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  • 1.
    Blanken, T. C.
    et al.
    Eindhoven Univ Technol, Control Syst Technol Grp, Dept Mech Engn, POB 513, NL-5600 MB Eindhoven, Netherlands.;Eindhoven Univ Technol, POB 513, NL-5600 MB Eindhoven, Netherlands..
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Fridström, Richard
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Jonsson, T.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vignitchouk, Ladislas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Dori, V
    Univ Split, Fac Elect Engn Mech Engn & Naval Architecture, R Boskovica 32, Split 21000, Croatia..
    Real-time plasma state monitoring and supervisory control on TCV2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 2, article id 026017Article in journal (Refereed)
    Abstract [en]

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

  • 2.
    Dumont, R. J.
    et al.
    CEA, IRFM, F-13108 St Paul Les Durance, France..
    Mailloux, J.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Aslanyan, V
    MIT, PSFC, 175 Albany St, Cambridge, MA 02039 USA..
    Baruzzo, M.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    Challis, C. D.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Coffey, I
    Queens Univ, Dept Pure & Appl Phys, Belfast BT7 1NN, Antrim, North Ireland..
    Czarnecka, A.
    Inst Plasma Phys & Laser Microfus, Hery St 23, PL-00908 Warsaw, Poland..
    Delabie, E.
    Oak Ridge Natl Lab, Oak Ridge, TN USA..
    Eriksson, J.
    Uppsala Univ, Dept Phys & Astron, SE-75119 Uppsala, Sweden..
    Faustin, J.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Ferreira, J.
    Univ Lisbon, IST, Inst Plasmas & Fusao Nucl, Lisbon, Portugal..
    Fitzgerald, M.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Garcia, J.
    CEA, IRFM, F-13108 St Paul Les Durance, France..
    Giacomelli, L.
    Univ Milano Bicocca, Piazza Sci 3, I-20126 Milan, Italy..
    Giroud, C.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Hawkes, N.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Jacquet, Ph
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Joffrin, E.
    CEA, IRFM, F-13108 St Paul Les Durance, France..
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Keeling, D.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    King, D.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Kiptily, V
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Lomanowski, B.
    Aalto Univ, POB 14100, FIN-00076 Aalto, Finland..
    Lerche, E.
    Ass EUROFUS Belgian State, LPP ERM KMS, TEC Partner, Brussels, Belgium..
    Mantsinen, M.
    Barcelona Supercomp Ctr, Barcelona, Spain.;ICREA, Barcelona, Spain..
    Meneses, L.
    Univ Lisbon, IST, Inst Plasmas & Fusao Nucl, Lisbon, Portugal..
    Menmuir, S.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    McClements, K.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Moradi, S.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Nabais, F.
    Univ Lisbon, IST, Inst Plasmas & Fusao Nucl, Lisbon, Portugal..
    Nocente, M.
    Univ Milano Bicocca, Piazza Sci 3, I-20126 Milan, Italy..
    Patel, A.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Patten, H.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Puglia, P.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Scannell, R.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Sharapov, S.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Solano, E. R.
    CIEMAT, Lab Nacl Fus, Madrid, Spain..
    Tsalas, M.
    FOM Inst DIFFER, NL-3430 BE Nieuwegein, Netherlands.;ITER Org, Route Vinon Sur Verdon, F-13067 St Paul Les Durance, France..
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Weisen, H.
    Ecole Polytech Fed Lausanne, SPC, CH-1015 Lausanne, Switzerland..
    Scenario development for the observation of alpha-driven instabilities in JET DT plasmas2018In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 58, no 8, article id 082005Article in journal (Refereed)
    Abstract [en]

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

  • 3.
    Garcia-Munoz, M.
    et al.
    Univ Seville, Dept Atom Mol & Nucl Phys, Seville, Spain..
    Sharapov, S. E.
    Culham Sci Ctr, Abingdon, Oxon, England..
    Van Zeeland, M. A.
    Gen Atom, San Diego, CA USA..
    Ascasibar, E.
    CIEMAT, Madrid, Spain..
    Cappa, A.
    CIEMAT, Madrid, Spain..
    Chen, L.
    Zhejiang Univ, IFTS, Hangzhou, Zhejiang, Peoples R China.;Zhejiang Univ, Dept Phys, Hangzhou, Zhejiang, Peoples R China.;Univ Calif Irvine, Dept Phys & Astron, Irvine, CA USA..
    Ferreira, J.
    IST, Lisbon, Portugal..
    Galdon-Quiroga, J.
    Univ Seville, Dept Atom Mol & Nucl Phys, Seville, Spain..
    Geiger, B.
    Max Planck Inst Plasma Phys, Garching, Germany..
    Gonzalez-Martin, J.
    Univ Seville, Dept Atom Mol & Nucl Phys, Seville, Spain..
    Heidbrink, W. W.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA USA..
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Lauber, Ph
    Max Planck Inst Plasma Phys, Garching, Germany..
    Mantsinen, M.
    Barcelona Supercomp Ctr, Barcelona, Spain.;ICREA, Pg Lluis Companys 23, Barcelona, Spain..
    Melnikov, A. , V
    Nabais, F.
    Univ Calif Irvine, Dept Phys & Astron, Irvine, CA USA..
    Rivero-Rodriguez, J. F.
    Univ Seville, Dept Atom Mol & Nucl Phys, Seville, Spain..
    Sanchis-Sanchez, L.
    Univ Seville, Dept Atom Mol & Nucl Phys, Seville, Spain..
    Schneider, P.
    Max Planck Inst Plasma Phys, Garching, Germany..
    Stober, J.
    Max Planck Inst Plasma Phys, Garching, Germany..
    Suttrop, W.
    Max Planck Inst Plasma Phys, Garching, Germany..
    Todo, Y.
    Natl Inst Fus Sci, Toki, Gifu, Japan..
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Zonca, F.
    Zhejiang Univ, IFTS, Hangzhou, Zhejiang, Peoples R China.;Zhejiang Univ, Dept Phys, Hangzhou, Zhejiang, Peoples R China.;ENEA, Fus & Nucl Safety Dept, CR Frascati, Rome, Italy..
    Meyer, H.
    Active control of Alfven eigenmodes in magnetically confined toroidal plasmas2019In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 5, article id 054007Article in journal (Refereed)
    Abstract [en]

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

  • 4.
    Hellsten, Torbjörn
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Vallejos, Pablo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    An iterative method for including Doppler shift in global wave solvers using FEM decomposition2014In: Journal of Physics: Conference series, ISSN 1742-6596, Vol. 561Article in journal (Refereed)
    Abstract [en]

    A method for calculating the wave field for spatial dispersive media is proposed suitable for FEM. The method is based on operator splitting by separating the induced current and wave field calculations, and solving the system by means of iterations. In order to take into account several coexisting waves with different poloidal mode numbers when calculating the induced current the wave field is decomposed into wavelets, for which the current is calculated assuming the plasma to be weakly non-uniform.

  • 5. Sharapov, S. E.
    et al.
    Garcia-Munoz, M.
    Van Zeeland, M. A.
    Bobkov, B.
    Classen, I. G. J.
    Ferreira, J.
    Figueiredo, A.
    Fitzgerald, M.
    Galdon-Quiroga, J.
    Gallart, D.
    Geiger, B.
    Gonzalez-Martin, J.
    Johnson, T.
    Lauber, P.
    Mantsinen, M.
    Nabais, F.
    Nikolaeva, V.
    Rodriguez-Ramos, M.
    Sanchis-Sanchez, L.
    Schneider, P. A.
    Snicker, A.
    Vallejos, Pablo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    The effects of electron cyclotron heating and current drive on toroidal Alfven eigenmodes in tokamak plasmas2018In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 60, no 1, article id 014026Article in journal (Refereed)
    Abstract [en]

    Dedicated studies performed for toroidal Alfven eigenmodes (TAEs) in ASDEX-Upgrade (AUG) discharges with monotonic q-profiles have shown that electron cyclotron resonance heating (ECRH) can make TAEs more unstable. In these AUG discharges, energetic ions driving TAEs were obtained by ion cyclotron resonance heating (ICRH). It was found that off-axis ECRH facilitated TAE instability, with TAEs appearing and disappearing on timescales of a few milliseconds when the ECRH power was switched on and off. On-axis ECRH had a much weaker effect on TAEs, and in AUG discharges performed with co- and counter-current electron cyclotron current drive (ECCD), the effects of ECCD were found to be similar to those of ECRH. Fast ion distributions produced by ICRH were computed with the PION and SELFO codes. A significant increase in T-e caused by ECRH applied off-axis is found to increase the fast ion slowing-down time and fast ion pressure causing a significant increase in the TAE drive by ICRH-accelerated ions. TAE stability calculations show that the rise in T-e causes also an increase in TAE radiative damping and thermal ion Landau damping, but to a lesser extent than the fast ion drive. As a result of the competition between larger drive and damping effects caused by ECRH, TAEs become more unstable. It is concluded, that although ECRH effects on AE stability in present-day experiments may be quite significant, they are determined by the changes in the plasma profiles and are not particularly ECRH specific.

  • 6.
    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, Superseded Departments (pre-2005), Physics. 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.

  • 7.
    Tierens, W.
    et al.
    Max Planck Inst Plasma Phys, Garching, Germany..
    Frassinetti, Lorenzo
    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.
    Petersson, Per
    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.
    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.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vallejos Olivares, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vignitchouk, Ladislas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Zuin, M.
    Consorzio RFX, Padua, Italy..
    et al.,
    Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 4, article id 046001Article in journal (Refereed)
    Abstract [en]

    In this paper we validate the finite element code RAPLICASOL, which models radiofrequency wave propagation in edge plasmas near ICRF antennas, against calculations with the TOPICA code. We compare the output of both codes for the ASDEX Upgrade 2-strap antenna, and for a 4-strap WEST-like antenna. Although RAPLICASOL requires considerably fewer computational resources than TOPICA, we find that the predicted quantities of experimental interest (including reflection coefficients, coupling resistances, S- and Z-matrix entries, optimal matching settings, and even radiofrequency electric fields) are in good agreement provided we are careful to use the same geometry in both codes.

  • 8.
    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.

  • 9.
    Vallejos, Pablo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    A numerical tool based on FEM and wavelets to account for spatial dispersion in ICRH simulations2018In: Journal of Physics: Conference Series, Institute of Physics Publishing , 2018, no 1Conference paper (Refereed)
    Abstract [en]

    Modeling of Ion Cyclotron Resonance Heating (ICRH) is difficult because of spatial dispersion. Numerical methods based on finite element or finite difference have difficulties in handling spatial dispersive effects, because the response is non-local. Fourier spectral methods can handle spatial dispersion, however, these methods have difficulties in handling the complex geometries outside the plasma domain and tend to produce dense matrices that are time consuming to invert. In this study, we investigate the potential of a new numerical method for solving the spatially dispersive wave equation based on FEM and wavelets. The spatially dispersive terms in the wave equation are evaluated using wavelets, and its contribution is represented as an induced current density in the wave equation. The wave equation is then solved using a finite element scheme, where the induced current density is represented as an inhomogeneous term and added using a fixed point iteration scheme. The method is applied to a case of one dimensional fast wave minority heating, including the up- and downshift in the parallel wave number, where we show that convergence can be obtained in a few iterations.

  • 10.
    Vallejos, Pablo
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    An iterative method to include spatial dispersion for waves in nonuniform plasmas using wavelet decomposition2016In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 775, no 1, article id 012016Article in journal (Refereed)
    Abstract [en]

    A novel method for solving wave equations with spatial dispersion is presented, suitable for applications to ion cyclotron resonance heating. The method splits the wave operator into a dispersive and a non-dispersive part. The latter can be inverted with e.g. finite element methods. The spatial dispersion is evaluated using a wavelet representation of the dielectric kernel and added by means of iteration. The method has been successfully tested on a low frequency kinetic Alfvén wave with second order Larmor radius effects in a nonuniform plasma slab.

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