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| 2. |
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| 3. |
- Bombarda, F., et al.
(författare)
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Runaway electron beam control
- 2019
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 61:1
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Tidskriftsartikel (refereegranskat)
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| 4. |
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| 5. |
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| 6. |
- Borgdorff, J., et al.
(författare)
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Performance of distributed multiscale simulations
- 2014
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Ingår i: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. - : The Royal Society. - 1364-503X .- 1471-2962. ; 372:2021
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Tidskriftsartikel (refereegranskat)abstract
- Multiscale simulations model phenomena across natural scales using monolithic or component-based code, running on local or distributed resources. In this work, we investigate the performance of distributed multiscale computing of component-based models, guided by six multiscale applications with different characteristics and from several disciplines. Three modes of distributed multiscale computing are identified: supplementing local dependencies with large-scale resources, load distribution over multiple resources, and load balancing of small- and large-scale resources. We find that the first mode has the apparent benefit of increasing simulation speed, and the second mode can increase simulation speed if local resources are limited. Depending on resource reservation and model coupling topology, the third mode may result in a reduction of resource consumption.
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| 8. |
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| 9. |
- Fazendeiro, Luis, 1976, et al.
(författare)
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Gyrokinetic simulations of turbulent transport in JET-like plasmas
- 2013
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Ingår i: 40th European Physical Society Conference on Plasma Physics. ; 2, s. 1074-1077
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this work turbulent transport in JET-like plasma discharges is analyzed, with main emphasison impurity transport driven by ITG/TEM modes. Gyrokinetic (GK) simulations are performedusing the GENE code [1, 2], in both quasilinear (QL) and nonlinear (NL) mode,1 and the resultsare compared with a computationally efficient fluid model [3, 4]. Particle transport is quantifiedby locally finding density gradients (R/Ln ) that yield zero particle flux, signifying a balancebetween convective and diffusive transport.The impact of the magnetic equilibrium (circular, s − α and realistic magnetic geometry) onthe various models is discussed, as well as the effects of collisionality (in both fluid and GK)and the inclusion of a (2%) Carbon background (in GK), as per JET CFC wall conditions. Theeffect of sheared toroidal rotation was also investigated and found to be important, although notfor the particular JET discharge studied in this work.
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| 10. |
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| 11. |
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| 12. |
- Hoenen, Olivier, et al.
(författare)
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Designing and running turbulence transport simulations using a distributed multiscale computing approach
- 2013
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Ingår i: 40th European Physical Society Conference on Plasma Physics. ; 2, s. 1094-1097
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Multiscale simulation involving slow transport and fast turbulent timescales is one amongstthree key computational challenges for Magnetic Confinement Plasmas, as identified in thePRACE report “The Scientific Case for HPC in Europe 2012-2020”. Whereas in global gy-rokinetic simulation the main challenge is parallelization efficiency (global gyrokinetic codesscaling to a huge amount of cores), the difficulty of the mulstiscale approach rely more on easeand performance of coupling single scale models together. This coupling requires generic meth-ods which have to be efficient and portable, especially when one (or more) single scale model isexecuted remotely as it may require specific hardware, bigger HPC systems or local databasesaccess.The MAPPER project is developing a software infrastructure dedicated to the design and theexecution of such distributed multiscale applications. It relies on a coupling library (MUSCLE)and few other to control the workflow execution and perform data communication betweenthe different single scale components (“kernels”). Communication is done in a transparent waywhether the kernels run locally or on a remote HPC system.We have implemented such application by using the MAPPER infrastructure and stand alonecodes developed within the EFDA Integrated Tokamak Modelling (ITM): 1-D transport equa-tions solver, 2-D geometry given by an equilibrium code, and transport coefficients given by a3-D fluxtube code. Due to the non-intrusive approach of the coupling library and to ITM efforton generic data structures, implementation of kernels is straightforward and the whole appli-cation is modular. This contribution presents the implementation, performance and preliminaryresults obtained with such multiscale method applied on present-day Tokamak configurations.
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| 13. |
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Krasilnikov, A., et al.
(författare)
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Evidence of 9 Be + p nuclear reactions during 2ω CH and hydrogen minority ICRH in JET-ILW hydrogen and deuterium plasmas
- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:2
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Tidskriftsartikel (refereegranskat)abstract
- The intensity of 9Be + p nuclear fusion reactions was experimentally studied during second harmonic (2ω CH) ion-cyclotron resonance heating (ICRH) and further analyzed during fundamental hydrogen minority ICRH of JET-ILW hydrogen and deuterium plasmas. In relatively low-density plasmas with a high ICRH power, a population of fast H+ ions was created and measured by neutral particle analyzers. Primary and secondary nuclear reaction products, due to 9Be + p interaction, were observed with fast ion loss detectors, γ-ray spectrometers and neutron flux monitors and spectrometers. The possibility of using 9Be(p, d)2α and 9Be(p, α)6Li nuclear reactions to create a population of fast alpha particles and study their behaviour in non-active stage of ITER operation is discussed in the paper.
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| 18. |
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| 21. |
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| 23. |
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| 24. |
- Skyman, Andreas, 1982, et al.
(författare)
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Effects of the equilibrium model on impurity transport in tokamaks
- 2014
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 54:1, s. 013009-
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Tidskriftsartikel (refereegranskat)abstract
- Gyrokinetic simulations of ion temperature gradient mode and trapped electron mode driven impurity transport in a realistic tokamak geometry are presented and compared with results using simplified geometries. The gyrokinetic results, obtained with the GENE code in both linear and non-linear modes are compared with data and analysis for a dedicated impurity injection discharge at JET. The impact of several factors on heat and particle transport is discussed, lending special focus to tokamak geometry and rotational shear. To this end, results using s–α and concentric circular equilibria are compared with results with magnetic geometry from a JET experiment. To further approach experimental conditions, non-linear gyrokinetic simulations are performed with collisions and a carbon background included.The impurity peaking factors, computed by finding local density gradients corresponding to zero particle flux, are discussed. The impurity peaking factors are seen to be reduced by a factor of ~2 in realistic geometry compared with the simplified geometries, due to a reduction of the convective pinch. It is also seen that collisions reduce the peaking factor for low-Z impurities, while increasing it for high charge numbers, which is attributed to a shift in the transport spectra towards higher wavenumbers with the addition of collisions. With the addition of roto-diffusion, an overall reduction of the peaking factors is observed, but this decrease is not sufficient to explain the flat carbon profiles seen at JET.
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| 25. |
- Skyman, Andreas, 1982, et al.
(författare)
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Particle transport in ion and electron scale turbulence
- 2012
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Ingår i: Proceedings of 24th Fusion Energy Conference -- IAEA CN-197.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work deals with transport of main ions and impurities in micro turbulence driven by ion and electron temperature gradients, and trapped electrons. Results are obtained for both non- and quasi-linear simulations, using the gyrokinetic code GENE. Transport properties are quantified by the gradient of zero particle flux for steady state in source free regions.Results are compared with results obtained using a computationally efficient fluid model. Of particular interest are conditions of steep gradients, relevant to eg. transport barriers. Results from s–α geometry are compared with results with a JET-like magnetic equilibrium, and the effects on transport investigated. Further, the quality of He ash removal is studied.
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| 26. |
- Skyman, Andreas, 1982, et al.
(författare)
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Particle transport in ion and electron scale turbulence
- 2012
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Ingår i: Proceedings of 24th Fusion Energy Conference -- IAEA CN-197.
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Konferensbidrag (refereegranskat)abstract
- Micro turbulent modes have important and non-trivial effects on transport in tokamaks. This paper deals with transport of main ions and impurities in ion and electron scale turbulence, driven by ion and electron temperature gradients, and trapped electrons. Using the gyrokinetic Vlasov code GENE, results are obtained from both nonlinear and quasi-linear simulations. The transport properties are quantified by calculating the gradient of zero particle flux for steady state in source free regions of the plasma. The results are compared and contrasted with results obtained using a computationally efficient fluid model.Of particular interest are conditions of steep gradients, relevant to e.g. transport barrier conditions. Further, results from a simple s–α geometry are compared with results obtained using a JET-like magnetic equilibrium, and the effects on transport investigated.
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| 27. |
- Skyman, Andreas, 1982, et al.
(författare)
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Turbulent particle transport driven by ion and electron modes
- 2012
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Ingår i: EPS 2012.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The topic of this work is turbulent transport of main ionsand impurities driven by ion (ITG) and electron modes (TE and electron scale ETG) in tokamaks. Regions relevant to the pedestal of H-mode plasmas (i.e. steep density gradients) are of particular interest. Using the code GENE, quasilinear (QL) and nonlinear (NL) gyrokinetic simulations are performed. Results are compared with a computation ally efficient fluid model.Transport is quantified by the density gradient of zero particle flux, related to the balance of convection and diffusion. This measure of the impurity peaking is calculated for ITG and TE mode turbulence, and conditions for zero main ion flux is investigated for ETG. Further, the quality of He ash removal is studied.
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| 28. |
- Skyman, Andreas, 1982, et al.
(författare)
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Turbulent particle transport driven by ion and electron modes
- 2012
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Ingår i: Proceedings of EPS 2012, Europhysics Conference Abstracts. - 2914771797 ; 36F, s. P5.033-
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Konferensbidrag (refereegranskat)abstract
- The topic of the present work is the turbulent transport of main ions and impurities driven by ion modes (ITG) and electron modes (TE and electron scale ETG). Particle transport in regions relevant to the pedestal region of H-mode plasmas, i.e. with steep density gradients, are of particular interest. Using the code GENE, quasi- and nonlinear gyrokinetic simulations are performed, and the results are compared with a computationally efficient fluid model.The transport properties are quantified by locally finding density gradients (R/Ln ) yielding zero particle flux, which are directly related to the balance of convective and diffusive transport.This measure of the impurity peaking is calculated for ITG and TE mode turbulence in source-free regions of the plasma, and scalings are obtained for the driving gradients and the impurity charge number (Z). Further, the quality of the helium ash removal is studied for ITG and TE mode drive turbulence. For ETG modes, the focus is on the main ion transport, and the density gradient leading to zero main ion particle flux, related to the formation and sustainment of the edge pedestal, is estimated.
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| 29. |
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| 30. |
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| 31. |
- Tegnered, Daniel, 1987, et al.
(författare)
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Predictive simulations of impurity transport at JET
- 2013
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Konferensbidrag (refereegranskat)abstract
- Impurity transport in the Joint European Torus is analysed using the coupling between the transport codes JETTO (for main ions) and SANCO (for impurities) for predictive simulations of dedicated impurity injection experiments. The experimentally injected trace levels of Ne, Ar and Ni in a 2% C background are considered together with numerical experiments covering a broad range of impurities from Be to W. Transport coefficients due to Ion-Temperature-Gradient (ITG) mode and Trapped-Electron (TE) mode turbulence are used together with neoclassical transport from NCLASS. The transport coefficients obtained using the Chalmers fluid model are compared with gyrokinetic results using the code GENE. An updated, multiple ion species version of the Chalmers model called EDWM (Extended Drift Wave Model) has been used for the transport coefficients. Self-consistent simulations of electron and ion temperatures, main ion and impurity densities and toroidal momentum are performed. The role of neoclassical impurity transport is evaluated and the dependence of the simulated profiles on impurity charge number Z, collisionality, ExB shearing, rotation gradient (roto-diffusion), and impurity charge fraction (Zeff) are discussed. For the NBI heated JET L-mode discharges considered, the predictive simulations show that the impurity transport in the bulk of the plasma is dominated by ITG driven transport resulting in impurity peaking factors substantially below the neoclassical predictions for low to intermediate charge numbers. For larger Z-values as well as in the inner core region (ρ
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| 32. |
- Tegnered, Daniel, 1987, et al.
(författare)
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Predictive simulations of impurity transport at JET
- 2013
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Ingår i: 40th European Physical Society Conference on Plasma Physics.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The impact of sheared toroidal rotation on impurity transport is studied by means of predictive simulations of JET L-mode and H-mode discharges with carbon wall using the coupling between the transport codes JETTO for main ions and SANCO for impurities. The simulations are based on a fluid model for Ion-Temperature-Gradient (ITG) mode and Trapped-Electron (TE) mode driven turbulence and neoclassical transport. The fluid impurity transport coefficients are compared with gyrokinetic simulations using the code GENE. Predictive simulations of temperatures (Te, Ti=TZ) and densities (ne, nZ) are performed while the toroidal rotation is treated interpretatively.
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| 33. |
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- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:9
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Tidskriftsartikel (refereegranskat)
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| 34. |
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- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:1
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Forskningsöversikt (refereegranskat)
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