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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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| 8. |
- Angioni, C., et al.
(författare)
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Dependence of the turbulent particle flux on hydrogen isotopes induced by collisionality
- 2018
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Ingår i: Physics of Plasmas. - : American Institute of Physics (AIP). - 1070-664X .- 1089-7674 .- 1070-6631 .- 1089-7666. ; 25:8
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Tidskriftsartikel (refereegranskat)abstract
- The impact of the change of the mass of hydrogen isotopes on the turbulent particle flux is studied. The trapped electron component of the turbulent particle convection induced by collisionality, which is outward in ion temperature gradient turbulence, increases with decreasing thermal velocity of the isotope. Thereby, the lighter is the isotope, the stronger is the turbulent pinch, and the larger is the predicted density gradient at the null of the particle flux. The passing particle component of the flux increases with decreasing mass of the isotope and can also affect the predicted density gradient. This effect is however subdominant for usual core plasma parameters. The analytical results are confirmed by means of both quasi-linear and nonlinear gyrokinetic simulations, and an estimate of the difference in local density gradient produced by this effect as a function of collisionality has been obtained for typical plasma parameters at mid-radius. Analysis of currently available experimental data from the JET and the ASDEX Upgrade tokamaks does not show any clear and general evidence of inconsistency with this theoretically predicted effect outside the errorbars and also allows the identification of cases providing weak evidence of qualitative consistency.
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- Aslanyan, V, et al.
(författare)
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Gyrokinetic simulations of toroidal Alfven eigenmodes excited by energetic ions and external antennas on the Joint European Torus
- 2019
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Ingår i: Nuclear Fusion. - : IOP PUBLISHING LTD. - 0029-5515 .- 1741-4326. ; 59:2
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Tidskriftsartikel (refereegranskat)abstract
- The gyrokinetic toroidal code (GTC) has been used to study toroidal Alfven eigenmodes (TAEs) in high-performance plasmas. Experiments performed at the Joint European Torus (JET), where TAEs were driven by energetic particles arising from neutral beams, ion cyclotron resonant heating, and resonantly excited by dedicated external antennas, have been simulated. Modes driven by populations of energetic particles are observed, matching the TAE frequency seen with magnetic probes in JET experiments. A synthetic antenna, composed of one toroidal and two neighboring poloidal harmonics has been used to probe the modes' damping rates and quantify mechanisms for this damping in GTC simulations. This method was also applied to frequency and damping rate measurements of stable TAEs made by the Alfven eigenmode active diagnostic in these discharges.
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- Baron-Wiechec, A., et al.
(författare)
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Thermal desorption spectrometry of beryllium plasma facing tiles exposed in the JET tokamak
- 2018
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Ingår i: Fusion engineering and design. - : ELSEVIER SCIENCE SA. - 0920-3796 .- 1873-7196. ; 133, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- The phenomena of retention and de-trapping of deuterium (D) and tritium (T) in plasma facing components (PFC) and supporting structures must be understood in order to limit or control total T inventory in larger future fusion devices such as ITER, DEMO and commercial machines. The goal of this paper is to present details of the thermal desorption spectrometry (TDS) system applied in total fuel retention assessment of PFC at the Joint European Torus (JET). Examples of TDS results from beryllium (Be) wall tile samples exposed to JET plasma in PFC configuration mirroring the planned ITER PFC is shown for the first time. The method for quantifying D by comparison of results from a sample of known D content was confirmed acceptable. The D inventory calculations obtained from Ion Beam Analysis (IBA) and TDS agree well within an error associated with the extrapolation from very few data points to a large surface area.
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