| 1. |
- Anderson, Johan, 1973, et al.
(author)
-
High frequency geodesic acoustic modes in electron scale turbulence
- 2013
-
In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:12, s. article nr. 123016-
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Journal article (peer-reviewed)abstract
- In this work the finite β-effects of an electron branch of the geodesic acoustic mode (el-GAM) driven by electron temperature gradient (ETG) modes is presented. The work is based on a fluid description of the ETG mode retaining non-adiabatic ions and the dispersion relation for el-GAMs driven non-linearly by ETG modes is derived. The ETG growth rate from the fluid model is compared with the results found from gyrokinetic simulations with good agreement. A new saturation mechanism for ETG turbulence through the interaction with el-GAMs is found, resulting in a significantly enhanced ETG turbulence saturation level compared with the mixing length estimate. It is shown that the el-GAM may be stabilized by an increase in finite β as well as by increasing non-adiabaticity. The decreased GAM growth rates is due to the inclusion of the Maxwell stress.
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| 2. |
- Anderson, Johan, 1973, et al.
(author)
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High Frequency Geodesic Acoustic Modes in Electron Scale Turbulence
- 2012
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In: Proceedings 24th IAEA FEC, San Diego 8-13 October 2012.
-
Conference paper (peer-reviewed)abstract
- In this work the first demonstration of a high frequency branch of the geodesic acoustic mode (GAM) driven by electron temperature gradient (ETG) modes is presented. The work is based on a fluid description of the ETG mode retaining non-adiabatic ions and the dispersion relation for high frequency GAMs driven nonlinearly by ETG modes is derived. A new saturation mechanism for ETG turbulence through the interaction with high frequency GAMs is found, resulting in a significantly enhanced ETG turbulence saturation level compared to the mixing length estimate.
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| 3. |
- Eriksson, Frida, 1986, et al.
(author)
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Impact of fast ions on density peaking in JET : fluid and gyrokinetic modeling
- 2019
-
In: Plasma Physics and Controlled Fusion. - : Institute of Physics Publishing (IOPP). - 0741-3335 .- 1361-6587. ; 61:7
-
Journal article (peer-reviewed)abstract
- The effect of fast ions on turbulent particle transport, driven by ion temperature gradient (ITG)/trapped electron mode turbulence, is studied. Two neutral beam injection (NBI) heated JET discharges in different regimes are analyzed at the radial position rho(t) = 0.6, one of them an L-mode and the other one an H-mode discharge. Results obtained from the computationally efficient fluid model EDWM and the gyro-fluid model TGLF are compared to linear and nonlinear gyrokinetic GENE simulations as well as the experimentally obtained density peaking. In these models, the fast ions are treated as a dynamic species with a Maxwellian background distribution. The dependence of the zero particle flux density gradient (peaking factor) on fast ion density, temperature and corresponding gradients, is investigated. The simulations show that the inclusion of a fast ion species has a stabilizing influence on the ITG mode and reduces the peaking of the main ion and electron density profiles in the absence of sources. The models mostly reproduce the experimentally obtained density peaking for the L-mode discharge whereas the H-mode density peaking is significantly underpredicted, indicating the importance of the NBI particle source for the H-mode density profile.
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| 4. |
- Fazendeiro, Luis, 1976, et al.
(author)
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Gyrokinetic simulations of turbulent transport in JET-like plasmas
- 2013
-
In: 40th European Physical Society Conference on Plasma Physics. ; 2, s. 1074-1077
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Conference paper (other academic/artistic)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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| 5. |
- Nordman, Hans, 1957, et al.
(author)
-
Fluid and gyrokinetic simulations of impurity transport at JET
- 2011
-
In: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 53:10, s. 105005-
-
Journal article (peer-reviewed)abstract
- Impurity transport coefficients due to Ion-Temperature-Gradient (ITG) mode and Trapped-Electron (TE) mode turbulence are calculated using profile data from dedicated impurity injection experiments at JET. Results obtained with a multi-fluid model are compared with quasi-linear and nonlinear gyrokinetic simulation results obtained with the code GENE. The sign of the impurity convective velocity (pinch) and its various contributions are discussed. The dependence of the impurity transport coefficients and impurity peaking factor -∇nZ/nZ on plasma parameters like impurity charge number Z, ion logarithmic temperature gradient, collisionality, ExB shearing, and charge fraction are investigated. It is found that for the studied ITG dominated JET discharges, both the fluid and gyrokinetic results show an increase of the impurity peaking factor for low Z-values followed by a saturation at moderate values of impurity peaking, much below the neoclassical predictions, for large values of Z. The results are in qualitative agreement with the experimental trends observed for the injected impurities (Ne, Ar, Ni) whereas for the background carbon species the observed flat or weakly hollow C profiles are not well reproduced by the simulations.
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| 6. |
- Nordman, Hans, 1957, et al.
(author)
-
Modelling of impurity transport experiments at the Joint European Torus
- 2010
-
In: Proceedings of EPS 2010, Europhysics Conference Abstracts. - 2914771622 ; 34A
-
Conference paper (peer-reviewed)abstract
- Impurity transport in JET is studied using interpretative analysis and predictive simulations of JET discharges. The simulations are based on transport models for Ion-Temperature-Gradient (ITG) mode and Trapped-Electron (TE) mode driven turbulence and neoclassicaltransport. The properties of the impurity transport coefficients obtained with fluid as well as quasi-linear and nonlinear gyrokinetic simulations using the code GENE are compared and discussed. In particular, the sign of the impurity convective velocity (pinch) and the scaling of the normalised impurity density peaking factor -R∇nZ/nZ with impurity charge number is investigated. Predictive simulations of temperatures (Te, Ti=TZ) and densities (ne,nZ) are performed with the JETTO/SANCO core transport code.The scaling of impurity transport with impurity charge Z is crucial for the performance and optimisation of a fusion reactor. In the present study, a set of dedicated JET impurity injection experiments are analysed. The impurities were injected by laser ablation (Ni) and gas injection (Ne, Ar) and the diffusivity DZ and convective velocity VZ were determined by matching spectroscopic data with predictive results obtained with the transport code UTC-SANCO.
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| 7. |
- Skyman, Andreas, 1982, et al.
(author)
-
Effects of the equilibrium model on impurity transport in tokamaks
- 2014
-
In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 54:1, s. 013009-
-
Journal article (peer-reviewed)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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| 8. |
- Skyman, Andreas, 1982, et al.
(author)
-
Gyrokinetic modelling of stationary electron and impurity profiles in tokamaks
- 2014
-
In: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 21:9, s. 092305-
-
Journal article (peer-reviewed)abstract
- Particle transport due to Ion Temperature Gradient (ITG)/Trapped Electron Mode (TEM) turbulence is investigated using the gyrokinetic code GENE. Both a reduced quasilinear treatment and nonlinear simulations are performed for typical tokamak parameters corresponding to ITG dominated turbulence. The gyrokinetic results are compared and contrasted with results from a computationally efficient fluid model. A selfconsistent treatment is used, where the stationary local profiles are calculated corresponding to zero particle flux simultaneously for electrons and trace impurities. The scaling of the stationary profiles with magnetic shear, safety factor, electron-to-ion temperature ratio, collisionality, toroidal sheared rotation, plasma β, triangularity, and elongation is investigated. In addition, the effect of different main ion mass on the zero flux condition is discussed. The electron density gradient can significantly affect the stationary impurity profile scaling. It is therefore expected that a selfconsistent treatment will yield results more comparable to experimental results for parameter scans where the stationary background density profile is sensitive. This is shown to be the case in scans over magnetic shear, collisionality, elongation, and temperature ratio, for which the simultaneous zero flux electron and impurity profiles are calculated. A slight asymmetry between hydrogen, deuterium, and tritium with respect to profile peaking is obtained, in particular, for scans in collisionality and temperature ratio.
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| 9. |
- Skyman, Andreas, 1982
(author)
-
Gyrokinetic simulations of turbulent transport in tokamak plasmas
- 2014
-
Doctoral thesis (other academic/artistic)abstract
- With the enormous growth of high performance computing (HPC) over the last few decades, plasma physicists have gained access to a valuable instrument for investigating turbulent plasma behaviour. In this thesis, these tools are utilised for the study of particle transport in fusion devices of the tokamak variety.The transport properties of impurities is a major part of the work. This is of high relevance for the performance and optimisation of magnetic fusion devices. For instance, the possible accumulation of He ash in the core of the reactor plasma will serve to dilute the fuel, thus lowering fusion power. Heavier impurity species, originating from the plasma-facing surfaces, may also accumulate in the core, and wall-impurities of relatively low density may lead to unacceptable energy losses in the form of radiation. In an operational power plant, such as the ITER device, both impurities of low and high charge numbers will be present.This thesis studies turbulent particle transport driven by two different modes of drift wave turbulence: the trapped electron (TE) and ion temperature gradient (ITG) modes. Results for ITG mode driven impurity transport are also compared with experimental results from the Joint European Torus.Principal focus is on the balance of convective and diffusive transport, as quantified by the stationary density gradient of zero flux (“peaking factor”, PF). Quasi- and nonlinear results are obtained using the gyrokinetic code GENE, and compared with results from a computationally efficient multi-fluid model. The results are scalings of PF with the driving background gradients of temperature and density, and other parameters, including plasma shape and sheared toroidal rotation.
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| 10. |
- Skyman, Andreas, 1982, et al.
(author)
-
Impurity transport in ITG and TE mode dominated turbulence
- 2010
-
In: EPS 2010.
-
Conference paper (other academic/artistic)abstract
- The transport properties of impurities is of high relevancefor the performance and optimisation of magnetic fusiondevices. For instance, impurities from plasma-facing surfaces accumulating in the core dilute the plasma and leadto unacceptable energy loss in the form of radiation.In the present study, turbulent impurity transport in tokamak plasmas, driven by Ion Temperature Gradient (ITG)and Trapped Electron (TE) modes, is investigated usingfluid and gyrokinetic models. Quasilinear (QL) results obtained from the GENE code are compared with fluidresults for ITG and TE mode dominated turbulence.Scalings of the peaking factor with impurity charge (Z) andvarious parameters are studied. Of particular interest areconditions favouring an outward convective impurity flux.
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| 11. |
- Skyman, Andreas, 1982, et al.
(author)
-
Impurity transport in ITG and TE mode dominated turbulence
- 2010
-
In: Proceedings of EPS 2010, Europhysics Conference Abstracts. - 2914771622 ; 34A
-
Conference paper (peer-reviewed)abstract
- The transport properties of impurities is of high relevancefor the performance and optimisation of magnetic fusion devices. For instance, if impurities from the plasmafacingsurfaces accumulate in the core, wall-impurities of relatively low density suffice to dilute the plasma and leadto unacceptable energy losses in the form of radiation.In the present study, turbulent impurity transport in Deuterium tokamak plasmas, driven by Ion TemperatureGradient (ITG) and Trapped Electron (TE) modes, hasbeen investigated using fluid and gyrokinetic models. The impurity diffusivity (DZ) and convective velocity (VZ) are calculated, and from these the zero-flux peaking factor (PF0) is derived.
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| 12. |
- Skyman, Andreas, 1982, et al.
(author)
-
Impurity transport in temperature gradient driven turbulence
- 2012
-
In: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 19:3, s. 032313-
-
Journal article (peer-reviewed)abstract
- In the present paper, the transport of impurities driven by trapped electron (TE) mode turbulence is studied. Non-linear (NL) gyrokinetic simulations using the code GENE are compared with results from quasilinear (QL) gyrokinetic simulations and a computationally efficient fluid model. The main focus is on model comparisons for electron temperature gradient driven turbulence regarding the sign of the convective impurity velocity (pinch) and the impurity density gradient R/LnZ (peaking factor) for zero impurity flux. In particular, the scaling of the impurity peaking factors with impurity charge Z and with driving temperature gradient is investigated and compared with results for the more studied ion temperature gradient (ITG) driven turbulence. The question of helium ash removal in TE mode turbulence is also investigated. In addition, the impurity peaking is compared to the main ion peaking obtained by a self-consistent fluid calculation of the density gradients corresponding to zero particle fluxes. For the scaling of the peaking factor with impurity charge Z, a weak dependence is obtained from NL GENE and fluid simulations. The QL GENE results show a stronger dependence for low Z impurities and overestimates the peaking factor by up to a factor of two in this region. As in the case of ITG dominated turbulence, the peaking factors saturate as Z increases, at a level much below neoclassical predictions. The scaling with Z is, however, weak or reversed as compared to the ITG case. The results indicate that TE mode turbulence is as efficient as ITG turbulence at removing He ash, with DHe/χeff>1.0. The scaling of impurity peaking with the background temperature gradients is found to be weak in the NL GENE and fluid simulations. The QL results are also here found to significantly overestimate the peaking factor for low Z values. For the parameters considered, the background density gradient for zero particle flux is found to be slightly larger than the corresponding impurity zero flux gradient.
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| 13. |
- Skyman, Andreas, 1982, et al.
(author)
-
Particle transport in density gradient driven TE mode turbulence
- 2012
-
In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 52:11, s. 114015-
-
Journal article (peer-reviewed)abstract
- The turbulent transport of main ion and trace impurities in a tokamak device in the presence of steep electron density gradients has been studied. The parameters are chosen for trapped electron mode turbulence, driven primarily by steep electron density gradients relevant to H-mode physics. Results obtained through nonlinear and quasilinear gyrokinetic simulations using the GENE code are compared with results obtained from a fluid model. Impurity transport is studied by examining the balance of convective and diffusive transport, as quantified by the density gradient corresponding to zero particle flux (impurity peaking factor). Scalings are obtained for the impurity peaking with the background electron density gradient and the impurity charge number. It is shown that the impurity peaking factor is weakly dependent on impurity charge and significantly smaller than the driving electron density gradient.
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| 14. |
- Skyman, Andreas, 1982, et al.
(author)
-
Particle transport in ion and electron scale turbulence
- 2012
-
In: Proceedings of 24th Fusion Energy Conference -- IAEA CN-197.
-
Conference paper (other academic/artistic)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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| 15. |
- Skyman, Andreas, 1982, et al.
(author)
-
Particle transport in ion and electron scale turbulence
- 2012
-
In: Proceedings of 24th Fusion Energy Conference -- IAEA CN-197.
-
Conference paper (peer-reviewed)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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| 16. |
- Skyman, Andreas, 1982, et al.
(author)
-
Turbulence, Fusion and Clean Energy
- 2013
-
In: PDC Newsletter. - 1401-9671. ; 13:1, s. 4-8
-
Journal article (other academic/artistic)abstract
- In 1926 Sir Arthur Eddington published his treatiseThe Internal Constitution of the Stars, the first comprehensive work on fusion, and with its publication the vision of fusion as a power source was kindled. Since then, taming the nuclear furnace and bringing the power of the Sun to Earth has been the ambition of generations of physicists and engineers. With the ITER experiment (www.iter.org) planned for 2020, the goal seems within reach, appropriately around the centennial of Sir Arthur’s theory.
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| 17. |
- Skyman, Andreas, 1982, et al.
(author)
-
Turbulent impurity transport driven by temperature and density gradients
- 2011
-
In: 13th International Workshop on H-mode Physics and Transport Barriers.
-
Conference paper (other academic/artistic)abstract
- The modelling of a modern fusion device is very challenging both theoretically and numerically, much owing to turbulence driven by sharp gradients in density and temperature. However, understanding the resulting transport is crucial for the success of future fusion devices such as ITER.In this work, the turbulent transport of trace impurities in a tokamak device has been studied through quasilinear (QL) and non-linear (NL) gyrokinetic simulations using the GENE code.The parameters are chosen for trapped electron (TE) mode turbulence, driven primarily by steep electron density gradients relevant to H-mode physics, but with a transition to temperature gradient driven turbulence as the density gradient flattens.The results are quantitative assessments of the transport properties of several impurity species, and the dependence thereof on various plasma parameters.
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| 18. |
- Skyman, Andreas, 1982, et al.
(author)
-
Turbulent impurity transport in fusion plasmas
- 2010
-
In: RUSA conference 2010.
-
Conference paper (other academic/artistic)abstract
- The modern fusion device is very challenging both theoretically and numerically, much owing to turbulence driven by sharp gradients in density and temperature. However, understanding the resulting transport is crucial for the success of future fusion devices such as ITER.In this work, the turbulent transport of trace impurities in a tokamak device has been studied through quasilinear (QL) and non-linear (NL) gyrokinetic simulations using the GENE code, and with QL fluid imulations. The results are quantitative and qualitative assessments of the transport properties of several impurity species, and the dependence thereof on various plasma parameters.
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| 19. |
- Skyman, Andreas, 1982
(author)
-
Turbulent impurity transport in tokamak fusion plasmas
- 2011
-
Licentiate thesis (other academic/artistic)abstract
- With the enormous growth of high performance computing (HPC) over the last few decades, plasma physicists have gained access to a valuable instrument for investigating turbulent plasma behaviour. In this thesis, these tools are utilised for the study of particle transport in fusion devices of the tokamak variety, focusing in particular on the transport of impurities.The transport properties of impurities is of high relevance for the performance and optimisation of magnetic fusion devices. For instance, the possible accumulation of He ash in the core of the reactor plasma will serve to dilute the fuel, thus lowering fusion power. Heavier impurity species, originating from the plasma-facing surfaces, may also accumulate in the core, and wall-impurities of relatively low density may lead to unacceptable energy losses in the form of radiation. In an operational power plant, such as the ITER device, both impurities of low and high charge numbers will be present.This thesis studies turbulent impurity transport driven by two different modes of drift wave turbulence: the trapped electron (TE) and ion temperature gradient (ITG) modes. Principal focus is on the balance of convective and diffusive impurity transport, as quantified by the impurity density gradient of zero flux (“peaking factor”, PF ). The results are scalings of PF with impurity charge number, as well as with the driving background gradients of temperature and density, as well as other plasma parameters.Quasi- and nonlinear results are obtained using the gyrokinetic code GENE, and compared with results from a computationally efficient multi-fluid model. In general, the three models show a good qualitative agreement. Results for ITG mode driven impurity transport are also compared with experimental results from the Joint European Torus, and also in this case a good qualitative agreement is obtained.
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| 20. |
- Skyman, Andreas, 1982, et al.
(author)
-
Turbulent particle transport driven by ion and electron modes
- 2012
-
In: EPS 2012.
-
Conference paper (other academic/artistic)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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| 21. |
- Skyman, Andreas, 1982, et al.
(author)
-
Turbulent particle transport driven by ion and electron modes
- 2012
-
In: Proceedings of EPS 2012, Europhysics Conference Abstracts. - 2914771797 ; 36F, s. P5.033-
-
Conference paper (peer-reviewed)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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| 22. |
- Strand, Pär, 1968, et al.
(author)
-
Core transport studies in fusion devices
- 2010
-
In: SNIC progress report : 2008-2009. Swedish national infrastructure for computing..
-
Book chapter (other academic/artistic)abstract
- Comprehensive first principles modelling of fusion plasmas is a numerically challenging: the complicated magnetic geometry and long range electromagnetic interactionsbetween multiple species introduce complex collective behaviour in the plasma. In addition, steep density and temperature gradients combined with an inhomogeneousmagnetic field drives instabilities, resulting in non-linear dynamics and turbulence.The turbulence in magnetically confined fusion plasmas has important and non-trivial effects on the quality of the energy confinement. These effects are hard to make a quantitative assessment of analytically. The problem investigated in this article is the transport of energy and particles, in particular impurities, in a Tokamak plasma. Impurities from the walls of the plasma vessel cause energy losses if they reach the plasma core. It is therefore important to understand the transport mechanisms to prevent impurity accumulation and minimize losses. This is an areaof research where turbulence plays a major role and is intimately associated with the performance of future fusion reactors, such as ITER.
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| 23. |
- Strand, Pär, 1968, et al.
(author)
-
Core transport studies in fusion devices
- 2010
-
In: PDC 20th Anniversary and SNIC Interaction Conference 2010.
-
Conference paper (other academic/artistic)abstract
- Comprehensive first principles modelling of fusion plasmascontains many numerical and theoretical challenges: a complicated magnetic geometry, long range electromagnetic interactions, collective modes, and extreme density and temperature gradients driving turbulent fluctuations, to name just a few. HPC provides the tools for tackling these challenges and is the focus of a major undertaking within the European fusion community. In this work, the turbulent transport of trace impurities in a tokamak device has been studied using quasi-linear and non-linear gyrokinetic simulations from the GENE code. The results are quantitative and qualitative assessments of the transport properties of several impurity species, and the dependence thereof on various plasma parameters.
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| 24. |
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| 25. |
- Tegnered, Daniel, 1987, et al.
(author)
-
Predictive simulations of impurity transport at JET
- 2013
-
Conference paper (peer-reviewed)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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| 26. |
- Tegnered, Daniel, 1987, et al.
(author)
-
Predictive simulations of impurity transport at JET
- 2013
-
In: 40th European Physical Society Conference on Plasma Physics.
-
Conference paper (other academic/artistic)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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| 27. |
- Zackrisson, Martin, et al.
(author)
-
Scan-o-matic: High-Resolution Microbial Phenomics at a Massive Scale
- 2016
-
In: G3: Genes, Genomes, Genetics. - : Oxford University Press (OUP). - 2160-1836. ; 6:9, s. 3003-3014
-
Journal article (peer-reviewed)abstract
- The capacity to map traits over large cohorts of individuals—phenomics—lags far behind the explosive development in genomics. For microbes, the estimation of growth is the key phenotype because of its link to fitness. We introduce an automated microbial phenomics framework that delivers accurate, precise, and highly resolved growth phenotypes at an unprecedented scale. Advancements were achieved through the introduction of transmissive scanning hardware and software technology, frequent acquisition of exact colony population size measurements, extraction of population growth rates from growth curves, and removal of spatial bias by reference-surface normalization. Our prototype arrangement automatically records and analyzes close to 100,000 growth curves in parallel. We demonstrate the power of the approach by extending and nuancing the known salt-defense biology in baker’s yeast. The introduced framework represents a major advance in microbial phenomics by providing high-quality data for extensive cohorts of individuals and generating well-populated and standardized phenomics databases
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