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  • 1.
    Yordanova, Emiliya
    et al.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Voros, Zoltan
    Austrian Acad Sci, Space Res Inst, Graz, Austria.;Res Ctr Astron & Earth Sci, Geodet & Geophys Inst, Sopron, Hungary..
    Raptis, Savvas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Karlsson, Tomas
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Current Sheet Statistics in the Magnetosheath2020In: FRONTIERS IN ASTRONOMY AND SPACE SCIENCES, ISSN 2296-987X, Vol. 7, article id 2Article in journal (Refereed)
    Abstract [en]

    The magnetosheath (MSH) plasma turbulence depends on the structure and properties of the bow shock (BS). Under quasi-parallel (Q(||)) and quasi-perpendicular (Q(perpendicular to)) BS configurations the electromagnetic field and plasma quantities possess quite distinct behavior, e.g., being highly variable and structured in the Q(||) case. Previous studies have reported abundance of thin current sheets (with typical scales of the order of the plasma kinetic scales) in the Q(||) MSH, associated with magnetic reconnection, plasma heating, and acceleration. Here we use multipoint observations from Magnetospheric MultiScale (MMS) mission, where for the first time a comparative study of discontinuities and current sheets in both MSH geometries at very small spacecraft separation (of the order of the ion inertial length) is performed. In Q(||) MSH the current density distribution is characterized by a heavy tail, populated by strong currents. There is high correlation between these currents and the discontinuities associated with large magnetic shears. Whilst, this seems not to be the case in Q(perpendicular to) MSH, where current sheets are virtually absent. We also investigate the effect of the discontinuities on the scaling of electromagnetic fluctuations in the MHD range and in the beginning of the kinetic range. There are two (one) orders of magnitude higher power in the magnetic (electric) field fluctuations in the Q(||) MSH, as well as different spectral scaling, in comparison to the Q(perpendicular to) MSH configuration. This is an indication that the incoming solar wind turbulence is completely locally reorganized behind Q(perpendicular to) BS while even though modified by Q(||) BS geometry, the downstream turbulence properties are still reminiscent to the ones upstream, the latter confirming previous observations. We show also that the two geometries are associated with different temperature anisotropies, plasma beta, and compressibility, where the Q(perpendicular to) MSH is unstable to mostly mirror mode plasma instability, while the Q(||) MSH is unstable also to oblique and parallel fire-hose, and ion-cyclotron instabilities.

  • 2. Eriksson, E.
    et al.
    Vaivads, Andris
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics. Swedish Institute of Space Physics, Uppsala, Sweden.
    Alm, L.
    Graham, D. B.
    Khotyaintsev, Y. V.
    André, M.
    Electron Acceleration in a Magnetotail Reconnection Outflow Region Using Magnetospheric MultiScale Data2020In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 47, no 1, article id e2019GL085080Article in journal (Refereed)
    Abstract [en]

    We study Magnetospheric MultiScale observations in the outflow region of magnetotail reconnection. We estimate the power density converted via the three fundamental electron acceleration mechanisms: Fermi, betatron, and parallel electric fields. The dominant mechanism, both on average and the peak values, is Fermi acceleration with a peak power density of about +200 pW/m3. The magnetic field curvature during the most intense Fermi acceleration is comparable to the electron gyroradius, consistent with efficient electron scattering. The peak power densities due to the betatron acceleration are a factor of 3 lower than that for the Fermi acceleration, the average betatron acceleration is close to zero and slightly negative. The contribution from parallel electric fields is significantly smaller than those from the Fermi and betatron acceleration. However, the observational uncertainties in the parallel electric field measurement prevent further conclusions. There is a strong variation in the power density on a characteristic ion time scale.

  • 3. Li, W. Y.
    et al.
    Graham, D. B.
    Khotyaintsev, Y. V.
    Vaivads, Andris
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    André, M.
    Min, K.
    Liu, K.
    Tang, B. B.
    Wang, C.
    Fujimoto, K.
    Norgren, C.
    Toledo-Redondo, S.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Ergun, R. E.
    Torbert, R. B.
    Rager, A. C.
    Dorelli, J. C.
    Gershman, D. J.
    Giles, B. L.
    Lavraud, B.
    Plaschke, F.
    Magnes, W.
    Le Contel, O.
    Russell, C. T.
    Burch, J. L.
    Electron Bernstein waves driven by electron crescents near the electron diffusion region2020In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 11, no 1, article id 141Article in journal (Refereed)
    Abstract [en]

    The Magnetospheric Multiscale (MMS) spacecraft encounter an electron diffusion region (EDR) of asymmetric magnetic reconnection at Earth’s magnetopause. The EDR is characterized by agyrotropic electron velocity distributions on both sides of the neutral line. Various types of plasma waves are produced by the magnetic reconnection in and near the EDR. Here we report large-amplitude electron Bernstein waves (EBWs) at the electron-scale boundary of the Hall current reversal. The finite gyroradius effect of the outflow electrons generates the crescent-shaped agyrotropic electron distributions, which drive the EBWs. The EBWs propagate toward the central EDR. The amplitude of the EBWs is sufficiently large to thermalize and diffuse electrons around the EDR. The EBWs contribute to the cross-field diffusion of the electron-scale boundary of the Hall current reversal near the EDR.

  • 4.
    Li, W. Y.
    et al.
    Chinese Acad Sci, State Key Lab Space Weather, Natl Space Sci Ctr, Beijing 100190, Peoples R China.;Swedish Inst Space Phys, SE-75121 Uppsala, Sweden.;Macau Univ Sci & Technol, State Key Lab Lunar & Planetary Sci, Macau, Peoples R China..
    Graham, D. B.
    Swedish Inst Space Phys, SE-75121 Uppsala, Sweden..
    Khotyaintsev, Yu. V.
    Swedish Inst Space Phys, SE-75121 Uppsala, Sweden..
    Vaivads, Andris
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Andre, M.
    Swedish Inst Space Phys, SE-75121 Uppsala, Sweden..
    Min, K.
    Chungnam Natl Univ, Dept Astron & Space Sci, Daejeon 34134, South Korea..
    Liu, K.
    Southern Univ Sci & Technol, Dept Earth & Space Sci, Shenzhen 518055, Peoples R China..
    Tang, B. B.
    Chinese Acad Sci, State Key Lab Space Weather, Natl Space Sci Ctr, Beijing 100190, Peoples R China..
    Wang, C.
    Chinese Acad Sci, State Key Lab Space Weather, Natl Space Sci Ctr, Beijing 100190, Peoples R China..
    Fujimoto, K.
    Beihang Univ, Sch Space & Environm, Beijing 100191, Peoples R China..
    Norgren, C.
    Univ Bergen, Dept Phys & Technol, N-5020 Bergen, Norway..
    Toledo-Redondo, S.
    Univ Toulouse, Inst Rech Astrophys & Planetol, CNRS, UPS,CNES, F-31028 Toulouse, France.;Univ Murcia, Dept Electromagnetism & Elect, Murcia 30003, Spain..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Ergun, R. E.
    Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA..
    Torbert, R. B.
    Univ New Hampshire, Ctr Space Sci, Durham, NH 03824 USA..
    Rager, A. C.
    Catholic Univ Amer, Washington, DC 20064 USA.;NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.;Univ Maryland, Dept Astron, College Pk, MD 20742 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, CNRS, UPS,CNES, F-31028 Toulouse, France..
    Plaschke, F.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria..
    Magnes, W.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria..
    Le Contel, O.
    Univ Paris Sud, Lab Phys Plasmas, Ecole Polytech, CNRS,Sorbonne Univ,Observ Paris, F-75252 Paris, France..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Electron Bernstein waves driven by electron crescents near the electron diffusion region2020In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 11, no 1, article id 141Article in journal (Refereed)
    Abstract [en]

    The Magnetospheric Multiscale (MMS) spacecraft encounter an electron diffusion region (EDR) of asymmetric magnetic reconnection at Earth's magnetopause. The EDR is characterized by agyrotropic electron velocity distributions on both sides of the neutral line. Various types of plasma waves are produced by the magnetic reconnection in and near the EDR. Here we report large-amplitude electron Bernstein waves (EBWs) at the electron-scale boundary of the Hall current reversal. The finite gyroradius effect of the outflow electrons generates the crescent-shaped agyrotropic electron distributions, which drive the EBWs. The EBWs propagate toward the central EDR. The amplitude of the EBWs is sufficiently large to thermalize and diffuse electrons around the EDR. The EBWs contribute to the cross-field diffusion of the electron-scale boundary of the Hall current reversal near the EDR.

  • 5.
    Khotyaintsev, Yu, V
    et al.
    Swedish Inst Space Phys, S-75121 Uppsala, Sweden..
    Graham, D. B.
    Swedish Inst Space Phys, S-75121 Uppsala, Sweden..
    Steinvall, K.
    Swedish Inst Space Phys, S-75121 Uppsala, Sweden..
    Alm, L.
    Swedish Inst Space Phys, S-75121 Uppsala, Sweden..
    Vaivads, Andris
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Johlander, A.
    Univ Helsinki, Dept Phys, Helsinki 00014, Finland..
    Norgren, C.
    Univ Bergen, N-5007 Bergen, Norway..
    Li, W.
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing 100190, Peoples R China..
    Divin, A.
    St Petersburg State Univ, Earth Phys Dept, St Petersburg 198504, Russia..
    Fu, H. S.
    Beihang Univ, Sch Space & Environm, Beijing 100083, Peoples R China..
    Hwang, K-J
    Southwest Res Inst, San Antonio, TX 78228 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78228 USA..
    Ahmadi, N.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA..
    Le Contel, O.
    Univ Paris Sud, Sorbonne Univ, Ecole Polytech, Lab Phys Plasmas,CNRS, F-75252 Paris 05, France.;Observ Paris, F-75252 Paris 05, France..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Code 916, Greenbelt, MD 20771 USA..
    Russell, C. T.
    Univ Calif Los Angeles, Los Angeles, CA 90095 USA..
    Torbert, R. B.
    Univ New Hampshire, Durham, NH 03824 USA..
    Electron Heating by Debye-Scale Turbulence in Guide-Field Reconnection2020In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 124, no 4, article id 045101Article in journal (Refereed)
    Abstract [en]

    We report electrostatic Debye-scale turbulence developing within the diffusion region of asymmetric magnetopause reconnection with amoderate guide field using observations by the Magnetospheric Multiscale mission. We show that Buneman waves and beam modes cause efficient and fast thermalization of the reconnection electron jet by irreversible phase mixing, during which the jet kinetic energy is transferred into thermal energy. Our results show that the reconnection diffusion region in the presence of a moderate guide field is highly turbulent, and that electrostatic turbulence plays an important role in electron heating.

  • 6.
    Amano, T.
    et al.
    Univ Tokyo, Dept Earth & Planetary Sci, Tokyo 1130033, Japan..
    Katou, T.
    Univ Tokyo, Dept Earth & Planetary Sci, Tokyo 1130033, Japan..
    Kitamura, N.
    Univ Tokyo, Dept Earth & Planetary Sci, Tokyo 1130033, Japan..
    Oka, M.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Matsumoto, Y.
    Chiba Univ, Dept Phys, Chiba 2638522, Japan..
    Hoshino, M.
    Univ Tokyo, Dept Earth & Planetary Sci, Tokyo 1130033, Japan..
    Saito, Y.
    Inst Space & Astronaut Sci, Sagamihara, Kanagawa 2525210, Japan..
    Yokota, S.
    Osaka Univ, Dept Earth & Space Sci, Toyonaka, Osaka 5600043, Japan..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA..
    Le Contel, O.
    Univ Paris Sud, Sorbonne Univ, CNRS, Lab Phys Plasmas,Ecole Polytech,Obs Paris, F-75252 Paris, France..
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Turner, D. L.
    Aerosp Corp, Space Sci Dept, El Segundo, CA 90245 USA..
    Fennell, J. F.
    Aerosp Corp, Space Sci Dept, El Segundo, CA 90245 USA..
    Blake, J. B.
    Aerosp Corp, Space Sci Dept, El Segundo, CA 90245 USA..
    Observational Evidence for Stochastic Shock Drift Acceleration of Electrons at the Earth's Bow Shock2020In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 124, no 6, article id 065101Article in journal (Refereed)
    Abstract [en]

    The first-order Fermi acceleration of electrons requires an injection of electrons into a mildly relativistic energy range. However, the mechanism of injection has remained a puzzle both in theory and observation. We present direct evidence for a novel stochastic shock drift acceleration theory for the injection obtained with Magnetospheric Multiscale observations at the Earth's bow shock. The theoretical model can explain electron acceleration to mildly relativistic energies at high-speed astrophysical shocks, which may provide a solution to the long-standing issue of electron injection.

  • 7.
    Volwerk, Martin
    et al.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Goetz, Charlotte
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterr Phys, Braunschweig, Germany.;European Space Agcy, Estec, Keplerlaan 1, NL-2201 AZ Noordwijk, Netherlands..
    Plaschke, Ferdinand
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Karlsson, Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Heyner, Daniel
    Tech Univ Carolo Wilhelmina Braunschweig, Inst Geophys & Extraterr Phys, Braunschweig, Germany..
    Anderson, Brian
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    On the magnetic characteristics of magnetic holes in the solar wind between Mercury and Venus2020In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 38, no 1, p. 51-60Article in journal (Refereed)
    Abstract [en]

    The occurrence rate of linear and pseudo magnetic holes has been determined during MESSENGER's cruise phase starting from Venus (2007) and arriving at Mercury (2011). It is shown that the occurrence rate of linear magnetic holes, defined as a maximum of 10 degrees rotation of the magnetic field over the hole, slowly decreases from Mercury to Venus. The pseudo magnetic holes, defined as a rotation between 10 and 45 degrees over the hole, have mostly a constant occurrence rate.

  • 8.
    Gumbel, Jorg
    et al.
    Stockholm Univ, Dept Meteorol MISU, Stockholm, Sweden..
    Megner, Linda
    Stockholm Univ, Dept Meteorol MISU, Stockholm, Sweden..
    Christensen, Ole Martin
    Stockholm Univ, Dept Meteorol MISU, Stockholm, Sweden.;Chalmers Univ Technol, Earth & Space Sci, Gothenburg, Sweden..
    Ivchenko, Nickolay
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Murtagh, Donal P.
    Chalmers Univ Technol, Earth & Space Sci, Gothenburg, Sweden..
    Chang, Seunghyuk
    Ctr Integrated Smart Sensors, KAIST Dogok Campus, Seoul, South Korea..
    Dillner, Joachim
    Stockholm Univ, Dept Meteorol MISU, Stockholm, Sweden..
    Ekebrand, Terese
    Omnisys Instruments AB, August Barks Gata 6B, Vastra Frolunda, Sweden..
    Giono, Gabriel
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Hammar, Arvid
    Chalmers Univ Technol, Dept Microtechnol & Nanosci, Gothenburg, Sweden.;Omnisys Instruments AB, August Barks Gata 6B, Vastra Frolunda, Sweden..
    Hedin, Jonas
    Stockholm Univ, Dept Meteorol MISU, Stockholm, Sweden..
    Karlsson, Bodil
    Stockholm Univ, Dept Meteorol MISU, Stockholm, Sweden..
    Krus, Mikael
    Omnisys Instruments AB, August Barks Gata 6B, Vastra Frolunda, Sweden..
    Li, Anqi
    Chalmers Univ Technol, Earth & Space Sci, Gothenburg, Sweden..
    McCallion, Steven
    Omnisys Instruments AB, August Barks Gata 6B, Vastra Frolunda, Sweden..
    Olentsenko, Georgi
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Pak, Soojong
    Kyung Hee Univ, Sch Space Res, Yongin, South Korea..
    Park, Woojin
    Kyung Hee Univ, Sch Space Res, Yongin, South Korea..
    Rouse, Jordan
    Omnisys Instruments AB, August Barks Gata 6B, Vastra Frolunda, Sweden..
    Stegman, Jacek
    Stockholm Univ, Dept Meteorol MISU, Stockholm, Sweden..
    Witt, Georg
    Stockholm Univ, Dept Meteorol MISU, Stockholm, Sweden..
    The MATS satellite mission - gravity wave studies by Mesospheric Airglow/Aerosol Tomography and Spectroscopy2020In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 20, no 1, p. 431-455Article in journal (Refereed)
    Abstract [en]

    Global three-dimensional data are a key to understanding gravity waves in the mesosphere and lower thermosphere. MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) is a new Swedish satellite mission that addresses this need. It applies space-borne limb imaging in combination with tomographic and spectroscopic analysis to obtain gravity wave data on relevant spatial scales. Primary measurement targets are O-2 atmospheric band dayglow and nightglow in the near infrared, and sunlight scattered from noctilucent clouds in the ultraviolet. While tomography provides horizontally and vertically resolved data, spectroscopy allows analysis in terms of mesospheric temperature, composition, and cloud properties. Based on these dynamical tracers, MATS will produce a climatology on wave spectra during a 2-year mission. Major scientific objectives include a characterization of gravity waves and their interaction with larger-scale waves and mean flow in the mesosphere and lower thermosphere, as well as their relationship to dynamical conditions in the lower and upper atmosphere. MATS is currently being prepared to be ready for a launch in 2020. This paper provides an overview of scientific goals, measurement concepts, instruments, and analysis ideas.

  • 9.
    Toneli, D. A.
    et al.
    Univ Fed Sao Paulo, Dept Sci & Technol, BR-12231280 Sao Jose Dos Campos, Brazil..
    Pessoa, R. S.
    Technol Inst Aeronaut, Dept Phys, BR-12228900 Sao Jose Dos Campos, Brazil..
    Roberto, M.
    Technol Inst Aeronaut, Dept Phys, BR-12228900 Sao Jose Dos Campos, Brazil..
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland.
    A global model study of low pressure high density CF4 discharge2019In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 28, no 2, article id 025007Article in journal (Refereed)
    Abstract [en]

    We present a revised reaction set for low pressure high density CF4 plasma modelling. A global model (volume averaged) was developed to study a CF4 discharge that includes the neutral species CF4, CF3, CF2, CF, F-2, F, and C, the metastable states CF(a(4)Sigma(-) ) and CF2(B-3(1)), the positive ions CF3+, CF2+, CF+, CF2+, F+ and C+, the negative ions CF3-, F-2(-), and F- and electrons. The main reactions that contribute to the production and loss of each species are pointed out with an emphasis on the radicals CF2, CF and F, the dominant positive ion CF3+, and the dominant negative ion F-. We find wall processes to have a significant influence on the discharge. The density of F-2 is high due to recombination of F atoms at the walls and the losses of the radicals F, CF, and CF3 are mainly through wall recombination. As the pressure is increased, F- becomes the dominant negative charged species. The discharge is found to be weakly electronegative below similar to 10 mTorr and the electronegativity decreases with increased absorbed power.

  • 10.
    Pau, A.
    et al.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland.;Univ Cagliari, Elect & Elect Engn Dept, Piazza DArmi, I-09123 Cagliari, Italy.;Univ Cagliari, Dept Elect & Elect Engn, Piazza Armi 09123, Cagliari, Italy..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    A machine learning approach based on generative topographic mapping for disruption prevention and avoidance at JET2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 10, article id 106017Article in journal (Refereed)
    Abstract [en]

    The need for predictive capabilities greater than 95% with very limited false alarms are demanding requirements for reliable disruption prediction systems in tokamaks such as JET or, in the near future, ITER. The prediction of an upcoming disruption must be provided sufficiently in advance in order to apply effective disruption avoidance or mitigation actions to prevent the machine from being damaged. In this paper, following the typical machine learning workflow, a generative topographic mapping (GTM) of the operational space of JET has been built using a set of disrupted and regularly terminated discharges. In order to build the predictive model, a suitable set of dimensionless, machine-independent, physics-based features have been synthesized, which make use of 1D plasma profile information, rather than simple zero-D time series. The use of such predicting features, together with the power of the GTM in fitting the model to the data, obtains, in an unsupervised way, a 2D map of the multi-dimensional parameter space of JET, where it is possible to identify a boundary separating the region free from disruption from the disruption region. In addition to helping in operational boundaries studies, the GTM map can also be used for disruption prediction exploiting the potential of the developed GTM toolbox to monitor the discharge dynamics. Following the trajectory of a discharge on the map throughout the different regions, an alarm is triggered depending on the disruption risk of these regions. The proposed approach to predict disruptions has been evaluated on a training and an independent test set and achieves very good performance with only one tardive detection and a limited number of false detections. The warning times are suitable for avoidance purposes and, more important, the detections are consistent with physical causes and mechanisms that destabilize the plasma leading to disruptions.

  • 11. Paganini, L.
    et al.
    Villanueva, G. L.
    Roth, Lorenz
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Mandell, A. M.
    Hurford, T. A.
    Retherford, K. D.
    Mumma, M. J.
    A measurement of water vapour amid a largely quiescent environment on Europa2019In: Nature Astronomy, E-ISSN 2397-3366Article in journal (Refereed)
    Abstract [en]

    Previous investigations proved the existence of local density enhancements in Europa’s atmosphere, advancing the idea of a possible origination from water plumes. These measurement strategies, however, were sensitive either to total absorption or atomic emissions, which limited the ability to assess the water content. Here we present direct searches for water vapour on Europa spanning dates from February 2016 to May 2017 with the Keck Observatory. Our global survey at infrared wavelengths resulted in non-detections on 16 out of 17 dates, with upper limits below the water abundances inferred from previous estimates. On one date (26 April 2016) we measured 2,095 ± 658 tonnes of water vapour at Europa’s leading hemisphere. We suggest that the outgassing of water vapour on Europa occurs at lower levels than previously estimated, with only rare localized events of stronger activity.

  • 12.
    Garcia, J.
    et al.
    CEA, IRFM, F-13108 St Paul Les Durance, France.;EUROfus Consortium JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;CEA, IRFM, F-13108 St Paul Les Durance, France..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Fridström, Richard
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Moon, Sunwoo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I
    EUROfus Consortium JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;Natl Ctr Nucl Res NCBJ, PL-05400 Otwock, Poland..
    et al,
    A new mechanism for increasing density peaking in tokamaks: improvement of the inward particle pinch with edge E x B shearing2019In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 10, article id 104002Article in journal (Refereed)
    Abstract [en]

    Developing successful tokamak operation scenarios, as well as confident extrapolation of present-day knowledge requires a rigorous understanding of plasma turbulence, which largely determines the quality of the confinement. In particular, accurate particle transport predictions are essential due to the strong dependence of fusion power or bootstrap current on the particle density details. Here, gyrokinetic turbulence simulations are performed with physics inputs taken from a JET power scan, for which a relatively weak degradation of energy confinement and a significant density peaking is obtained with increasing input power. This way physics parameters that lead to such increase in the density peaking shall be elucidated. While well-known candidates, such as the collisionality, previously found in other studies are also recovered in this study, it is furthermore found that edge E x B shearing may adopt a crucial role by enhancing the inward pinch. These results may indicate that a plasma with rotational shear could develop a stronger density peaking as compared to a non-rotating one, because its inward convection is increased compared to the outward diffusive particle flux as long as this rotation has a significant on E x B flow shear stabilization. The possibly significant implications for future devices, which will exhibit much less torque compared to present day experiments, are discussed.

  • 13.
    Zanca, P.
    et al.
    Univ Padua, Acciaierie Veneto Spa, INFN, Consorzio RFX,CNR,ENEA, Padua, Italy..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    A power-balance model of the density limit in fusion plasmas: application to the L-mode tokamak2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 12, article id 126011Article in journal (Refereed)
    Abstract [en]

    A power-balance model, with radiation losses from impurities and neutrals, gives a unified description of the density limit (DL) of the stellarator, the L-mode tokamak, and the reversed field pinch (RFP). The model predicts a Sudo-like scaling for the stellarator, a Greenwald- like scaling, alpha I-p(8/9), for the RFP and the ohmic tokamak, a mixed scaling, alpha (PIp4/9)-I-4/9, for the additionally heated L-mode tokamak. In a previous paper (Zanca et al 2017 Nucl. Fusion 57 056010) the model was compared with ohmic tokamak, RFP and stellarator experiments. Here, we address the issue of the DL dependence on heating power in the L-mode tokamak. Experimental data from high-density disrupted L-mode discharges performed at JET, as well as in other machines, arc taken as a term of comparison. The model fits the observed maximum densities better than the pure Greenwald limit.

  • 14.
    Pamela, S.
    et al.
    JET, EUROfus Consortium, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;CCFE, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;CCFE Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    A wall-aligned grid generator for non-linear simulations of MHD instabilities in tokamak plasmas2019In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 243, p. 41-50Article in journal (Refereed)
    Abstract [en]

    Block-structured mesh generation techniques have been well addressed in the CFD community for automobile and aerospace studies, and their applicability to magnetic fusion is highly relevant, due to the complexity of the plasma-facing wall structures inside a tokamak device. Typically applied to non-linear simulations of MHD instabilities relevant to magnetically confined fusion, the JOREK code was originally developed with a 2D grid composed of isoparametric bi-cubic Bezier finite elements, that are aligned to the magnetic equilibrium of tokamak plasmas (the third dimension being represented by Fourier harmonics). To improve the applicability of these simulations, the grid-generator has been generalised to provide a robust extension method, using a block-structured mesh approach, which allows the simulations of arbitrary domains of tokamak vacuum vessels. Such boundary-aligned grids require the adaptation of boundary conditions along the edge of the new domain. Demonstrative non-linear simulations of plasma edge instabilities are presented to validate the robustness of the new grid, and future potential physics applications for tokamak plasmas are discussed. The methods presented here may be of interest to the wider community, beyond tokamak physics, wherever imposing arbitrary boundaries to quadrilateral finite elements is required.

  • 15.
    Vignitchouk, Ladislas
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Pitts, R. A.
    ITER Org, Route Vinon Sur Verdon,CS 90 046, F-13067 St Paul Les Durance, France..
    De Temmerman, G.
    ITER Org, Route Vinon Sur Verdon,CS 90 046, F-13067 St Paul Les Durance, France..
    Lehnen, M.
    ITER Org, Route Vinon Sur Verdon,CS 90 046, F-13067 St Paul Les Durance, France..
    Kiramov, D.
    Natl Res Ctr, Kurchatov Inst, Pl Kurchatova 1, Moscow 123182, Russia.;Natl Res Nucl Univ MEPhI, Moscow 115409, Russia..
    Accumulation of beryllium dust in ITER diagnostic ports after off-normal events2019In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 20, article id UNSP 100684Article in journal (Refereed)
    Abstract [en]

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

  • 16.
    Murari, A.
    et al.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Univ Padua, Acciaierie Venete SpA, Ist Nazl Fis Nucl, Consorzio RFX,CNR,ENEA, Corso Stati Uniti 4, I-35127 Padua, Italy.;EUROfus Consortium JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy.;Culham Sci Ctr, EUROfus Programme Management Unit, Culham OX14 3DB, England..
    Lungaroni, M.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Univ Roma Tor Vergata, Dept Ind Engn, Via Politecn 1, Rome, Italy.;EUROfus Consortium JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;Univ Roma Tor Vergata, Via Politecn 1, Rome, Italy..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Fridström, Richard
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Moon, Sunwoo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I
    EUROfus Consortium JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;Natl Ctr Nucl Res NCBJ, PL-05400 Otwock, Poland..
    et al,
    Adaptive learning for disruption prediction in non-stationary conditions2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 8, article id 086037Article in journal (Refereed)
    Abstract [en]

    For many years, machine learning tools have proved to be very powerful disruption predictors in tokamaks. On the other hand, the vast majority of the techniques deployed assume that the input data is independent and is sampled from exactly the same probability distribution for the training set, the test set and the final real time deployment. This hypothesis is certainly not verified in practice, since the experimental programmes evolve quite rapidly, resulting typically in ageing of the predictors and consequent suboptimal performance. This paper describes various adaptive training strategies that have been tested to maintain the performance of disruption predictors in non-stationary conditions. The proposed approaches have been implemented using new ensembles of classifiers, explicitly developed for the present application. The improvements in performance are unquestionable and, given the difficulties encountered so far in translating predictors from one device to another, the proposed adaptive methods from scratch can therefore be considered a useful option in the arsenal of alternatives envisaged for the next generation of devices, particularly at the very beginning of their operation.

  • 17.
    Henderson, S. S.
    et al.
    CCFE, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;Univ Strathclyde, Dept Phys & Appl Phys, Glasgow G4 ONG, Lanark, Scotland..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    An assessment of nitrogen concentrations from spectroscopic measurements in the JET and ASDEX upgrade divertor2019In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 18, p. 147-152Article in journal (Refereed)
    Abstract [en]

    The impurity concentration in the tokamak divertor plasma is a necessary input for predictive scaling of divertor detachment, however direct measurements from existing tokamaks in different divertor plasma conditions are limited. To address this, we have applied a recently developed spectroscopic N II line ratio technique for measuring the N concentration in the divertor to a range of H-mode and L-mode plasma from the ASDEX Upgrade and JET tokamaks, respectively. The results from both devices show that as the power crossing the separatrix, P-sep, is increased under otherwise similar core conditions (e.g. density), a higher N concentration is required to achieve the same detachment state. For example, the N concentrations at the start of detachment increase from approximate to 2% to approximate to 9% as P-sep, is increased from approximate to 2.5 MW to approximate to 7 MW. These results tentatively agree with scaling law predictions (e.g. Goldston et al.) motivating a further study examining the parameters which affect the N concentration required to reach detachment. Finally, the N concentrations from spectroscopy and the ratio of D and N gas valve fluxes agree within experimental uncertainty only when the vessel surfaces are fully-loaded with N.

  • 18.
    Ström, Petter
    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.
    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.
    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.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tholerus, Simon
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. 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.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Johnson, T.
    Stefanikova, E.
    Zhou, Y.
    Zychor, I.
    et al.,
    Analysis of deposited layers with deuterium and impurity elements on samples from the divertor of JET with ITER-like wall2019In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 516, p. 202-213Article in journal (Refereed)
    Abstract [en]

    Inconel-600 blocks and stainless steel covers for quartz microbalance crystals from remote corners in the JET-ILW divertor were studied with time-of-flight elastic recoil detection analysis and nuclear reaction analysis to obtain information about the areal densities and depth profiles of elements present in deposited material layers. Surface morphology and the composition of dust particles were examined with scanning electron microscopy and energy-dispersive X-ray spectroscopy. The analyzed components were present in JET during three ITER-like wall campaigns between 2010 and 2017. Deposited layers had a stratified structure, primarily made up of beryllium, carbon and oxygen with varying atomic fractions of deuterium, up to more than 20%. The range of carbon transport from the ribs of the divertor carrier was limited to a few centimeters, and carbon/deuterium co-deposition was indicated on the Inconel blocks. High atomic fractions of deuterium were also found in almost carbon-free layers on the quartz microbalance covers. Layer thicknesses up to more than 1 micrometer were indicated, but typical values were on the order of a few hundred nanometers. Chromium, iron and nickel fractions were less than or around 1% at layer surfaces while increasing close to the layer-substrate interface. The tungsten fraction depended on the proximity of the plasma strike point to the divertor corners. Particles of tungsten, molybdenum and copper with sizes less than or around 1 micrometer were found. Nitrogen, argon and neon were present after plasma edge cooling and disruption mitigation. Oxygen-18 was found on component surfaces after injection, indicating in-vessel oxidation. Compensation of elastic recoil detection data for detection efficiency and ion-induced release of deuterium during the measurement gave quantitative agreement with nuclear reaction analysis, which strengthens the validity of the results.

  • 19.
    Causa, F.
    et al.
    CNR, Ist Fis Plasma Piero Caldirola, Via R Cozzi 53, I-20125 Milan, Italy.;CNR, Ist Fis Plasma, Via R Cozzi 53, I-20125 Milan, Italy..
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Zito, P.
    ENEA, Fus & Nucl Safety Dept, CR Frascati, Via E Fermi 45, I-00044 Rome, Italy..
    Analysis of runaway electron expulsion during tokamak instabilities detected by a single-channel Cherenkov probe in FTU2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 4, article id 046013Article in journal (Refereed)
    Abstract [en]

    The expulsion of runaway electrons (REs) during different types of tokamak instabilities is analysed by means of a Cherenkov probe inserted into the scrape-off layer of the FTU tokamak. One such type of instability, the well-known tearing mode, is involved in disruptive plasma termination events, during which the risk of RE avalanche multiplication is highest. The second type, known as anomalous Doppler instability, influences RE dynamics by enhancing pitch angle scattering. Three scenarios are analysed here, characterised by different RE generation rates and mechanisms. The main conclusions are drawn from correlations between the Cherenkov probe and other diagnostics. In particular, the Cherenkov probe permits the detection of fast electron expulsion with a high level of detail, presenting peaks with 100% signal contrast during tearing mode growth and rotation, and sub-peak structures reflecting the interplay between the magnetic island formed by the tearing mode, RE diffusion during island rotation and the geometry of obstacles in the vessel. Correlations between the Cherenkov signal, hard x-ray emission and electron cyclotron emission reveal the impulsive development of the anomalous Doppler instability with instability rise time in the microsecond scale resolved by the high time-resolution of the Cherenkov probe.

  • 20.
    Romazanov, J.
    et al.
    Forschungszentrum Julich, Inst Energie & Klimaforsch, Plasmaphys, Partner Trilateral Euregio Cluster TEC, D-5242 Julich, Germany.;Forschungszentrum Julich GmbH, Inst Energie & Klimaforsch Plasmaphys, D-52425 Julich, Germany..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    Beryllium global erosion and deposition at JET-ILW simulated with ERO2.02019In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 18, p. 331-338Article in journal (Refereed)
    Abstract [en]

    The recently developed Monte-Carlo code ERO2.0 is applied to the modelling of limited and diverted discharges at JET with the ITER-like wall (ILW). The global beryllium (Be) erosion and deposition is simulated and compared to experimental results from passive spectroscopy. For the limiter configuration, it is demonstrated that Be self-sputtering is an important contributor (at least 35%) to the Be erosion. Taking this contribution into account, the ERO2.0 modelling confirms previous evidence that high deuterium (D) surface concentrations of up to similar to 50% atomic fraction provide a reasonable estimate of Be erosion in plasma-wetted areas. For the divertor configuration, it is shown that drifts can have a high impact on the scrape-off layer plasma flows, which in turn affect global Be transport by entrainment and lead to increased migration into the inner divertor. The modelling of the effective erosion yield for different operational phases (ohmic, L- and H-mode) agrees with experimental values within a factor of two, and confirms that the effective erosion yield decreases with increasing heating power and confinement.

  • 21.
    Keraudy, Julien
    et al.
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden.;Oerlikon Surface Solut AG, Oerlikon Balzers, Iramali 18, LI-9496 Balzers, Liechtenstein..
    Viloan, Rommel Paulo B.
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden..
    Raadu, Michael A.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Brenning, Nils
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Lundin, Daniel
    Univ Paris Saclay, Univ Paris Sud, CNRS, LPGP,UMR 8578, F-91405 Orsay, France..
    Helmersson, Ulf
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden..
    Bipolar HiPIMS for tailoring ion energies in thin film deposition2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 359, p. 433-437Article in journal (Refereed)
    Abstract [en]

    The effects of a positive pulse following a high-power impulse magnetron sputtering (HiPIMS) pulse are studied using energy-resolved mass spectrometry. This includes exploring the influence of a 200 mu s long positive voltage pulse (U-rev = 10-150 V) following a typical HiPIMS pulse on the ion-energy distribution function (IEDF) of the various ions. We find that a portion of the Ti+ flux is affected and gains an energy which corresponds to the acceleration over the full potential U-rev. The Ar+ IEDF on the other hand illustrates that a large fraction of the accelerated Ar+, gain energies corresponding to only a portion of U-rev. The Ti+ IEDFs are consistent with the assumption that practically all the TO-, that are accelerated during the reverse pulse, originates from a region adjacent to the target, in which the potential is uniformly increased with the applied potential U-rev while much of the Ar+ originates from a region further away from the target over which the potential drops from U-rev to a lower potential consistent with the plasma potential achieved without the application of U-rev. The deposition rate is only slightly affected and decreases with U-rev, reaching 90% at U-rev = 150 V. Both the Ti IEDF and the small deposition rate change indicate that the potential increase in the region close to the target is uniform and essentially free of electric fields, with the consequence that the motion of ions inside the region is not much influenced by the application of U-rev. In this situation, Ti will flow towards the outer boundary of the target adjacent region, with the momentum gained during the HiPIMS discharge pulse, independently of whether the positive pulse is applied or not. The metal ions that cross the boundary in the direction towards the substrate, and do this during the positive pulse, all gain an energy corresponding to the full positive applied potential U-rev.

  • 22. Hamrin, M.
    et al.
    Gunell, H.
    Goncharov, O.
    De Spiegeleer, A.
    Fuselier, S.
    Mukherjee, J.
    Vaivads, Andris
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Pitkänen, T.
    Torbert, R. B.
    Giles, B.
    Can Reconnection be Triggered as a Solar Wind Directional Discontinuity Crosses the Bow Shock?: A Case of Asymmetric Reconnection2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 11, p. 8507-8523Article in journal (Refereed)
    Abstract [en]

    Here we present some unique observations of reconnection at a quasi‐perpendicular bow shock as an interplanetary directional discontinuity (DD) is crossing it simultaneously with the Magnetospheric Multiscale (MMS) mission. There are no burst data, but available data show indications of ongoing reconnection at the shock southward of MMS: a bifurcated current sheet with signatures of Hall magnetic and electric fields, normal magnetic fields indicating a magnetic connection between the two reconnecting regions, field‐aligned currents and electric fields, E·J>0 indicating a conversion of magnetic to kinetic energy, and subspin resolution ion energy‐time spectrograms indicating ions being accelerated away from the X‐line. The DD is also observed by four upstream spacecraft (ACE, WIND, Geotail, and ARTEMIS P1) and one downstream in the magnetosheath (Cluster 4), but none of them resolve signatures of ongoing reconnection. We therefore suggest that reconnection was temporarily triggered as the DD was compressed by the shock. Reconnection at the bow shock is inevitably asymmetric with both the density and magnetic field strength being higher on one side of the X‐line (magnetosheath side) than on the other side where the plasma flow also is supersonic (solar wind side). This is different from the asymmetry exhibited at the more commonly studied case of asymmetric reconnection at the magnetopause. Asymmetric reconnection of the bow shock type has never been studied before, and the data discussed here present some first indications of the properties of the reconnection region for this type of reconnection.

  • 23.
    Khotyaintsev, Yuri, V
    et al.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Graham, Daniel B.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Norgren, Cecilia
    Univ Bergen, Dept Phys & Technol, Bergen, Norway..
    Vaivads, Andris
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Collisionless Magnetic Reconnection and Waves: Progress Review2019In: Frontiers in Astronomy and Space Sciences, ISSN 2296-987X, Vol. 6, article id 70Article, review/survey (Refereed)
    Abstract [en]

    Magnetic reconnection is a fundamental process whereby microscopic plasma processes cause macroscopic changes in magnetic field topology, leading to explosive energy release. Waves and turbulence generated during the reconnection process can produce particle diffusion and anomalous resistivity, as well as heat the plasma and accelerate plasma particles, all of which can impact the reconnection process. We review progress on waves related to reconnection achieved using high resolution multi-point in situ observations over the last decade, since early Cluster and THEMIS observations and ending with recent Magnetospheric Multiscale results. In particular, we focus on the waves most frequently observed in relation to reconnection, ranging from low-frequency kinetic Alfven waves (KAW), to intermediate frequency lower hybrid and whistler-mode waves, electrostatic broadband and solitary waves, as well as the high-frequency upper hybrid, Langmuir, and electron Bernstein waves. Significant progress has been made in understanding localization of the different wave modes in the context of the reconnection picture, better quantification of generation mechanisms and wave-particle interactions, including anomalous resistivity. Examples include: temperature anisotropy driven whistlers in the flux pileup region, anomalous effects due to lower-hybrid waves, upper hybrid wave generation within the electron diffusion region, wave-particle interaction of electrostatic solitary waves. While being clearly identified in observations, some of the wave processes remain challenging for reconnection simulations (electron Bernstein, upper hybrid, Langmuir, whistler), as the instabilities (streaming, loss-cone, shell) which drive these waves require high resolution of distribution functions in phase space, and realistic ratio of Debye to electron inertia scales. We discuss how reconnection configuration, i.e., symmetric vs. asymmetric, guide-field vs. antiparallel, affect wave occurrence, generation, effect on particles, and feedback on the overall reconnection process. Finally, we outline some of the major open questions, such as generation of electromagnetic radiation by reconnection sites and role of waves in triggering/onset of reconnection.

  • 24.
    Pajuste, Elina
    et al.
    Univ Latvia, Inst Chem Phys, Jelgtvas St 1, LV-1004 Riga, Latvia..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Pajuste, E.
    Univ Latvia, 19 Raina Blvd, LV-1586 Riga, Latvia. Univ Lorraine, CNRS, UMR7198, YIJL, Nancy, France..
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    Comparison of the structure of the plasma-facing surface and tritium accumulation in beryllium tiles from JET ILW campaigns 2011-2012 and 2013-20142019In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 19, p. 131-136Article in journal (Refereed)
    Abstract [en]

    In this study, beryllium tiles from Joint European Torus (JET) vacuum vessel wall were analysed and compared regarding their position in the vacuum vessel and differences in the exploitation conditions during two campaigns of ITER-Like-Wall (ILW) in 2011-2012 (ILW1) and 2013-2014 (ILW2) Tritium content in beryllium samples were assessed. Two methods were used to measure tritium content in the samples - dissolution under controlled conditions and tritium thermal desorption. Prior to desorption and dissolution experiments, scanning electron microscopy and energy dispersive x-ray spectroscopy were used to study structure and chemical composition of plasma-facing-surfaces of the beryllium samples. Experimental results revealed that tritium content in the samples is in range of 2.10(11)-2.10(13) tritium atoms per square centimetre of the surface area with its highest content in the samples from the outer wall of the vacuum vessel (up to 1.9.10(13) atoms/cm(2) in ILW1 campaign and 2.4.10(13) atoms/cm(2) in ILW2). The lowest content of tritium was found in the upper part of the vacuum vessel (2.0.10(12) atoms/cm(2) and 2.0.10(11) atoms/cm(2) in ILW1 and ILW2, respectively). Results obtained from scanning electron microscopy has shown that surface morphology is different within single tile, however if to compare two campaigns main tendencies remains similar.

  • 25.
    Telesca, G.
    et al.
    Culham Sci Ctr, EUROfus Consortium, JET, Abingdon OX14 3DB, Oxon, England.;Inst Plasma Phys & Laser Microfus, Warsaw, Poland.;EUROfus Consortium JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;UG Ghent Univ, Dept Appl Phys, St Pietersnieuwstr 41, B-9000 Ghent, Belgium.;Inst Plasma Phys & Laser Microfus, Hery 23, PL-01497 Warsaw, Poland..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Fridström, Richard
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Moon, Sunwoo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I
    EUROfus Consortium JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;Natl Ctr Nucl Res NCBJ, PL-05400 Otwock, Poland..
    et al,
    COREDIV numerical simulation of high neutron rate JET-ILW DD pulses in view of extension to JET-ILW DT experiments2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 5, article id 056026Article in journal (Refereed)
    Abstract [en]

    Two high performance JET-ILW pulses, pertaining to the 2016 experimental campaign, have been numerically simulated with the self-consistent code COREDIV with the aim of predicting the ELM-averaged power load to the target when extrapolated to DT plasmas. The input power of about 33 MW as well as the total radiated power and the average density are similar in the two pulses, but for one of them the density is provided by combined low gas puff and pellet injection, characterized by low SOL density, for the other one by gas fuelling only, at higher SOT. density. Considering the magnetic configuration of theses pulses and the presence of a significant amount of Ni (not included in the version of the code used for these simulations), a number of assumptions are made in order to reproduce numerically the main core and SOL experimental data. The extrapolation to DT plasmas at the original input power of 33 MW, and taking into account only the thermal component of the alpha-power, does not show any significant difference regarding the power to the target with respect to the DD case. In contrast, the simulations at auxiliary power 40 MW, both at the original I-p = 3 MA and at I-p = 4 MA, show that the power to the target for both pulses is possibly too high to be sustained for about 5 s by strike-point sweeping alone without any control by Ne seeding. Even though the target power load may decrease to about 13-15 MW with substantial Ne seeding for both pulses, as from numerical predictions, there are indications suggesting that the control of the power load may be more critical for the pulse with pellet injection, due to the reduced SOL radiation.

  • 26. Tang, B. -B
    et al.
    Li, W. Y.
    Chinese Acad Sci, State Key Lab Space Weather, Natl Space Sci Ctr, Beijing, Peoples R China.;Swedish Inst Space Phys, Uppsala, Sweden..
    Graham, D. B.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Rager, A. C.
    Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA.;NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Wang, C.
    Chinese Acad Sci, State Key Lab Space Weather, Natl Space Sci Ctr, Beijing, Peoples R China.;Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing, Peoples R China..
    Khotyaintsev, Yu. V.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, Toulouse, France..
    Hasegawa, H.
    Japan Aerosp Explorat Agcy, Inst Space & Astronaut Sci, Sagamihara, Kanagawa, Japan..
    Zhang, Y. -C
    Dai, L.
    Chinese Acad Sci, State Key Lab Space Weather, Natl Space Sci Ctr, Beijing, Peoples R China..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90024 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Crescent-Shaped Electron Distributions at the Nonreconnecting Magnetopause: Magnetospheric Multiscale Observations2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 6, p. 3024-3032Article in journal (Refereed)
    Abstract [en]

    Crescent-shaped electron distributions perpendicular to the magnetic field are an important indicator of the electron diffusion region in magnetic reconnection. They can be formed by the electron finite gyroradius effect at plasma boundaries or by demagnetized electron motion. In this study, we present Magnetospheric Multiscale mission observations of electron crescents at the flank magnetopause on 20 September 2017, where reconnection signatures are not observed. These agyrotropic electron distributions are generated by electron gyromotion at the thin electron-scale magnetic boundaries of a magnetic minimum after magnetic curvature scattering. The variation of their angular range in the perpendicular plane is in good agreement with predictions. Upper hybrid waves are observed to accompany the electron crescents at all four Magnetospheric Multiscale spacecraft as a result of the beam-plasma instability associated with these agyrotropic electron distributions. This study suggests electron crescents can be more frequently formed at the magnetopause. Plain Language Summary In this study, we present Magnetospheric Multiscale mission observations of electron crescents at the flank magnetopause and these agyrotropic electron distributions are formed at thin electron-scale magnetic boundaries after electron pitch angle scattering by the curved magnetic field. These results suggest that agyrotropic electron distributions can be more frequently formed at the magnetopause: (1) magnetic reconnection is not necessary, although electron crescents are taken as one of the observational signatures of the electron diffusion region, and (2) agyrotropic electron distributions can cover a large local time range to the flank magnetopause. In addition, upper hybrid waves accompanied with the electron crescents are observed as a result of the beam-plasma interaction associated with these agyrotropic electron distributions. This suggests that high-frequency waves play a role in electron dynamics through wave-particle interactions.

  • 27.
    Mlynar, Jan
    et al.
    CAS, Inst Plasma Phys, Prague 18200, Czech Republic..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Mlynar, J.
    Inst Plasma Phys AS CR, Za Slovankou 1782-3, Prague 18200 8, Czech Republic..
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    Current Research into Applications of Tomography for Fusion Diagnostics2019In: Journal of fusion energy, ISSN 0164-0313, E-ISSN 1572-9591, Vol. 38, no 3-4, p. 458-466Article in journal (Refereed)
    Abstract [en]

    Retrieving spatial distribution of plasma emissivity from line integrated measurements on tokamaks presents a challenging task due to ill-posedness of the tomography problem and limited number of the lines of sight. Modern methods of plasma tomography therefore implement a-priori information as well as constraints, in particular some form of penalisation of complexity. In this contribution, the current tomography methods under development (Tikhonov regularisation, Bayesian methods and neural networks) are briefly explained taking into account their potential for integration into the fusion reactor diagnostics. In particular, current development of the Minimum Fisher Regularisation method is exemplified with respect to real-time reconstruction capability, combination with spectral unfolding and other prospective tasks.

  • 28.
    Carvalho, D. D.
    et al.
    Culham Sci Ctr, JET, EUROfus Consortium, Abingdon OX14 3DB, Oxon, England.;Univ Lisbon, Inst Plasmas & Fusao Nucl Inst Super Tecn, P-1049001 Lisbon, Portugal.;EUROfus Consortium JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;Univ Lisbon, Inst Super Tecn, Inst Plasmas & Fusao Nucl, Lisbon, Portugal..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Fridström, Richard
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Moon, Sunwoo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I
    EUROfus Consortium JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;Natl Ctr Nucl Res NCBJ, PL-05400 Otwock, Poland..
    et al,
    Deep neural networks for plasma tomography with applications to JET and COMPASS2019In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 14, article id C09011Article in journal (Refereed)
    Abstract [en]

    Convolutional neural networks (CNNs) have found applications in many image processing tasks, such as feature extraction, image classification, and object recognition. It has also been shown that the inverse of CNNs, so-called deconvolutional neural networks, can be used for inverse problems such as plasma tomography. In essence, plasma tomography consists in reconstructing the 2D plasma profile on a poloidal cross-section of a fusion device, based on line-integrated measurements from multiple radiation detectors. Since the reconstruction process is computationally intensive, a deconvolutional neural network trained to produce the same results will yield a significant computational speedup, at the expense of a small error which can be assessed using different metrics. In this work, we discuss the design principles behind such networks, including the use of multiple layers, how they can be stacked, and how their dimensions can be tuned according to the number of detectors and the desired tomographic resolution for a given fusion device. We describe the application of such networks at JET and COMPASS, where at JET we use the bolometer system, and at COMPASS we use the soft X-ray diagnostic based on photodiode arrays.

  • 29.
    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.

  • 30.
    Widdowson, A.
    et al.
    Culham Sci Ctr, Culham Ctr Fus Energy, Abingdon OX14 3DB, Oxon, England..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    Deposition of impurity metals during campaigns with the JET ITER-like Wall2019In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 19, p. 218-224Article in journal (Refereed)
    Abstract [en]

    Post mortem analysis shows that mid and high atomic number metallic impurities are present in deposits on JET plasma facing components with the highest amount of Ni and W, and therefore the largest sink, being found at the top of the inner divertor. Sources are defined as "continuous" or "specific", in that "continuous" sources arise from ongoing erosion from plasma facing surfaces and "specific" are linked with specific events which decrease over time until they no longer act as a source. This contribution evaluates the sinks and estimates sources, and the balance gives an indication of the dominating processes. Charge exchange neutral erosion is found to be the main source of nickel, whereas erosion of divertor plasma facing components is the main source of tungsten. Specific sources are shown to have little influence over the global mid- and high-Z impurity concentrations in deposits.

  • 31.
    Neverov, V. S.
    et al.
    EUROfus Consortium, JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;Natl Res Ctr Kurchatov Inst, Moscow 123182, Russia. Natl Res Nucl Univ MEPhI, Moscow 115409, Russia. Moscow Inst Phys & Technol, Dolgoprudnyi 141700, Moscow Region, Russia..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I
    Natl Ctr Nucl Res NCBJ, Otwock, Poland..
    et al,
    Determination of isotope ratio in the divertor of JET-ILW by high-resolution H alpha spectroscopy: H-D experiment and implications for D-T experiment2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 4, article id 046011Article in journal (Refereed)
    Abstract [en]

    The data of the H alpha high-resolution spectroscopy, collected on the multiple lines of sight, which cover the entire divertor space in poloidal cross-section, during the recent hydrogen-deuterium experiments in JET-ILW (ITER-like wall), are processed. A strong spatial inhomogeneity of the hydrogen concentration, H/(H + D), in divertor is found in many pulses. Namely, the H/(H + D) ratio may be lower in the inner divertor than that in the outer divertor by the values of 0.15-0.35, depending on the conditions of gas puffing and plasma heating. This effect suggests the necessity of spatially-resolved measurements of isotope ratio in the divertor in the upcoming deuterium-tritium experiments. Also, separation of the overlapped T alpha and D alpha spectral lines is shown to be a challenging task especially when the local Doppler-broadened (Gaussian) line shapes are noticeably distorted by the net inward flux of fast non-Maxwellian neutral atoms. We use the respective, formerly developed model of an asymmetric spectral line shape, while analysing the data of the first deuterium-tritium experiment in JET-C (carbon wall), and test the model via comparing the isotope ratio results with another diagnostic's measurements. This model is shown to increase the accuracy of tritium concentration measurements in the divertor.

  • 32.
    Salewski, M.
    et al.
    Tech Univ Denmark, Lyngby, Denmark.;Tech Univ Denmark, Dept Phys, Bldg 309, DK-2800 Lyngby, Denmark..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    Diagnostic of fast-ion energy spectra and densities in magnetized plasmas2019In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 14, article id C05019Article in journal (Refereed)
    Abstract [en]

    The measurement of the energy spectra and densities of alpha-particles and other fast ions are part of the ITER measurement requirements, highlighting the importance of energy-resolved energetic-particle measurements for the mission of ITER. However, it has been found in recent years that the velocity-space interrogation regions of the foreseen energetic-particle diagnostics do not allow these measurements directly. We will demonstrate this for gamma-ray spectroscopy (GRS), collective Thomson scattering (CTS), neutron emission spectroscopy and fast-ion D-alpha spectroscopy by invoking energy and momentum conservation in each case, highlighting analogies and differences between the different diagnostic velocity-space sensitivities. Nevertheless, energy spectra and densities can be inferred by velocity-space tomography which we demonstrate using measurements at JET and ASDEX Upgrade. The measured energy spectra agree well with corresponding simulations. At ITER, alpha-particle energy spectra and densities can be inferred for energies larger than 1.7 MeV by velocity-space tomography based on GRS and CTS. Further, assuming isotropy of the alpha-particles in velocity space, their energy spectra and densities can be inferred by 1D inversion of spectral single-detector measurements down to about 300 keV by CTS. The alpha-particle density can also be found by fitting a model to the CTS measurements assuming the alpha-particle distribution to be an isotropic slowing-down distribution.

  • 33.
    Hatch, D. R.
    et al.
    Univ Texas Austin, Inst Fus Studies, Austin, TX 78712 USA.;Univ Texas Austin, Inst Fus Studies, Austin, TX 78712 USA..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    Direct gyrokinetic comparison of pedestal transport in JET with carbon and ITER-like walls2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 8, article id 086056Article in journal (Refereed)
    Abstract [en]

    This paper compares the gyrokinetic instabilities and transport in two representative JET pedestals, one (pulse 78697) from the JET configuration with a carbon wall

  • 34.
    Denis, J.
    et al.
    CEA, IRFM, F-13108 St Paul Les Durance, France.;CEA, IRFM, F-13108 St Paul Les Durance, France..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    Dynamic modelling of local fuel inventory and desorption in the whole tokamak vacuum vessel for auto-consistent plasma-wall interaction simulations2019In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 19, p. 550-557Article in journal (Refereed)
    Abstract [en]

    An extension of the SolEdge2D-EIRENE code package, named D-WEE, has been developed to add the dynamics of thermal desorption of hydrogen isotopes from the surface of plasma facing materials. To achieve this purpose, D-WEE models hydrogen isotopes implantation, transport and retention in those materials. Before launching autoconsistent simulation (with feedback of D-WEE on SolEdge2D-EIRENE), D-WEE has to be initialised to ensure a realistic wall behaviour in terms of dynamics (pumping or fuelling areas) and fuel content. A methodology based on modelling is introduced to perform such initialisation. A synthetic plasma pulse is built from consecutive SolEdge2D-EIRENE simulations. This synthetic pulse is used as a plasma background for the D-WEE module. A sequence of plasma pulses is simulated with D-WEE to model a tokamak operation. This simulation enables to extract at a desired time during a pulse the local fuel inventory and the local desorption flux density which could be used as initial condition for coupled plasma-wall simulations. To assess the relevance of the dynamic retention behaviour obtained in the simulation, a confrontation to post-pulse experimental pressure measurement is performed. Such confrontation reveals a qualitative agreement between the temporal pressure drop obtained in the simulation and the one observed experimentally. The simulated dynamic retention during the consecutive pulses is also studied.

  • 35. Chankin, A. , V
    et al.
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Chankin, A.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, P
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    et al,
    EDGE2D-EIRENE simulations of the influence of isotope effects and anomalous transport coefficients on near scrape-off layer radial electric field2019In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 7, article id 075010Article in journal (Refereed)
    Abstract [en]

    EDGE2D-EIRENE (the 'code') simulations show that radial electric field, Er, in the near scrape-off layer (SOL) of tokamaks can have large variations leading to a strong local E x B shear greatly exceeding that in the core region. This was pointed out in simulations of JET plasmas with varying divertor geometry, where the magnetic configuration with larger predicted near SOL E-r was found to have lower H-mode power threshold, suggesting that turbulence suppression in the SOL by local E. x. B shear can be a player in the L-H transition physics (Delabie et al 2015 42nd EPS Conf. on Plasma Physics (Lisbon, Portugal, 22-26 June 2015) paper O3.113 (http://ocs.ciemat.es/EPS2015PAP/pdf/O3.113.pdf), Chankin et al 2017 Nucl. Mater. Energy 12 273). Further code modeling of JET plasmas by changing hydrogen isotopes (H-D-T) showed that the magnitude of the near SOL E-r is lower in H cases in which the H-mode threshold power is higher (Chankin et al 2017 Plasma Phys. Control. Fusion 59 045012). From the experiment it is also known that hydrogen plasmas have poorer particle and energy confinement than deuterium plasmas, consistent with the code simulation results showing larger particle diffusion coefficients at the plasma edge, including SOL, in hydrogen plasmas (Maggi et al 2018 Plasma Phys. Control. Fusion 60 014045). All these experimental observations and code results support the hypothesis that the near SOL E x B shear can have an impact on the plasma confinement. The present work analyzes neutral ionization patterns of JET plasmas with different hydrogen isotopes in L-mode cases with fixed input power and gas puffing rate, and its impact on target electron temperature, T-e, and SOL E-r. The possibility of a self-feeding mechanism for the increase in the SOL E-r via the interplay between poloidal E x B drift and target T-e is discussed. It is also shown that reducing anomalous turbulent transport coefficients, particle diffusion and electron and ion heat conductivities, leads to higher peak target T-e and larger E-r, suggesting the possibility of a positive feedback loop, under an implicitly made assumption that the E x B shear in the SOL is capable of suppressing turbulence.

  • 36.
    Kateb, Movaffaq
    et al.
    Univ Iceland, Inst Sci, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Inst Sci, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Ingvarsson, Snorri
    Univ Iceland, Inst Sci, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Effect of atomic ordering on the magnetic anisotropy of single crystal Ni80Fe202019In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 9, no 3, article id 035308Article in journal (Refereed)
    Abstract [en]

    We investigate the effect of atomic ordering on the magnetic anisotropy of Ni80Fe20 at.% (Py). To this end, Py films were grown epitaxially on MgO(001) using dc magnetron sputtering (dcMS) and high power impulse magnetron sputtering (HiPIMS). Aside from twin boundaries observed in the latter case, both methods present high quality single crystals with cube-on-cube epitaxial relationship as verified by the polar mapping of important crystal planes. However, X-ray diffraction results indicate higher order for the dcMS deposited film towards L1(2) Ni3Fe superlattice. This difference can be understood by the very high deposition rate of HiPIMS during each pulse which suppresses adatom mobility and ordering. We show that the dcMS deposited film presents biaxial anisotropy while HiPIMS deposition gives well defined uniaxial anisotropy. Thus, higher order achieved in the dcMS deposition behaves as predicted by magnetocrystalline anisotropy i.e. easy axis along the [111] direction that forced in the plane along the [110] direction due to shape anisotropy. The uniaxial behaviour in HiPIMS deposited film then can be explained by pair ordering or more recent localized composition non-uniformity theories. Further, we studied magnetoresistance of the films along the [100] directions using an extended van der Pauw method. We find that the electrical resistivities of the dcMS deposited film are lower than in their HiPIMS counterparts verifying the higher order in the dcMS case.

  • 37.
    Sultan, M. T.
    et al.
    Reykjavik Univ, Sch Sci & Engn, IS-101 Reykjavik, Iceland..
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Univ Iceland, Sci Inst, Dunhaga 3, IS-107 Reykjavik, Iceland..
    Manolescu, A.
    Reykjavik Univ, Sch Sci & Engn, IS-101 Reykjavik, Iceland..
    Teodorescu, V. S.
    Natl Inst Mat Phys, Magurele 077125, Romania..
    Ciurea, M. L.
    Natl Inst Mat Phys, Magurele 077125, Romania.;Acad Romanian Scientists, Bucharest 050094, Romania..
    Svavarsson, H. G.
    Reykjavik Univ, Sch Sci & Engn, IS-101 Reykjavik, Iceland..
    Efficacy of annealing and fabrication parameters on photo-response of SiGe in TiO2 matrix2019In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 30, no 36, article id 365604Article in journal (Refereed)
    Abstract [en]

    SiGe nanoparticles dispersed in a dielectric matrix exhibit properties different from those of bulk and have shown great potential in devices for application in advanced optoelectronics. Annealing is a common fabrication step used to increase crystallinity and to form nanoparticles in such a system. A frequent downside of such annealing treatment is the formation of insulating SiO2 layer at the matrix/SiGe interface, degrading the optical properties of the structure. An annealing process that could bypass this downside would therefore be of great interest. In this work, a short-time furnace annealing of a SiGe/TiO2 system is applied to obtain SiGe nanoparticles without formation of the undesired SiO2 layer between the dielectric matrix (TiO2) and SiGe. The structures were prepared by depositing alternate layers of TiO2 and SiGe films, using direct-current magnetron sputtering technique. A wide range spectral response with a response-threshold up to similar to 1300 nm was obtained, accompanied with an increase in photo-response of more than two-orders of magnitude. Scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectroscopy and grazing incidence x-ray diffraction were used to analyze the morphological changes in respective structures. Photoconductive properties were studied by measuring photocurrent spectra using applied dc-voltages at various temperatures.

  • 38. Chen, L. -J
    et al.
    Wang, S.
    Hesse, M.
    Ergun, R. E.
    Moore, T.
    Giles, B.
    Bessho, N.
    Russell, C.
    Burch, J.
    Torbert, R. B.
    Genestreti, K. J.
    Paterson, W.
    Pollock, C.
    Lavraud, B.
    Le Contel, O.
    Strangeway, R.
    Khotyaintsev, Y. V.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Electron Diffusion Regions in Magnetotail Reconnection Under Varying Guide Fields2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 12, p. 6230-6238Article in journal (Refereed)
    Abstract [en]

    Kinetic structures of electron diffusion regions (EDRs) under finite guide fields in magnetotail reconnection are reported. The EDRs with guide fields 0.14–0.5 (in unit of the reconnecting component) are detected by the Magnetospheric Multiscale spacecraft. The key new features include the following: (1) cold inflowing electrons accelerated along the guide field and demagnetized at the magnetic field minimum while remaining a coherent population with a low perpendicular temperature, (2) wave fluctuations generating strong perpendicular electron flows followed by alternating parallel flows inside the reconnecting current sheet under an intermediate guide field, and (3) gyrophase bunched electrons with high parallel speeds leaving the X-line region. The normalized reconnection rates for the three EDRs range from 0.05 to 0.3. The measurements reveal that finite guide fields introduce new mechanisms to break the electron frozen-in condition.

  • 39. Phan, T. D.
    et al.
    Eastwood, J. P.
    Shay, M. A.
    Drake, J. F.
    Sonnerup, B. U. O.
    Fujimoto, M.
    Cassak, P. A.
    Oieroset, M.
    Burch, J. L.
    Torbert, R. B.
    Rager, A. C.
    Dorelli, J. C.
    Gershman, D. J.
    Pollock, C.
    Pyakurel, P. S.
    Haggerty, C. C.
    Khotyaintsev, Y.
    Lavraud, B.
    Saito, Y.
    Oka, M.
    Ergun, R. E.
    Retino, A.
    Le Contel, O.
    Argall, M. R.
    Giles, B. L.
    Moore, T. E.
    Wilder, F. D.
    Strangeway, R. J.
    Russell, C. T.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Magnes, W.
    Electron magnetic reconnection without ion coupling in Earth's turbulent magnetosheath (vol 557, pg 202, 2018)2019In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 569, no 7757, p. E9-E9Article in journal (Refereed)
  • 40.
    Oka, M.
    et al.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Otsuka, F.
    Kyushu Univ, Fukuoka, Fukuoka, Japan..
    Matsukiyo, S.
    Kyushu Univ, Fukuoka, Fukuoka, Japan..
    Wilson, L. B. , I I I
    Argall, M. R.
    Univ New Hampshire, Phys Dept, Durham, NH 03824 USA.;Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Amano, T.
    Univ Tokyo, Tokyo, Japan..
    Phan, T. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Hoshino, M.
    Univ Tokyo, Tokyo, Japan..
    Le Contel, O.
    Univ Paris 06, Univ Paris Sud, UPMC, CNRS,Ecole Polytech,Obs Paris,LPP,UMR 7648, Pl Jussieu, F-75252 Paris 05, France..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78228 USA..
    Torbert, R. B.
    Univ New Hampshire, Phys Dept, Durham, NH 03824 USA.;Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA.;Southwest Res Inst, San Antonio, TX 78228 USA..
    Dorelli, J. C.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80303 USA..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA 90095 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Electron Scattering by Low-frequency Whistler Waves at Earth?s Bow Shock2019In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 886, no 1, article id 53Article in journal (Refereed)
    Abstract [en]

    Electrons are accelerated to nonthermal energies at shocks in space and astrophysical environments. While shock drift acceleration (SDA) has been considered a key process of electron acceleration at Earth?s bow shock, it has also been recognized that SDA needs to be combined with an additional stochastic process to explain the observed power-law energy spectra. Here, we show mildly energetic (?0.5 keV) electrons are locally scattered (and accelerated while being confined) by magnetosonic-whistler waves within the shock transition layer, especially when the shock angle is large (<CDATA<i). When measured by the Magnetospheric Multiscale mission at a high cadence, ?0.5 keV electron flux increased exponentially in the shock transition layer. However, the flux profile was not entirely smooth and the fluctuation showed temporal/spectral association with large-amplitude (<CDATA<i), low-frequency (<CDATA<i where <CDATA<i is the cyclotron frequency), obliquely propagating (<CDATA<i, where <CDATA<i is the angle between the wave vector and background magnetic field) whistler waves, indicating that the particles were interacting with the waves. Particle simulations demonstrate that, although linear cyclotron resonances with ?0.5 keV electrons are unlikely due to the obliquity and low frequencies of the waves, the electrons are still scattered beyond 90; pitch angle by (1) resonant mirroring (transit-time damping), (2) non-resonant mirroring, and (3) subharmonic cyclotron resonances. Such coupled nonlinear scattering processes are likely to provide the stochasticity needed to explain the power-law formation.

  • 41.
    Zhou, M.
    et al.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang 330031, Jiangxi, Peoples R China.;Nanchang Univ, Sch Environm & Chem Engn, Minist Educ, Key Lab Poyang Lake Environm & Resource Utilizat, Nanchang 330031, Jiangxi, Peoples R China..
    Huang, J.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang 330031, Jiangxi, Peoples R China.;Nanchang Univ, Sch Sci, Dept Phys, Nanchang 330031, Jiangxi, Peoples R China..
    Man, H. Y.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang 330031, Jiangxi, Peoples R China.;Nanchang Univ, Sch Sci, Dept Phys, Nanchang 330031, Jiangxi, Peoples R China..
    Deng, X. H.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang 330031, Jiangxi, Peoples R China..
    Zhong, Z. H.
    Nanchang Univ, Inst Space Sci & Technol, Nanchang 330031, Jiangxi, Peoples R China.;Nanchang Univ, Sch Resources Environm & Chem Engn, Nanchang 330031, Jiangxi, Peoples R China..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth Planetary & Space Sci, Los Angeles, CA USA..
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Royal Inst Technol, SE-75121 Stockholm, Sweden..
    Khotyaintsev, Y. , V
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    Electron-scale Vertical Current Sheets in a Bursty Bulk Flow in the Terrestrial Magnetotail2019In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 872, no 2, article id L26Article in journal (Refereed)
    Abstract [en]

    We report Magnetospheric Multiscale observations of multiple vertical current sheets (CSs) in a bursty bulk flow in the near-Earth magnetotail. Two of the CSs were fine structures of a dipolarization front (DF) at the leading edge of the flow. The other CSs were a few Earth radii tailward of the DF; that is, in the wake of the DF. Some of these vertical CSs were a few electron inertial lengths thick and were converting energy from magnetic field to plasma. The currents of the CSs in the DF wake were carried by electrons that formed flow shear layers. These electron-scale CSs were probably formed during the turbulent evolution of the bursty bulk flow and are important for energy conversion associated with fast flows.

  • 42.
    Trier, E.
    et al.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    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.
    Johnson, Thomas
    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 V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and 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.
    Vignitchouk, Ladislas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Zuin, M.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    ELM-induced cold pulse propagation in ASDEX Upgrade2019In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 4, article id 045003Article in journal (Refereed)
    Abstract [en]

    In ASDEX Upgrade, the propagation of cold pulses induced by type-I edge localized modes (ELMs) is studied using electron cyclotron emission measurements, in a dataset of plasmas with moderate triangularity. It is found that the edge safety factor or the plasma current are the main determining parameters for the inward penetration of the T-e perturbations. With increasing plasma current the ELM penetration is more shallow in spite of the stronger ELMs. Estimates of the heat pulse diffusivity show that the corresponding transport is too large to be representative of the inter-ELM phase. Ergodization of the plasma edge during ELMs is a possible explanation for the observed properties of the cold pulse propagation, which is qualitatively consistent with non-linear magneto-hydro-dynamic simulations.

  • 43. Vines, S. K.
    et al.
    Allen, R. C.
    Anderson, B. J.
    Engebretson, M. J.
    Fuselier, S. A.
    Russell, C. T.
    Strangeway, R. J.
    Ergun, R. E.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Torbert, R. B.
    Burch, J. L.
    EMIC Waves in the Outer Magnetosphere: Observations of an Off-Equator Source Region2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 11, p. 5707-5716Article in journal (Refereed)
    Abstract [en]

    Electromagnetic ion cyclotron (EMIC) waves at large L shells were observed away from the magnetic equator by the Magnetospheric MultiScale (MMS) mission nearly continuously for over four hours on 28 October 2015. During this event, the wave Poynting vector direction systematically changed from parallel to the magnetic field (toward the equator), to bidirectional, to antiparallel (away from the equator). These changes coincide with the shift in the location of the minimum in the magnetic field in the southern hemisphere from poleward to equatorward of MMS. The local plasma conditions measured with the EMIC waves also suggest that the outer magnetospheric region sampled during this event was generally unstable to EMIC wave growth. Together, these observations indicate that the bidirectionally propagating wave packets were not a result of reflection at high latitudes but that MMS passed through an off-equator EMIC wave source region associated with the local minimum in the magnetic field.

  • 44.
    Nabais, F.
    et al.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Univ Lisbon, Inst Super Tecn, Inst Plasmas & Fusao Nucl, P-1049001 Lisbon, Portugal.;Univ Lisbon, Inst Plasma & Fus Nucl, Inst Super Tecn, Lisbon, Portugal..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, S.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Y.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    Energetic ion losses 'channeling' mechanism and strategy for mitigation2019In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 8, article id 084008Article in journal (Refereed)
    Abstract [en]