Abstract:Abstract. The influence of the ion mass on filament propagation in the scrape-off layer of toroidal magnetised plasmas is analysed for various fusion relevant majority species, like hydrogen isotopes and helium, on the basis of a computational isothermal gyrofluid model for the plasma edge. Heavy hydrogen isotope plasmas show slower outward filament propagation and thus improved confinement properties compared to light isotope plasmas, regardless of collisionality regimes. Similarly, filaments in fully ionised… Show more
“…The blob propagation for the case with high mass-to-charge density is visibly slower, but both blobs have for the later times retained the characteristic laminar mushroom top-like shapes. The overall scaling of the full-F blob velocity is a generalisation of the isotopic mass scaling found in delta-F simulations in Meyer & Kendl (2017) towards non-isotopic arbitrary impurities. Figure 3.Propagation of two cold () full-F blobs containing impurities with parameters () and () at the initial time (left) and in two evolved phases.…”
Section: Background Impurity Effects On Interchange Blob Evolutionsupporting
confidence: 60%
“…the later times retained the characteristic laminar mushroom top-like shapes. The overall scaling of the full-F blob velocity is a generalisation of the isotopic mass scaling found in delta-F simulations in Meyer & Kendl (2017) towards non-isotopic arbitrary impurities.…”
Section: Background Impurity Effects On Interchange Blob Evolutionsupporting
A full-F isothermal gyro-fluid model and code (which is based on the full distribution function F compared to only small fluctuations) is extended to handle self-consistent coupling of multiple quasi-neutral ion species via the polarisation equation in the long wavelength approximation. The numerical model is used to determine two-dimensional interchange driven ‘blob’ transport in a plasma with intrinsic impurity content for a range of impurity parameters. With the same model, the self-consistent advective interaction of a main plasma species blob with a non-trace impurity cloud is studied. For homogeneous impurity distributions an increased effective mass reduces blob transport, whereas it is found that localised impurity clouds can lead either to acceleration or slowing down of blob propagation depending on the alignment of the impurity density gradient during the acceleration phase of the main ion species blob.
“…The blob propagation for the case with high mass-to-charge density is visibly slower, but both blobs have for the later times retained the characteristic laminar mushroom top-like shapes. The overall scaling of the full-F blob velocity is a generalisation of the isotopic mass scaling found in delta-F simulations in Meyer & Kendl (2017) towards non-isotopic arbitrary impurities. Figure 3.Propagation of two cold () full-F blobs containing impurities with parameters () and () at the initial time (left) and in two evolved phases.…”
Section: Background Impurity Effects On Interchange Blob Evolutionsupporting
confidence: 60%
“…the later times retained the characteristic laminar mushroom top-like shapes. The overall scaling of the full-F blob velocity is a generalisation of the isotopic mass scaling found in delta-F simulations in Meyer & Kendl (2017) towards non-isotopic arbitrary impurities.…”
Section: Background Impurity Effects On Interchange Blob Evolutionsupporting
A full-F isothermal gyro-fluid model and code (which is based on the full distribution function F compared to only small fluctuations) is extended to handle self-consistent coupling of multiple quasi-neutral ion species via the polarisation equation in the long wavelength approximation. The numerical model is used to determine two-dimensional interchange driven ‘blob’ transport in a plasma with intrinsic impurity content for a range of impurity parameters. With the same model, the self-consistent advective interaction of a main plasma species blob with a non-trace impurity cloud is studied. For homogeneous impurity distributions an increased effective mass reduces blob transport, whereas it is found that localised impurity clouds can lead either to acceleration or slowing down of blob propagation depending on the alignment of the impurity density gradient during the acceleration phase of the main ion species blob.
“…x φ with respect to ion mass, hence, the ratio ω E /γ L ∼ µ β i with β > 0, providing at least a qualitative argument that the shear flow dynamics may favorably influence the confinement improvement in terms of reduced detection frequency for heavier isotopes. Another explanation may be reduced radial propagation velocities for heavier isotopes such as found in [28], together with overall slower dynamics (increased autocorrelation time), cf. [23], for edge turbulence, producing fewer blobs in a given time for increased ion mass.…”
Section: Discussionmentioning
confidence: 99%
“…Similar parameters for this numerical setup have been employed in [35]. The collisionality parameter is set to C = 50, since this is known to increase radial blob velocity [28]. Lower collisionality requires longer simulation times since fewer (and slower) blobs are produced.…”
Section: Gyrofluid Model and Computationmentioning
Abstract. We investigate time-series obtained from gyrofluid simulations in coupled edge/scrape-off layer turbulence characteristic for fusion edge-region plasmas. Blob birth near the separatrix produces intermittent signals whose statistics depend on the ion mass of the reactor fuel, pointing towards overall slower dynamics for heavier isotopes. We find that a recently established shot-noise stochastic model for scrape-off layer fluctuations coincides reasonably well with the numerical simulations performed in this contribution.
“…The effects of variations in the effective mass on interchange driven filaments and turbulence in the edge and scrape-off layer of tokamak fusion plasmas has been recently investigated for the similar ion masses in hydrogen isotope mixtures [26][27][28], where relevant changes have been found, so that even stronger effects can be expected for the e-p-i system with large mass differences between the positive species. Significant changes should occur at least for ion density ratios a i > µ −1 i .…”
Section: A Inertial Mass Effect Through Polarizationmentioning
Interchange drive and cross-field transport of density filaments in quasi-neutral inhomogeneously magnetized electron-positron plasmas is shown to be strongly reduced by the presence of minority ions. Two mechanisms are identified for the reduction in radial propagation and plasma transport: effective mass related inertia, and collisionality dependent Boltzmann spin-up of the filaments. Numerical results are obtained with a three-dimensional full-F multi-species gyrofluid model.
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