford, Rudolf Peierls Ctr Theoret Phys, Oxford, England.;Culham Ctr Fus Energy, Abingdon, Oxon, England..
    Hogeweij, D.
    FOM Inst DIFFER Dutch Inst Fundamental Energy Res, Eindhoven, Netherlands..
    Hogge, J. -Ph.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Honore, C.
    Ecole Polytech, CNRS, UMR7648, Lab Phys Plasmas, F-91128 Palaiseau, France..
    Hopf, C.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Horacek, J.
    Inst Plasma Phys AS CR, Za Slovankou 1782-3, Prague 18200, Czech Republic..
    Huang, Z.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Igochine, V.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Innocente, P.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Schrittwieser, C. Ionita
    Univ Innsbruck, Inst Ionen & Angew Phys, Tech Str 25, A-6020 Innsbruck, Austria..
    Isliker, H.
    Aristotle Univ Thessaloniki, Thessaloniki, Greece..
    Jacquier, R.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Jardin, A.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Kamleitner, J.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Karpushov, A.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Keeling, D. L.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Kirneva, N.
    Kurchatov Inst, Natl Res Ctr, Inst Phys Tokamaks, Kurchatov Sq 1, Moscow 123182, Russia.;Natl Res Nucl Univ MEPhI, Moscow Engn Phys Inst, Kashirskoe Sh 31, Moscow 115409, Russia..
    Kong, M.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Koubiti, M.
    Aix Marseille Univ, CNRS, PIIM, F-13013 Marseille, France..
    Kovacic, J.
    Jozef Stefan Inst, Jamova 39, SI-1000 Ljubljana, Slovenia..
    Kramer-Flecken, A.
    Forschungszentrum Julich, Inst Energie & Klimaforsch, Plasmaphys, D-52425 Julich, Germany..
    Krawczyk, N.
    Inst Plasma Phys & Laser Microfus, Hery 23, PL-01497 Warsaw, Poland..
    Kudlacek, O.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany.;Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Labit, B.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Lazzaro, E.
    CNR, IFP, Via R Cozzi 53, I-20125 Milan, Italy..
    Le, H. B.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Lipschultz, B.
    Univ York, York Plasma Inst, Dept Phys, York YO10 5DD, N Yorkshire, England..
    Llobet, X.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Lomanowski, B.
    Univ Durham, Dept Phys, Durham DH1 3LE, England..
    Loschiavo, V. P.
    Univ Napoli Federico II, Consorzio CREATE, Via Claudio 21, I-80125 Naples, Italy..
    Lunt, T.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Maget, P.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Maljaars, E.
    Eindhoven Univ Technol, POB 513, NL-5600 MB Eindhoven, Netherlands..
    Malygin, A.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Maraschek, M.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Marini, C.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Martin, P.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Martin, Y.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Mastrostefano, S.
    Univ Napoli Parthenope, Consorzio CREATE, Via Claudio 21, I-80125 Naples, Italy..
    Maurizio, R.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Mavridis, M.
    Aristotle Univ Thessaloniki, Thessaloniki, Greece..
    Mazon, D.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    McAdams, R.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    McDermott, R.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Merle, A.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Meyer, H.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Militello, F.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Miron, I. G.
    Natl Inst Laser Plasma & Radiat Phys, POB MG-36, Bucharest, Romania..
    Cabrera, P. A. Molina
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Moret, J. -M
    Moro, A.
    CNR, IFP, Via R Cozzi 53, I-20125 Milan, Italy..
    Moulton, D.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Naulin, V.
    Tech Univ Denmark, Dept Phys, Bldg 309, DK-2800 Lyngby, Denmark..
    Nespoli, F.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Nielsen, A. H.
    Tech Univ Denmark, Dept Phys, Bldg 309, DK-2800 Lyngby, Denmark..
    Nocente, M.
    Univ Milano Bicocca, Dept Phys G Occhialini, Piazza Sci 3, I-20126 Milan, Italy..
    Nouailletas, R.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Nowak, S.
    CNR, IFP, Via R Cozzi 53, I-20125 Milan, Italy..
    Odstrcil, T.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Papp, G.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Paprok, R.
    Inst Plasma Phys AS CR, Za Slovankou 1782-3, Prague 18200, Czech Republic..
    Pau, A.
    Univ Cagliari, Dept Elect & Elect Engn, Piazza Armi, I-09123 Cagliari, Italy..
    Pautasso, G.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Ridolfini, V. Pericoli
    Univ Napoli Parthenope, Consorzio CREATE, Via Claudio 21, I-80125 Naples, Italy..
    Piovesan, P.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Piron, C.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Pisokas, T.
    Aristotle Univ Thessaloniki, Thessaloniki, Greece..
    Porte, L.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Preynas, M.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Ramogida, G.
    ENEA CR Frascati, Unita Tecn Fus, Via E Fermi 45, I-00044 Rome, Italy..
    Rapson, C.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Rasmussen, J. Juul
    Tech Univ Denmark, Dept Phys, Bldg 309, DK-2800 Lyngby, Denmark..
    Reich, M.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Reimerdes, H.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Reux, C.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Ricci, P.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Rittich, D.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Riva, F.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Robinson, T.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Saarelma, S.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Saint-Laurent, F.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Sauter, O.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Scannell, R.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Schlatter, Ch.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Schneider, B.
    Univ Innsbruck, Inst Ionen & Angew Phys, Tech Str 25, A-6020 Innsbruck, Austria..
    Schneider, P.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Schrittwieser, R.
    Univ Innsbruck, Inst Ionen & Angew Phys, Tech Str 25, A-6020 Innsbruck, Austria..
    Sciortino, F.
    MIT, Plasma Sci & Fusion Ctr, 77 Massachusetts Ave, Cambridge, MA 02139 USA..
    Sertoli, M.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Sheikh, U.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Sieglin, B.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Silva, M.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Sinha, J.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Sozzi, C.
    CNR, IFP, Via R Cozzi 53, I-20125 Milan, Italy..
    Spolaore, M.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Stange, T.
    Max Planck Inst Plasma Phys, Teilinst Greifswald, D-17491 Greifswald, Germany..
    Stoltzfus-Dueck, T.
    Princeton Univ, Princeton, NJ 08544 USA..
    Tamain, P.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Teplukhina, A.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Testa, D.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Theiler, C.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Thornton, A.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Tophoj, L.
    Tech Univ Denmark, Dept Phys, Bldg 309, DK-2800 Lyngby, Denmark..
    Tran, M. Q.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Tsironis, C.
    Natl Tech Univ Athens, Athens, Greece..
    Tsui, C.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland.;Univ Calif San Diego, Energy Res Ctr, La Jolla, CA 92093 USA..
    Uccello, A.
    CNR, IFP, Via R Cozzi 53, I-20125 Milan, Italy..
    Vartanian, S.
    IRFM, CEA, F-13108 St Paul Les Durance, France..
    Verdoolaege, G.
    UG Ghent Univ, Dept Appl Phys, St Pietersnieuwstraat 41, B-9000 Ghent, Belgium..
    Verhaegh, K.
    Univ York, York Plasma Inst, Dept Phys, York YO10 5DD, N Yorkshire, England..
    Vermare, L.
    Ecole Polytech, CNRS, UMR7648, Lab Phys Plasmas, F-91128 Palaiseau, France..
    Vianello, N.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland.;Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Vijvers, W. A. J.
    FOM Inst DIFFER Dutch Inst Fundamental Energy Res, Eindhoven, Netherlands..
    Vlahos, L.
    Aristotle Univ Thessaloniki, Thessaloniki, Greece..
    Vu, N. M. T.
    Inst Polytech Grenoble, Lab Concept & Integrat Syst, BP54, F-26902 Valence 09, France..
    Walkden, N.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Wauters, T.
    Ecole Royale Mil, Koninklijke Mil Sch, Lab Plasma Phys, Renaissancelaan 30 Ave Renaissance, B-1000 Brussels, Belgium..
    Weisen, H.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Wischmeier, M.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Zestanakis, P.
    Natl Tech Univ Athens, Athens, Greece..
    Zuin, M.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    A Variable Structure Control Scheme Proposal for the Tokamak a Configuration Variable2019In: Complexity, ISSN 1076-2787, E-ISSN 1099-0526, article id 2319560Article in journal (Refereed)
    Abstract [en]

    Fusion power is the most significant prospects in the long-term future of energy in the sense that it composes a potentially clean, cheap, and unlimited power source that would substitute the widespread traditional nonrenewable energies, reducing the geographical dependence on their sources as well as avoiding collateral environmental impacts. Although the nuclear fusion research started in the earlier part of 20th century and the fusion reactors have been developed since the 1950s, the fusion reaction processes achieved have not yet obtained net power, since the generated plasma requires more energy to achieve and remain in necessary particular pressure and temperature conditions than the produced profitable energy. For this purpose, the plasma has to be confined inside a vacuum vessel, as it is the case of the Tokamak reactor, which consists of a device that generates magnetic fields within a toroidal chamber, being one of the most promising solutions nowadays. However, the Tokamak reactors still have several issues such as the presence of plasma instabilities that provokes a decay of the fusion reaction and, consequently, a reduction in the pulse duration. In this sense, since long pulse reactions are the key to produce net power, the use of robust and fast controllers arises as a useful tool to deal with the unpredictability and the small time constant of the plasma behavior. In this context, this article focuses on the application of robust control laws to improve the controllability of the plasma current, a crucial parameter during the plasma heating and confinement processes. In particular, a variable structure control scheme based on sliding surfaces, namely, a sliding mode controller (SMC) is presented and applied to the plasma current control problem. In order to test the validity and goodness of the proposed controller, its behavior is compared to that of the traditional PID schemes applied in these systems, using the RZIp model for the Tokamak a Configuration Variable (TCV) reactor. The obtained results are very promising, leading to consider this controller as a strong candidate to enhance the performance of the PID-based controllers usually employed in this kind of systems.

  • 34.
    Moon, Sunwoo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Fortuna-Zalesna, E.
    Widdowson, A.
    Jachmich, S.
    Litnovsky, A.
    Alves, E.
    Contributors, J E T
    First mirror test in JET for ITER: Complete overview after three ILW campaigns2019In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 19, p. 59-66Article in journal (Refereed)
    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.

  • 35.
    Otsuka, T.
    et al.
    Kindai Univ, 3-4-1 Kowakae, Higashiosaka, Osaka 5778502, Japan..
    Masuzaki, S.
    Natl Inst Fus Sci, 322-6 Oroshi Cho, Toki, Gifu 5095292, Japan..
    Ashikawa, N.
    Natl Inst Fus Sci, 322-6 Oroshi Cho, Toki, Gifu 5095292, Japan..
    Hatano, Y.
    Univ Toyama, Gofuku 3190, Toyama 9308555, Japan..
    Asakura, Y.
    Natl Inst Quantum, Aomori 0393212, Japan.;Natl Inst Radiol Sci & Technol, Aomori 0393212, Japan..
    Suzuki, Tatsuya
    Natl Inst Quantum, Aomori 0393212, Japan.;Natl Inst Radiol Sci & Technol, Aomori 0393212, Japan..
    Suzuki, Takumi
    Natl Inst Quantum, Aomori 0393212, Japan.;Natl Inst Radiol Sci & Technol, Aomori 0393212, Japan..
    Isobe, K.
    Natl Inst Quantum, Aomori 0393212, Japan.;Natl Inst Radiol Sci & Technol, Aomori 0393212, Japan..
    Hayashi, T.
    Natl Inst Quantum, Aomori 0393212, Japan.;Natl Inst Radiol Sci & Technol, Aomori 0393212, Japan..
    Tokitani, M.
    Natl Inst Fus Sci, 322-6 Oroshi Cho, Toki, Gifu 5095292, Japan..
    Oya, Y.
    Shizuoka Univ, Shizuoka 4228529, Japan..
    Hamaguchi, D.
    Natl Inst Quantum, Aomori 0393212, Japan.;Natl Inst Radiol Sci & Technol, Aomori 0393212, Japan..
    Kurotaki, H.
    Natl Inst Quantum, Aomori 0393212, Japan.;Natl Inst Radiol Sci & Technol, Aomori 0393212, Japan..
    Sakamoto, R.
    Natl Inst Fus Sci, 322-6 Oroshi Cho, Toki, Gifu 5095292, Japan..
    Tanigawa, Hiroyasu
    Natl Inst Quantum, Aomori 0393212, Japan.;Natl Inst Radiol Sci & Technol, Aomori 0393212, Japan..
    Nakamichi, M.
    Natl Inst Quantum, Aomori 0393212, Japan.;Natl Inst Radiol Sci & Technol, Aomori 0393212, Japan..
    Widdowson, A.
    Culham Sci Ctr, Culham Ctr Fus Energy, Abingdon OX14 3DB, Oxon, England..
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tritium retention characteristics in dust particles in JET with ITER-like wall2018In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 17, p. 279-283Article in journal (Refereed)
    Abstract [en]

    A tritium imaging plate technique (TIPT) in combination with an electron-probe microscopic analysis (EPMA) were applied to examine tritium (T) retention characteristics in individual dust particles collected in the Joint European Torus with the ITER-like Wall (JET-ILW) after the first campaign in 2011-2012. A lot of carbon pre-existing carbon deposits in the JET-C or released carbon particles from the remaining carbon-fiber components in the JET-ILW. Most of T was retained at the surface of and/or in the C-dominated dust particles. The retention in tungsten, beryllium and other metal-dominated dust particles is relatively lower by a factor of 10-100 in comparison with that in the Cdominated particles.

  • 36. Oya, Y.
    et al.
    Masuzaki, S.
    Tokitani, M.
    Azuma, K.
    Oyaidzu, M.
    Isobe, K.
    Asakura, N.
    Widdowson, A. M.
    Heinola, K.
    Jachmich, S.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Contributors, JET
    Correlation of surface chemical states with hydrogen isotope retention in divertor tiles of JET with ITER-Like Wall2018In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 132, p. 24-28Article in journal (Refereed)
    Abstract [en]

    To understand the fuel retention mechanism correlation of surface chemical states and hydrogen isotope retention behavior determined by XPS (X-ray photoelectron spectroscopy) and TDS (Thermal desorption spectroscopy), respectively, for JET ITER-Like Wall samples from operational period 2011–2012 were investigated. It was found that the deposition layer was formed on the upper part of the inner vertical divertor area. At the inner plasma strike point region, the original surface materials, W or Mo, were found, indicating to an erosion-dominated region, but deposition of impurities was also found. Higher heat load would induce the formation of metal carbide. At the outer horizontal divertor tile, mixed material layer was formed with iron as an impurity. TDS showed the H and D desorption behavior and the major D desorption temperature for the upper part of the inner vertical tile was located at 370 °C and 530 °C. At the strike point region, the D desorption temperature was clearly shifted toward higher release temperatures, indicating the stabilization of D trapping by higher heat load.

  • 37. Pinches, S. D.
    et al.
    Abadie, L.
    Appel, L. C.
    Artaud, J. -F
    Castro, R.
    Van Dellen, L. T. H.
    Van Eester, D.
    Hollocombe, J.
    Hosokawa, M.
    Imbeaux, F.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Khayrutdinov, R. R.
    Kim, S. H.
    Konovalov, S. V.
    Lerche, E.
    Lukash, V. E.
    Lupelli, I.
    Makushok, Y.
    Medvedev, S.
    Muir, D.
    Polevoi, A.
    Sauter, O.
    Schneider, M.
    Urban, J.
    Implementation of plasma simulators and plasma reconstruction workflows in ITER’s Integrated Modelling & Analysis Suite (IMAS)2017In: 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS) , 2017Conference paper (Refereed)
    Abstract [en]

    IMAS has been installed within the majority of the ITER Members and is being used to support ITPA activities including code benchmarking and validation. Sophisticated workflows, such as Plasma Simulators and those describing H&CD systems, have been adapted to IMAS and applied to ITER scenarios. The framework is considered sufficiently flexible to handle all foreseen approaches to the integrated (probabilistic) determination of measurement parameters (and their errors). The inclusion of UDA within the IMAS data Access Layer has allowed the fetching of IDSs directly from experimental databases and the demonstration of the first plasma reconstruction chain. An interactive Live Display in which signals are selected through a web interface has also been demonstrated. 

  • 38. Pokol, G. I.
    et al.
    Aradi, M.
    Erdos, B.
    Papp, G.
    Hadar, A.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Coster, D.
    Kalupin, D.
    Strand, P.
    Ferreira, J.
    Development of the runaway electron modelling capabilities of the European transport simulator2017In: 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS) , 2017Conference paper (Refereed)
  • 39.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Fusion Neutrons: Tritium Breeding and Impact on Wall Materials and Components of Diagnostic Systems2019In: Journal of fusion energy, ISSN 0164-0313, E-ISSN 1572-9591, Vol. 38, no 3-4, p. 315-329Article in journal (Refereed)
    Abstract [en]

    A concise overview is given on the impact of fusion neutrons on various classes of materials applied in reactor technology: plasma-facing, structural and functional tested for tritium production and for diagnostic systems. Tritium breeding in the reactor blanket, fuel cycle and separation of hydrogen isotopes are described together with issues related to primary (tritium) and induced radioactivity. Neutron-induced damage and degradation of material properties are addressed. Material testing under neutron fluxes and safety issues associated with handling components in the radioactive environment are described. A comprehensive list of references to monographs and research papers is included to help navigation in literature.

  • 40. Saarelma, S.
    et al.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Bilkova, P.
    Challis, C. D.
    Chankin, A.
    Fridström, Richard
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Garzotti, L.
    Horvath, L.
    Maggi, C. F.
    Contributors, J E T
    Self-consistent pedestal prediction for JET-ILW in preparation of the DT campaign2019In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 26, no 7, article id 072501Article in journal (Refereed)
    Abstract [en]

    The self-consistent core-pedestal prediction model of a combination of EPED1 type pedestal prediction and a simple stiff core transport model is able to predict Type I ELMy (edge localized mode) pedestals of a large JET-ILW (ITER-like wall) database at the similar accuracy as is obtained when the experimental global plasma β is used as input. The neutral penetration model [R. J. Groebner et al., Phys. Plasmas 9, 2134 (2002)] with corrections that take into account variations due to gas fueling and plasma triangularity is able to predict the pedestal density with an average error of 15%. The prediction of the pedestal pressure in hydrogen plasma that has higher core heat diffusivity compared to a deuterium plasma with similar heating and fueling agrees with the experiment when the isotope effect on the stability, the increased diffusivity, and outward radial shift of the pedestal are included in the prediction. However, the neutral penetration model that successfully predicts the deuterium pedestal densities fails to predict the isotope effect on the pedestal density in hydrogen plasmas.

  • 41.
    Scheffel, Jan
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Free Will of an Ontologically Open MindManuscript (preprint) (Other academic)
    Abstract [en]

    Combining elements from algorithmic information theory and quantum mechanics, it has earlier been argued that consciousness is epistemically and ontologically emergent. Accordingly, consciousness is irreducible to neural low-level states, in spite of assuming causality and supervenience on these states. The mind-body problem is thus found to be unsolvable. In this paper the implications on free will is studied. In the perspective of a modified definition of free will, enabling scientific decidability, the ontological character of interactions of the cortical neural network is discussed. Identifying conscious processes as ontologically open, it is asserted that conscious states are indeterminable in principle. We argue that this leads to freedom of the will.

  • 42.
    Scheffel, Jan
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    On the Solvability of the Mind-Body ProblemManuscript (preprint) (Other academic)
    Abstract [en]

    The mind-body problem is analyzed in a physicalist perspective. By combining the concepts of emergence and algorithmic information theory in a thought experiment employing a basic nonlinear process, it is shown that epistemically strongly emergent properties may develop in a physical system. Turning to the significantly more complex neural network of the brain it is subsequently argued that consciousness is epistemically emergent. Thus reductionist understanding of consciousness appears not possible; the mind-body problem does not have a reductionist solution. The ontologically emergent character of consciousness is then identified from a combinatorial analysis relating to universal limits set by quantum mechanics, implying that consciousness is fundamentally irreducible to low-level phenomena.

  • 43.
    Scheffel, Jan
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    On the Solvability of the Mind–Body Problem2019In: Axiomathes, ISSN 1122-1151, E-ISSN 1572-8390Article in journal (Refereed)
    Abstract [en]

    The mind–body problem is analyzed in a physicalist perspective. By combining the concepts of emergence and algorithmic information theory in a thought experiment, employing a basic nonlinear process, it is shown that epistemologically emergent properties may develop in a physical system. Turning to the signi cantly more com- plex neural network of the brain it is subsequently argued that consciousness is epis- temologically emergent. Thus reductionist understanding of consciousness appears not possible; the mind–body problem does not have a reductionist solution. The ontologically emergent character of consciousness is then identi ed from a com- binatorial analysis relating to universal limits set by quantum mechanics, implying that consciousness is fundamentally irreducible to low-level phenomena.

  • 44.
    Scheffel, Jan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Lindvall, Kristoffer
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Optimizing Time-Spectral Solution of Initial-Value Problems2018In: American Journal of Computational Mathematics, ISSN 2161-1203, E-ISSN 2161-1211, Vol. 8, no 1, p. 7-26, article id 82900Article in journal (Refereed)
    Abstract [en]

    Time-spectral solution of ordinary and partial differential equations is often regarded as an inefficient approach. The associated extension of the time domain, as compared to finite difference methods, is believed to result in uncomfortably many numerical operations and high memory requirements. It is shown in this work that performance is substantially enhanced by the introduction of algorithms for temporal and spatial subdomains in combination with sparse matrix methods. The accuracy and efficiency of the recently developed time spectral, generalized weighted residual method (GWRM) are compared to that of the explicit Lax-Wendroff and implicit Crank-Nicolson methods. Three initial-value PDEs are employed as model problems; the 1D Burger equation, a forced 1D wave equation and a coupled system of 14 linearized ideal magnetohydrodynamic (MHD) equations. It is found that the GWRM is more efficient than the time-stepping methods at high accuracies. The advantageous scalings Nt**1.0*Ns**1.43 and Nt**0.0*Ns**1.08 were obtained for CPU time and memory requirements, respectively, with Nt and Ns denoting the number of temporal and spatial subdomains. For time-averaged solution of the two-time-scales forced wave equation, GWRM performance exceeds that of the finite difference methods by an order of magnitude both in terms of CPU time and memory requirement. Favorable subdomain scaling is demonstrated for the MHD equations, indicating a potential for efficient solution of advanced initial-value problems in, for example, fluid mechanics and MHD. 

  • 45.
    Scheffel, Jan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Lindvall, Kristoffer
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    SIR—An efficient solver for systems of equations2018In: Software Quality Professional, ISSN 1522-0540, Vol. 7, p. 59-62Article in journal (Refereed)
    Abstract [en]

    The Semi-Implicit Root solver (SIR) is an iterative method for globally convergent solution of systems of nonlinear equations. We here present MATLAB and MAPLE codes for SIR, that can be easily implemented in any application where linear or nonlinear systems of equations need be solved efficiently. The codes employ recently developed efficient sparse matrix algorithms and improved numerical differentiation. SIR convergence is quasi-monotonous and approaches second order in the proximity of the real roots. Global convergence is usually superior to that of Newton's method, being a special case of the method. Furthermore the algorithm cannot land on local minima, as may be the case for Newton's method with line search. 

  • 46.
    Sheikh, U. A.
    et al.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Dunne, M.
    Max Planck Inst Plasma Phys, Garching, Germany..
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Blanchard, P.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Duval, B. P.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Labit, B.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Merle, A.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Sauter, O.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Theiler, C.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Tsui, C.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Pedestal structure and energy confinement studies on TCV2019In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 1, article id 014002Article in journal (Refereed)
    Abstract [en]

    High external gas injection rates are foreseen for future devices to reduce divertor heat loads and this can influence pedestal stability. Fusion yield has been estimated to vary as strongly as T-e,ped(2) so an understanding of the underlying pedestal physics in the presence of additional fuelling and seeding is required. To address this, a database scanning plasma triangularity, fuelling and nitrogen seeding rates in neutral beam (NBH) heated ELM-y H-mode plasmas was constructed on TCV. Low nitrogen seeding was observed to increase pedestal top pressure but all other gas injection rates led to a decrease. Lower triangularity discharges were found to be less sensitive to variations in gas injection rates. No clear trend was measured between plasma top P-e and stored energy which is attributed to the non-stiffness of core plasma pressure profiles. Peeling ballooning stability analysis put these discharges close to the ideal MHD stability boundary. A constant for D in the relation pedestal width w = D root beta(Ped)(theta), was not found. Experimentally inferred values of D were used in EPED1 simulations and gave good agreement for pedestal width. Pedestal height agreed well for high triangularity but was overestimated for low triangularity. IPED simulations showed that relative shifts in pedestal position were contributing significantly to the pedestal height and were able to reproduce the measured profiles more accurately.

  • 47. Sheikh, U. A.
    et al.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Blanchard, P.
    Dunne, M.
    Duval, B. P.
    Merle, A.
    Meyer, H.
    Theiler, C.
    Verhaegh, K.
    H-Mode pedestal studies with seeding and fuelling on TCV2017In: 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS) , 2017Conference paper (Refereed)
  • 48. Sipilä, S.
    et al.
    Varje, J.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Kurki-Suonio, T.
    Galdón Quiroga, J.
    González Martín, J.
    Monte Carlo ion cyclotron heating and fast ion loss detector simulations in ASDEX Upgrade2018In: 45th EPS Conference on Plasma Physics, EPS 2018, European Physical Society (EPS) , 2018, p. 773-776Conference paper (Refereed)
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    Stefániková, Estera
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Nunes, I.
    Rimini, F.
    Garzotti, L.
    Lerche, E.
    Lomas, P.
    Saarelma, S.
    Loarte, A.
    Drewelow, P.
    Kruezi, U.
    Lomanowski, B.
    De La Luna, E.
    Meneses, L.
    Peterka, M.
    Viola, B.
    Giroud, C.
    Maggi, C.
    Pedestal structure in high current scenarios in JET-ILW and JET-C2017In: 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS) , 2017Conference paper (Refereed)
  • 50. Stefániková, Estera
    et al.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Nunes, I.
    Rimini, F.
    Garzotti, L.
    Lerche, E.
    Lomas, P.
    Saarelma, S.
    Loarte, A.
    Drewelow, P.
    Kruezi, U.
    Lomanowski, B.
    De La Luna, E.
    Meneses, L.
    Peterka, M.
    Viola, B.
    Giroud, C.
    Maggi, C.
    Pedestal structure in high current scenarios in JET-ILW and JET-C2017In: 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS) , 2017Conference paper (Refereed)
12 1 - 50 of 77
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