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Dumont, R. J., Mailloux, J., Aslanyan, V., Baruzzo, M., Challis, C. D., Coffey, I., . . . Weisen, H. (2018). Scenario development for the observation of alpha-driven instabilities in JET DT plasmas. Nuclear Fusion, 58(8), Article ID 082005.
Open this publication in new window or tab >>Scenario development for the observation of alpha-driven instabilities in JET DT plasmas
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2018 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 58, no 8, article id 082005Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2018
Keywords
JET, alphas, instabilities, TAEs, scenario, DT plasmas
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-232387 (URN)10.1088/1741-4326/aab1bb (DOI)000436930000002 ()
Note

QC 20180727

Available from: 2018-07-27 Created: 2018-07-27 Last updated: 2018-07-27Bibliographically approved
Bonanomi, N., Mantica, P., Di Siena, A., Delabie, E., Giroud, C., Johnson, T., . . . Van Eester, D. (2018). Turbulent transport stabilization by ICRH minority fast ions in low rotating JET ILW L-mode plasmas. Nuclear Fusion, 58(5), Article ID 056025.
Open this publication in new window or tab >>Turbulent transport stabilization by ICRH minority fast ions in low rotating JET ILW L-mode plasmas
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2018 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 58, no 5, article id 056025Article in journal (Refereed) Published
Abstract [en]

The first experimental demonstration that fast ion induced stabilization of thermal turbulent transport takes place also at low values of plasma toroidal rotation has been obtained in JET ILW (ITER-like wall) L-mode plasmas with high (He-3)-D ICRH (ion cyclotron resonance heating) power. A reduction of the gyro-Bohm normalized ion heat flux and higher values of the normalized ion temperature gradient have been observed at high ICRH power and low NBI (neutral beam injection) power and plasma rotation. Gyrokinetic simulations indicate that ITG (ion temperature gradient) turbulence stabilization induced by the presence of high-energetic He-3 ions is the key mechanism in order to explain the experimental observations. Two main mechanisms have been identified to be responsible for the turbulence stabilization: a linear electrostatic wave-fast particle resonance mechanism and a nonlinear electromagnetic mechanism. The dependence of the stabilization on the He-3 distribution function has also been studied.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2018
Keywords
gyro-kinetic simulations, JET tokamak, Turbulent transport, fast ions
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-226746 (URN)10.1088/1741-4326/aab733 (DOI)000429233600001 ()2-s2.0-85045935759 (Scopus ID)
Note

QC 20180504

Available from: 2018-05-04 Created: 2018-05-04 Last updated: 2018-05-04Bibliographically approved
Kazakov, Y. O. O., Ongena, J., Wright, J. C., Wukitch, S. J., Lerche, E., Mantsinen, M. J., . . . Weisen, H. (2017). Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating. Nature Physics, 13(10), 973-+
Open this publication in new window or tab >>Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating
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2017 (English)In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 13, no 10, p. 973-+Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Nature Publishing Group, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-216627 (URN)10.1038/NPHYS4167 (DOI)000412181200018 ()2-s2.0-85021251328 (Scopus ID)
Note

QC 20171102

Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2017-11-02Bibliographically approved
Tholerus, E., Johnson, T. & Hellsten, T. (2017). FOXTAIL: Modeling the nonlinear interaction between Alfven eigenmodes and energetic particles in tokamaks. Computer Physics Communications, 214, 39-51
Open this publication in new window or tab >>FOXTAIL: Modeling the nonlinear interaction between Alfven eigenmodes and energetic particles in tokamaks
2017 (English)In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 214, p. 39-51Article in journal (Refereed) Published
Abstract [en]

FOXTAIL is a new hybrid magnetohydrodynamic-kinetic code used to describe interactions between energetic particles and Alfven eigenmodes in tokamaks with realistic geometries. The code Simulates the nonlinear dynamics of the amplitudes of individual eigenmodes and of a set of discrete markers in five dimensional phase space representing the energetic particle distribution. Action angle coordinates of the equilibrium system are used for efficient tracing of energetic particles, and the particle acceleration by the wave fields of the eigenmodes is Fourier decomposed in the same angles. The eigenmodes are described using temporally constant eigenfunctions with dynamic complex amplitudes. Possible applications of the code are presented, e.g., making a quantitative validity evaluation of the one-dimensional bump-on-tail approximation of the system. Expected effects of the fulfillment of the Chirikov criterion in two-mode scenarios have also been verified.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2017
Keywords
Magnetohydrodynamic waves, Tokamaks, Fast particle effects, Nonlinear dynamics
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-205427 (URN)10.1016/j.cpc.2017.01.007 (DOI)000397358400005 ()2-s2.0-85011005108 (Scopus ID)
Funder
Swedish Research Council, 621-2011-5387
Note

QC 20170522

Available from: 2017-05-22 Created: 2017-05-22 Last updated: 2017-06-08Bibliographically approved
Vallejos, P., Johnson, T. & Hellsten, T. (2016). An iterative method to include spatial dispersion for waves in nonuniform plasmas using wavelet decomposition. Paper presented at 29 August 2016 through 2 September 2016. Journal of Physics, Conference Series, 775(1), Article ID 012016.
Open this publication in new window or tab >>An iterative method to include spatial dispersion for waves in nonuniform plasmas using wavelet decomposition
2016 (English)In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 775, no 1, article id 012016Article in journal (Refereed) Published
Abstract [en]

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

Keywords
Cyclotron resonance, Finite element method, Fusion reactions, Iterative methods, Wave equations, Wavelet decomposition, Ion cyclotron resonance heating, Larmor radius effects, Nonuniform plasma, Second orders, Solving wave equations, Spatial dispersion, Wave operators, Wavelet representation, Dispersion (waves)
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-201866 (URN)10.1088/1742-6596/775/1/012016 (DOI)2-s2.0-85009809630 (Scopus ID)
Conference
29 August 2016 through 2 September 2016
Note

QC 20170308

Available from: 2017-03-08 Created: 2017-03-08 Last updated: 2017-11-29Bibliographically approved
Tholerus, E., Johnson, T. & Hellsten, T. (2016). FOXTAIL: Modeling the nonlinear interaction between Alfvén eigenmodes and energetic particles in tokamaks. Computer Physics Communications
Open this publication in new window or tab >>FOXTAIL: Modeling the nonlinear interaction between Alfvén eigenmodes and energetic particles in tokamaks
2016 (English)In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944Article in journal (Refereed) Submitted
Abstract [en]

FOXTAIL is a new hybrid magnetohydrodynamic-kinetic code used to describe interactions between energetic particles and Alfvén eigenmodes in tokamaks with realistic geometries. The code simulates the nonlinear dynamics of the amplitudes of individual eigenmodes and of a set of discrete markers in five-dimensional phase space representing the energetic particle distribution. Action-angle coordinates of the equilibrium system are used for efficient tracing of energetic particles, and the particle acceleration by the wave fields of the eigenmodes is Fourier decomposed in the same angles. The eigenmodes are described using temporally constant eigenfunctions with dynamic complex amplitudes. Possible applications of the code are presented, e.g., making a quantitative validity evaluation of the one-dimensional bump-on-tail approximation of the system. Expected effects of the fulfillment of the Chirikov criterion in two-mode scenarios have also been verified.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Magnetohydrodynamic waves, Tokamaks, Fast particle effects, Nonlinear dynamics, Hybrid plasma simulation methods, Lagrangian and Hamiltonian mechanics
National Category
Fusion, Plasma and Space Physics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-192923 (URN)
Funder
Swedish Research Council, 621-2011-5387
Note

QC 20160927

Available from: 2016-09-22 Created: 2016-09-22 Last updated: 2017-06-08Bibliographically approved
Sharapov, S. E., Hellsten, T., Kiptily, V. G., Craciunescu, T., Eriksson, J., Fitzgerald, M., . . . Zoita, V. (2016). Fusion product studies via fast ion D-D and D-He-3 fusion on JET. Paper presented at 14th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems, 2015, Vienna, AUSTRIA. Nuclear Fusion, 56(11), Article ID 112021.
Open this publication in new window or tab >>Fusion product studies via fast ion D-D and D-He-3 fusion on JET
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2016 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 56, no 11, article id 112021Article in journal (Refereed) Published
Abstract [en]

Dedicated fast ion D-D and D-He-3 fusion experiments were performed on JET with carbon wall (2008) and ITER-like wall (2014) for testing the upgraded neutron and energetic ion diagnostics of fusion products. Energy spectrum of D-D neutrons was the focus of the studies in pure deuterium plasmas. A significant broadening of the energy spectrum of neutrons born in D-D fast fusion was observed, and dependence of the maximum D and D-D neutron energies on plasma density was established. Diagnostics of charged products of aneutronic D-He-3 fusion reactions, 3.7 MeV alpha-particles similar to those in D-T fusion, and 14.6 MeV protons, were the focus of the studies in D-He-3 plasmas. Measurements of 16.4 MeV gamma-rays born in the weak secondary branch of D(He-3, gamma)Li-5 reaction were used for assessing D-He-3 fusion power. For achieving high yield of D-D and D-He-3 reactions at relatively low levels of input heating power, an acceleration of D beam up to the MeV energy range was used employing 3rd harmonic (f = 3f(CD)) ICRH technique. These results were compared to the techniques of D beam injection into D-He-3 mixture, and He-3-minority ICRH in D plasmas.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2016
Keywords
fusion, neutrons, ICRH, NBI, JET, Deuterium, Helium-3
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-200769 (URN)10.1088/0029-5515/56/11/112021 (DOI)000391393900021 ()
Conference
14th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems, 2015, Vienna, AUSTRIA
Note

QC 20170207

Available from: 2017-02-07 Created: 2017-02-02 Last updated: 2017-11-29Bibliographically approved
Tholerus, E., Johnson, T. & Hellsten, T. (2016). Modelling the Dynamics of Energetic Ions and MHD Modes Influenced by ICRH. KTH Royal Institute of Technology
Open this publication in new window or tab >>Modelling the Dynamics of Energetic Ions and MHD Modes Influenced by ICRH
2016 (English)Report (Other academic)
Abstract [en]

FOXTAIL is a code used to describe the nonlinear interactions between toroidal Alfvén eigenmodes and an ensemble of resonant energetic particles in tokamaks with realistic geometries. This report introduces an extension of the code, including effects from ion cyclotron resonance heating (ICRH) of energetic ions using a quasilinear diffusion operator in adiabatic invariant space. First results of the effects of ICRH diffusion on the system consisting of a single Alfvén eigenmode linearly excited by resonant ions are presented. It is shown that the presence of ICRH diffusion allows for the mode amplitude to grow larger than in the case of nonlinear saturation in the absence of sources and sinks. Gradually increasing the strength of ICRH diffusion also decreases the linear growth rate of the mode. Both these phenomena are previously observed also for the case of a finite phase decorrelation operator in bump-on-tail systems with a single eigenmode.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016
Series
TRITA-EE, ISSN 1653-5146 ; 2016:142
Keywords
Monte Carlo model, wave-particle interactions, bump-on-tail instabilities, nonlinear dynamics, toroidal Alfvén eigenmodes, ion cyclotron resonance heating
National Category
Fusion, Plasma and Space Physics
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-192924 (URN)
Funder
Swedish Research Council, 621-2011-5387
Note

QC 20160927

Available from: 2016-09-22 Created: 2016-09-22 Last updated: 2016-09-27Bibliographically approved
Di Siena, A., Görier, T., Doerk, H., Citrin, J., Johnson, T., Schneider, M. & Poli, E. (2016). Non-Maxwellian background effects in gyrokinetic simulations with GENE. Paper presented at 29 August 2016 through 2 September 2016. Journal of Physics, Conference Series, 775(1), Article ID 012003.
Open this publication in new window or tab >>Non-Maxwellian background effects in gyrokinetic simulations with GENE
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2016 (English)In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 775, no 1, article id 012003Article in journal (Refereed) Published
Abstract [en]

The interaction between fast particles and core turbulence has been established as a central issue for a tokamak reactor. Recent results predict significant enhancement of electromagnetic stabilisation of ITG turbulence in the presence of fast ions. However, most of these simulations were performed with the assumption of equivalent Maxwellian distributed particles, whereas to rigorously model fast ions, a non-Maxwellian background distribution function is needed. To this aim, the underlying equations in the gyrokinetic code GENE have been re-derived and implemented for a completely general background distribution function. After verification studies, a previous investigation on a particular JET plasma has been revised with linear simulations. The plasma is composed by Deuterium, electron, Carbon impurities, NBI fast Deuterium and ICRH 3He. Fast particle distributions have been modelled with a number of different analytic choices in order to study the impact of non-Maxwellian distributions on the plasma turbulence: slowing down and anisotropic Maxwellian. Linear growth rates are studied as a function of the wave number and compared with those obtained using an equivalent Maxwellian. Generally, the choice of the 3He distribution seems to have a stronger impact on the microinstabilities than that of the fast Deuterium.

Keywords
Carbon, Deuterium, Distribution functions, Fusion reactions, Genes, Plasma turbulence, Background effects, Distributed particles, Gyrokinetic codes, Gyrokinetic simulations, Linear growth rate, Linear simulation, Microinstabilities, Non-Maxwellian distribution, Magnetoplasma
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-201865 (URN)10.1088/1742-6596/775/1/012003 (DOI)2-s2.0-85009752468 (Scopus ID)
Conference
29 August 2016 through 2 September 2016
Note

QC 20170308

Available from: 2017-03-08 Created: 2017-03-08 Last updated: 2017-11-29Bibliographically approved
Lerche, E., Goniche, M., Jacquet, P., Van Eester, D., Bobkov, V., Colas, L., . . . Valisa, M. (2016). Optimization of ICRH for core impurity control in JET-ILW. Nuclear Fusion, 56(3), Article ID 036022.
Open this publication in new window or tab >>Optimization of ICRH for core impurity control in JET-ILW
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2016 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 56, no 3, article id 036022Article in journal (Refereed) Published
Abstract [en]

Ion cyclotron resonance frequency (ICRF) heating has been an essential component in the development of high power H-mode scenarios in the Jet European Torus ITER-like wall (JET-ILW). The ICRF performance was improved by enhancing the antenna-plasma coupling with dedicated main chamber gas injection, including the preliminary minimization of RF-induced plasma-wall interactions, while the RF heating scenarios where optimized for core impurity screening in terms of the ion cyclotron resonance position and the minority hydrogen concentration. The impact of ICRF heating on core impurity content in a variety of 2.5 MA JET-ILW H-mode plasmas will be presented, and the steps that were taken for optimizing ICRF heating in these experiments will be reviewed.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2016
Keywords
ICRF heating, tokamak, ITER-like wall, JET
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-186013 (URN)10.1088/0029-5515/56/3/036022 (DOI)000373378200023 ()2-s2.0-84960394948 (Scopus ID)
Note

QC 20160509

Available from: 2016-05-09 Created: 2016-04-29 Last updated: 2017-11-30Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7142-7103

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