2021
5.
Neto, E. Lascas; Graves, J. P.; Raghunathan, M.; Sommariva, C.; Pfefferlé, D.; Contributors, J. E. T.
Heavy Impurity Transport in Tokamaks Subject to Plasma Rotation, NTV and the Influence of Saturated Ideal MHD Perturbations Journal Article
In: Plasma Physics and Controlled Fusion, vol. 64, no. 1, pp. 014002, 2021, ISSN: 0741-3335.
Links | BibTeX | Tags: impurities, internal kink, neoclassical transport, plasma flow, VENUS-LEVIS
@article{netoHeavyImpurityTransport2021,
title = {Heavy Impurity Transport in Tokamaks Subject to Plasma Rotation, NTV and the Influence of Saturated Ideal MHD Perturbations},
author = {E. Lascas Neto and J. P. Graves and M. Raghunathan and C. Sommariva and D. Pfefferl\'{e} and J. E. T. Contributors},
doi = {10.1088/1361-6587/ac3964},
issn = {0741-3335},
year = {2021},
date = {2021-11-01},
urldate = {2021-11-01},
journal = {Plasma Physics and Controlled Fusion},
volume = {64},
number = {1},
pages = {014002},
publisher = {IOP Publishing},
keywords = {impurities, internal kink, neoclassical transport, plasma flow, VENUS-LEVIS},
pubstate = {published},
tppubtype = {article}
}
2019
4.
Lanthaler, S; Graves, J P; Pfefferlé, D; Cooper, W A
Guiding-centre theory for kinetic-magnetohydrodynamic modes in strongly flowing plasmas Journal Article
In: Plasma Physics and Controlled Fusion, vol. 61, no. 7, pp. 074006, 2019.
Abstract | Links | BibTeX | Tags: drift-kinetic, guiding-centre, MHD, plasma flow
@article{lanthaler-2019,
title = {Guiding-centre theory for kinetic-magnetohydrodynamic modes in strongly flowing plasmas},
author = {S Lanthaler and J P Graves and D Pfefferl\'{e} and W A Cooper},
url = {https://doi.org/10.1088%2F1361-6587%2Fab1d21},
doi = {10.1088/1361-6587/ab1d21},
year = {2019},
date = {2019-05-01},
journal = {Plasma Physics and Controlled Fusion},
volume = {61},
number = {7},
pages = {074006},
publisher = {IOP Publishing},
abstract = {A kinetic-magnetohydrodynamic model with kinetic pressure closure is derived from a consistent guiding-centre framework. Higher-order (gyroviscous) corrections to the pressure tensor are derived in complex geometry from a reduced kinetic equation. The proposed model allows for flows of the order of the thermal ion velocity, taking into account important centrifugal effects due to the ExB flow, as well as the effects of diamagnetic flows associated with finite Larmor radius corrections to both ion fluid inertia and long mean-free path contributions. Wave\textendashparticle interactions, such as toroidal drift-resonance, are retained. Furthermore, the linearised model includes a quasi-neutrality equation, allowing the effects of a parallel electric field to be studied in fast rotating tokamak plasmas.},
keywords = {drift-kinetic, guiding-centre, MHD, plasma flow},
pubstate = {published},
tppubtype = {article}
}
A kinetic-magnetohydrodynamic model with kinetic pressure closure is derived from a consistent guiding-centre framework. Higher-order (gyroviscous) corrections to the pressure tensor are derived in complex geometry from a reduced kinetic equation. The proposed model allows for flows of the order of the thermal ion velocity, taking into account important centrifugal effects due to the ExB flow, as well as the effects of diamagnetic flows associated with finite Larmor radius corrections to both ion fluid inertia and long mean-free path contributions. Wave–particle interactions, such as toroidal drift-resonance, are retained. Furthermore, the linearised model includes a quasi-neutrality equation, allowing the effects of a parallel electric field to be studied in fast rotating tokamak plasmas.
2017
3.
Raghunathan, M; Graves, J P; Nicolas, T; Cooper, W A; Garbet, X; Pfefferlé, D
Heavy impurity confinement in hybrid operation scenario plasmas with a rotating 1/1 continuous mode Journal Article
In: Plasma Physics and Controlled Fusion, vol. 59, no. 12, pp. 124002, 2017.
Abstract | Links | BibTeX | Tags: fast particles, impurities, neoclassical transport, plasma flow, VENUS-LEVIS
@article{raghunathan-2017,
title = {Heavy impurity confinement in hybrid operation scenario plasmas with a rotating 1/1 continuous mode},
author = {M Raghunathan and J P Graves and T Nicolas and W A Cooper and X Garbet and D Pfefferl\'{e}},
url = {https://iopscience.iop.org/article/10.1088/1361-6587/aa896f},
doi = {10.1088/1361-6587/aa896f},
year = {2017},
date = {2017-10-09},
journal = {Plasma Physics and Controlled Fusion},
volume = {59},
number = {12},
pages = {124002},
abstract = {In future tokamaks like ITER with tungsten walls, it is imperative to control tungsten accumulation in the core of operational plasmas, especially since tungsten accumulation can lead to radiative collapse and disruption. We investigate the behavior of tungsten trace impurities in a JET-like hybrid scenario with both axisymmetric and saturated 1/1 ideal helical core in the presence of strong plasma rotation. For this purpose, we obtain the equilibria from VMEC and use VENUS-LEVIS, a guiding-center orbit-following code, to follow heavy impurity particles. In this work, VENUS-LEVIS has been modified to account for strong plasma flows with associated neoclassical effects arising from such flows. We find that the combination of helical core and plasma rotation augments the standard neoclassical inward pinch compared to axisymmetry, and leads to a strong inward pinch of impurities towards the magnetic axis despite the strong outward diffusion provided by the centrifugal force, as frequently observed in experiments.},
keywords = {fast particles, impurities, neoclassical transport, plasma flow, VENUS-LEVIS},
pubstate = {published},
tppubtype = {article}
}
In future tokamaks like ITER with tungsten walls, it is imperative to control tungsten accumulation in the core of operational plasmas, especially since tungsten accumulation can lead to radiative collapse and disruption. We investigate the behavior of tungsten trace impurities in a JET-like hybrid scenario with both axisymmetric and saturated 1/1 ideal helical core in the presence of strong plasma rotation. For this purpose, we obtain the equilibria from VMEC and use VENUS-LEVIS, a guiding-center orbit-following code, to follow heavy impurity particles. In this work, VENUS-LEVIS has been modified to account for strong plasma flows with associated neoclassical effects arising from such flows. We find that the combination of helical core and plasma rotation augments the standard neoclassical inward pinch compared to axisymmetry, and leads to a strong inward pinch of impurities towards the magnetic axis despite the strong outward diffusion provided by the centrifugal force, as frequently observed in experiments.
2015
2.
Cooper, W A; Brunetti, D; Faustin, J M; Graves, J P; Pfefferlé, D; Raghunathan, M; Sauter, O; Tran, T M; Chapman, I T; Ham, C J; Aiba, N; team, The MAST; contributors, JET
Free boundary equilibrium in 3D tokamaks with toroidal rotation Journal Article
In: Nuclear Fusion, vol. 55, no. 6, pp. 063032, 2015.
Abstract | Links | BibTeX | Tags: internal kink, MHD equilibrium, plasma flow
@article{cooper-2015,
title = {Free boundary equilibrium in 3D tokamaks with toroidal rotation},
author = {W A Cooper and D Brunetti and J M Faustin and J P Graves and D Pfefferl\'{e} and M Raghunathan and O Sauter and T M Tran and I T Chapman and C J Ham and N Aiba and The MAST team and JET contributors},
url = {http://stacks.iop.org/0029-5515/55/i=6/a=063032},
doi = {10.1088/0029-5515/55/6/063032},
year = {2015},
date = {2015-05-22},
journal = {Nuclear Fusion},
volume = {55},
number = {6},
pages = {063032},
abstract = {The three-dimensional VMEC equilibrium solver has been adapted to numerically investigate the approximate toroidal rotation model we have derived. We concentrate our applications on the simulation of JET snakes and MAST long-lived modes under free boundary conditions. Helical core solutions are triggered when 〈β〉 exceeds a threshold value, typically 2.7% in JET-like plasmas. A large plasma current and edge bootstrap current can drive helical core formations at arbitrarily small 〈β〉 in which the ideal saturated internal kink coexists with an ideal saturated external kink structure of opposite phase. The centrifugal force linked with the rotation has the effect of displacing the plasma column away from the major axis, but does not alter significantly the magnitude of the edge corrugation of the plasma. Error field correction coil currents in JET-like configurations increase the outer midplane distortions by 2 cm. The edge bootstrap current enhances the edge modulation of the plasma driven by the core snake deformations in MAST.},
keywords = {internal kink, MHD equilibrium, plasma flow},
pubstate = {published},
tppubtype = {article}
}
The three-dimensional VMEC equilibrium solver has been adapted to numerically investigate the approximate toroidal rotation model we have derived. We concentrate our applications on the simulation of JET snakes and MAST long-lived modes under free boundary conditions. Helical core solutions are triggered when 〈β〉 exceeds a threshold value, typically 2.7% in JET-like plasmas. A large plasma current and edge bootstrap current can drive helical core formations at arbitrarily small 〈β〉 in which the ideal saturated internal kink coexists with an ideal saturated external kink structure of opposite phase. The centrifugal force linked with the rotation has the effect of displacing the plasma column away from the major axis, but does not alter significantly the magnitude of the edge corrugation of the plasma. Error field correction coil currents in JET-like configurations increase the outer midplane distortions by 2 cm. The edge bootstrap current enhances the edge modulation of the plasma driven by the core snake deformations in MAST.
2014
1.
Cooper, W A; Hirshman, S P; Chapman, I T; Brunetti, D; Faustin, J M; Graves, J P; Pfefferlé, D; Raghunathan, M; Sauter, O; Tran, T M; Aiba, N
An approximate single fluid 3-dimensional magnetohydrodynamic equilibrium model with toroidal flow Journal Article
In: Plasma Physics and Controlled Fusion, vol. 56, no. 9, pp. 094004, 2014.
Abstract | Links | BibTeX | Tags: internal kink, MHD equilibrium, plasma flow
@article{cooper-2014,
title = {An approximate single fluid 3-dimensional magnetohydrodynamic equilibrium model with toroidal flow},
author = {W A Cooper and S P Hirshman and I T Chapman and D Brunetti and J M Faustin and J P Graves and D Pfefferl\'{e} and M Raghunathan and O Sauter and T M Tran and N Aiba},
url = {http://stacks.iop.org/0741-3335/56/i=9/a=094004},
doi = {10.1088/0741-3335/56/9/094004},
year = {2014},
date = {2014-08-13},
journal = {Plasma Physics and Controlled Fusion},
volume = {56},
number = {9},
pages = {094004},
abstract = {An approximate model for a single fluid three-dimensional (3D) magnetohydrodynamic (MHD) equilibrium with pure isothermal toroidal flow with imposed nested magnetic flux surfaces is proposed. It recovers the rigorous toroidal rotation equilibrium description in the axisymmetric limit. The approximation is valid under conditions of nearly rigid or vanishing toroidal rotation in regions with significant 3D deformation of the equilibrium flux surfaces. Bifurcated helical core equilibrium simulations of long-lived modes in the MAST device demonstrate that the magnetic structure is only weakly affected by the flow but that the 3D pressure distortion is important. The pressure is displaced away from the major axis and therefore is not as noticeably helically deformed as the toroidal magnetic flux under the subsonic flow conditions measured in the experiment. The model invoked fails to predict any significant screening by toroidal plasma rotation of resonant magnetic perturbations in MAST free boundary computations.},
keywords = {internal kink, MHD equilibrium, plasma flow},
pubstate = {published},
tppubtype = {article}
}
An approximate model for a single fluid three-dimensional (3D) magnetohydrodynamic (MHD) equilibrium with pure isothermal toroidal flow with imposed nested magnetic flux surfaces is proposed. It recovers the rigorous toroidal rotation equilibrium description in the axisymmetric limit. The approximation is valid under conditions of nearly rigid or vanishing toroidal rotation in regions with significant 3D deformation of the equilibrium flux surfaces. Bifurcated helical core equilibrium simulations of long-lived modes in the MAST device demonstrate that the magnetic structure is only weakly affected by the flow but that the 3D pressure distortion is important. The pressure is displaced away from the major axis and therefore is not as noticeably helically deformed as the toroidal magnetic flux under the subsonic flow conditions measured in the experiment. The model invoked fails to predict any significant screening by toroidal plasma rotation of resonant magnetic perturbations in MAST free boundary computations.