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  • 301.
    Hellsten, Torbjörn
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Johnson, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    On Current Drive and Wave Induced Bootstrap Current in Toroidal Plasmas2008Ingår i: Theory of Fusion Plasmas: Joint Varenna - Lausanne International Workshop, Melville, New York, USA: AMER INST PHYSICS , 2008, s. 88-99Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A comprehensive treatment of wave-particle interactions in toroidal plasmas including collisional relaxation. applicable to heating or anomalous wave induced transport, has been obtained by using Monte Carlo operators satisfying quasi-neutrality. This approach enables a self-consistent treatment of wave-particle interactions applicable to the banana regime in the neoclassical theory. It allows an extension into a regime with large temperature and density gradients, losses and transport of particles by wave-particle interactions making the method applicable to transport barriers. It is found that at large gradients the relationship between radial electric field, parallel velocity, temperature and density gradient in the neoclassical theory is modified such that coefficient in front of the logarithmic ion temperature gradient, which in the standard neoclassical theory is small and counteracts the electric field caused by the density gradient, now changes sign and contributes to the built up of the radial electric field. The Possibility to drive current by absorbing the waves on trapped particles has been studied and flow the wave-particle interactions affect the bootstrap current. Two new current drive mechanisms are studied: current drive by wave induced bootstrap current and selective detrapping into passing orbits by directed waves.

  • 302.
    Hellsten, Torbjörn
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Johnson, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Self-Consistent ICRH Modelling2014Ingår i: Radiofrequency power in plasmas, 2014, Vol. 1580, s. 295-297Konferensbidrag (Refereegranskat)
    Abstract [en]

    Self-consistent modelling of ICRH requires calculations of the wave field consistent with the distribution function of the resonant species. Because of the difference in time scales for wave propagation and the evolution of distribution functions this is commonly done by iterations. A robust code SELFO-light, suitable for routine calculations was recently developed, based on coupling a 1D time dependent Fokker-Planck code with the global wave solver LION using a FEM. Here the structure of an upgraded version of the SELFO-light code is presented calculating the distribution function with a 2D Fokker-Planck code. This requires new interfaces calculating the quasi-linear diffusion coefficient from the wave field and the susceptibility tensor from distribution functions.

  • 303.
    Hellsten, Torbjörn
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Johnson, Thomas J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Van Eester, D.
    Lerche, E.
    Lin, Y.
    Mayoral, M-L
    Ongena, J.
    Calabro, G.
    Crombe, K.
    Frigione, D.
    Giroud, C.
    Lennholm, M.
    Mantica, P.
    Nave, M. F. F.
    Naulin, V.
    Sozzi, C.
    Studholme, W.
    Tala, T.
    Versloot, T.
    Observations of rotation in JET plasmas with electron heating by ion cyclotron resonance heating2012Ingår i: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 54, nr 7, s. 074007-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The rotation of L-mode plasmas in the JET tokamak heated by waves in the ion cyclotron range of frequencies (ICRF) damped on electrons, is reported. The plasma in the core is found to rotate in the counter-current direction with a high shear and in the outer part of the plasma with an almost constant angular rotation. The core rotation is stronger in magnitude than observed for scenarios with dominating ion cyclotron absorption. Two scenarios are considered: the inverted mode conversion scenarios and heating at the second harmonic He-3 cyclotron resonance in H plasmas. In the latter case, electron absorption of the fast magnetosonic wave by transit time magnetic pumping and electron Landau damping (TTMP/ELD) is the dominating absorption mechanism. Inverted mode conversion is done in (He-3)-H plasmas where the mode converted waves are essentially absorbed by electron Landau damping. Similar rotation profiles are seen when heating at the second harmonic cyclotron frequency of He-3 and with mode conversion at high concentrations of He-3. The magnitude of the counter-rotation is found to decrease with an increasing plasma current. The correlation of the rotation with the electron temperature is better than with coupled power, indicating that for these types of discharges the dominating mechanism for the rotation is related to indirect effects of electron heat transport, rather than to direct effects of ICRF heating. There is no conclusive evidence that mode conversion in itself affects rotation for these discharges.

  • 304.
    Hellsten, Torbjörn
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Johnson, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Sharapov, S. E.
    Kiptily, V.
    Eriksson, J.
    Mantsinen, M.
    Schneider, M.
    Rimini, F.
    Tsalas, M.
    RF Heating for Fusion Product Studies2015Ingår i: RADIOFREQUENCY POWER IN PLASMAS, American Institute of Physics (AIP), 2015, artikel-id UNSP 060007Konferensbidrag (Refereegranskat)
    Abstract [en]

    Third harmonic cyclotron heating is an effective tool for accelerating deuterium (D) beams to the MeV energy range, suitable for studying ITER relevant fast particle physics in plasmas without significant tritium content. Such experiments were recently conducted in JET with an ITER like wall in D plasmas with He-3 concentrations up to 30% in order to boost the fusion reactivity by D-He-3 reactions. The harmonic cyclotron heating produces high-energy tails in the MeV range of D ions by on-axis heating and of He-3 ions by tangential off-axis heating. The discharges are characterized by long sawtooth free periods and a rich spectrum of MHD modes excited by the fast D and He-3 ions. The partitions of the power, which depend on the distribution function of D, vary strongly over several slowing down times. Self-consistent modelling of the distribution function with the SELFO-light code are presented and compared with experimental data from fast particle diagnostics.

  • 305.
    Hellsten, Torbjörn
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Johnson, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Vallejos, Pablo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    An iterative method for including Doppler shift in global wave solvers using FEM decomposition2014Ingår i: Journal of Physics: Conference series, ISSN 1742-6596, Vol. 561Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 306.
    Hellsten, Torbjörn
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Laxåback, Martin
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Bergkvist, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Johnson, T
    Meo, F
    Nguyen, F
    Petty, C
    Mantsinen, M
    Matthews, G
    Noterdaeme, M
    Tala, T
    Van Eester, D
    Andrew, P
    Beaumont, P
    Bobkov, V
    Brix, M
    Brzozowski, J
    Eriksson, G
    Giroud, C
    Joffrin, E
    Kiptily, V
    Mailloux, J
    Mayoral, L
    Monakhov, I
    Sartori, R
    Staebler, A
    Rachlew, E
    Tennfors, E
    Tuccillo, A
    Walden, A
    Zastrow, D
    On the parasitic absorption in FWCD experiments in JET ITB plasmas2005Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 45, nr 7, s. 706-720Artikel i tidskrift (Refereegranskat)
  • 307.
    Hellsten, Torbjörn
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Laxåback, Martin
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Bergkvist, Tommy
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Johnson, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Zastrow, K.-D.
    et, al
    Fast Wave Current Drive and Direct Electron Heating in JET ITB Plasmas2006Ingår i: Proc 21st IAEA Fusion Energy Conference, 2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    Experiments with Fast Wave Current Drive, FWCD, and heating have been carried out in JET Internal Transport Barrier (ITB) discharges with strongly reversed magnetic shear. In order to maximize the current drive efficiency and increase the electron damping, and at the same time modifying the current profile in the transport barrier, hot low density ITB plasmas with strongly reversed magnetic shear, close to current hole, were created with Lower Hybrid Current Drive. It was difficult to strongly modify the central plasma current, even though the calculated current drive efficiency in terms of ampere per watts absorbed by the electrons was fairly high, 0.07A/W, because of: the strongly inductive nature of the plasma current due to the high electric conductivity; the interplay between the fast wave driven current and the bootstrap current, which, due to the dependence of the bootstrap current on the poloidal magnetic field, decreases the bootstrap current as the driven current increases; and parasitic absorption of the waves that decreased the power absorbed by the electrons. The power absorbed by the electrons was measured with a power modulation technique and the associated fast wave current drive calculated. Current diffusion simulations using the JETTO transport code, assuming neoclassical resistivity, were then carried out to calculate what changes to the plasma current profile could be expected from the current drive. The simulations showed a much slower response to the current drive compared to the measured central current densities suggesting a faster current penetration in the experiments than expected from neoclassical theory. Whereas the direct electron heating by fast magnetosonic waves using dipole spectra has proven to be an effective method to heat electrons in high-temperature ITB plasmas, even for a single pass damping of only a few percent, the heating in FWCD experiments with + 90o and - 90o antenna phasings were, for similar single pass damping as for the dipole, strongly degraded by parasitic losses, and with a heating efficiency of about half that of the dipole. Observations supporting that the losses are primarily caused by the presence of rectified RF-sheath potentials come from the large differences in performance and in Beryllium-II and Carbon-IV line radiation intensities between the dipole and ±90o phasings.

  • 308.
    Hellsten, Torbjörn
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. JET Joint Undertaking, Oxfordshire OX14 3EA, UK.
    Scheffel, Jan
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Continuous Double Adiabatic Spectrum in Toroidal Plasmas1984Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 30, s. 78-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The continuous spectrum of an anisotropic and axisymmetric toroidal plasma is investigated using the double adiabatic theory. The continuum is given by an eigenvalue problem of a fourth order system of ordinary differential equations. In contrast to the magnetohydrodynamic continuum the double adiabatic continuum may become unstable. The stability depends upon the parallel and perpendicular pressure distributions along the field lines. In absence of a toroidal magnetic field, the fourth order system decouples into two second order differential equations for which specific stability criteria are derived.

  • 309. Hirai, T.
    et al.
    Linke, J.
    Rubel, Marek J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Coad, J. P.
    Likonen, J.
    Lungu, C. P.
    Matthews, G. F.
    Philipps, V.
    Wessel, E.
    Thermal load testing of erosion-monitoring beryllium marker tile for the ITER-Like Wall Project at JET2008Ingår i: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 83, nr 7-9, s. 1072-1076Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    ITER-Like Wall Project has been launched at JET in order to perform a fully integrated test of plasma-facing materials. During the next major shutdown a full metal wall will be installed: tungsten in the divertor and beryllium in the main chamber. Beryllium erosion is one of key issues to be addressed. Special marker tiles have been designed for this purpose. Test coupons of such markers have been manufactured and examined. The performance test under high power deposition was carried in the electron beam facility JUDITH. The results of material characterization before and after high heat flux loads are presented. The samples survived, without macroscopic damage, power loads of up to 4.5 MW/m(2) for 10s (surface temperature similar to 650 degrees C) and 50 cyclic loads at 3.5 MW/m(2) lasting 10s each (surface temperature similar to 600 degrees C).

  • 310. Hirai, T.
    et al.
    Linke, J.
    Sundelin, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Rubel, Marek J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Kuehnlein, W.
    Wessel, E.
    Coad, J. P.
    Lungu, C. P.
    Matthews, G. F.
    Pedrick, L.
    Piazza, G.
    Characterization and heat flux testing of beryllium coatings on Inconel for JET ITER-like wall project2007Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T128, s. 166-170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to perform a fully integrated material test, JET has launched the ITER-like wall project with the aim of installing a full metal wall during the next major shutdown. The material foreseen for the main chamber wall is bulk Be at the limiters and Be coatings on inconel tiles elsewhere. R&D process comprises global characterization ( structure, purity etc) of the evaporated films and testing of their performance under heat loads. The major results are (i) the layers have survived energy loads of 20 MJ m(-2) which is significantly above the required level of 5 - 10 MJ m(-2), (ii) melting limit of beryllium coating would be at the energy level of 30 MJ m(-2), (iii) cyclic thermal load of 10 MJ m(-2) for up to 50 cycles have not induced any noticeable damage such as flaking or detachment.

  • 311. Hirai, T.
    et al.
    Maier, H.
    Rubel, Marek J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Mertens, Ph
    Neu, R.
    Gauthier, E.
    Likonen, J.
    Lungu, C.
    Maddaluno, G.
    Matthews, G. F.
    Mitteau, R.
    Neubauer, O.
    Piazza, G.
    Philipps, V.
    Riccardi, B.
    Ruset, C.
    Uytdenhouwen, I.
    R&D on full tungsten divertor and beryllium wall for JET ITER-like wall project2007Ingår i: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 82, nr 15-24, s. 1839-1845Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ITER reference materials have been tested separately in tokamaks, plasma simulators, ion beams and high heat flux test beds. In order to perform a fully integrated material test JET has launched the ITER-like Wall Project with the aim of installing a full metal wall during the next major shutdown. As a result of R&D projects in 2005-2006, bulk tungsten tiles are foreseen at the outer horizontal target and tungsten coating at the other divertor tiles. In some regions of the main chamber, beryllium coated Inconel tiles and bulk beryllium tiles are utilised which include marker tiles as erosion diagnostics. This paper gives an overview of the R&D carried out in the frame of the ITER-like Wall Project on the development of an inertially cooled bulk tungsten tile design and the characterization of tungsten and beryllium coating technologies.

  • 312.
    Hoelzl, M.
    et al.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Huijsmans, G. T. A.
    CEA, IRFM, St Paul Les Durance, France.;Eindhoven Univ Technol, Eindhoven, Netherlands..
    Orain, F.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Artola, F. J.
    Aix Marseille Univ, CNRS, Marseille 20, France..
    Pamela, S.
    Culham Sci Ctr, CCFE, Abingdon, Oxon, England..
    Becoulet, M.
    CEA, IRFM, St Paul Les Durance, France..
    van Vugt, D.
    Eindhoven Univ Technol, Eindhoven, Netherlands..
    Liu, F.
    CEA, IRFM, St Paul Les Durance, France.;Univ Cote dAzur, Lab JA Dieudonne, CNRS, UMR 7351,UNS, Nice 02, France..
    Futatani, S.
    Barcelona Supercomp Ctr, Barcelona, Spain..
    Lessig, A.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Wolfrum, E.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Mink, F.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Trier, E.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Dunne, M.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Viezzer, E.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Eich, T.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Vanovac, B.
    Dutch Inst Fundamental Energy Res, DIFFER, Eindhoven, Netherlands..
    Frassinetti, Lorenzo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Guenter, S.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Lackner, K.
    Max Planck Inst Plasma Phys, Boltzmannstr 2, D-85748 Garching, Germany..
    Krebs, I.
    Princeton Plasma Phys Lab, POB 451, Princeton, NJ 08543 USA..
    Insights into type-I edge localized modes and edge localized mode control from JOREK non-linear magneto-hydrodynamic simulations2018Ingår i: Contributions to Plasma Physics, ISSN 0863-1042, E-ISSN 1521-3986, Vol. 58, nr 6-8, s. 518-528Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 313. Horvath, L.
    et al.
    Maggi, C. F.
    Belonohy, E.
    Delabie, E. G.
    Flanagan, J.
    Frassinetti, Lorenzo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Giroud, C.
    Keeling, D.
    King, D.
    Maslov, M.
    Matthews, G. F.
    Menmuir, S.
    Saarelma, S.
    Silburn, S. A.
    Sips, A. C. C.
    Weisen, H.
    Gibson, K. J.
    Pedestal structure and stability in H and D isotope experiments on JET-ILW2017Ingår i: 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS) , 2017Konferensbidrag (Refereegranskat)
  • 314. Horvath, L.
    et al.
    Maggi, C. F.
    Casson, F. J.
    Frassinetti, L.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Dunne, M. G.
    Hobirk, J.
    Lupelli, I.
    Gibson, K. J.
    Evolution of the bootstrap current profile during the type I ELM cycle of JET-ILWH-mode plasmas2016Ingår i: 43rd European Physical Society Conference on Plasma Physics, EPS 2016, European Physical Society (EPS) , 2016Konferensbidrag (Refereegranskat)
  • 315. Huber, A.
    et al.
    Brezinsek, S.
    Kirschner, A.
    Ström, Petter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Sergienko, G.
    Huber, V.
    Borodkina, I.
    Douai, D.
    Jachmich, S.
    Linsmeier, Ch.
    Lomanowski, B.
    Matthews, G.F
    Mertens, P.h
    Determination of tungsten sources in the JET-ILW divertor by spectroscopic imaging in the presence of a strong plasma continuum2019Ingår i: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 18, s. 118-124Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 316.
    Höök, Josef
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. Association VR-Euratom, Sweden .
    Hellsten, Torbjörn
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. Association VR-Euratom, Sweden .
    Adaptive delta f Monte Carlo Method for Simulation of RF-heating and Transport in Fusion Plasmas2009Ingår i: Radio Frequency Power in Plasmas, American Institute of Physics (AIP), 2009, Vol. 1187, s. 589-592Konferensbidrag (Refereegranskat)
    Abstract [en]

    Essential for modeling heating and transport of fusion plasma is determining the distribution function of the plasma species. Characteristic for RF-heating is creation of particle distributions with a high energy tail. In the high energy region the deviation from a Maxwellian distribution is large while in the low energy region the distribution is close to a Maxwellian due to the velocity dependency of the collision frequency. Because of geometry and orbit topology Monte Carlo methods are frequently used. To avoid simulating the thermal part, delta f methods are beneficial. Here we present a new delta f Monte Carlo method with an adaptive scheme for reducing the total variance and sources, suitable for calculating the distribution function for RF-heating

  • 317.
    Höök, Josef
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Hellsten, Torbjörn
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    An Adaptive delta f Monte Carlo Method2010Ingår i: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 38, nr 9, s. 2190-2197Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new adaptive delta f Monte Carlo method is presented with an application to radio frequency heating and transport in fusion plasmas. The method is suitable when an initial zeroth-order approximation of the distribution function is known. The difference between our method and earlier delta f methods is that we model the source term, obtained from the delta f ansatz, by adding particles. The rate of particles is defined by the inhomogeneous term in the Fokker-Planck equation. We develop an adaptive scheme for modifying the unperturbed part G(x) such that the number of particles used in the simulation for a fixed weight is minimized. This implicitly reduces the variance and improves computational efficiency. The method is tested on a one-dimensional Fokker-Planck model for RF-heating and compared against the analytical stationary solution.

  • 318.
    Höök, L. Josef
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Johnson, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Composition schemes for the stochastic differential equation describing collisional pitch-angle diffusion2014Ingår i: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 185, nr 2, s. 590-594Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two new second order accurate Monte Carlo integration schemes are derived for the stochastic differential equation describing pitch-angle scattering by Coulomb collisions in magnetized plasmas. Here the pitch-angle is the angle between the magnetic field and the particle velocity vectors. Mathematically this collision process corresponds to diffusion in the polar angle of a spherical coordinate system. The schemes are simple to implement, they are naturally bounded to the solution domain and their convergences are shown to compare favourably against commonly used alternative integration schemes.

  • 319.
    Höök, Lars Josef
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Kernel density estimation using the RBF-Galerkin method2012Rapport (Övrigt vetenskapligt)
  • 320.
    Höök, Lars Josef
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Numerical solution of quasilinear kinetic diffusion equations in toroidal plasmas2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    One of the main challenges for the realization of a working fusion power plant is an increased detailed understanding of kinetic phenomena in toroidal plasmas. The tokamak is a toroidal, magnetically confined plasma device and is currently the main line towards a power plant. The spatial and temporal scales in a tokamak plasma are extreme and the only tractable path for quantitative studies is to rely on computer simulations. Present day simulation codes can resolve only some of these scales. Nevertheless they still require the largest high performance computing (HPC) resources available in the world. In combination with the increase of computational performance, it is therefore necessary to improve the numerical algorithms used in the simulations.

    In this thesis we have developed new numerical methods designed for Monte Carlo simulation of plasma kinetic diffusion. Examples are simulation of fast-ion thermalization and radio-frequency heating. The aim has been to reduce the statistical random noise in particle codes, produced by a finite number of particles (or markers). Traditionally the statistical noise is improved by increasing the number of particles (N) or by simulating the perturbation of the distribution (with particles) from a known distribution function. This is the well known δf method. In this thesis we have developed a new type of δf method, which minimizes the number of particles used in a simulation. The computational speedup of the new method is substantial. In this thesis, we have further benchmarked quasi-Monte Carlo techniques that improve the convergence rate from N−1/2 to N−1 for some cases.

    In Monte Carlo simulations, error appears also from the time step discretization. Based on the mathematics of operator splitting, a new scheme for the pitch-angle scattering diffusion process has been developed that outperforms the standard methods. Finally this thesis also presents a new code, SELFO-light, for self-consistent simulations of ion cyclotron resonance heating, suitable for routine calculations, which couples a one dimensional Fokker-Planck model with the finite element wave solver LION.

  • 321.
    Höök, Lars Josef
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Variance reduction methods for numerical solution of plasma kinetic diffusion2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Performing detailed simulations of plasma kinetic diffusion is a challenging task and currently requires the largest computational facilities in the world. The reason for this is that, the physics in a confined heated plasma occur on a broad range of temporal and spatial scales. It is therefore of interest to improve the computational algorithms together with the development of more powerful computational resources. Kinetic diffusion processes in plasmas are commonly simulated with the Monte Carlo method, where a discrete set of particles are sampled from a distribution function and advanced in a Lagrangian frame according to a set of stochastic differential equations. The Monte Carlo method introduces computational error in the form of statistical random noise produced by a finite number of particles (or markers) N and the error scales as αNβ where β = 1/2 for the standard Monte Carlo method. This requires a large number of simulated particles in order to obtain a sufficiently low numerical noise level. Therefore it is essential to use techniques that reduce the numerical noise. Such methods are commonly called variance reduction methods. In this thesis, we have developed new variance reduction methods with application to plasma kinetic diffusion. The methods are suitable for simulation of RF-heating and transport, but are not limited to these types of problems. We have derived a novel variance reduction method that minimizes the number of required particles from an optimization model. This implicitly reduces the variance when calculating the expected value of the distribution, since for a fixed error the  optimization model ensures that a minimal number of particles are needed. Techniques that reduce the noise by improving the order of convergence, have also been considered. Two different methods have been tested on a neutral beam injection scenario. The methods are the scrambled Brownian bridge method and a method here called the sorting and mixing method of L´ecot and Khettabi[1999]. Both methods converge faster than the standard Monte Carlo method for modest number of time steps, but fail to converge correctly for large number of time steps, a range required for detailed plasma kinetic simulations. Different techniques are discussed that have the potential of improving the convergence to this range of time steps.

  • 322.
    Höök, Lars Josef
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Johnson, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Hellsten, Torbjörn
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Multilevel Monte Carlo and control-variate simulation of Coulomb collisionsManuskript (preprint) (Övrigt vetenskapligt)
  • 323.
    Höök, Lars Josef
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Johnson, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Hellsten, Torbjörn
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Randomized quasi-Monte Carlo simulation of fast-ion thermalization2012Ingår i: Computational Science & Discovery, ISSN 1749-4680, E-ISSN 1749-4699, Vol. 5, nr 1, s. 014010-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work investigates the applicability of the randomized quasi-Monte Carlo method for simulation of fast-ion thermalization processes in fusion plasmas, e.g. for simulation of neutral beam injection and radio frequency heating. In contrast to the standard Monte Carlo method, the quasi-Monte Carlo method uses deterministic numbers instead of pseudo-random numbers and has a statistical weak convergence close to O(N -1), where N is the number of markers. We have compared different quasi-Monte Carlo methods for a neutral beam injection scenario, which is solved by many realizations of the associated stochastic differential equation, discretized with the Euler-Maruyama scheme. The statistical convergence of the methods is measured for time steps up to 2 14.

  • 324.
    Höök, Lars Josef
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Johnson, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Äkäslompolo, S.
    Composition schemes forthe stochastic differential equation describing collisional pitch-angle diffusionArtikel i tidskrift (Övrigt vetenskapligt)
  • 325. Ingesson, L. C.
    et al.
    Campbell, D. J.
    Cecconello, Marco
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Ciattaglia, E.
    Dirken, P.
    Hawkes, N.
    Walsh, M.
    von Hellermann, M.
    Kalvin, S.
    McCarthy, P.
    Neubauer, O.
    Petrizzi, L.
    Progress on common aspects of the EU-supplied ITER diagnostics and prediction of diagnostic performance2006Ingår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 77, nr 10, s. 10F502-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The European Union will supply a number of diagnostics for ITER. Significant progress has been made on the design and integration of these diagnostics. Specific topics, in common for several of the diagnostics, discussed are port-plug integration, simplification of labyrinths against neutron streaming, and design measures to protect and to be able to replace sensitive optical components. Performance analysis to predict the likely capability of the diagnostics to meet the ITER measurement requirements will be an important aspect of the design process. The interpretation of the measurement requirements, specifically of spatial resolution in the case of indirect measurements, is discussed on the basis of two examples, and methods of performance analysis are compared.

  • 326.
    Ivanova, Darya
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Fuel retention and fuel removal from first wall components in tokamaks2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Fuel inventory and generation of carbon and metal dust in a tokamak are perceived to be serious safety and economy issues for a steady-state operation of a fusion reactor, e.g. ITER. These topics have been explored in the on-going Ph.D. work in order to contribute to the better understanding and development of methods for controlling and curtailing fuel accumulation and dust formation in controlled fusion devices. The work was carried out with material facing fusion plasmas in three tokamaks: TEXTOR in Forschungszentrum Jülich (Germany), Tore Supra in Cadarache (France) and JET in Culham Centre for Fusion Energy (United Kingdom).

     This thesis provides an account on studies of fuel removal techniques from plasmafacing components (PFCs) and on consequences of dust formation. Following issues are addressed: (a)  properties of carbon and metal dust formed in the TEXTOR tokamak;  (b)  dust generation associated with removal of fuel and co-deposited layers from carbon PFCs from TEXTOR and Tore Supra;  (c)  surface morphology of wall components after different cleaning treatments;  (d)  surface properties of diagnostic mirrors tested at JET for ITER. The study dealt with carbon, tungsten and beryllium, i.e. with the three major elements being used for PFC in present-day devices and foreseen for a next-step machine.

     Some essential results are summarised by the following.

     (i)  The amount of loose dust found on the floor of the TEXTOR liner does not exceed 2 grams with particle size range 0.1 mm – 1 mm. The presence of fine (up to 1 mm) crystalline graphite in the collected matter suggests that brittle destruction of carbon PFC could take place during off-normal events. Carbon is the main component, but there are also magnetic and non-magnetic metal agglomerates. The results obtained strongly indicate that in a carbon wall machine the disintegration of flaking co-deposits on PFC is the main source of dust:  (ii)  The fuel content in dust and co-deposits varies from 10% on the main limiters to 0.03% on the neutralizer plates as determined by thermal desorption and ionbeam methods:  (iii)  Fuel removal by annealing in vacuum or by oxidative methods disintegrates codeposits. In the case of thick layers, the treatment makes them brittle thus reducing the adherence to the target and, as a consequence, this leads to the formation of dust:  (iv)   Application of thermal methods for fuel removal from carbon-rich layers is effective only at high temperatures (above 800 K), i.e. in the range exceeding the allowed baking temperature of the ITER divertor:  (v)   Photonic cleaning by laser pulses effectively removes fuel-rich deposited layers, but it also produces debris, especially under ablation conditions:  (vi)  Photonic cleaning of mirrors exposed in JET results in partial recovery of reflectivity, but surfaces are modified by laser pulses.

    The presentation of results is accompanied by a discussion of their consequences for the future development and the application of fuel and dust removal methods in a next-step fusion device.

  • 327.
    Ivanova, Darya
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Plasma-Facing Components in Tokamaks: Material Modification and Fuel Retention2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Fuel inventory and generation of carbon and metal dust in a tokamak are perceived to be serious safety and economy issues for the steady-state operation of a fusion reactor, e.g. ITER. These topics have been explored in this thesis in order to contribute to a better understanding and the development of methods for controlling and curtailing fuel accumulation and dust formation in controlled fusion devices. The work was carried out with material facing fusion plasmas in three tokamaks: TEXTOR in Forschungszentrum Jülich (Germany), Tore Supra in the Nuclear Research Center Cadarache (France) and JET in Culham Centre for Fusion Energy (United Kingdom). Following issues were addressed: (a) properties of material migration products, i.e. co-deposited layers and dust particles; (b) impact of fuel removal methods on dust generation and on modification of plasma-facing components; (c) efficiency of fuel and deposit removal techniques; (d) degradation mechanism of diagnostic components - mirrors - and methods of their regeneration.

  • 328.
    Ivanova, Darya
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Likonen, Jari
    Widdowson, Anna
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Petersson, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    De Temmerman, Gregory
    Assessment of Cleaning Methods for First Mirrors Tested in JET for ITER2013Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 438, nr Suppl., s. S1241-S1244Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two cleaning techniques were used for removal of co-deposits from the tested first mirrors exposed in JET: (a) ultrasonic bath; (b) a broad range of polishing conditions from manual buffing to machine polishing with the diamond grain size of up to 3 lm. Reflectivity measurements were performed after each step in the cleaning procedure. Surfaces were also examined with electron microscopy and ion beam analysis methods. Ultrasonic cleaning leads to partial recovery of reflectivity due to enhanced detachment of deposits. Typically 30-50% of the original reflectivity was recovered in the visible light and 50-90% in the infrared region. One mirror was cleaned completely. Polishing with diamond paste may lead to successful removal of deposits but the damage to the surface in case of the large diamond grains was observed. Recovery of up to 100% of the initial reflectivity was achieved for some mirrors.

  • 329.
    Ivanova, Darya
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Rubel, Marek J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Philipps, V.
    Institute for Energy Research, Forschungszentrum Jülich, Association EURATOM-FZJ, Germany.
    Freisinger, M.
    Institute for Energy Research, Forschungszentrum Jülich, Association EURATOM-FZJ, Germany.
    Huang, Z.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Penkalla, H.
    Institute for Energy Research, Forschungszentrum Jülich, Association EURATOM-FZJ, Germany.
    Schweer, B.
    Institute for Energy Research, Forschungszentrum Jülich, Association EURATOM-FZJ, Germany.
    Sergienko, G.
    Institute for Energy Research, Forschungszentrum Jülich, Association EURATOM-FZJ, Germany.
    Sundelin, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Wessel, E.
    Institute for Energy Research, Forschungszentrum Jülich, Association EURATOM-FZJ, Germany.
    Survey of dust formed in the TEXTOR tokamak: structure and fuel retention2009Ingår i: Physica scripta. T, ISSN 0281-1847, Vol. T138, s. 014025-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A detailed survey of erosion and deposition on plasma-facing components was performed in the TEXTOR tokamak. Co-deposits and dust particles were collected from graphite limiters and from several locations on the Inconel liner. The total amount of dust (loose material), originating mainly from carbon-rich co-deposits detached from the limiters and the liner, was around 2 g, with sizes from 0.1 mu m to 1 mm. The morphology and fuel retention was determined using microscopy methods, ion beam analysis and thermal desorption spectrometry. The study revealed differences in structure and fuel content between deposits from the toroidal and main poloidal limiters. There were also splashes, up to 1 mm in diameter, of molten metal (mainly nickel) on the toroidal limiters. Issues of the dust conversion factor (erosion-to-dust) are addressed and a comparison with results of previous dust surveys at TEXTOR is also briefly presented.

  • 330.
    Ivanova, Darya
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Rubel, Marek J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Philipps, V.
    Institute for Energy Research, Forschungszentrum Jülich, Association EURATOM-FZJ, Germany.
    Schweer, B.
    Institute for Energy Research, Forschungszentrum Jülich, Association EURATOM-FZJ, Germany.
    Freisinger, M.
    Institute for Energy Research, Forschungszentrum Jülich, Association EURATOM-FZJ, Germany.
    Huber, A.
    Institute for Energy Research, Forschungszentrum Jülich, Association EURATOM-FZJ, Germany.
    Gierse, N.
    Institute for Energy Research, Forschungszentrum Jülich, Association EURATOM-FZJ, Germany.
    Penkalla, H.
    Institute for Energy Research, Forschungszentrum Jülich, Association EURATOM-FZJ, Germany.
    Petersson, P.
    Ångström Laboratory, Uppsala University, Association EURATOM-VR.
    Dittmar, T.
    CEA-Cadarche, IRFM, Association EURATOM-CEA, France.
    Laser-based and thermal methods for fuel removal and cleaning of plasma-facing components2011Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 415, nr 1, s. S801-S804Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The efficiency of two methods for in-situ fuel removal has been tested on carbon and tungsten limiters retrieved from the TEXTOR and Tore Supra tokamaks: laser-inducedablation of co-deposits and annealing in vacuum at elevated temperature. The analyses of gas phase and surfaces performed with thermal desorption spectrometry, optical spectroscopy, ion beam analysis, surface profilometry and microscopy methods have shown: (i) the ablation leads to the generation of dust particles of 50 nm – 2μm; (ii) volatile products of ablation undergo condensation on surrounding surfaces; (iii) D/C ratio in such condensate is in the range 0.02-0.03; (iv) long-term annealing of 623 K for 70 hours results in release of not more ~10 % of deuterium accumulated in plasma-facing components; (v) effective removal is reached by heating to 900-1300 K.

  • 331.
    Ivanova, Darya
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Petersson, Per
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Kreter, A.
    Möller, S.
    Philipps, V.
    Freisinger, M.
    Wauters, T.
    Impact of thermal treatment and ICWC on fuel inventory in Co-deposits2012Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics: volume 1, 2012, s. 317-320Konferensbidrag (Refereegranskat)
  • 332.
    Ivanova, Darya
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Philipps, V.
    Institute of Energy Research, Forschungszentrum Jülich.
    Freisinger, M.
    Institute of Energy Research, Forschungszentrum Jülich.
    Dittmar, T.
    CEA-Cadarache, IRFM.
    Huber, A.
    Institute of Energy Research, Forschungszentrum Jülich.
    Petersson, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Schweer, B.
    Institute of Energy Research, Forschungszentrum Jülich.
    Sergienko, G.
    Institute of Energy Research, Forschungszentrum Jülich.
    Wessel, E.
    Institute of Energy Research, Forschungszentrum Jülich.
    Dust Particles in Controlled Fusion Devices: Generation Mechanism and Analysis2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Generation and in-vessel accumulation of carbon and metal dust are perceived to be serious safety andeconomy issues for a steady-state operation of a fusion reactor, e.g. ITER. This contribution provides acomprehensive account on: (a) properties of carbon and metal dust formed in the TEXTOR tokamak; (b) dustgeneration associated with removal of fuel and co-deposit from carbon PFC from TEXTOR and Tore Supra; (c)surface morphology of wall components after different cleaning treatments. The amount of loose dust found on thefloor of the TEXTOR liner does not exceed 2 grams with particle size range 0.1 m – 1 mm. The presence of fine(up to 1 m) crystalline graphite in the collected matter suggests that brittle destruction of carbon PFC could takeplace during off-normal events. Carbon is the main component, but there are also magnetic and non-magnetic metalagglomerates. The fuel content in dust and co-deposits varies from 10% on the main limiters to 0.03% on theneutralizer plates. Fuel removal by oxidative methods or by annealing in vacuum disintegrates co-deposits and, in thecase of thick layers, makes them brittle thus reducing the adherence to the target. Also photonic cleaning by laserpulses produces debris, especially under ablation conditions. The results obtained strongly indicate that in a carbonwall machine the disintegration of flaking co-deposits on PFC is the main source of dust.

  • 333.
    Ivanova, Darya
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Philipps, Volker
    Institute for Energy and Climate Research, Plasma Physics, Forschungszentrum Jülich.
    Schweer, Bernd
    Institute for Energy and Climate Research, Plasma Physics, Forschungszentrum Jülich.
    Petersson, Per
    Ångström Laboratory, Uppsala University.
    Freisinger, Michaele
    Institute for Energy and Climate Research, Plasma Physics, Forschungszentrum Jülich.
    Schmidt, Axel
    Institute for Energy and Climate Research, Plasma Physics, Forschungszentrum Jülich.
    Fuel re-absorption by thermally treated co-deposited carbon layers2011Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T145, s. 014006-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Systematic studies have been conducted to address the fuel re-absorption by carbon deposits under repeated exposure to plasma after cleaning procedures. The investigation was done with graphite tiles from ALT-II (Advanced Limiter Test II), i.e. the main limiter at the TEXTOR tokamak. Pure graphite plates were used as the reference material. The experimental programme comprised the following: pre-characterization of specimens; D desorption by baking the tile at 1273 K; surface analyses of the fuel-depleted layers; exposure to deuterium in a laboratory plasma device and in TEXTOR; and quantitative assessment of deuterium re-absorption. The main result is that fuel retention in the re-exposed deposits is 30–40 times lower than that in the original co-deposit, showing that fuel re-absorption does not lead to an immediate re-saturation of deposits. Annealing at high temperatures enhances layer brittleness, leading eventually to detachment of co-deposits.

  • 334.
    Ivanova, Darya
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Widdowson, A.
    Petersson, Per
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Likonen, J.
    Marot, L.
    Alves, E.
    Garcia-Carrasco, Alvaro
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Pintsuk, G.
    An overview of the comprehensive First Mirror Test in JET with ITER-like wall2014Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T159, s. 014011-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The First Mirror Test in Joint European Torus (JET) with the International Thermonuclear Experimental Reactor-like wall was performed with polycrystalline molybdenum mirrors. Two major types of experiments were done. Using a reciprocating probe system in the main chamber, a short-term exposure was made during a 0.3 h plasma operation in 71 discharges. The impact on reflectivity was negligible. In a long-term experiment lasting 19 h with 13 h of X-point plasma, 20 Mo mirrors were exposed, including four coated with a 1 mu m-thick Rh layer. Optical performance of all mirrors exposed in the divertor was degraded by up to 80% because of beryllium, carbon and tungsten co-deposits on surfaces. Total reflectivity of most Mo mirrors facing plasma in the main chamber was only slightly affected in the spectral range 400-1600 nm, while the Rh-coated mirror lost its high original reflectivity by 30%, thus decreasing to the level typical of molybdenum surfaces. Specular reflectivity was decreased most strongly in the 250-400 nm UV range. Surface measurements with x-ray photoelectron spectroscopy and depth profiling with secondary ion mass spectrometry and heavy-ion elastic recoil detection analysis (ERDA) revealed that the very surface region on both types of mirrors had been modified by neutrals, resulting eventually in the composition change: Be, C, D at the level below 1x10(16) cm(-2) mixed with traces of Ni, Fe in the layer 10-30 nm thick. On several exposed mirrors, the original matrix material (Mo) remained as the major constituent of the modified layer. The data obtained in two major phases of the JET operation with carbon and full metal walls are compared. The implications of these results for first mirrors and their maintenance in a reactor-class device are discussed.

  • 335.
    Ivanova, Darya
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Widdowson, A.
    CCFE/EURATOM Fusion Association, Culham Science Centre.
    Likonen, J.
    Association EURATOM–TEKES, VTT, Espoo.
    Marot, L.
    Department of Physics, University of Basel.
    Koivuranta, K.
    EURATOM-TEKES, VTT.
    Coad, J. P.
    CCFE/EURATOM Fusion Association, Culham Science Centre.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Temmerman, G. De
    FOM Institute for Plasma Physics.
    Petersson, P.
    Ångström Laboratory, Uppsala University.
    Assessment of cleaning methods for rst mirrors tested in JET for ITERArtikel i tidskrift (Övrigt vetenskapligt)
  • 336. Jacob, Wolfgang
    et al.
    Linsmeier, Christian
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    13th International Workshop on Plasma-Facing Materials and Components for Fusion Applications/1st International Conference on Fusion Energy Materials Science2011Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T145, s. 011001-Artikel i tidskrift (Övrigt vetenskapligt)
  • 337.
    Jepu, I
    et al.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Magurele 077125, Romania.;Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Matthews, G. F.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Widdowson, A.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Rubel, Marek
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik. EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.
    Fortuna-Zalesna, E.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Warsaw Univ Technol, PL-02507 Warsaw, Poland..
    Zdunek, J.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Magurele 077125, Romania..
    Petersson, Per
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik. EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.
    Thompson, V
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Dinca, P.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Magurele 077125, Romania..
    Porosnicu, C.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Magurele 077125, Romania..
    Coad, P.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Heinola, K.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Univ Helsinki, POB 64, Helsinki 00560, Finland..
    Catarino, N.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Univ Lisbon, Inst Super Tecn, IPFN, Av Rovisco Pais, P-1049001 Lisbon, Portugal..
    Pompilian, O. G.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Magurele 077125, Romania..
    Lungu, C. P.
    EUROfus Consortium, Culham Sci Ctr, JET, Abingdon OX14 3DB, Oxon, England.;Natl Inst Laser Plasma & Radiat Phys, Magurele 077125, Romania..
    Beryllium melting and erosion on the upper dump plates in JET during three ITER-like wall campaigns2019Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, nr 8, artikel-id 086009Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Data on erosion and melting of beryllium upper limiter tiles, so-called dump plates (DP), are presented for all three campaigns in the JET tokamak with the ITER-like wall. High-resolution images of the upper wall of JET show clear signs of flash melting on the ridge of the roofshaped tiles. The melt layers move in the poloidal direction from the inboard to the outboard tile, ending on the last DP tile with an upward going waterfall-like melt structure. Melting was caused mainly by unmitigated plasma disruptions. During three ILW campaigns, around 15% of all 12376 plasma pulses were catalogued as disruptions. Thermocouple data from the upper dump plates tiles showed a reduction in energy delivered by disruptions with fewer extreme events in the third campaign, ILW-3, in comparison to ILW-1 and ILW-2. The total Be erosion assessed via precision weighing of tiles retrieved from JET during shutdowns indicated the increasing mass loss across campaigns of up to 0.6 g from a single tile. The mass of splashed melted Be on the upper walls was also estimated using the high-resolution images of wall components taken after each campaign. The results agree with the total material loss estimated by tile weighing (similar to 130 g). Morphological and structural analysis performed on Be melt layers revealed a multilayer structure of re-solidified material composed mainly of Be and BeO with some heavy metal impurities Ni, Fe, W. IBA analysis performed across the affected tile ridge in both poloidal and toroidal direction revealed a low D concentration, in the range 1-4 x 10(17) D atoms cm(-2).

  • 338. Joffrin, E.
    et al.
    Baruzzo, M.
    Beurskens, M.
    Bourdelle, C.
    Brezinsek, S.
    Bucalossi, J.
    Buratti, P.
    Calabro, G.
    Challis, C. D.
    Clever, M.
    Coenen, J.
    Delabie, E.
    Dux, R.
    Lomas, P.
    de la Luna, E.
    de Vries, P.
    Flanagan, J.
    Frassinetti, Lorenzo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Frigione, D.
    Giroud, C.
    Groth, M.
    Hawkes, N.
    Hobirk, J.
    Lehnen, M.
    Maddison, G.
    Mailloux, J.
    Maggi, C. F.
    Matthews, G.
    Mayoral, M.
    Meigs, A.
    Neu, R.
    Nunes, I.
    Puetterich, T.
    Rimini, F.
    Sertoli, M.
    Sieglin, B.
    Sips, A. C. C.
    van Rooij, G.
    Voitsekhovitch, I.
    First scenario development with the JET new ITER-like wall2014Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 54, nr 1, s. 013011-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the recent JET experimental campaigns with the new ITER-like wall (JET-ILW), major progress has been achieved in the characterization and operation of the H-mode regime in metallic environments: (i) plasma breakdown has been achieved at the first attempt and X-point L-mode operation recovered in a few days of operation; (ii) stationary and stable type-I ELMy H-modes with beta(N) similar to 1.4 have been achieved in low and high triangularity ITER-like shape plasmas and are showing that their operational domain at H = 1 is significantly reduced with the JET-ILW mainly because of the need to inject a large amount of gas (above 10(22) Ds(-1)) to control core radiation; (iii) in contrast, the hybrid H-mode scenario has reached an H factor of 1.2-1.3 at beta(N) of 3 for 2-3 s; and, (iv) in comparison to carbon equivalent discharges, total radiation is similar but the edge radiation is lower and Z(eff) of the order of 1.3-1.4. Strong core radiation peaking is observed in H-mode discharges at a low gas fuelling rate (i. e. below 0.5 x 10(22) Ds(-1)) and low ELM frequency (typically less than 10 Hz), even when the tungsten influx from the diverter is constant. High-Z impurity transport from the plasma edge to the core appears to be the dominant factor to explain these observations. This paper reviews the major physics and operational achievements and challenges that an ITER-like wall configuration has to face to produce stable plasma scenarios with maximized performance.

  • 339. Joffrin, E.
    et al.
    Bergsåker, Henric
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Bykov, Igor
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Frassinetti, Lorenzo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Fridström, Richard
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Garcia Carrasco, Alvaro
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Hellsten, Torbjörn
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Jonsson, Thomas
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Moon, Sunwoo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Petersson, Per
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Rachlew, Elisabeth
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Ratynskaia, Svetlana V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Rymd- och plasmafysik.
    Rubel, Marek
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Stefániková, Estera
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Ström, Petter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Tholerus, Emmi
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Tolias, Panagiotis
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Rymd- och plasmafysik.
    Vallejos, Pablo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Weckmann, Armin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Zhou, Yushan
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Zychor, I
    et al.,
    Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall2019Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, nr 11, artikel-id 112021Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des. 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D-T mixtures since 1997 and the first ever D-T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D-T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D-T preparation. This intense preparation includes the review of the physics basis for the D-T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D-T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfven eigenmode antennas, neutral gauges, radiation hard imaging systems...) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D-T campaign provides an incomparable source of information and a basis for the future D-T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.

  • 340. Joffrin, E
    et al.
    De Vries, P
    Baruzzo, M
    Beurskens, M
    Bourdelle, C
    Bucalossi, J
    Brezinsek, S
    Calabro, C
    Challis, C
    Clever, M
    Coenen, J
    Delabie, E
    Dux, R
    Lomas, P
    de la Luna, E
    Flanagan, J
    Frassinetti, Lorenzo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Frigione, D
    Giroud, C
    Groth, M
    Hawks, N
    Hobirk, J
    Lehnen, J
    Maddison, G
    Mailleaux, M
    Maggi, C
    Matthews, G
    Mayoral, M
    Meigs, M
    Neu, R
    Nunes, I
    Scenarios Development at JET with the New ITER-like Wall2012Ingår i: 24th IAEA Fusion Energy Conference - IAEA CN-197: Book of abstracts, 2012, s. EX/1-1-Konferensbidrag (Refereegranskat)
  • 341. Joffrin, E.
    et al.
    Tamain, P.
    Belonohy, E.
    Bufferand, H.
    Buratti, P.
    Challis, C. D.
    Delabie, E.
    Drewelow, P.
    Dodt, D.
    Frassinetti, Lorenzo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Garcia, J.
    Giroud, C.
    Groth, M.
    Hobirk, J.
    Jarvinen, A. E.
    Kim, H. -T
    Koechl, F.
    Kruezi, U.
    Lipschutz, B.
    Lomas, P. J.
    de la Luna, E.
    Loarer, T.
    Maget, P.
    Maggi, C.
    Matthews, G.
    Maviglia, F.
    Meigs, A.
    Nunes, I.
    Pucella, G.
    Rimini, F.
    Saarelma, S.
    Solano, E.
    Sips, A. C. C.
    Tsalas, M.
    Voitsekhovitch, I.
    Weisen, H.
    Impact of divertor geometry on H-mode confinement in the JET metallic wall2017Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, nr 8, artikel-id 086025Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent experiments with the ITER-like wall have demonstrated that changes in divertor strike point position are correlated with strong modification of the global energy confinement. The impact on energy confinement is observable both on the pedestal confinement and core normalised gradients. The corner configuration shows an increased core density gradient length and ion pressure indicating a better ion confinement. The study of neutral re-circulation indicates the neutral pressure in the main chamber varies inversely with the energy confinement and a correlation between the pedestal total pressure and the neutral pressure in the main chamber can be established. It does not appear that charge exchange losses nor momentum losses could explain this effect, but it may be that changes in edge electric potential are playing a role at the plasma edge. This study emphasizes the importance of the scrape-off layer (SOL) conditions on the pedestal and core confinement.

  • 342.
    Johansson, Lars
    et al.
    Kalmar University.
    Rubel, Marek J.KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    17th International Vacuum Congress (IVC-17), 13th International Conference on Surface Science (ICSS-13) and International Conference on Nanoscience and technology (ICN+T 2007)2008Proceedings (redaktörskap) (Refereegranskat)
  • 343.
    Johnson, T.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Lönnroth, J.
    de Vries, P. C.
    Salmi, A.
    Eriksson, L.-G.
    Hynönen, V.
    Jenkins, I.
    Ongena, J.
    Oyama, N.
    Parail, V.
    Saibene, G.
    Sharapov, S.
    Shinohara, K.
    Modelling of Fast Particle Transport and Losses with TF Ripple in JET2007Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In preparation for ripple experiments at JET the heat loads from fast ions to plasma facing components were calculated by orbit following Monte Carlo codes. The calculations show that losses are generated by two mechanisms, ripple-trapping and ripple-banana diffusion, and that the heat loads could cause damage to plasma facing components. During the experiments the auxiliary power was therefore kept below the limits inferred from the simulations. Measurements of the losses of fast ions from NBI using visible-light and infrared cameras have been shown to be in agreement with the predictions from the simulations. Finally, interactions between fast ions and the non-axisymmetric magnetic field are shown to generate a toroidal torque, which in JET with ~1% ripple is of the same order as that from neutral beam injection.

  • 344. Johnson, Thomas
    et al.
    Hellsten, Torbjörn
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Eriksson, Lars-Göran
    Analysis of a quasilinear model for ion-cyclotron interactions in tokamaks2005Ingår i: Radio Frequency Power in Plasmas / [ed] Wukitch, SJ; Bonoli, PT, MELVILLE: AMER INST PHYSICS , 2005, Vol. 787, s. 54-57Konferensbidrag (Refereegranskat)
    Abstract [en]

    The quasilinear diffusion coefficient deviates significantly from the lowest order Larmor radius scaling D proportional to nu(2n)(perpendicular to). This is not only caused by the finite Larmor radius effects, but also by the inhomogeneous electric field polarisation and the changes of the guiding centre orbits. The regions with strong interaction and the boundaries for resonant interaction are identified. At these boundaries the quasi linear diffusion coefficient becomes discontinuous. Anew Monte Carlo scheme has been developed to treat problems with discontinuous diffusion coefficients.

  • 345.
    Johnson, Thomas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Hynönen, V.
    Parail, V.
    Jenkins, I.
    Kiviniemi, T.
    Kurki-Suonio, T.
    Lönnroth, J.
    Salmi, A.
    Numerical Modelling of Ripple Induced Transport2006Ingår i: Proceedings of the 33rd EPS Conference on Plasma Physics, 2006, s. 408-411Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The ASCOT code has been used to analyse transport and calculate the thermal conductivity in plasmas with toroidal field ripple. The scaling of the thermal conductivity with dimensionless plasma parameters is similar to transport in the ripple plateau regime [1]. The ripple in machines with toroidal field coils similar to those in JET and JT-60U are quite different; while the maximum ripple is larger with 16 JET coils, the ripple at the X-point is larger with the JT-60U coils. The results are that the heat conductivity is similar in the two plasmas, while the particle losses are higher with the JT-60U coils.

  • 346.
    Johnson, Thomas J.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Hellsten, Torbjörn A. K.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Eriksson, L. G.
    Analysis of a quasilinear model for ion cyclotron interactions in tokamaks2006Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 46, nr 7, s. S433-S441Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An orbit averaged quasilinear operator for resonant ion cyclotron interactions is analysed. The regions in phase space where the interactions are strong and the boundaries between regions with resonant and non-resonant ion orbits are identified. At these boundaries the quasilinear diffusion coefficient becomes discontinuous, causing the standard Monte Carlo scheme to induce an unphysical flow of test particles into the region with lower diffusion coefficient. A new Monte Carlo scheme that balances the flows across discontinuities is proposed. Moreover, the quasilinear diffusion coefficient is shown to deviate significantly from the lowest order Larmor radius scaling vertical bar delta H vertical bar(2) proportional to v(perpendicular to)(2n), where delta H is the perturbed Hamiltonian. This is not only caused by the finite Larmor radius effects, but also by the inhomogeneous electric field polarization and by the changes to the guiding centre orbits during the wave-particle interactions.

  • 347.
    Johnson, Thomas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Salmi, A.
    Steinbrecher, G.
    Eriksson, L. -G
    Hellsten, T.
    Höök, Josef
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Schneider, M.
    Library for RF Interactions in Orbit Following Codes2011Ingår i: RADIO FREQUENCY POWER IN PLASMAS: PROCEEDINGS OF THE 19TH TOPICAL CONFERENCE, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    A new code-library has been developed to handle quasi-linear wave particle interactions in orbit following Monte Carlo codes, RFOF (RF interactions in Orbit Following codes). This library will enable a large number of orbit following codes to model fast ion acceleration during ICRF and Lower Hybrid heating. The RFOF consists of two main modules: one evaluates the resonance condition, the other the resulting RF acceleration. The resonance condition is tested at each step along the orbit and the location of the next upcoming resonance is predicted. When a particle reaches the resonance, a quasi-linear acceleration is calculated with a novel Monte Carlo technique that avoids the time-consuming evaluation of phase-space derivatives of the interaction strength. In RFOF the wave-particles interactions are assumed to be localized to a single point on the orbit. This is often valid for the ion cyclotron and lower hybrid frequency ranges, but prevents the treatment of bounce and precessional resonances. The RFOF has been developed within the European Task Force for Integrated Tokamak Modelling, enabling interaction between experts in different fields. As a result the code is designed with a simple and generic interface, with a minimum of assumpti