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  • 1.
    Aho-Mantila, L.
    et al.
    VTT Tech Res Ctr Finland, POB 1000, FI-02044 Espoo, Finland.;VTT Tech Res Ctr Finland, FIN-02044 Espoo, Finland..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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 (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Assessment of SOLPS5.0 divertor solutions with drifts and currents against L-mode experiments in ASDEX Upgrade and JET2017In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 59, no 3, article id 035003Article in journal (Refereed)
    Abstract [en]

    The divertor solutions obtained with the plasma edge modelling tool SOLPS5.0 are discussed. The code results are benchmarked against carefully analysed L-mode discharges at various density levels with and without impurity seeding in the full-metal tokamaks ASDEX Upgrade and JET. The role of the cross-field drifts and currents in the solutions is analysed in detail, and the improvements achieved by fully activating the drift and current terms in view of matching the experimental signals are addressed. The persisting discrepancies are also discussed.

  • 2.
    Angioni, C.
    et al.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany.;Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Gyrokinetic study of turbulent convection of heavy impurities in tokamak plasmas at comparable ion and electron heat fluxes2017In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 2, article id 022009Article in journal (Refereed)
    Abstract [en]

    In tokamaks, the role of turbulent transport of heavy impurities, relative to that of neoclassical transport, increases with increasing size of the plasma, as clarified by means of general scalings, which use the ITER standard scenario parameters as reference, and by actual results from a selection of discharges from ASDEX Upgrade and JET. This motivates the theoretical investigation of the properties of the turbulent convection of heavy impurities by nonlinear gyrokinetic simulations in the experimentally relevant conditions of comparable ion and electron heat fluxes. These conditions also correspond to an intermediate regime between dominant ion temperature gradient turbulence and trapped electron mode turbulence. At moderate plasma toroidal rotation, the turbulent convection of heavy impurities, computed with nonlinear gyrokinetic simulations, is found to be directed outward, in contrast to that obtained by quasi-linear calculations based on the most unstable linear mode, which is directed inward. In this mixed turbulence regime, with comparable electron and ion heat fluxes, the nonlinear results of the impurity transport can be explained by the coexistence of both ion temperature gradient and trapped electron modes in the turbulent state, both contributing to the turbulent convection and diffusion of the impurity. The impact of toroidal rotation on the turbulent convection is also clarified.

  • 3. Angioni, C.
    et al.
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    et al.,
    The impact of poloidal asymmetries on tungsten transport in the core of JET H-mode plasmas2015In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 22, no 5, article id 055902Article in journal (Refereed)
    Abstract [en]

    Recent progress in the understanding and prediction of the tungsten behaviour in the core of JET H-mode plasmas with ITER-like wall is presented. Particular emphasis is given to the impact of poloidal asymmetries of the impurity density. In particular, it is shown that the predicted reduction of temperature screening induced by the presence of low field side localization of the tungsten density produced by the centrifugal force is consistent with the observed tungsten behaviour in a JET discharge in H-mode baseline scenario. This provides first evidence of the role of poloidal asymmetries in reducing the strength of temperature screening. The main differences between plasma parameters in JET baseline and hybrid scenario discharges which affect the impact of poloidally asymmetric density on the tungsten radial transport are identified. This allows the conditions by which tungsten accumulation can be avoided to be more precisely defined.

  • 4.
    Arnichand, H.
    et al.
    CEA, IRFM, F-13108 St Paul Les Durance, France.;IRFM, CEA, F-13108 St Paul Les Durance, France..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Johnson, Thomas J.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    Discriminating the trapped electron modes contribution in density fluctuation spectra2015In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 9, article id 093021Article in journal (Refereed)
    Abstract [en]

    Quasi-coherent (QC) modes have been reported for more than 10 years in reflectometry fluctuations spectra in the core region of fusion plasmas. They have characteristics in-between coherent and broadband fluctuations as they oscillate at a marked frequency but have a wide spectrum. This work presents further evidences of the link recently established between QC modes and the trapped electron modes (TEM) instabilities (Arnichand et al 2014 Nucl. Fusion 54 123017). In electron cyclotron resonance heated discharges of Tore Supra, an enhancement of QC modes amplitude is observed in a region where TEM cause impurity transport and turbulence. In JET Ohmic plasmas, QC modes disappear during density ramp-up and current ramp-down. This is reminiscent of Tore Supra and TEXTOR observations during transitions from the linear Ohmic confinement (LOC) to the saturated Ohmic confinement (SOC) regimes. Evidencing TEM activity then becomes experimentally possible via analysis of fluctuation spectra.

  • 5.
    Baiocchi, B.
    et al.
    CEA, IRFM, F-13108 St Paul Les Durance, France.;IRFM, CEA, F-13108 St Paul Les Durance, France..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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 (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    Turbulent transport analysis of JET H-mode and hybrid plasmas using QuaLiKiz and Trapped Gyro Landau Fluid2015In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 57, no 3, article id 035003Article in journal (Refereed)
    Abstract [en]

    The physical transport processes at the basis of JET typical inductive H-mode scenarios and advanced hybrid regimes, with improved thermal confinement, are analyzed by means of some of the newest and more sophisticated quasi-linear transport models: trapped gyro Landau fluid (TGLF) and QuaLiKiz. The temporal evolution of JET pulses is modelled by CRONOS where the turbulent transport is modelled by either QuaLiKiz or TGLF. Both are first principle models with a more comprehensive physics than the models previously developed and therefore allow the analysis of the physics at the basis of the investigated scenarios. For H-modes, ion temperature gradient (ITG) modes are found to be dominant and the transport models are able to properly reproduce temperature profiles in self-consistent simulations. However, for hybrid regimes, in addition to ITG trapped electron modes (TEM) are also found to be important and different physical mechanisms for turbulence reduction play a decisive role. Whereas E x B flow shear and plasma geometry have a limited impact on turbulence, the presence of a large population of fast ions, quite important in low density regimes, can stabilize core turbulence mainly when the electromagnetic effects are taken into account. The TGLF transport model properly captures these mechanisms and correctly reproduces temperatures.

  • 6.
    Baiocchi, B.
    et al.
    CEA, IRFM, F-13108 St Paul Les Durance, France.;CEA, IRFM, F-13108 St Paul Les Durance, France. EUROfus Consortium, JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;IRFM, CEA, F-13108 St Paul Les Durance, France..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    --.
    et al.,
    Transport analysis and modelling of the evolution of hollow density profiles plasmas in JET and implication for ITER2015In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 12, article id 123001Article in journal (Refereed)
    Abstract [en]

    The density evolution during the transient phase just after the L-H transition is investigated using theoretical transport models. Cases characterized by core densities which evolve in longer timescales than the edge densities, leading to hollow density profiles (R/L-n = -R del n/n < 0) are modelled. This density evolution is particularly interesting because it has been shown to be beneficial in the view of the access to burning plasma conditions in ITER (Loarte et al 2013 Nucl. Fusion 53 083031). Self-consistent simulations of the JET discharge 79676 of the density-only, and of the density and the temperatures are carried out using a quasilinear gyrokinetic code, QuaLiKiz (Bourdelle et al 2007 Phys. Plasmas 14 112501), coupled with a transport code CRONOS (Artaud et al 2010 Nucl. Fusion 50 043001). The slow evolution of the hollow density, associated with the self-consistently calculated hollow NBI particle deposition, is well reproduced in the plasma core. Indeed, QuaLiKiz is shown to reproduce nonlinear gyrokinetic heat and particle fluxes well for both positive and negative R/L-n. That gives a theoretical and general basis for the persistence of the hollowness, laying the groundwork for the extrapolation to ITER.

  • 7. Batistoni, P.
    et al.
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, Sheena
    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, Atomic and Molecular Physics.
    Rubel, Marek
    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, Simon
    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.
    Zychor, I.
    et al.,
    Benchmark experiments on neutron streaming through JET Torus Hall penetrations2015In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 5, article id 053028Article in journal (Refereed)
    Abstract [en]

    Neutronics experiments are performed at JET for validating in a real fusion environment the neutronics codes and nuclear data applied in ITER nuclear analyses. In particular, the neutron fluence through the penetrations of the JET torus hall is measured and compared with calculations to assess the capability of state-of-art numerical tools to correctly predict the radiation streaming in the ITER biological shield penetrations up to large distances from the neutron source, in large and complex geometries. Neutron streaming experiments started in 2012 when several hundreds of very sensitive thermo-luminescence detectors (TLDs), enriched to different levels in (LiF)-Li-6/(LiF)-Li-7, were used to measure the neutron and gamma dose separately. Lessons learnt from this first experiment led to significant improvements in the experimental arrangements to reduce the effects due to directional neutron source and self-shielding of TLDs. Here we report the results of measurements performed during the 2013-2014 JET campaign. Data from new positions, at further locations in the South West labyrinth and down to the Torus Hall basement through the air duct chimney, were obtained up to about a 40m distance from the plasma neutron source. In order to avoid interference between TLDs due to self-shielding effects, only TLDs containing natural Lithium and 99.97% Li-7 were used. All TLDs were located in the centre of large polyethylene (PE) moderators, with Li-nat and Li-7 crystals evenly arranged within two PE containers, one in horizontal and the other in vertical orientation, to investigate the shadowing effect in the directional neutron field. All TLDs were calibrated in the quantities of air kerma and neutron fluence. This improved experimental arrangement led to reduced statistical spread in the experimental data. The Monte Carlo N-Particle (MCNP) code was used to calculate the air kerma due to neutrons and the neutron fluence at detector positions, using a JET model validated up to the magnetic limbs. JET biological shield and penetrations, the PE moderators and TLDs were modelled in detail. Different tallying methods were used in the calculations, which are routinely used in ITER nuclear analyses: the mesh tally and the track length estimator with multiple steps calculations using the surface source write/read capability available in MCNP. In both cases, the calculated neutron fluence (C) was compared to the measured fluence (E) and hence C/E comparisons have been obtained and are discussed. These results provide a validation of neutronics numerical tools, codes and nuclear data, used for ITER design.

  • 8.
    Batistoni, P.
    et al.
    ENEA, Dept Fus & Nucl Safety Technol, I-00044 Frascati, Rome, Italy.;EUROfus Consortium, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;ENEA CR Frascati, Unita Tecn Fus, I-00044 Rome, Italy..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Technical preparations for the in-vessel 14 MeV neutron calibration at JET2017In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 117, p. 107-114Article in journal (Refereed)
    Abstract [en]

    The power output of fusion devices is measured from their neutron yields which relate directly to the fusion yield. In this paper we describe the devices and methods that have been prepared to perform a new in situ 14 MeV neutron calibration at JET in view of the new DT campaign planned at JET in the next years. The target accuracy of this calibration is 10% as required for ITER, where a precise neutron yield measurement is important, e.g., for tritium accountancy. In this paper, the constraints and early decisions which defined the main calibration approach are discussed, e.g., the choice of 14 MeV neutron source and the deployment method. The physics preparations, source issues, safety and engineering aspects required to calibrate directly the JET neutron detectors are also discussed. The existing JET remote-handling system will be used to deploy the neutron source inside the JET vessel. For this purpose, compatible tooling and systems necessary to ensure safe and efficient deployment have been developed. The scientific programme of the preparatory phase is devoted to fully characterizing the selected 14 MeV neutron generator to be used as the calibrating source, obtain a better understanding of the limitations of the calibration, optimise the measurements and other provisions, and to provide corrections for perturbing factors (e.g., anisotropy of the neutron generator, neutron energy spectrum dependence on emission angle). Much of this work has been based on an extensive programme of Monte-Carlo calculations which provide support and guidance in developing the calibration strategy.

  • 9.
    Batistoni, P.
    et al.
    ENEA, Dipartimento Fus & Sicurezza Nucl, Via E Fermi 45, I-00044 Frascati, Roma, Italy.;ENEA CR Frascati, Unita Tecn Fus, I-00044 Rome, Italy..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Technological exploitation of Deuterium-Tritium operations at JET in support of ITER design, operation and safety2016In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 109, p. 278-285Article in journal (Refereed)
    Abstract [en]

    Within the framework of the EUROfusion programme, a work-package of technology projects (WPJET3) is being carried out in conjunction with the planned Deuterium-Tritium experiment on JET (DTE2) with the objective of maximising the scientific and technological return of DT operations at JET in support of ITER. This paper presents the progress since the start of the project in 2014 in the preparatory experiments, analyses and studies in the areas of neutronics, neutron induced activation and damage in ITER materials, nuclear safety, tritium retention, permeation and outgassing, and waste production in preparation of DTE2.

  • 10. Beal, J.
    et al.
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Deposition in the inner and outer corners of the JET divertor with carbon wall and metallic ITER-like wall2016In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, article id 014052Article in journal (Refereed)
    Abstract [en]

    Rotating collectors and quartz microbalances (QMBs) are used in JET to provide time-dependent measurements of erosion and deposition. Rotation of collector discs behind apertures allows recording of the long term evolution of deposition. QMBs measure mass change via the frequency deviations of vibrating quartz crystals. These diagnostics are used to investigate erosion/deposition during JET-C carbon operation and JET-ILW (ITER-like wall) beryllium/tungsten operation. A simple geometrical model utilising experimental data is used to model the time-dependent collector deposition profiles, demonstrating good qualitative agreement with experimental results. Overall, the JET-ILW collector deposition is reduced by an order of magnitude relative to JET-C, with beryllium replacing carbon as the dominant deposit. However, contrary to JET-C, in JET-ILW there is more deposition on the outer collector than the inner. This reversal of deposition asymmetry is investigated using an analysis of QMB data and is attributed to the different chemical properties of carbon and beryllium.

  • 11. Bernardo, J.
    et al.
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, Sheena
    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.
    Rubel, Marek
    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, Simon
    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.
    Zychor, I.
    et al.,
    Ion temperature and toroidal rotation in JET's low torque plasmas2016In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 87, no 11, article id 11E557Article in journal (Refereed)
    Abstract [en]

    This paper reports on the procedure developed as the best method to provide an accurate and reliable estimation of the ion temperature T-i and the toroidal velocity v(phi) from Charge-eXchange Recombination Spectroscopy (CXRS) data from intrinsic rotation experiments at the Joint European Torus with the carbon wall. The low impurity content observed in such plasmas, resulting in low active CXRS signal, alongside low Doppler shifts makes the determination of Ti and v(phi) particularly difficult. The beam modulation method will be discussed along with the measures taken to increase photon statistics and minimise errors from the absolute calibration and magneto-hydro-dynamics effects that may impact the CXRS passive emission.

  • 12.
    Bernert, M.
    et al.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany.;Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    Power exhaust by SOL and pedestal radiation at ASDEX Upgrade and JET2017In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 12, p. 111-118Article in journal (Refereed)
    Abstract [en]

    Future fusion reactors require a safe, steady state divertor operation. A possible solution for the power exhaust challenge is the detached divertor operation in scenarios with high radiated power fractions. The radiation can be increased by seeding impurities, such as N for dominant scrape-off-layer radiation, Ne or Ar for SOL and pedestal radiation and Kr for dominant core radiation. Recent experiments on two of the all-metal tokamaks, ASDEX Upgrade (AUG) and JET, demonstrate operation with high radiated power fractions and a fully-detached divertor by N, Ne or Kr seeding with a conventional divertor in a vertical target geometry. For both devices similar observations can be made. In the scenarios with the highest radiated power fraction, the dominant radiation originates from the confined region, in the case of N and Ne seeding concentrated in a region close to the X-point. Applying these seed impurities for highly radiative scenarios impacts local plasma parameters and alters the impurity transport in the pedestal region. Thus, plasma confinement and stability can be affected. A proper understanding of the effects by these impurities is required in order to predict the applicability of such scenarios for future devices.

  • 13.
    Binda, F.
    et al.
    Uppsala Univ, Dept Phys & Astron, Uppsala, Sweden.;Uppsala Univ, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Calculation of the profile-dependent neutron backscatter matrix for the JET neutron camera system2017In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 123, p. 865-868Article in journal (Refereed)
    Abstract [en]

    We investigated the dependence of the backscatter component of the neutron spectrum on the emissivity profile. We did so for the JET neutron camera system, by calculating a profile-dependent backscatter matrix for each of the 19 camera channels using a MCNP model of the JET tokamak. We found that, when using a low minimum energy for the summation of the counts in the neutron pulse height spectrum, the backscatter contribution can depend significantly on the emissivity profile. The maximum variation in the backscatter level was 24% (8.0% when compared to the total emission). This effect needs to be considered when a correction for the backscatter contribution is applied to the measured profile. (C) 2017 The Authors. Published by Elsevier B.V.

  • 14.
    Binda, F.
    et al.
    Uppsala Univ, Dept Phys & Astron, Uppsala, Sweden.;Uppsala Univ, Dept Phys & Astron, SE-75120 Uppsala, Sweden..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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 (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    et al.,
    Generation of the neutron response function of an NE213 scintillator for fusion applications2017In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 866, p. 222-229Article in journal (Refereed)
    Abstract [en]

    In this work we present a method to evaluate the neutron response function of an NE213 liquid scintillator. This method is particularly useful when the proton light yield function of the detector has not been measured, since it is based on a proton light yield function taken from literature, MCNPX simulations, measurements of gammarays from a calibration source and measurements of neutrons from fusion experiments with ohmic plasmas. The inclusion of the latter improves the description of the proton light yield function in the energy range of interest (around 2.46 MeV). We apply this method to an NE213 detector installed at JET, inside the radiation shielding of the magnetic proton recoil (MPRu) spectrometer, and present the results from the calibration along with some examples of application of the response function to perform neutron emission spectroscopy (NES) of fusion plasmas. We also investigate how the choice of the proton light yield function affects the NES analysis, finding that the result does not change significantly. This points to the fact that the method for the evaluation of the neutron response function is robust and gives reliable results. (C) 2017 Published by Elsevier B.V.

  • 15.
    Bisoffi, Andrea
    et al.
    Univ Trento, Dipartimento Ingn Ind, Trento, Italy..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Hybrid cancellation of ripple disturbances arising in AC/DC converters2017In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 77, p. 344-352Article in journal (Refereed)
    Abstract [en]

    In AC/DC converters, a peculiar periodic nonsmooth waveform arises, the so-called ripple. In this paper we propose a novel model that captures this nonsmoothness by means of a hybrid dynamical system performing state jumps at certain switching instants, and we illustrate its properties with reference to a three phase diode bridge rectifier. As the ripple corrupts an underlying desirable signal, we propound two observer schemes ensuring asymptotic estimation of the ripple, the first with and the second without knowledge of the switching instants. Our theoretical developments are well placed in the context of recent techniques for hybrid regulation and constitute a contribution especially for our second observer, where the switching instants are estimated. Once asymptotic estimation of the ripple is achieved, the ripple can be conveniently canceled from the desirable signal, and thanks to the inherent robustness properties of the proposed hybrid formulation, the two observer schemes require only that the desirable signal is slowly time varying compared to the ripple. Exploiting this fact, we illustrate the effectiveness of our second hybrid observation law on experimental data collected from the Joint European Torus tokamak.

  • 16. Bolshakova, I.
    et al.
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Jonsson, Thomas
    Menmuir, Sheena
    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, Atomic and Molecular Physics.
    Rubel, Marek
    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, Simon
    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.
    Zychor, I.
    et al.,
    Experimental evaluation of stable long term operation of semiconductor magnetic sensors at ITER relevant environment2015In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 8, article id 083006Article in journal (Refereed)
    Abstract [en]

    The paper deals with radiation resistant sensors and their associated measuring instrumentation developed in the course of R and D activities carried out in the framework of an international collaboration. The first trial tests of three-dimensional (3D) probes with Hall sensors have been performed in European tokamaks TORE SUPRA (2004) and JET (2005). Later in 2009 six sets of 3D probes were installed in JET and now continue to operate. The statistical analysis performed in 2014 on the basis of the JET database have demonstrated stable long term operation of all 18 sensors of 3D probes. The results of measurements conducted at the neutron fluxes of nuclear reactors have demonstrated the operability of the sensors up to high neutron fluences of F > 10(18)n , cm(-2) that exceeds the maximum one for the locations of steady state sensors in ITER over its total lifetime.

  • 17.
    Boltruczyk, G.
    et al.
    NCBJ, PL-05400 Otwock, Poland..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    et al.,
    Development of MPPC-based detectors for high count rate DT campaigns at JET2017In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 123, p. 940-944Article in journal (Refereed)
    Abstract [en]

    The products of fusion reactions at JET are measured using different diagnostic techniques. One of the methods is based on measurements of gamma-rays, originating from reactions between fast ions and plasma impurities. During the forthcoming deuterium-tritium (DT) campaign a particular attention will be paid to 4.44 MeV gamma-rays emitted in the Be-9(alpha,n gamma)C-12 reaction. Gamma-ray detectors foreseen for measurements in DT campaigns have to be able to register spectra at high count rates, up to approximately 500 kHz. For the Gamma-ray Camera at JET a new setup will be based on scintillators with a short decay time, e.g., CeBr3, and a multi-pixel photon counter (MPPC). We present two methods of output signal shortening in modules based on MPPC. A short detector output signal is necessary in order to minimize the number of pile up events at high count rates. One method uses a passive RC circuit with a pole zero cancellation, whereas an active transimpedance amplifier is used in the other one. Due to the strong dependence of MPPC properties on temperature variation, a special device MTCD@NCBJ was designed and produced to stabilize the gain in MPPC-based scintillation detectors. We show that this device guarantees stable working conditions.

  • 18.
    Bonanomi, N.
    et al.
    Ist Fis Plasma CNR, I-20125 Milan, Italy. Culham Sci Ctr, JET, EUROfus Consortium, Abingdon OX14 3DB, Oxon, England.;Ist Fis Plasma CNR, I-20125 Milan, Italy.;Univ Milano Bicocca, I-20126 Milan, Italy..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Trapped electron mode driven electron heat transport in JET: experimental investigation and gyro-kinetic theory validation2015In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 11, article id 113016Article in journal (Refereed)
    Abstract [en]

    The main purpose of this work is to study the dependence of trapped electron modes (TEM) threshold and of electron stiffness on the most relevant plasma parameters. Dedicated transport experiments based on heat flux scans and T-e modulation have been performed in JET in TEM dominated plasmas with pure ICRH electron heating and a numerical study using gyrokinetic simulations has been performed with the code GKW. Using multilinear regressions on the experimental data, the stabilizing effect of magnetic shear predicted by theory for our plasma parameters is confirmed while no significant effect of safety factor was found. Good quantitative agreement is found between the TEM thresholds found in the experiments and calculated with linear GKW simulations. Non-linear simulations have given further confirmation of the threshold values and allowed comparison with the values of stiffness found experimentally. Perturbative studies using RF power modulation indicate the existence of an inward convective term for the electron heat flux. Adding NBI power, ion temperature gradient (ITG) modes become dominant and a reduction of vertical bar del T-e vertical bar/T-e with respect to pure ICRH, TEM dominant discharges has been experimentally observed, in spite of increased total electron power. Possible explanations are discussed.

  • 19.
    Borodin, D.
    et al.
    Forschungszentrum Julich GmbH, Inst Energie & Klimaforsch Plasmaphys, D-52425 Julich, Germany.;Forsch Zentrum Julich GmbH, Inst Energie & Klimaforsch Plasmaphys, D-52425 Julich, Germany..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Improved ERO modelling for spectroscopy of physically and chemically assisted eroded beryllium from the JET-ILW2016In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 9, p. 604-609Article in journal (Refereed)
    Abstract [en]

    Physical and chemical assisted physical sputtering were characterised by the Be I and Be II line and BeD band emission in the observation chord measuring the sightline integrated emission in front of the inner beryllium limiter at the torus midplane. The 3D local transport and plasma-surface interaction Monte-Carlo modelling (ERO code [18]) is a key for the interpretation of the observations in the vicinity of the shaped solid Be limiter. The plasma parameter variation (density scan) in limiter regime has provided a useful material for the simulation benchmark. The improved background plasma parameters input, the new analytical expression for particle tracking in the sheath region and implementation of the BeD release into ERO has helped to clarify some deviations between modelling and experiments encountered in the previous studies [4,5]. Reproducing the observations provides additional confidence in our 'ERO-min' fit for the physical sputtering yields for the plasma-wetted areas based on simulated data.

  • 20.
    Borodkina, I.
    et al.
    Natl Res Nucl Univ MephI, Kashirskoe Sh 31, Moscow, Russia.;Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, D-52425 Julich, Germany..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Johnson, Thomas Joe
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    An analytical expression for ion velocities at the wall including the sheath electric field and surface biasing for erosion modeling at JET ILW2017In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 12, p. 341-345Article in journal (Refereed)
    Abstract [en]

    For simulation of plasma-facing component erosion in fusion experiments, an analytical expression for the ion velocity just before the surface impact including the local electric field and an optional surface biasing effect is suggested. Energy and angular impact distributions and the resulting effective sputtering yields were produced for several experimental scenarios at JET ILW mostly involving PFCs exposed to an oblique magnetic field. The analytic solution has been applied as an improvement to earlier ERO modelling of localized, Be outer limiter, RF-enhanced erosion, modulated by toggling of a remote, however magnetically connected ICRH antenna. The effective W sputtering yields due to D and Be ion impact in Type-I and Type-III ELMs and inter-ELM conditions were also estimated using the analytical approach and benchmarked by spectroscopy. The intra-ELM W sputtering flux increases almost 10 times in comparison to the inter-ELM flux.

  • 21. Borodkina, I.
    et al.
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    et al.,
    An Analytical Expression for the Electric Field and Particle Tracing in Modelling of Be Erosion Experiments at the JET ITER-like Wall2016In: Contributions to Plasma Physics, ISSN 0863-1042, E-ISSN 1521-3986, Vol. 56, no 6-8, p. 640-645Article in journal (Refereed)
    Abstract [en]

    A new analytical approximation for the electric potential profile in the presence of an oblique magnetic field and the analytical solution for the particle motion just before the impact with a plasma-facing surface are presented. These approximations are in good agreement with fluid solutions and the corresponding PIC simulations. These expressions were applied to provide effective physical erosion yields for Be, which have in a second step been used in ERO code simulations of spectroscopy at Be limiters of the JET ITER-like wall. These new analytical expressions lead to an increase of the effective physical sputtering yields of Be by deuteron impact up to 30% in comparison with earlier pure numerical simulations. (

  • 22.
    Bourdelle, C.
    et al.
    CEA, IRFM, F-13108 St Paul Les Durance, France..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, Sheena
    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, Atomic and Molecular Physics.
    Rubel, Marek
    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, Simon
    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.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    L to H mode transition: parametric dependencies of the temperature threshold2015In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 7, article id 073015Article in journal (Refereed)
    Abstract [en]

    The L to H mode transition occurs at a critical power which depends on various parameters, such as the magnetic field, the density, etc. Experimental evidence on various tokamaks (JET, ASDEX-Upgrade, DIII-D, Alcator C-Mod) points towards the existence of a critical temperature characterizing the transition. This criterion for the L-H transition is local and is therefore easier to be compared to theoretical approaches. In order to shed light on the mechanisms of the transition, simple theoretical ideas are used to derive a temperature threshold (T-th). They are based on the stabilization of the underlying turbulence by a mean radial electric field shear. The nature of the turbulence varies as the collisionality decreases, from resistive ballooning modes to ion temperature gradient and trapped electron modes. The obtained parametric dependencies of the derived T-th are tested versus magnetic field, density, effective charge. Various robust experimental observations are reproduced, in particular T-th increases with magnetic field B and increases with density below the density roll-over observed on the power threshold.

  • 23.
    Bourdelle, C.
    et al.
    CEA, IRFM, F-13108 St Paul Les Durance, France..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, Sheena
    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, Atomic and Molecular Physics.
    Rubel, Marek
    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, Simon
    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.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    WEST Physics Basis2015In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 6, article id 063017Article in journal (Refereed)
    Abstract [en]

    With WEST (Tungsten Environment in Steady State Tokamak) (Bucalossi et al 2014 Fusion Eng. Des. 89 907-12), the Tore Supra facility and team expertise (Dumont et al 2014 Plasma Phys. Control. Fusion 56 075020) is used to pave the way towards ITER divertor procurement and operation. It consists in implementing a divertor configuration and installing ITER-like actively cooled tungsten monoblocks in the Tore Supra tokamak, taking full benefit of its unique long-pulse capability. WEST is a user facility platform, open to all ITER partners. This paper describes the physics basis of WEST: the estimated heat flux on the divertor target, the planned heating schemes, the expected behaviour of the L-H threshold and of the pedestal and the potential W sources. A series of operating scenarios has been modelled, showing that ITER-relevant heat fluxes on the divertor can be achieved in WEST long pulse H-mode plasmas.

  • 24.
    Bourdelle, C.
    et al.
    CEA, IRFM, F-13108 St Paul Les Durance, France..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Core turbulent transport in tokamak plasmas: bridging theory and experiment with QuaLiKiz2016In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 58, no 1, article id 014036Article in journal (Refereed)
    Abstract [en]

    Nonlinear gyrokinetic codes allow for detailed understanding of tokamak core turbulent transport. However, their computational demand precludes their use for predictive profile modeling. An alternative approach is required to bridge the gap between theoretical understanding and prediction of experiments. A quasilinear gyrokinetic model, QuaLiKiz (Bourdelle et al 2007 Phys. Plasmas 14 112501), is demonstrated to be rapid enough to ease systematic interface with experiments. The derivation and approximation of this approach are reviewed. The quasilinear approximation is proven valid over a wide range of core plasma parameters. Examples of profile prediction using QuaLiKiz coupled to the CRONOS integrated modeling code (Artaud et al 2010 Nucl. Fusion 50 043001) are presented. QuaLiKiz is being coupled to other integrated modeling platforms such as ETS and JETTO. QuaLiKiz quasilinear gyrokinetic turbulent heat, particle and angular momentum fluxes are available to all users. It allows for extensive stand-alone interpretative analysis and for first principle based integrated predictive modeling.

  • 25.
    Boyer, Helen
    et al.
    CCFE, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England. EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    JET Tokamak, preparation of a safety case for tritium operations2016In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 109, p. 1308-1312Article in journal (Refereed)
    Abstract [en]

    A new Safety Case is required to permit tritium operations on JET during the forthcoming DTE2 campaign. The outputs, benefits and lessons learned associated with the production of this Safety Case are presented. The changes that have occurred to the Safety Case methodology since the last JET tritium Safety Case are reviewed. Consideration is given to the effects of modifications, particularly ITER related changes, made to the JET and the impact these have on the hazard assessments as well as normal operations. Several specialized assessments, including recent MELCOR modelling, have been undertaken to support the production of this Safety Case and the impact of these assessments is outlined. Discussion of the preliminary actions being taken to progress implementation of this Safety Case is provided, highlighting new methods to improve the dissemination of the key Safety Case results to the plant operators. Finally, the work required to complete this Safety Case, before the next tritium campaign, is summarized. (C) 2016 EURATOM. Published by Elsevier B.V. All rights reserved.

  • 26.
    Bravenec, R.
    et al.
    Fourth State Res, Austin, TX 78701 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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    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, Sheena
    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.
    Rubel, Marek
    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.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al,
    Benchmarking the GENE and GYRO codes through the relative roles of electromagnetic and E x B stabilization in JET high-performance discharges2016In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 58, no 12, article id 125018Article in journal (Refereed)
    Abstract [en]

    Nonlinear gyrokinetic simulations using the GENE code have previously predicted a significant nonlinear enhanced electromagnetic stabilization in certain JET discharges with high neutral-beam power and low core magnetic shear (Citrin et al 2013 Phys. Rev. Lett. 111 155001, 2015 Plasma Phys. Control. Fusion 57 014032). This dominates over the impact of E x B flow shear in these discharges. Furthermore, fast ions were shown to be a major contributor to the electromagnetic stabilization. These conclusions were based on results from the GENE gyrokinetic turbulence code. In this work we verify these results using the GYRO code. Comparing results (linear frequencies, eigenfunctions, and nonlinear fluxes) from different gyrokinetic codes as a means of verification (benchmarking) is only convincing if the codes agree for more than one discharge. Otherwise, agreement may simply be fortuitous. Therefore, we analyze three discharges, all with a carbon wall: a simplified, two-species, circular geometry case based on an actual JET discharge; an L-mode discharge with a significant fast-ion pressure fraction; and a low-triangularity high-beta hybrid discharge. All discharges were analyzed at normalized toroidal flux coordinate rho = 0.33 where significant ion temperature peaking is observed. The GYRO simulations support the conclusion that electromagnetic stabilization is strong, and dominates E x B shear stabilization.

  • 27. Brezinsek, S.
    et al.
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    et al.,
    Characterisation of the deuterium recycling at the W divertor target plates in JET during steady-state plasma conditions and ELMs2016In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, article id 014076Article in journal (Refereed)
    Abstract [en]

    Experiments in the JET tokamak equipped with the ITER-like wall (ILW) revealed that the inner and outer target plate at the location of the strike points represent after one year of operation intact tungsten (W) surfaces without any beryllium (Be) surface coverage. The dynamics of near-surface retention, implantation, desorption and recycling of deuterium (D) in the divertor of plasma discharges are determined by W target plates. As the W plasma-facing components (PFCs) are not actively cooled, the surface temperature (T-surface) is increasing with plasma exposure, varying the balance between these processes in addition to the impinging deuteron fluxes and energies. The dynamic behaviour on a slow time scale of seconds was quantified in a series of identical L-mode discharges (JET Pulse Number (JPN)#81938-73) by intra-shot gas analysis providing the reduction of deuterium retention in W PFCs by 1/3 at a base temperature (T-base) range at the outer target plate between 65 degrees C and 150 degrees C equivalent to a T-surface span of 150 degrees C and 420 degrees C. The associated recycling and molecular D desorption during the discharge varies only at lowest temperatures moderately, whereas desorption between discharges rises significantly with increasing T-base. The retention measurements represent the sum of inner and outer divertor interaction at comparable T-surface. The dynamic behaviour on a fast time scale of ms was studied in a series of identical H-mode discharges (JPN #83623-83974) and coherent edge-localized mode (ELM) averaging. High energetic ELMs of about 3 keV are impacting on the W PFCs with fluxes of 3 x 10(23) D+ s(-1) m(-2) which is about four times higher than inter-ELM ion fluxes with an impact energy of about E-im = 200 eV. This intra-ELM ion flux is associated with a high heat flux of about 60 MW m(-2) to the outer target plate which causes T-surface rise by Delta T = 100 K per ELM covering finally the range between 160 degrees C and 1400 degrees C during the flat-top phase. ELM-induced desorption from saturated near-surface implantation regions as well as deep ELM-induced deuterium implantation areas under varying baseline temperature takes place. Subsequent refuelling by intra-ELM deuteron fluxes occurs and a complex interplay between deuterium fuelling and desorption can be observed in the temporal ELM footprint of the surface temperature (IR thermography), the impinging deuteron flux (Langmuir probes), and the Balmer radiation (emission spectroscopy) as representative for the deuterium recycling flux. In contrast to JET-C, a pronounced second peak, similar or equal to 8 ms delayed with respect to the initial ELM crash, in the D-alpha radiation and the ion flux has been observed. The peak can be related to desorption of implanted energetic intra-ELM D+ diffusing to the W surface, and performing local recycling.

  • 28. Brezinsek, S.
    et al.
    Jachmich, S.
    Stamp, M. F.
    Meigs, A. G.
    Coenen, J. W.
    Krieger, K.
    Giroud, C.
    Groth, M.
    Philipps, V.
    Grünhagen, S.
    Smith, R.
    Van Rooij, G. J.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Matthews, G. F.
    Residual carbon content in the initial ITER-Like Wall experiments at JET2013In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 438, no Suppl., p. S303-S308Article in journal (Refereed)
    Abstract [en]

    The residual carbon content and carbon edge flux in JET have been assessed by three independent diagnostic techniques after start of plasma operation with the ITER-Like Wall (ILW) with beryllium first wall and tungsten divertor: (i) in-situ measurements with optical spectroscopy on low ionisation stages of carbon, (ii) charge-exchange recombination spectroscopy, and (iii) residual gas composition analysis in dedicated global gas balance experiments. Direct comparison experiments in L-mode discharges were carried out between references from the previously installed material configuration with plasma-facing components made of carbon-fibre composite (JET-CFC) and the JET-ILW. The temporal evolution of the C divertor flux since installation of the ILW has been studied in the ohmic phase of dedicated monitoring discharges which have been executed regularly throughout the experimental exploitation so far (60000 plasma seconds). The C flux behaviour in the divertor can be divided in three phases: initial fast drop, moderate reduction phase, and a long lasting phase with almost constant C flux. The Be flux in both divertor legs mirrors the behaviour of C. All experiments and diagnostic techniques demonstrate a strong reduction in C fluxes and C content of more than one order of magnitude with respect to JET-CFC which is in line with the reduction in long-term fuel retention due to co-deposition. There is no evidence of an increase in residual carbon in time, thus no indication that a damage of the thin tungsten coatings on CFC substrate in the divertor occurred.

  • 29.
    Budny, R. V.
    et al.
    Princeton Univ, Princeton, NJ 08540 USA..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Core fusion power gain and alpha heating in JET, TFTR, and ITER2016In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 56, no 5, article id 056002Article in journal (Refereed)
    Abstract [en]

    Profiles of the ratio of fusion power and the auxiliary heating power (MT are calculated for the TFTR and JET discharges with the highest neutron emission rates, and arc predicted for ITER. Core values above 1.3 for JET and 0.8 for TFTR are obtained, Values above 20 are predicted for ITER baseline plasmas.

  • 30. Buratti, P.
    et al.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    et al.,
    Diagnostic application of magnetic islands rotation in JET2016In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 56, no 7, article id 076004Article in journal (Refereed)
    Abstract [en]

    Measurements of the propagation frequency of magnetic islands in JET are compared with diamagnetic drift frequencies, in view of a possible diagnostic application to the determination of markers for the safety factor profile. Statistical analysis is performed for a database including many well-diagnosed plasma discharges. Propagation in the plasma frame, i.e. with subtracted E x B Doppler shift, results to be in the ion diamagnetic drift direction, with values ranging from 0.8 (for islands at the q = 2 resonant surface) to 1.8 (for more internal islands) times the ion diamagnetic drift frequency. The diagnostic potential of the assumption of island propagation at exactly the ion diamagnetic frequency is scrutinised. Rational-q locations obtained on the basis of this assumption are compared with the ones measured by equilibrium reconstruction including motional Stark effect measurements as constraints. Systematic shifts and standard deviations are determined for islands with (poloidal, toroidal) periodicity indexes of (2, 1), (3, 2), (4, 3) and (5, 3) and possible diagnostic applications are indicated.

  • 31. Cannas, Barbara
    et al.
    Pisano, Fabio
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Nonlinear dynamic analysis of D-alpha signals for type I edge localized modes characterization on JET with a carbon wall2018In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 60, no 2, article id 025010Article in journal (Refereed)
    Abstract [en]

    In this paper, the dynamic characteristics of type-I ELM time-series from the JET tokamak, the world's largest magnetic confinement plasma physics experiment, have been investigated. The dynamic analysis has been focused on the detection of nonlinear structure in D a radiation time series. Firstly, the method of surrogate data has been applied to evaluate the statistical significance of the null hypothesis of static nonlinear distortion of an underlying Gaussian linear process. Several nonlinear statistics have been evaluated, such us the time delayed mutual information, the correlation dimension and the maximal Lyapunov exponent. The obtained results allow us to reject the null hypothesis, giving evidence of underlying nonlinear dynamics. Moreover, no evidence of low-dimensional chaos has been found; indeed, the analysed time series are better characterized by the power law sensitivity to initial conditions which can suggest a motion at the 'edge of chaos', at the border between chaotic and regular non-chaotic dynamics. This uncertainty makes it necessary to further investigate about the nature of the nonlinear dynamics. For this purpose, a second surrogate test to distinguish chaotic orbits from pseudoperiodic orbits has been applied. In this case, we cannot reject the null hypothesis which means that the ELM time series is possibly pseudo-periodic. In order to reproduce pseudo-periodic dynamical properties, a periodic state-of-the-art model, proposed to reproduce the ELM cycle, has been corrupted by a dynamical noise, obtaining time series qualitatively in agreement with experimental time series.

  • 32.
    Carralero, D.
    et al.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany.;Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Experimental Validation of a Filament Transport Model in Turbulent Magnetized Plasmas2015In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 115, no 21, article id 215002Article in journal (Refereed)
    Abstract [en]

    In a wide variety of natural and laboratory magnetized plasmas, filaments appear as a result of interchange instability. These convective structures substantially enhance transport in the direction perpendicular to the magnetic field. According to filament models, their propagation may follow different regimes depending on the parallel closure of charge conservation. This is of paramount importance in magnetic fusion plasmas, as high collisionality in the scrape-off layer may trigger a regime transition leading to strongly enhanced perpendicular particle fluxes. This work reports for the first time on an experimental verification of this process, linking enhanced transport with a regime transition as predicted by models. Based on these results, a novel scaling for global perpendicular particle transport in reactor relevant tokamaks such as ASDEX-Upgrade and JET is found, leading to important implications for next generation fusion devices.

  • 33. Chankin, A. V.
    et al.
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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 (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    et al.,
    Influence of the E X B drift in high recycling divertors on target asymmetries2015In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 57, no 9, article id 095002Article in journal (Refereed)
    Abstract [en]

    Detailed analysis of convective fluxes caused by E x B drifts is carried out in a realistic JET configuration, based on a series of EDGE2D-EIRENE runs. The EDGE2D-EIRENE code includes all guiding centre drifts, E x B as well as. B and centrifugal drifts. Particle sources created by divergences of radial and poloidal components of the E x B drift are separately calculated for each flux tube in the divertor. It is demonstrated that in high recycling divertor conditions radial E x B drift creates particle sources in the common flux region (CFR) consistent with experimentally measured divertor and target asymmetries, with the poloidal E x B drift creating sources of an opposite sign but smaller in absolute value. That is, the experimentally observed asymmetries in the CFR are the opposite to what poloidal E x B drift by itself would cause. In the private flux region (PFR), the situation is reversed, with poloidal E x B drift being dominant. In this region poloidal E x B drift by itself contributes to experimentally observed asymmetries. Thus, in each region, the dominant component of the E x B drift acts so as to create the density (and hence, also temperature) asymmetries that are observed both in experiment and in 2D edge fluid codes. Since the total number of charged particles is much greater in the CFR than in PFR, divertor asymmetries caused by the E x B drift should be attributed primarily to particle sources in the CFR caused by radial E x B drift.

  • 34.
    Chankina, A. V.
    et al.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Munich, Germany..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Johnson, Thomas Joe
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    Possible influence of near SOL plasma on the H-mode power threshold2017In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 12, p. 273-277Article in journal (Refereed)
    Abstract [en]

    A strong effect of divertor configuration on the threshold power for the L-H transition (P-LH) was observed in recent JET experiments in the new ITER-like Wall (ILW) [1-3]. Following a series of EDGE2D-EIRENE code simulations with Be impurity and drifts a possible mechanism for the P-LH variation with the divertor geometry is proposed. Both experiment and code simulations show that in the configuration with lower neutral recycling near the outer strike point (OSP), electron temperature (T-e) peaks near the OSP prior to the L-H transition, while in the configuration with higher OSP recycling T-e peaks further out in the scrape-offlayer (SOL) and the plasma stays in the L-mode at the same input power. Code results show large positive radial electric field (E-r) in the near SOL under lower recycling conditions leading to a large E x B shear across the separatrix which may trigger earlier (at lower input power) edge turbulence suppression and lower P-LH. Suppressed T-e's at OSP in configurations with strike points on vertical targets (VT) were observed earlier and explained by a geometrical effect of neutral recycling near this particular position, whereas in configurations with strike points on horizontal targets (HT) the OSP appears to be more open for neutrals (see e.g. review paper [4]).

  • 35. Chapman, I. T.
    et al.
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    et al.,
    Advances in understanding and utilising ELM control in JET2016In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 58, no 1, article id 014017Article in journal (Refereed)
    Abstract [en]

    Edge localised mode (ELM) control may be essential to develop ITER scenarios with a reasonable lifetime of divertor components, whilst ELM pacing may be essential to develop stationary ITER scenarios with a tungsten divertor. Resonant magnetic perturbations (RMPs) have mitigated ELMs in high collisionality plasmas in JET. The efficacy of RMPs in mitigating the ELMs is found to depend on plasma shaping, with the change in magnetic boundary achieved when non-axisymmetric fields are applied facilitating access to small ELM regimes. The understanding of ELM pacing by vertical kicks or pellets has also been improved in a range of pedestal conditions in JET (T-ped = 0.7-1.3 keV) encompassing the ITER-expected domain (beta(N) = 1.4-2.4, H-98(y,H- 2) = 0.8-1.2, f(GW) similar to 0.7). ELM triggering is reliable provided the perturbation is above a threshold which depends on pedestal parameters. ELM triggering is achieved even in the first 10% of the natural ELM cycle suggesting no inherent maximum frequency. At high normalised pressure, the peeling-ballooning modes are stabilised as predicted by ELITE, necessitating a larger perturbation from either kicks or pellets in order to trigger ELMs. Both kicks and pellets have been used to pace ELMs for tungsten flushing. This has allowed stationary plasma conditions with low gas injection in plasmas where the natural ELM frequency is such that it would normally preclude stationary conditions.

  • 36. Chapman, S. C.
    et al.
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    et al.,
    The global build-up to intrinsic ELM bursts and comparison with pellet triggered ELMs seen in JET2017In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 2, article id 022017Article in journal (Refereed)
    Abstract [en]

    We focus on JET plasmas in which ELMs are triggered by pellets in the presence of ELMs which occur naturally. We perform direct time domain analysis of signals from fast radial field coils and toroidal full flux azimuthal loops. These toroidally integrating signals provide simultaneous high time resolution measurements of global plasma dynamics and its coupling to the control system. We examine the time dynamics of these signals in plasmas where pellet injection is used to trigger ELMs in the presence of naturally occurring ELMs. Pellets whose size and speed are intended to provide maximum local perturbation for ELM triggering are launched at pre-programmed times, without correlation to the occurrence times of intrinsic ELMs. Pellet rates were sufficiently low to prevent sustained changes of the underlying plasma conditions and natural ELM behaviour. We find a global signature of the build-up to natural ELMs in the temporal analytic phase of both the full flux loops and fast radial field coil signals. Before a natural ELM, the signal phases align to the same value on a similar to 2-5 ms timescale. This global build up to a natural ELM occurs whilst the amplitude of the full flux loop and fast radial field coil signals are at their background value: it precedes the response seen in these signals to the onset of ELMing. In contrast these signals do not clearly phase align before the ELM for ELMs which are the first to occur following pellet injection. This provides a direct test that can distinguish when an ELM is triggered by a pellet as opposed to occurring naturally. It further supports the idea [1-4] of a global build up phase that precedes natural ELMs; pellets can trigger ELMs even when the signal phase is at a value when a natural ELM is unlikely to occur.

  • 37.
    Chapman, S. C.
    et al.
    Univ Warwick, Dept Phys, Ctr Fus Space & Astrophys, Coventry CV4 7AL, W Midlands, England.;Max Planck Inst Phys Komplexer Syst, Dresden, Germany.;Univ Warwick, Dept Phys, Coventry CV4 7AL, W Midlands, England..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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 (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    The global build-up to intrinsic edge localized mode bursts seen in divertor full flux loops in JET2015In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 22, no 7, article id 072506Article in journal (Refereed)
    Abstract [en]

    A global signature of the build-up to an intrinsic edge localized mode (ELM) is found in the temporal analytic phase of signals measured in full flux azimuthal loops in the divertor region of JET. Toroidally integrating, full flux loop signals provide a global measurement proportional to the voltage induced by changes in poloidal magnetic flux; they are electromagnetically induced by the dynamics of spatially integrated current density. We perform direct time-domain analysis of the high time-resolution full flux loop signals VLD2 and VLD3. We analyze plasmas where a steady H-mode is sustained over several seconds during which all the observed ELMs are intrinsic; there is no deliberate intent to pace the ELMing process by external means. ELM occurrence times are determined from the Be II emission at the divertor. We previously [ Chapman et al., Phys. Plasmas 21, 062302 (2014); Chapman et al., in 41st EPS Conference on Plasma Physics, Europhysics Conference Abstracts (European Physical Society, 2014), Vol. 38F, ISBN 2-914771-90-8] found that the occurrence times of intrinsic ELMs correlate with specific temporal analytic phases of the VLD2 and VLD3 signals. Here, we investigate how the VLD2 and VLD3 temporal analytic phases vary with time in advance of the ELM occurrence time. We identify a build-up to the ELM in which the VLD2 and VLD3 signals progressively align to the temporal analytic phase at which ELMs preferentially occur, on a similar to 2 - 5ms timescale. At the same time, the VLD2 and VLD3 signals become temporally phase synchronized with each other, consistent with the emergence of coherent global dynamics in the integrated current density. In a plasma that remains close to a global magnetic equilibrium, this can reflect bulk displacement or motion of the plasma. This build-up signature to an intrinsic ELM can be extracted from a time interval of data that does not extend beyond the ELM occurrence time, so that these full flux loop signals could assist in ELM prediction or mitigation.

  • 38.
    Chiariello, Andrea Gaetano
    et al.
    Seconda Univ Napoli, Dept Ind & Informat Engn, Aversa, CE, Italy..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    A 3D electromagnetic model of the iron core in JET2017In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 123, p. 527-531Article in journal (Refereed)
    Abstract [en]

    The Magnet and Power Supplies system in JET includes a ferromagnetic core able to increase the transformer effect by improving the magnetic coupling with the plasma. The iron configuration is based on an inner cylindrical core and eight returning limbs; the ferromagnetic circuit is designed in such a way that the inner column saturates during standard operations [1]. The modelling of the magnetic circuit is a critical issue because of its impact on several applications, including equilibrium and reconstruction analysis required for control applications. The most used model in present applications is based on Equivalent Currents (ECs) placed on the iron boundary together with additional specific constraints, in a 2D axisymmetric frame. The (circular) ECs are chosen, by using the available magnetic measurements, to best represent the magnetic polarization effect [1]. Due to the axisymmetric assumption such approach is not well suited to deal with significant 3D effects, e.g. arising in operations with Error Field Correction Coils (EFCC). In this paper a new methodology is proposed, based on a set of 3D-shaped ECs and able to better model the actual 3D magnetization giving rise to a linear system to be solved. According to a well assessed approach [2], the 3D shape of ECs is represented by a set of elementary sources. The methodology has been successfully validated in a number of JET dry-run experiments where 3D effects are generated by EFCC currents. The new procedure has been designed to be easily coupled with equilibrium or reconstruction codes such as EFIT/V3FIT. The proposed model resulted to be very effective in representing 3D iron magnetization, especially if compared with typical 2D models.

  • 39. Clairet, F.
    et al.
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    et al.,
    Plasma turbulence measured with fast frequency swept reflectometry in JET H-mode plasmas2016In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 56, no 12, article id 126019Article in journal (Refereed)
    Abstract [en]

    In this work we present recent achievements to provide precise measurements of turbulence on JET H-mode plasmas using frequency sweeping reflectometry diagnostic. The plasma density fluctuations retrieved from swept reflected signals, first initiated with the Tore Supra reflectometry (Heuraux et al 2003 Rev. Sci. Instrum. 74 1501, Vermare et al 2006 Nucl. Fusion 46 S743, Gerbaud et al 2006 Rev. Sci. Instrum. 77 10E928), provides a radial profile of the density fluctuation level and its spectral structure. Using the complete set of the JET X-mode fast sweeping heterodyne reflectometers we have determined the temporal dynamic of the density fluctuation profile from the edge to the center during an H-mode discharge. At the L-H transition, the turbulence reduction seems to occur, at first, simultaneously from the edge to the center then deepens at the edge at rho similar to 0.95 and this deepening propagates toward the center with a steepening of the wavenumber spectra. During an edge localized mode (ELM) event, a substantial density fluctuations increase has been observed with a localized turbulent wave front propagating toward the center accompanying a particle transport. We also show that type-III ELMs sustain a steady and high level of plasma turbulence compare to type-I.

  • 40. Coenen, J. W.
    et al.
    Sertoli, M.
    Brezinsek, S.
    Coffey, I.
    Dux, R.
    Giroud, C.
    Groth, M.
    Huber, A.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Krieger, K.
    Lawson, K.
    Marsen, S.
    Meigs, A.
    Neu, R.
    Puetterich, T.
    van Rooij, G. J.
    Stamp, M. F.
    Long-term evolution of the impurity composition and impurity events with the ITER-like wall at JET2013In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 53, no 7, p. 073043-Article in journal (Refereed)
    Abstract [en]

    This paper covers aspects of long-term evolution of intrinsic impurities in the JET tokamak with respect to the newly installed ITER-like wall (ILW). At first the changes related to the change over from the JET-C to the JET-ILW with beryllium (Be) as the main wall material and tungsten (W) in the divertor are discussed. The evolution of impurity fluxes in the newly installed W divertor with respect to studying material migration is described. In addition, a statistical analysis of transient impurity events causing significant plasma contamination and radiation losses is shown. The main findings comprise a drop in carbon content (x20) (see also Brezinsek et al (2013 J. Nucl. Mater. 438 S303)), low oxygen content (x10) due to the Be first wall (Douai et al 2013 J. Nucl. Mater. 438 S1172-6) as well as the evolution of the material mix in the divertor. Initially, a short period of repetitive ohmic plasmas was carried out to study material migration (Krieger et al 2013 J. Nucl. Mater. 438 S262). After the initial 1600 plasma seconds the material surface composition is, however, still evolving. With operational time, the levels of recycled C are increasing slightly by 20% while the Be levels in the deposition-dominated inner divertor are dropping, hinting at changes in the surface layer material mix made of Be, C and W. A steady number of transient impurity events, consisting of W and constituents of inconel, is observed despite the increase in variation in machine operation and changes in magnetic configuration as well as the auxiliary power increase.

  • 41. Coenen, J. W.
    et al.
    Van Rooij, G. J.
    Aho-Mantila, L.
    Brezinsek, S.
    Clever, M.
    Dux, R.
    Groth, M.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Krieger, K.
    Marsen, S.
    Meigs, A.
    Müller, H. W.
    Neu, R.
    Potzel, S.
    Stamp, M. F.
    Tungsten erosion in the all-metal tokamaks JET and ASDEX Upgrade2012In: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics: Volume 1, 2012, 2012, p. 253-256Conference paper (Refereed)
    Abstract [en]

    The tungsten source in the all W outer divertor and Be main wall configuration has been quantified mainly during L-mode plasmas and compared to AUG Data both gained from local spectroscopy. Results so far show differences between AUG and JET based on impurities in the plasma changing the sputter behavior. This stresses the need for detailed analysis of the divertor impurity composition and detailed molding in the future analysis. The H-Mode examples indicate at ELM dominated sputtering and a rather low averaged sputtering yield in general. Nitrogen seeding can change the divertor conditions significantly either increasing W sputtering or suppressing it due to local cooling, JET and AUG behave similarly. All together it is clear that by having low divertor temperature or a beneficial impurity composition sputtering can be controlled and is rather low as expected in an all metal environment.

  • 42.
    Cooper, W. A.
    et al.
    Ecole Polytech Fed Lausanne, Ctr Rech Phys Plasmas, CH-1015 Lausanne, Switzerland..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics. KTH, EES, Fus Plasma Phys, SE-10044 Stockholm, Sweden..
    Menmuir, Sheena
    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, Atomic and Molecular Physics.
    Rubel, Marek
    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, Simon
    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.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Free boundary equilibrium in 3D tokamaks with toroidal rotation2015In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 6, article id 063032Article in journal (Refereed)
    Abstract [en]

    The three-dimensional VMEC equilibrium solver has been adapted to numerically investigate the approximate toroidal rotation model we have derived. We concentrate our applications on the simulation of JET snakes and MAST long-lived modes under free boundary conditions. Helical core solutions are triggered when <beta > exceeds a threshold value, typically 2.7% in JET-like plasmas. A large plasma current and edge bootstrap current can drive helical core formations at arbitrarily small <alpha > in which the ideal saturated internal kink coexists with an ideal saturated external kink structure of opposite phase. The centrifugal force linked with the rotation has the effect of displacing the plasma column away from the major axis, but does not alter significantly the magnitude of the edge corrugation of the plasma. Error field correction coil currents in JET-like configurations increase the outer midplane distortions by 2 cm. The edge bootstrap current enhances the edge modulation of the plasma driven by the core snake deformations in MAST.

  • 43.
    Craciunescu, T.
    et al.
    EUROfus Consortium, JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Str Atomistilor,409 POB MG-36, Bucharest 077125, Romania.;Natl Inst Laser Plasma & Radiat Phys, Magurele, Romania..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    Classification of JET Neutron and Gamma Emissivity Profiles2016In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 11, article id C05021Article in journal (Refereed)
    Abstract [en]

    In thermonuclear plasmas, emission tomography uses integrated measurements along lines of sight (LOS) to determine the two-dimensional (2-D) spatial distribution of the volume emission intensity. Due to the availability of only a limited number views and to the coarse sampling of the LOS, the tomographic inversion is a limited data set problem. Several techniques have been developed for tomographic reconstruction of the 2-D gamma and neutron emissivity on JET. In specific experimental conditions the availability of LOSs is restricted to a single view. In this case an explicit reconstruction of the emissivity profile is no longer possible. However, machine learning classification methods can be used in order to derive the type of the distribution. In the present approach the classification is developed using the theory of belief functions which provide the support to fuse the results of independent clustering and supervised classification. The method allows to represent the uncertainty of the results provided by different independent techniques, to combine them and to manage possible conflicts.

  • 44.
    Craciunescu, Teddy
    et al.
    Natl Inst Laser Plasma & Radiat Phys, Magurele, Romania..
    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.
    Craciunescu, T.
    Natl Inst Laser Plasma & Radiat Phys, Magurele, Romania..
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics. KTH, EES, Fus Plasma Phys, SE-10044 Stockholm, Sweden..
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, Sheena
    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.
    Rubel, Marek
    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.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al,
    Evaluation of reconstruction errors and identification of artefacts for JET gamma and neutron tomography2016In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 87, no 1, article id 013502Article in journal (Refereed)
    Abstract [en]

    The Joint European Torus (JET) neutron profile monitor ensures 2D coverage of the gamma and neutron emissive region that enables tomographic reconstruction. Due to the availability of only two projection angles and to the coarse sampling, tomographic inversion is a limited data set problem. Several techniques have been developed for tomographic reconstruction of the 2-D gamma and neutron emissivity on JET, but the problem of evaluating the errors associated with the reconstructed emissivity profile is still open. The reconstruction technique based on the maximum likelihood principle, that proved already to be a powerful tool for JET tomography, has been used to develop a method for the numerical evaluation of the statistical properties of the uncertainties in gamma and neutron emissivity reconstructions. The image covariance calculation takes into account the additional techniques introduced in the reconstruction process for tackling with the limited data set (projection resampling, smoothness regularization depending on magnetic field). The method has been validated by numerically simulations and applied to JET data. Different sources of artefacts that may significantly influence the quality of reconstructions and the accuracy of variance calculation have been identified.

  • 45.
    Curuia, Marian
    et al.
    Inst Atom Phys, Magurele, Ilfov, Romania..
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Upgrade of the tangential gamma-ray spectrometer beam-line for JET DT experiments2017In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 123, p. 749-753Article in journal (Refereed)
    Abstract [en]

    The JET tangential gamma-ray spectrometer is undergoing an extensive upgrade in order to make it compatible with the forthcoming deuterium-tritium (DT) experiments. The paper presents the results of the design for the main components for the upgrade of the spectrometer beam-line: tandem collimators, gamma-ray shields, and neutron attenuators. The existing tandem collimators will be upgraded by installing two additional collimator modules. Two gamma-ray shields will define the gamma-ray field of-view at the detector end of the spectrometer line-of-sight. A set of three lithium hydride neutron attenuators will be used to control the level of the fast neutron flux on the gamma-ray detector. The design of the upgraded spectrometer beam-line has been supported by extensive radiation (neutron and photon) transport calculations using both large volume and point radiation sources.

  • 46. de la Luna, E.
    et al.
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    et al.,
    Understanding the physics of ELM pacing via vertical kicks in JET in view of ITER2016In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 56, no 2, article id 026001Article in journal (Refereed)
    Abstract [en]

    Experiments on JET, with both the previous carbon wall (JET-C) and the new Be/W wall (JET-ILW), have demonstrated the efficacy of using a fast vertical plasma motion (known as vertical kicks in JET) for active ELM control. In this paper we report on a series of experiments that have been recently conducted in JET-ILW with the goal of further improving the physics understanding of the processes governing the triggering of ELMs via vertical kicks. This is a necessary step to confidently extrapolate this ELM control method to ITER. Experiments have shown that ELMs can be reliably triggered provided a minimum vertical plasma displacement and velocity is imposed. The magnitude of the minimum displacement depends on the plasma parameters, being smaller for higher pedestal temperatures and lower collisionalities, which is encouraging in view of ITER. Modelling and stability analysis suggest that a localized current density induced by the vertical plasma movement close to the separatrix plays a major role in the ELM triggering mechanism, which is consistent with the experimental observations. The implications of these results for the extrapolation of this ELM control scheme to ITER are discussed.

  • 47. de Vries, P. C.
    et al.
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    et al.,
    Scaling of the MHD perturbation amplitude required to trigger a disruption and predictions for ITER2016In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 56, no 2, article id 026007Article in journal (Refereed)
    Abstract [en]

    The amplitude of locked instabilities, likely magnetic islands, seen as precursors to disruptions has been studied using data from the JET, ASDEX Upgrade and COMPASS tokamaks. It was found that the thermal quench, that often initiates the disruption, is triggered when the amplitude has reached a distinct level. This information can be used to determine thresholds for simple disruption prediction schemes. The measured amplitude in part depends on the distance of the perturbation to the measurement coils. Hence the threshold for the measured amplitude depends on the mode location (i.e. the rational q-surface) and thus indirectly on parameters such as the edge safety factor, q(95), and the internal inductance, li(3), that determine the shape of the q-profile. These dependencies can be used to set the disruption thresholds more precisely. For the ITER baseline scenario, with typically q(95) = 3.2, li(3) = 0.9 and taking into account the position of the measurement coils on ITER, the maximum allowable measured locked mode amplitude normalized to engineering parameters was estimated to be a.B-ML(r

  • 48.
    Delabie, E.
    et al.
    EUROfus Consortium, JET, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;FOM Inst DIFFER, NL-3430 BE Nieuwegein, Netherlands..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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 (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Annan organisation.
    et al.,
    In situ wavelength calibration of the edge CXS spectrometers on JET2016In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 87, no 11, article id 11E525Article in journal (Refereed)
    Abstract [en]

    A method for obtaining an accurate wavelength calibration over the entire focal plane of the JET edge CXS spectrometers is presented that uses a combination of the fringe pattern created with a Fabry-Perot etalon and a neon lamp for cross calibration. The accuracy achieved is 0.03 angstrom, which is the same range of uncertainty as when neglecting population effects on the rest wavelength of the CX line. For the edge CXS diagnostic, this corresponds to a flow velocity of 4.5 km/s in the toroidal direction or 1.9 km/s in the poloidal direction.

  • 49.
    Devynck, P.
    et al.
    CEA IRFM, F-13108 St Paul Les Durance, France.;IRFM, CEA, F-13108 St Paul Les Durance, France..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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 (EES), Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    et al.,
    Scaling of the frequencies of the type one edge localized modes and their effect on the tungsten source in JET ITER-like wall2016In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 58, no 12, article id 125014Article in journal (Refereed)
    Abstract [en]

    A database of 250 pulses taken randomly during the experimental campaigns of JET with the ITER-like wall (ILW) is used to study the frequency dependences of the type I edge localized modes (ELM). A scaling of the ELM frequency is presented as a function of the pedestal density drop dN(ped) and a very simple model to interpret this scaling is discussed. In this model, the frequency of the ELMs is governed by the time needed by the neutral flux to refill the density of the pedestal. The filling rate is the result of a small imbalance between the neutral flux filling the pedestal and the outward flux that expels the particles to the SOL. The ELM frequency can be governed by such a mechanism if the recovery time of the temperature of the pedestal in JET occurs before or at the same time as the one of the density. This is observed to be the case. An effect of the fuelling is measured when the number of injected particles is less than 1 x 10(22) particles s(-1). In that case an increase of the inter-ELM time is observed which is related to the slower recovery of the density pedestal. Additionally, a scaling is found for the source of tungsten during the ELMs. The number of tungsten atoms eroded by the ELMs per second is proportional to dNped multiplied by the ELM frequency. This is possible only if the tungsten sputtering yield is independent of the energy of the impinging particle hitting the divertor. This result is in agreement with Guillemault et al (2015 Plasma Phys. Control. Fusion 57 085006) and is compatible with the D+ ions hitting the divertor having energies above 2 keV. Finally, by plotting the W-content/W-source ratio during ELM crash, a global decreasing behaviour with the ELM frequency is found. However at frequencies below 40 Hz a scatter towards upper values is found. This scatter is found to correlate with the gas injection level. In a narrow ELM frequency band around 20 Hz, it is found that both the ratio W-content/W-source and W-source decrease with the gas injection.

  • 50.
    Doerk, H.
    et al.
    Culham Sci Ctr, EUROfus Consortium, JET, Abingdon OX14 3DB, Oxon, England.;Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Bergsåker, Henric
    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.
    Elevant, Thomas
    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.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), 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.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    Gyrokinetic study of turbulence suppression in a JET-ILW power scan2016In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 58, no 11, article id 115005Article in journal (Refereed)
    Abstract [en]

    For exploring tokamak operation regimes that deliver both high beta and good energy confinement, power scans at JET with ITER-like wall have been performed. Relatively weak degradation of the confinement time coincides with increased core temperature of the ions at high power. The changes in core turbulence characteristics during a power scan with an optimized (broad) q profile are analyzed by means of nonlinear gyrokinetic simulations. The increase in beta is crucial for stabilizing ion temperature gradient driven turbulence, accompanied by increased ion to electron temperature ratio, the presence of a dynamic fast ion species, as well as the geometric stabilization by increased thermal and suprathermal pressure. A sensitivity study with respect to the q profile reveals that electromagnetic effects are more pronounced at larger values of q. Further, it is confirmed that turbulence suppression due to rotation becomes less effective in such strongly electromagnetic systems. Electrostatic simplified models may thus perform well in present-day devices, in which high beta is often correlated with high rotation, but provide poor extrapolation towards low rotation devices. Implications for ITER and reactor plasmas are discussed.

1234 1 - 50 of 178
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