| 1. |
- Anderson, Johan, 1973, et al.
(author)
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High frequency geodesic acoustic modes in electron scale turbulence
- 2013
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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. |
- Fazendeiro, Luis, 1976, et al.
(author)
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Gyrokinetic simulations of turbulent transport in JET-like plasmas
- 2013
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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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| 3. |
- Skyman, Andreas, 1982, et al.
(author)
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Turbulence, Fusion and Clean Energy
- 2013
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In: PDC Newsletter. - 1401-9671. ; 13:1, s. 4-8
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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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| 4. |
- Tegnered, Daniel, 1987, et al.
(author)
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Predictive simulations of impurity transport at JET
- 2013
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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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| 5. |
- Tegnered, Daniel, 1987, et al.
(author)
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Predictive simulations of impurity transport at JET
- 2013
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In: 40th European Physical Society Conference on Plasma Physics.
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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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