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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. Alegre, Daniel
    et al.
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Gasior, Pawel
    Kubkowska, Monika
    Kowalska-Strzeciwilk, Ewa
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tabares, Francisco L.
    Study of correlation of deuterium content in a-C:D dust induced by laser irradiation from the co-deposited surface with the grain size and velocity2014In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T161, p. 014010-Article in journal (Refereed)
    Abstract [en]

    In the study described here, the laser ablation method was applied to clean thick (40-60 m) a-C: D co-deposits on the ALT-II limiter blade from the TEXTOR tokamak, and at the same time to characterize the ejected particles formed during ablation and measure the amount of fuel carried by them. Ablation was accomplished by similar to 3.5 ns, 0.5 J Nd: YAG laser pulses in either vacuum or an O-2 atmosphere at different pressures. Fast camera tracking of the process provided an estimate of the population and velocity of up to 100ms(-1) for larger dust particles. In the same experiment, the dust particles were caught using ultra-light Si aerogel collectors placed in front of the ablation target. SEM analysis of aerogel surfaces verified the speed estimate, providing the trapped particles' size distribution and particle yield during ablation. The D/C atomic concentration ratio was measured with the 3HE ion beam nuclear reaction analysis method in deposited layers before ablation and with a micro-ion beam in individual particles on aerogel collectors. This indicated that most of the D was thermally released during ablation, leaving no more than 5% of its original amount in the particles. The effect of ablation conditions on the acceleration of ejected particles, their population, composition and D content is the main subject of this paper.

  • 3.
    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.

  • 4. 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.

  • 5.
    Angioni, C.
    et al.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany.;Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, 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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Yushan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    Dependence of the turbulent particle flux on hydrogen isotopes induced by collisionality2018In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, no 8, article id 082517Article in journal (Refereed)
    Abstract [en]

    The impact of the change of the mass of hydrogen isotopes on the turbulent particle flux is studied. The trapped electron component of the turbulent particle convection induced by collisionality, which is outward in ion temperature gradient turbulence, increases with decreasing thermal velocity of the isotope. Thereby, the lighter is the isotope, the stronger is the turbulent pinch, and the larger is the predicted density gradient at the null of the particle flux. The passing particle component of the flux increases with decreasing mass of the isotope and can also affect the predicted density gradient. This effect is however subdominant for usual core plasma parameters. The analytical results are confirmed by means of both quasi-linear and nonlinear gyrokinetic simulations, and an estimate of the difference in local density gradient produced by this effect as a function of collisionality has been obtained for typical plasma parameters at mid-radius. Analysis of currently available experimental data from the JET and the ASDEX Upgrade tokamaks does not show any clear and general evidence of inconsistency with this theoretically predicted effect outside the errorbars and also allows the identification of cases providing weak evidence of qualitative consistency.

  • 6. Antoni, V.
    et al.
    Bergsåker, Henric
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Cavazzana, R.
    Carbone, V.
    Drake, James R.
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Martines, E.
    Regnoli, G.
    Serianni, G.
    Spada, E.
    Spolaore, M.
    Vianello, N.
    Turbulence and anomalous transport in magnetized plasmas: Hints from the reversed field pinch configuration2004In: Contributions to Plasma Physics, ISSN 0863-1042, E-ISSN 1521-3986, Vol. 44, no 06-maj, p. 458-464Article in journal (Refereed)
    Abstract [en]

    The properties of plasma turbulence in the outer region of the Reversed Field Pinch experiments RFX and EXTRAP-T2R are reviewed. The statistical properties of fluctuations in the range of scales relevant for transport are presented. The observation of coherent structures emerging from the background turbulence and their interpretation in terms of vortices is reported. The interplay between these structures and the mean ExB flow of the plasma is demonstrated with emphasis to the action on the preferential rotation direction. The effect on the particle transport induced by the background turbulence and by the structures is discussed. Finally the methods tested to control turbulence and to mitigate the related transport are illustrated and discussed.

  • 7. Antoni, V.
    et al.
    Bergsåker, Henric
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Serianni, G.
    Spolaore, M.
    Vianello, N.
    Cavazzana, R.
    Regnoli, G.
    Spada, E.
    Martines, E.
    Bagatin, M.
    Drake, James R.
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Anomalous particle transport and flow shear in the edge region of RFP's2003In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 313, p. 972-975Article in journal (Refereed)
  • 8. Antoni, V
    et al.
    Cavanazza, R
    Martines, E
    Serianni, G
    Spada, E
    Spolaore, M
    Vianello, N
    Drake, James Robert
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Bergsåker, Henric
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Brunsell, Per R
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Cecconello, Marco
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Regnoli, G
    Turbulent transport and plasma flow in the reversed field pinch2004In: IAEA-CN-116, 2004Conference paper (Refereed)
  • 9. Antoni, V.
    et al.
    Drake, James R.
    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.
    Spada, E.
    Spolaore, M.
    Vianello, N.
    Bergsåker, Henric
    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.
    Cavazzana, R.
    Cecconello, Marco
    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.
    Martines, E.
    Serianni, G.
    Coherent structures and anomalous transport in reversed field pinch plasmas2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T122, p. 1-7Article in journal (Refereed)
    Abstract [en]

    The results leading to the identification of coherent structures emerging from the background turbulence in the edge region of the reversed field pinch experiments EXTRAP-T2R and RFX are reviewed. These structures have traits of vortices in velocity field and blobs in density, and the reconstruction of their spatial structure and of their time evolution is discussed focusing on the analysis tools applied. The role of these structures in the particle anomalous transport is addressed, showing that their collisions can contribute up to 50% the total particle losses. This process is shown to be responsible for bursts in particle flux and it is found to set a characteristic collision time, which is in agreement with the statistical properties of laminar times for particle flux bursts.

  • 10.
    Appel, L. C.
    et al.
    Culham Sci Ctr, CCFE, Abingdon 0X14 3DB, Oxon, England..
    Appel, L.
    CCFE Culham Sci Ctr, Abingdon OX14 3DB, Oxon, 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.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    Equilibrium reconstruction in an iron core tokamak using a deterministic magnetisation model2018In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 223, p. 1-17Article in journal (Refereed)
    Abstract [en]

    In many tokamaks ferromagnetic material, usually referred to as an iron-core, is present in order to improve the magnetic coupling between the solenoid and the plasma. The presence of the iron core in proximity to the plasma changes the magnetic topology with consequent effects on the magnetic field structure and the plasma boundary. This paper considers the problem of obtaining the free-boundary plasma equilibrium solution in the presence of ferromagnetic material based on measured constraints. The current approach employs, a model described by O'Brien et al. (1992) in which the magnetisation currents at the iron-air boundary are represented by a set of free parameters and appropriate boundary conditions are enforced via a set of quasi-measurements on the material boundary. This can lead to the possibility of overfitting the data and hiding underlying issues with the measured signals. Although the model typically achieves good fits to measured magnetic signals there are significant discrepancies in the inferred magnetic topology compared with other plasma diagnostic measurements that are independent of the magnetic field. An alternative approach for equilibrium reconstruction in iron-core tokamaks, termed the deterministic magnetisation model is developed and implemented in EFIT++. The iron is represented by a boundary current with the gradients in the magnetisation dipole state generating macroscopic internal magnetisation currents. A model for the boundary magnetisation currents at the iron-air interface is developed using B-Splines enabling continuity to arbitrary order; internal magnetisation currents are allocated to triangulated regions within the iron, and a method to enable adaptive refinement is implemented. The deterministic model has been validated by comparing it with a synthetic 2-D electromagnetic model of JET. It is established that the maximum field discrepancy is less than 1.5 mT throughout the vacuum region enclosing the plasma. The discrepancies of simulated magnetic probe signals are accurate to within 1% for signals with absolute magnitude greater than 100 mT; in all other cases agreement is to within 1 mT. The effect of neglecting the internal magnetisation currents increases the maximum discrepancy in the vacuum region to >20 mT, resulting in errors of 5%-10% in the simulated probe signals. The fact that the previous model neglects the internal magnetisation currents (and also has additional free parameters when fitting the measured data) makes it unsuitable for analysing data in the absence of plasma current. The discrepancy of the poloidal magnetic flux within the vacuum vessel is to within 0.1 Wb. Finally the deterministic model is applied to an equilibrium force-balance solution of a JET discharge using experimental data. It is shown that the discrepancies of the outboard separatrix position, and the outer strike-point position inferred from Thomson Scattering and Infrared camera data are much improved beyond the routine equilibrium reconstruction, whereas the discrepancy of the inner strike-point position is similar.

  • 11.
    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.

  • 12.
    Aslanyan, V
    et al.
    MIT PSFC, 175 Albany St, Cambridge, MA 02139 USA..
    Aslanyan, V.
    MIT, Plasma Sci & Fus Ctr, Cambridge, MA 02139 USA..
    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.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushun
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    Gyrokinetic simulations of toroidal Alfven eigenmodes excited by energetic ions and external antennas on the Joint European Torus2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 2, article id 026008Article in journal (Refereed)
    Abstract [en]

    The gyrokinetic toroidal code (GTC) has been used to study toroidal Alfven eigenmodes (TAEs) in high-performance plasmas. Experiments performed at the Joint European Torus (JET), where TAEs were driven by energetic particles arising from neutral beams, ion cyclotron resonant heating, and resonantly excited by dedicated external antennas, have been simulated. Modes driven by populations of energetic particles are observed, matching the TAE frequency seen with magnetic probes in JET experiments. A synthetic antenna, composed of one toroidal and two neighboring poloidal harmonics has been used to probe the modes' damping rates and quantify mechanisms for this damping in GTC simulations. This method was also applied to frequency and damping rate measurements of stable TAEs made by the Alfven eigenmode active diagnostic in these discharges.

  • 13.
    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.

  • 14.
    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.

  • 15.
    Baron-Wiechec, A.
    et al.
    UK Atom Energy Author, Culham Ctr Fus Energy, Abingdon OX14 3DB, Oxon, 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.
    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.
    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. CCFE Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England..
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics. KTH, Fusion Plasma Phys, EES, SE-10044 Stockholm, Sweden..
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Simon
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Yushan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    Thermal desorption spectrometry of beryllium plasma facing tiles exposed in the JET tokamak (vol 133, pg 135, 2018)2018In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 137, p. 48-48Article in journal (Refereed)
  • 16.
    Baron-Wiechec, A.
    et al.
    UK Atom Energy Author, Culham Ctr Fus Energy, Abingdon OX14 3DB, Oxon, 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.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushun
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al.,
    Thermal desorption spectrometry of beryllium plasma facing tiles exposed in the JET tokamak2018In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 133, p. 135-141Article in journal (Refereed)
    Abstract [en]

    The phenomena of retention and de-trapping of deuterium (D) and tritium (T) in plasma facing components (PFC) and supporting structures must be understood in order to limit or control total T inventory in larger future fusion devices such as ITER, DEMO and commercial machines. The goal of this paper is to present details of the thermal desorption spectrometry (TDS) system applied in total fuel retention assessment of PFC at the Joint European Torus (JET). Examples of TDS results from beryllium (Be) wall tile samples exposed to JET plasma in PFC configuration mirroring the planned ITER PFC is shown for the first time. The method for quantifying D by comparison of results from a sample of known D content was confirmed acceptable. The D inventory calculations obtained from Ion Beam Analysis (IBA) and TDS agree well within an error associated with the extrapolation from very few data points to a large surface area.

  • 17.
    Basiuk, V.
    et al.
    CEA Cadarache, IRFM, F-13108 St Paul Les Durance, France.;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.
    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.
    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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushun
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics. KTH, Fusion Plasma Phys, EES, SE-10044 Stockholm, Sweden..
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al.,
    Towards self-consistent plasma modelisation in presence of neoclassical tearing mode and sawteeth: effects on transport coefficients2017In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 59, no 12, article id 125012Article in journal (Refereed)
    Abstract [en]

    The neoclassical tearing modes (NTM) increase the effective heat and particle radial transport inside the plasma, leading to a flattening of the electron and ion temperature and density profiles at a given location depending on the safety factor q rational surface (Hegna and Callen 1997 Phys. Plasmas 4 2940). In burning plasma such as in ITER, this NTM-induced increased transport could reduce significantly the fusion performance and even lead to a disruption. Validating models describing the NTM-induced transport in present experiment is thus important to help quantifying this effect on future devices. In this work, we apply an NTM model to an integrated simulation of current, heat and particle transport on JET discharges using the European transport simulator. In this model, the heat and particle radial transport coefficients are modified by a Gaussian function locally centered at the NTM position and characterized by a full width proportional to the island size through a constant parameter adapted to obtain the best simulations of experimental profiles. In the simulation, the NTM model is turned on at the same time as the mode is triggered in the experiment. The island evolution is itself determined by the modified Rutherford equation, using self-consistent plasma parameters determined by the transport evolution. The achieved simulation reproduces the experimental measurements within the error bars, before and during the NTM. A small discrepancy is observed on the radial location of the island due to a shift of the position of the computed q = 3/2 surface compared to the experimental one. To explain such small shift (up to about 12% with respect to the position observed from the experimental electron temperature profiles), sensitivity studies of the NTM location as a function of the initialization parameters are presented. First results validate both the transport model and the transport modification calculated by the NTM model.

  • 18. 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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    Batistoni, P.
    et al.
    Culham Sci Ctr, EUROfus Consortium, Abingdon OX14 3DB, Oxon, England.;ENEA, Dept Fus & Nucl Safety Technol, I-00044 Rome, Italy.;ENEA C R Frascati, Unit Tecn Fus, Via E Fermi 45, I-00044 Rome, 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.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushun
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics. KTH, Fusion Plasma Phys, EES, SE-10044 Stockholm, Sweden..
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al.,
    14 MeV calibration of JET neutron detectors-phase 1: calibration and characterization of the neutron source2018In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 58, no 2, article id UNSP 026012Article in journal (Refereed)
    Abstract [en]

    In view of the planned DT operations at JET, a calibration of the JET neutron monitors at 14 MeV neutron energy is needed using a 14 MeV neutron generator deployed inside the vacuum vessel by the JET remote handling system. The target accuracy of this calibration is +/- 10% as also required by ITER, where a precise neutron yield measurement is important, e.g. for tritium accountancy. To achieve this accuracy, the 14 MeV neutron generator selected as the calibration source has been fully characterised and calibrated prior to the in-vessel calibration of the JET monitors. This paper describes the measurements performed using different types of neutron detectors, spectrometers, calibrated long counters and activation foils which allowed us to obtain the neutron emission rate and the anisotropy of the neutron generator, i.e. the neutron flux and energy spectrum dependence on emission angle, and to derive the absolute emission rate in 4 pi sr. The use of high resolution diamond spectrometers made it possible to resolve the complex features of the neutron energy spectra resulting from the mixed D/T beam ions reacting with the D/T nuclei present in the neutron generator target. As the neutron generator is not a stable neutron source, several monitoring detectors were attached to it by means of an ad hoc mechanical structure to continuously monitor the neutron emission rate during the in-vessel calibration. These monitoring detectors, two diamond diodes and activation foils, have been calibrated in terms of neutrons/counts within +/- 5% total uncertainty. A neutron source routine has been developed, able to produce the neutron spectra resulting from all possible reactions occurring with the D/T ions in the beam impinging on the Ti D/T target. The neutron energy spectra calculated by combining the source routine with a MCNP model of the neutron generator have been validated by the measurements. These numerical tools will be key in analysing the results from the in-vessel calibration and to derive the response of the JET neutron detectors to DT plasma neutrons starting from the response to the generator neutrons, and taking into account all the calibration circumstances.

  • 22. 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.
    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.
    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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushun
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    et al.,
    14 MeV calibration of JET neutron detectors-phase 2: in-vessel calibration2018In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 58, no 10, article id 106016Article in journal (Refereed)
    Abstract [en]

    A new DT campaign (DTE2) is planned at JET in 2020 to minimize the risks of ITER operations. In view of DT operations, a calibration of the JET neutron monitors at 14 MeV neutron energy has been performed using a well calibrated 14 MeV neutron generator (NG) deployed, together with its power supply and control unit, inside the vacuum vessel by the JET remote handling system. The NG was equipped with two calibrated diamond detectors, which continuously monitored its neutron emission rate during the calibration, and activation foils which provided the time integrated yield. Cables embedded in the remote handling boom were used to power the neutron generator, the active detectors and pre-amplifier, and to transport the detectors' signal. The monitoring activation foils were retrieved at the end of each day for decay gamma-ray counting, and replaced by fresh ones. About 76 hours of irradiation, in 9 days, were needed with the neutron generator in 73 different poloidal and toroidal positions in order to calibrate the two neutron yield measuring systems available at JET, the U-235 fission chambers (KN1) and the inner activation system (KN2). The NG neutron emission rates provided by the monitoring detectors were in agreement within 3%. Neutronics calculations have been performed using MCNP code and a detailed model of JET to derive the response of the JET neutron detectors to DT plasma neutrons starting from the response to the NG neutrons, and taking into account the anisotropy of the neutron generator and all the calibration circumstances. These calculations have made use of a very detailed and validated geometrical description of the neutron generator and of the modified. MNCP neutron source subroutine producing neutron energy-angle distribution for the neutrons emitted by the NG. The KN1 calibration factor for a DT plasma has been determined with +/- 4.2%' experimental uncertainty. Corrections due to NG and remote handling effects and the plasma volume effect have been calculated by simulation modelling. The related additional uncertainties are difficult to estimate, however the results of the previous calibration in 2013 have demonstrated that such uncertainties due to modelling are globally <= +/- 3%. It has been found that the difference between KN1 response to DD neutrons and that to DT neutrons is within the uncertainties in the derived responses. KN2 has been calibrated using the Nb-93(n,2n)Nb-92m and Al-27(n,a)Na-24 activation reactions (energy thresholds 10 MeV and 5 MeV respectively). The total uncertainty on the calibration factors is +/- 6% for Nb-93(n,2n)Nb-92m and +/- 8% Al-27(n,a)Na-24 (1 sigma). The calibration factors of the two independent systems KN1 and KN2 will be validated during DT operations. The experience gained and the lessons learnt are presented and discussed in particular with regard to the 14 MeV neutron calibrations in ITER.

  • 23.
    Batistoni, P.
    et al.
    ENEA, Dept Fus & Technol Nucl Safety & Secur, I-00044 Rome, Italy.;ENEA, Dept Fus & Technol Nucl Safety & Secur, I-00123 Rome, Italy.;ENEA C R Frascati, Unit Tecn Fus, Via E Fermi 45, I-00044 Rome, 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.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushun
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al.,
    Overview of neutron measurements in jet fusion device2018In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 180, no 1-4, p. 102-108Article in journal (Refereed)
    Abstract [en]

    The design and operation of ITER experimental fusion reactor requires the development of neutron measurement techniques and numerical tools to derive the fusion power and the radiation field in the device and in the surrounding areas. Nuclear analyses provide essential input to the conceptual design, optimisation, engineering and safety case in ITER and power plant studies. The required radiation transport calculations are extremely challenging because of the large physical extent of the reactor plant, the complexity of the geometry, and the combination of deep penetration and streaming paths. This article reports the experimental activities which are carried-out at JET to validate the neutronics measurements methods and numerical tools used in ITER and power plant design. A new deuterium-tritium campaign is proposed in 2019 at JET: the unique 14 MeV neutron yields produced will be exploited as much as possible to validate measurement techniques, codes, procedures and data currently used in ITER design thus reducing the related uncertainties and the associated risks in the machine operation.

  • 24.
    Batistoni, Paola
    et al.
    ENEA, Dept Fus & Technol Nucl Safety & Secur, I-00044 Frascati, Rome, 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.
    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.
    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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushun
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics. KTH, Fusion Plasma Phys, EES, SE-10044 Stockholm, Sweden..
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al.,
    Calibration of neutron detectors on the Joint European Torus2017In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 88, no 10, article id 103505Article in journal (Refereed)
    Abstract [en]

    The present paper describes the findings of the calibration of the neutron yield monitors on the Joint European Torus (JET) performed in 2013 using a Cf-252 source deployed inside the torus by the remote handling system, with particular regard to the calibration of fission chambers which provide the time resolved neutron yield from JET plasmas. The experimental data obtained in toroidal, radial, and vertical scans are presented. These data are first analysed following an analytical approach adopted in the previous neutron calibrations at JET. In this way, a calibration function for the volumetric plasma source is derived which allows us to understand the importance of the different plasma regions and of different spatial profiles of neutron emissivity on fission chamber response. Neutronics analyses have also been performed to calculate the correction factors needed to derive the plasma calibration factors taking into account the different energy spectrum and angular emission distribution of the calibrating (point) Cf-252 source, the discrete positions compared to the plasma volumetric source, and the calibration circumstances. All correction factors are presented and discussed. We discuss also the lessons learnt which are the basis for the on-going 14 MeV neutron calibration at JET and for ITER.

  • 25. 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.

  • 26.
    Bergsåker, B. Henric M.
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Zhou, Yushan
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. EUROfusion Consortium, Culham Science Centre, JET, Abingdon, United Kingdom.
    Possnert, G.
    Likonen, J.
    Pettersson, J.
    Koivuranta, S.
    Widdowson, A. M.
    Deep deuterium retention and Be/W mixing at tungsten coated surfaces in the JET divertor2016In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, article id 014061Article in journal (Refereed)
    Abstract [en]

    Surface samples from a full poloidal set of divertor tiles exposed in JET through operations 2010-2012 with ITER-like wall have been investigated using SEM, SIMS, ICP-AES analysis and micro beam nuclear reaction analysis (μ-NRA). Deposition of Be and retention of D is microscopically inhomogeneous. With careful overlaying of μ-NRA elemental maps with SEM images, it is possible to separate surface roughness effects from depth profiles at microscopically flat surface regions, without pits. With (3He, p) μ-NRA at 3-5 MeV beam energy the accessible depth for D analysis in W is about 9 μm, sufficient to access the W/Mo and Mo/W interfaces in the coatings and beyond, while for Be in W it is about 6 μm. In these conditions, at all plasma wetted surfaces, D was found throughout the whole accessible depth at concentrations in the range 0.2-0.7 at% in W. Deuterium was found to be preferentially trapped at the W/Mo and Mo/W interfaces. Comparison is made with SIMS profiling, which also shows significant D trapping at the W/Mo interface. Mixing of Be and W occurs mainly in deposited layers.

  • 27.
    Bergsåker, H
    et al.
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Larsson, D
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Brunsell, P
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Möller, A
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Tramontin, L
    Wall conditioning and particle control in Extrap T21997In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 241-243, p. 993-997Article in journal (Refereed)
  • 28.
    Bergsåker, Henric
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), 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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushun
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    et al.,
    Assessment of the strength of kinetic effects of parallel electron transport in the SOL and divertor of JET high radiative H-mode plasmas using EDGE2D-EIRENE and KIPP codes2018In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 60, no 11, article id 115011Article in journal (Refereed)
    Abstract [en]

    The kinetic code for plasma periphery (KIPP) was used to assess the importance of the kinetic effects of parallel electron transport in the scrape-off layer (SOL) and divertor of JET high radiative H-mode inter-ELM plasma conditions with the ITER-like wall and strong nitrogen (N-2) injection. Plasma parameter profiles along a magnetic field from one of the EDGE2D-EIRENE simulation cases were used as an input for KIPP runs. Profiles were maintained by particle and power sources. KIPP generated electron distribution functions, f(e), parallel power fluxes, electron-ion thermoforces, Debye sheath potential drops and electron sheath transmission factors at divertor targets. For heat fluxes in the main SOL, KIPP results showed deviations from classical (e.g. Braginskii) fluxes by factors typically of similar to 1.5, sometimes up to 2, with the flux limiting for more upstream positions and flux enhancement near entrances to the divertor. In the divertor, at the same time, for radial positions closer to the separatrix, very large heat flux enhancement factors of up to ten or even higher, indicative of a strong nonlocal heat transport, were found at the outer target, with heat power flux density exhibiting bump-on-tail features at high energies. Under such extreme conditions, however, contributions of conductive power fluxes to total power fluxes were strongly reduced, with convective power fluxes becoming comparable, or sometimes exceeding, conductive power fluxes. Electron-ion thermoforce, on the other hand, which is known to be determined mostly by thermal and subthermal electrons, was found to be in good agreement with Braginskii formulas, including the Z(eff) dependence. Overall, KIPP results indicate, at least for the plasma conditions used in this modelling, a sizable, but not dominant, effect of kinetics on parallel electron transport.

  • 29.
    Bergsåker, Henric
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Possnert, G.
    Likonen, J.
    Koivuranta, S.
    Coad, J. P.
    Widdowson, A. M.
    Microstructure and inhomogeneous fuel trapping at divertor surfaces in the JET tokamak2014In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584, Vol. 332, p. 266-270Article in journal (Refereed)
    Abstract [en]

    The plasma deposited layers at divertor surfaces in the JET tokamak with carbon wall have been studied post mortem, using micro ion beam analysis (mu-IBA) methods, optical microscopy and scanning electron microscopy (SEM). The layers were formed during plasma operations over different periods through 1998-2009. They frequently have a columnar structure. For mu-IBA a 3 MeV He-3 beam was used, focused to about 5-15 mu m size. Nuclear reaction analysis was used to measure D, Be and C. Elemental mapping was carried out both at the original surface and on polished layer cross sections. Trapped deuterium is predominantly found in remote areas on the horizontal bottom divertor tiles and in regions with locally enhanced deuterium concentration on the vertical tiles. Pockets with enhanced deuterium concentration are found in the carbon fibre composite (CFC) substrate. Areas with dimensions of about 100 mu m with enhanced deuterium concentration are also found inside the deposited layers. The inhomogeneous fuel trapping is tentatively explained with co-deposition in partly protected pits in the substrate and by incorporation of dust particles in the growing layers.

  • 30.
    Bergsåker, Henric
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    Zhou, Yushan
    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.
    Possnert, G
    Likonen, J
    Pettersson, J
    Koivuranta, S
    Widdowson, A.M.
    contributors, JET
    Deep deuterium retention and Be/W mixingat tungsten coated surfaces in the JETdivertor2016In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896Article in journal (Refereed)
    Abstract [en]

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

  • 31.
    Bergsåker, Henric
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Emmoth, Birger
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Petersson, P.
    Possnert, Göran
    Coad, J. P.
    Likonen, J.
    Renvall, T.
    Nuclear reaction analysis with ion microbeam of cross sections of surface layers deposited in a tokamak divertor2007In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 362, no 03-feb, p. 215-221Article in journal (Refereed)
    Abstract [en]

    Ion micro beam analysis has been applied to the investigation of plasma deposited layers covering the divertor tiles in the JET tokamak. Since the layers are about 100 mu m thick they are too thick to be completely investigated by ordinary ion beam analysis. Cross sections of the layers were prepared by cutting and polishing. Elemental depth profiles were determined from the two dimensional images that could be derived by nuclear reaction analysis and resonant backscattering spectrometry, using ion beams focused to a few mu m spot size. A combination of analysis methods are shown, which allow measurements of the concentration profiles of carbon, beryllium, deuterium, oxygen and stainless steel components at levels of a few percent, with an accuracy better than 10%.

  • 32.
    Bergsåker, Henric
    et al.
    KTH, Superseded Departments (pre-2005), Alfvén Laboratory.
    Ilyinsky, L.
    Portnoff, G.
    Ion beam analysis of sputter-deposited gold films for quartz resonators2000In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 30, no 1, p. 620-622Article in journal (Refereed)
    Abstract [en]

    Sputter deposition using a focused ion beam has been investigated as an alternative to magnetron sputtering for the deposition of thin-film gold electrodes onto quartz resonators. One potential concern is the inclusion of argon in the growing film when argon ions are used for sputtering. Argon retention in sputter-deposited gold films using an 11.5 keV argon ion beam was investigated with Rutherford backscattering spectrometry and it was found that in layers deposited at close to normal ejection angles the argon trapping was at the level of less than or equal to 1 at,%, similar to magnetron-deposited layers, whereas argon incorporation increased with the ejection angle up to several per cent at large angles.

  • 33.
    Bergsåker, Henric
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drake, James R.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Metal impurity fluxes and plasma-surface interactions in EXTRAP T2R2008In: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY, 2008, Vol. 100Conference paper (Refereed)
    Abstract [en]

    The EXTRAP T2R is a large aspect ratio Reversed Field Pinch device. The main focus of interest for the experiments is the active feedback control of resistive wall modes [1]. With feedback it has been possible to prolong plasma discharges in T2R from about 20 ms to nearly 100 ms. In a series of experiments in T2R, in H- and D- plasmas with and without feedback, quantitative spectroscopy and passive collector probes have been used to study the flux of metal impurities. Time resolved spectroscopic measurements of Cr and Mo lines showed large metal release towards discharge termination without feedback. Discharge integrated fluxes of Cr, Fe, Ni and Mo were also measured with collector probes at wall position. Reasonable quantitative agreement was found between the spectroscopic and collector probe measurements. The roles of sputtering, thermal evaporation and arcing in impurity production are evaluated based on the composition of the measured impurity flux.

  • 34.
    Bergsåker, Henric
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Possnert, G.
    Likonen, J.
    Koivuranta, S.
    Coad, J. P.
    Widdowson, A. M.
    Microanalysis of deposited layers in the divertor of JET following operations with carbon wall2013In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 438, no Suppl., p. S668-S672Article in journal (Refereed)
    Abstract [en]

    Elemental mapping of cross sections of deposited layers on inboard tiles in the JET divertor after exposure to plasma operations with carbon wall are presented. The study was made using microbeam ion beam analysis methods in combination with optical microscopy and SEM. The surfaces had been exposed to plasma through different periods of operation (1998-2007, 2007-2009 and 1998-2009). The texture and composition of the layers are non-uniform. The physical structures include columnar, lamellar and disordered globular appearances. The distribution of trapped deuterium was frequently found to be lamellar, with well-defined sub layers with higher deuterium concentration. However, 3D regions with dimensions of about 100 μm with enhanced deuterium content were also found, both at the layer surfaces and in the layer cross sections. The distributions of beryllium and Inconel components were lamellar but did not otherwise show large non-uniformity on the same scale length as the deuterium.

  • 35.
    Bergsåker, Henric
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Possnert, G.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Heinola, K.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Miettunen, J.
    Widdowson, A.
    Riccardo, V.
    Nunes, I.
    Stamp, M.
    Brezinsek, S.
    Groth, M.
    Kurki-Suonio, T.
    Likonen, J.
    Coad, J. P.
    Borodin, D.
    Kirschner, A.
    Schmid, K.
    Krieger, K.
    First results from the Be-10 marker experiment in JET with ITER-like wall2014In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 54, no 8, p. 082004-Article in journal (Refereed)
    Abstract [en]

    When the ITER-like wall was installed in JET, one of the 218 Be inner wall guard limiter tiles had been enriched with Be-10 as a bulk isotopic marker. During the shutdown in 2012-2013, a set of tiles were sampled nondestructively to collect material for accelerator mass spectroscopy measurements of Be-10 concentration. The letter shows how the marker experiment was set up, presents first results and compares them to preliminary predictions of marker redistribution, made with the ASCOT numerical code. Finally an outline is shown of what experimental data are likely to become available later and the possibilities for comparison with modelling using the WallDYN, ERO and ASCOT codes are discussed.

  • 36.
    Bergsåker, Henric
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Possnert, G.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Heinola, K.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Miettunen, J.
    Widdowson, C.
    Riccardo, V.
    Nunes, I.
    Stamp, M.
    et al.,
    First results from10Be marker experiment in JET with ITER-like wallManuscript (preprint) (Other academic)
  • 37.
    Bergsåker, Henric
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Litnovsky, A.
    Ogata, Douglas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Sahle, Wubeshet
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Studies of mobile dust in scrape-off layer plasmas using silica aerogel collectors2011In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 415, no 1, p. S1089-S1093Article in journal (Refereed)
    Abstract [en]

    Dust capture with ultralow density silica aerogel collectors is a new method, which allows time resolved in situ capture of dust particles in the scrape-off layers of fusion devices, without substantially damaging the particles. Particle composition and morphology, particle flux densities and particle velocity distributions can be determined through appropriate analysis of the aerogel surfaces after exposure. The method has been applied in comparative studies of intrinsic dust in the TEXTOR tokamak and in the Extrap T2R reversed field pinch. The analysis methods have been mainly optical microscopy and SEM. The method is shown to be applicable in both devices and the results are tentatively compared between the two plasma devices, which are very different in terms of edge plasma conditions, time scale, geometry and wall materials.

  • 38.
    Bergsåker, Henrik
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Possnert, G.
    Likonen, J.
    Koivuranta, S.
    Coad, J. P.
    Van Renterghem, W.
    Uytdenhouwen, I.
    Widdowson, A. M.
    Microscopically nonuniform deposition and deuterium retention in the divertor in JET with ITER-like wall2015In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, p. 956-960Article in journal (Refereed)
    Abstract [en]

    The divertor surfaces in JET with ITER-like wall (ILW) have been studied using micro ion beam analysis (mu-IBA) methods and scanning electron microscopy (SEM). Deposited layers with beryllium as main constituent had been formed during plasma operations through 2011-2012. The deuterium trapping and impurity deposition were non-uniform, frequently enhanced within pits, cracks and valleys, regions reaching in size from 10 mu m to 200 mu m. The impurity deposition and fuel retention were correlated with the surface slope with respect to the direction of ion incidence. Typically more than 70% of the total measured areal density of trapped D was found in less than 30% of the surface area. This is of consequence for the interpretation of other surface analyses and in extrapolation from fuel retention in JET with ITER-like wall and rough divertor surfaces to ITER with smoother surfaces.

  • 39. 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.

  • 40.
    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.

  • 41.
    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.

  • 42.
    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.

  • 43.
    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.

  • 44.
    Bobkov, V
    et al.
    Max Planck Inst Plasmaphysik, Boltzmannstr 2, D-85748 Garching, Germany..
    Bergsåker, Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bobkov, V.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Menmuir, 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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zhou, Yushan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al,
    Impact of ICRF on the scrape-off layer and on plasma wall interactions: From present experiments to fusion reactor2019In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 18, p. 131-140Article in journal (Refereed)
    Abstract [en]

    Recent achievements in studies of the effects of ICRF (Ion Cyclotron Range of Frequencies) power on the SOL (Scrape-Off Layer) and PWI (Plasma Wall Interactions) in ASDEX Upgrade (AUG), Alcator C-Mod, and JET-ILW are reviewed. Capabilities to diagnose and model the effect of DC biasing and associated impurity production at active antennas and on magnetic field connections to antennas are described. The experiments show that ICRF near-fields can lead not only to E x B convection, but also to modifications of the SOL density, which for Alcator C-Mod are limited to a narrow region near antenna. On the other hand, the SOL density distribution along with impurity sources can be tailored using local gas injection in AUG and JET-ILW with a positive effect on reduction of impurity sources. The technique of RF image current cancellation at antenna limiters was successfully applied in AUG using the 3-strap AUG antenna and extended to the 4-strap Alcator C-Mod field-aligned antenna. Multiple observations confirmed the reduction of the impact of ICRF on the SOL and on total impurity production when the ratio of the power of the central straps to the total antenna power is in the range 0.6 < P-cen / P-total < 0.8. Near-field calculations indicate that this fairly robust technique can be applied to the ITER ICRF antenna, enabling the mode of operation with reduced PWI. On the contrary, for the A2 antenna in JET-ILW the technique is hindered by RF sheaths excited at the antenna septum. Thus, in order to reduce the effect of ICRF power on PWI in a future fusion reactor, the antenna design has to be optimized along with design of plasmafacing components.

  • 45.
    Bobkov, V.
    et al.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany.;Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    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.
    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.
    Johnson, 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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushun
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics. KTH, Fusion Plasma Phys, EES, SE-10044 Stockholm, Sweden..
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al.,
    Progress in reducing ICRF-specific impurity release in ASDEX upgrade and JET2017In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 12, p. 1194-1198Article in journal (Refereed)
    Abstract [en]

    Use of new 3-strap ICRF antennas with all-tungsten (W) limiters in ASDEX Upgrade results in a reduction of the W sources at the antenna limiters and of the W content in the confined plasma by at least a factor of 2 compared to the W-limiter 2-strap antennas used in the past. The reduction is observed with a broad range of plasma shapes. In multiple locations of antenna frame, the limiter W source has a minimum when RF image currents are decreased by cancellation of the RF current contributions of the central and the outer straps. In JET with ITER-like wall, ITER-like antenna produces about 20% less of main chamber radiation and of W content compared to the old A2 antennas. However the effect of the A2 antennas on W content is scattered depending on which antennas are powered. Experiments in JET with trace nitrogen (N-2) injection show that a presence of active ICRF antenna close to the midplane injection valve has little effect on the core N content, both in dipole and in -90 degrees phasing. This indicates that the effect of ICRF on impurity transport across the scape-off-layer is small in JET compared to the dominant effect on impurity sources leading to increased impurity levels during ICRF operation.

  • 46. 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.

  • 47.
    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.

  • 48.
    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.

  • 49.
    Bonanomi, N.
    et al.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Univ Milano Bicocca, Milan, Italy.;CNR, Ist Fis Plasma P Caldirola, Milan, Italy.;Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany.;Univ Milano Bicocca, Piazza Sci 3, 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.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushun
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    Impact of electron-scale turbulence and multi-scale interactions in the JET tokamak2018In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 58, no 12, article id 124003Article in journal (Refereed)
    Abstract [en]

    Experimental observations in JET tokamak plasmas and gyrokinetic simulations point to an important role, for electron heat transport, of electron-scale instabilities and of their interaction with ion-scale instabilities. Since these effects are maximized for strong electron heating and ion-scale modes close to marginal stability, these findings are of high relevance for ITER plasmas, featuring both conditions. Gyrokinetic and quasi-linear transport models accounting for multi-scale effects are assessed against JET experimental results.

  • 50.
    Bonanomi, N.
    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.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (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.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushun
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics. KTH, Fusion Plasma Phys, EES, SE-10044 Stockholm, Sweden..
    Zychor, I.
    et al.,
    Effects of nitrogen seeding on core ion thermal transport in JET ILW L-mode plasmas2018In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 58, no 2, article id 026028Article in journal (Refereed)
    Abstract [en]

    A set of experiments was carried out in JET ILW (Joint European Torus with ITER-Like Wall) L-mode plasmas in order to study the effects of light impurities on core ion thermal transport. N was puffed into some discharges and its profile was measured by active Charge Exchange diagnostics, while ICRH power was deposited on- and off-axis in (He-3) - D minority scheme in order to have a scan of local heat flux at constant total power with and without N injection. Experimentally, the ion temperature profiles are more peaked for similar heat fluxes when N is injected in the plasma. Gyro-kinetic simulations using the GENE code indicate that a stabilization of Ion Temperature Gradient driven turbulent transport due to main ion dilution and to changes in T-e/T-i and s/q is responsible of the enhanced peaking. The quasi-linear models TGLF and QuaLiKiz are tested against the experimental and the gyro-kinetic results.

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