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Garcia-Munoz, M., Sharapov, S. E., Van Zeeland, M. A., Ascasibar, E., Cappa, A., Chen, L., . . . Meyer, H. (2019). Active control of Alfven eigenmodes in magnetically confined toroidal plasmas. Plasma Physics and Controlled Fusion, 61(5), Article ID 054007.
Open this publication in new window or tab >>Active control of Alfven eigenmodes in magnetically confined toroidal plasmas
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2019 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 5, article id 054007Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2019
Keywords
Alfven, perturbations, waves, MHD, fusion, stellarator, tokamak
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-249849 (URN)10.1088/1361-6587/aaef08 (DOI)000462886300001 ()
Note

QC 20190503

Available from: 2019-05-03 Created: 2019-05-03 Last updated: 2019-05-03Bibliographically approved
Labit, B., Frassinetti, L., Jonsson, T., Ratynskaia, S. V., Thorén, E., Tolias, P., . . . Zuin, M. (2019). Dependence on plasma shape and plasma fueling for small edge-localized mode regimes in TCV and ASDEX Upgrade. Nuclear Fusion, 59(8), Article ID 086020.
Open this publication in new window or tab >>Dependence on plasma shape and plasma fueling for small edge-localized mode regimes in TCV and ASDEX Upgrade
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 8, article id 086020Article in journal (Refereed) Published
Abstract [en]

Within the EUROfusion MST1 work package, a series of experiments has been conducted on AUG and TCV devices to disentangle the role of plasma fueling and plasma shape for the onset of small ELM regimes. On both devices, small ELM regimes with high confinement are achieved if and only if two conditions are fulfilled at the same time. Firstly, the plasma density at the separatrix must be large enough (n(e,sep)/n(G) similar to 0.3), leading to a pressure profile flattening at the separatrix, which stabilizes type-I ELMs. Secondly, the magnetic configuration has to be close to a double null (DN), leading to a reduction of the magnetic shear in the extreme vicinity of the separatrix. As a consequence, its stabilizing effect on ballooning modes is weakened.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2019
Keywords
H-mode, type-II ELMs, grassy ELMs, plasma triangularity, separatrix density, ballooning modes
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-255302 (URN)10.1088/1741-4326/ab2211 (DOI)000473079500003 ()2-s2.0-85070909412 (Scopus ID)
Note

QC 20190807

Available from: 2019-08-07 Created: 2019-08-07 Last updated: 2019-10-04Bibliographically approved
Trier, E., Frassinetti, L., Fridström, R., Garcia Carrasco, A., Hellsten, T., Johnson, T., . . . Zuin, M. (2019). ELM-induced cold pulse propagation in ASDEX Upgrade. Plasma Physics and Controlled Fusion, 61(4), Article ID 045003.
Open this publication in new window or tab >>ELM-induced cold pulse propagation in ASDEX Upgrade
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2019 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 4, article id 045003Article in journal (Refereed) Published
Abstract [en]

In ASDEX Upgrade, the propagation of cold pulses induced by type-I edge localized modes (ELMs) is studied using electron cyclotron emission measurements, in a dataset of plasmas with moderate triangularity. It is found that the edge safety factor or the plasma current are the main determining parameters for the inward penetration of the T-e perturbations. With increasing plasma current the ELM penetration is more shallow in spite of the stronger ELMs. Estimates of the heat pulse diffusivity show that the corresponding transport is too large to be representative of the inter-ELM phase. Ergodization of the plasma edge during ELMs is a possible explanation for the observed properties of the cold pulse propagation, which is qualitatively consistent with non-linear magneto-hydro-dynamic simulations.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
ELMs, MHD instabilities, stochastic field, magnetic islands, cold pulse
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-245121 (URN)10.1088/1361-6587/aaf9c3 (DOI)000458986000002 ()
Note

QC 20190315

Available from: 2019-03-15 Created: 2019-03-15 Last updated: 2019-05-20Bibliographically approved
Joffrin, E., Bergsåker, H., Bykov, I., Frassinetti, L., Fridström, R., Garcia Carrasco, A., . . . et al., . (2019). Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall. Nuclear Fusion, 59(11), Article ID 112021.
Open this publication in new window or tab >>Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 11, article id 112021Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
fusion power, JET, tritium, isotope
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-260157 (URN)10.1088/1741-4326/ab2276 (DOI)000484122200001 ()2-s2.0-85070875113 (Scopus ID)
Note

QC 20190926

Available from: 2019-09-26 Created: 2019-09-26 Last updated: 2019-10-04Bibliographically approved
Tierens, W., Frassinetti, L., Hellsten, T., Petersson, P., Fridström, R., Garcia Carrasco, A., . . . et al., . (2019). Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments. Nuclear Fusion, 59(4), Article ID 046001.
Open this publication in new window or tab >>Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 4, article id 046001Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
ICRF, finite elements, simulation
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-243928 (URN)10.1088/1741-4326/aaf455 (DOI)000456197200001 ()
Note

QC 20190212

Available from: 2019-02-12 Created: 2019-02-12 Last updated: 2019-02-12Bibliographically approved
Vallejos, P., Hellsten, T. & Jonsson, T. (2018). A numerical tool based on FEM and wavelets to account for spatial dispersion in ICRH simulations. In: Journal of Physics: Conference Series. Paper presented at 2018 Joint Varenna-Lausanne International Workshop on the Theory of Fusion Plasmas, 27 August 2018 through 31 August 2018. Institute of Physics Publishing (1)
Open this publication in new window or tab >>A numerical tool based on FEM and wavelets to account for spatial dispersion in ICRH simulations
2018 (English)In: Journal of Physics: Conference Series, Institute of Physics Publishing , 2018, no 1Conference paper, Published paper (Refereed)
Abstract [en]

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

Place, publisher, year, edition, pages
Institute of Physics Publishing, 2018
Keywords
Cyclotron resonance, Finite element method, Fusion reactions, Iterative methods, Numerical methods, Wave equations, Complex geometries, Dispersive waves, Finite element schemes, Fixed point iteration, Ion cyclotron resonance heating, Numerical tools, Spatial dispersion, Spectral methods, Dispersion (waves)
National Category
Mathematics
Identifiers
urn:nbn:se:kth:diva-247044 (URN)10.1088/1742-6596/1125/1/012020 (DOI)2-s2.0-85058276573 (Scopus ID)
Conference
2018 Joint Varenna-Lausanne International Workshop on the Theory of Fusion Plasmas, 27 August 2018 through 31 August 2018
Note

QC 20190625

Available from: 2019-06-25 Created: 2019-06-25 Last updated: 2019-06-25Bibliographically approved
Sipilä, S., Varje, J., Johnson, T., Kurki-Suonio, T., Galdón Quiroga, J. & González Martín, J. (2018). Monte Carlo ion cyclotron heating and fast ion loss detector simulations in ASDEX Upgrade. In: 45th EPS Conference on Plasma Physics, EPS 2018: . Paper presented at 45th EPS Conference on Plasma Physics, EPS 2018, 2 July 2018 through 6 July 2018 (pp. 773-776). European Physical Society (EPS)
Open this publication in new window or tab >>Monte Carlo ion cyclotron heating and fast ion loss detector simulations in ASDEX Upgrade
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2018 (English)In: 45th EPS Conference on Plasma Physics, EPS 2018, European Physical Society (EPS) , 2018, p. 773-776Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
European Physical Society (EPS), 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-246567 (URN)2-s2.0-85057199633 (Scopus ID)
Conference
45th EPS Conference on Plasma Physics, EPS 2018, 2 July 2018 through 6 July 2018
Note

QC 20190527

Available from: 2019-05-27 Created: 2019-05-27 Last updated: 2019-05-27Bibliographically approved
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 ()2-s2.0-85050403274 (Scopus ID)
Note

QC 20180727

Available from: 2018-07-27 Created: 2018-07-27 Last updated: 2018-10-16Bibliographically 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
Pokol, G. I., Aradi, M., Erdos, B., Papp, G., Hadar, A., Johnson, T., . . . Ferreira, J. (2017). Development of the runaway electron modelling capabilities of the European transport simulator. In: 44th EPS Conference on Plasma Physics, EPS 2017: . Paper presented at 44th European Physical Society Conference on Plasma Physics, EPS 2017, 26 June 2017 through 30 June 2017. European Physical Society (EPS)
Open this publication in new window or tab >>Development of the runaway electron modelling capabilities of the European transport simulator
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2017 (English)In: 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS) , 2017Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
European Physical Society (EPS), 2017
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-246953 (URN)2-s2.0-85055027891 (Scopus ID)9781510849303 (ISBN)
Conference
44th European Physical Society Conference on Plasma Physics, EPS 2017, 26 June 2017 through 30 June 2017
Note

QC 20190619

Available from: 2019-06-19 Created: 2019-06-19 Last updated: 2019-06-19Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7142-7103

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