2020
8.
Patten, H W; Graves, J P; Cooper, W A; Eriksson, J; Pfefferlé, D
Identification of an Optimized Heating and Fast Ion Generation Scheme for the Wendelstein 7-X Stellarator Journal Article
In: Phys. Rev. Lett., vol. 124, pp. 155001, 2020.
Abstract | Links | BibTeX | Tags: fast particles, ion cyclotron resonance, neutral beam injection, stellarator
@article{PhysRevLett.124.155001,
title = {Identification of an Optimized Heating and Fast Ion Generation Scheme for the Wendelstein 7-X Stellarator},
author = {H W Patten and J P Graves and W A Cooper and J Eriksson and D Pfefferl\'{e}},
url = {https://link.aps.org/doi/10.1103/PhysRevLett.124.155001},
doi = {10.1103/PhysRevLett.124.155001},
year = {2020},
date = {2020-04-01},
journal = {Phys. Rev. Lett.},
volume = {124},
pages = {155001},
publisher = {American Physical Society},
abstract = {A Doppler shifted resonance minority species ion cyclotron range of frequency (ICRF) scheme for heating neutral beam ions has been identified and optimized for the Wendelstein 7-X stellarator. Compared with more conventional methods, the synergetic scheme increases the normalized core collisional power transfer to the background plasma, and induces larger concentrations of energetic ions. Simulations in the intricate 3D magnetic stellarator geometry reveal an energetic distribution function that is only weakly anisotropic, and is thus relevant to fast ion and alpha particle driven Alfv\'{e}n eigenmode experimental preparation. Quasilinear theory and simulations of the Joint European Torus indicate that the excellent confinement properties are due to increased velocity diffusion from ICRF interaction along the magnetic field lines. Agreement is found between SCENIC simulations and Joint European Torus experimental measurements for the total neutron rate and the energy distribution of the fast ions.},
keywords = {fast particles, ion cyclotron resonance, neutral beam injection, stellarator},
pubstate = {published},
tppubtype = {article}
}
A Doppler shifted resonance minority species ion cyclotron range of frequency (ICRF) scheme for heating neutral beam ions has been identified and optimized for the Wendelstein 7-X stellarator. Compared with more conventional methods, the synergetic scheme increases the normalized core collisional power transfer to the background plasma, and induces larger concentrations of energetic ions. Simulations in the intricate 3D magnetic stellarator geometry reveal an energetic distribution function that is only weakly anisotropic, and is thus relevant to fast ion and alpha particle driven Alfvén eigenmode experimental preparation. Quasilinear theory and simulations of the Joint European Torus indicate that the excellent confinement properties are due to increased velocity diffusion from ICRF interaction along the magnetic field lines. Agreement is found between SCENIC simulations and Joint European Torus experimental measurements for the total neutron rate and the energy distribution of the fast ions.
2017
7.
Kazakov, Ye O; al.,
Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating Journal Article
In: Nature Physics, vol. 13, 2017.
Abstract | Links | BibTeX | Tags: fast particles, heating, ion cyclotron resonance
@article{kazakov2017,
title = {Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating},
author = {Ye O Kazakov and al.},
url = {http://dx.doi.org/10.1038/nphys4167},
doi = {10.1038/nphys4167},
year = {2017},
date = {2017-06-19},
journal = {Nature Physics},
volume = {13},
abstract = {We describe a new technique for the efficient generation of high-energy ions with electromagnetic ion cyclotron waves in multi-ion plasmas. The discussed ‘three-ion’ scenarios are especially suited for strong wave absorption by a very low number of resonant ions. To observe this effect, the plasma composition has to be properly adjusted, as prescribed by theory. We demonstrate the potential of the method on the world-largest plasma magnetic confinement device, JET (Joint European Torus, Culham, UK), and the high-magnetic-field tokamak Alcator C-Mod (Cambridge, USA). The obtained results demonstrate efficient acceleration of 3He ions to high energies in dedicated hydrogen\textendashdeuterium mixtures. Simultaneously, effective plasma heating is observed, as a result of the slowing-down of the fast 3He ions. The developed technique is not only limited to laboratory plasmas, but can also be applied to explain observations of energetic ions in space-plasma environments, in particular, 3He-rich solar flares.},
keywords = {fast particles, heating, ion cyclotron resonance},
pubstate = {published},
tppubtype = {article}
}
We describe a new technique for the efficient generation of high-energy ions with electromagnetic ion cyclotron waves in multi-ion plasmas. The discussed ‘three-ion’ scenarios are especially suited for strong wave absorption by a very low number of resonant ions. To observe this effect, the plasma composition has to be properly adjusted, as prescribed by theory. We demonstrate the potential of the method on the world-largest plasma magnetic confinement device, JET (Joint European Torus, Culham, UK), and the high-magnetic-field tokamak Alcator C-Mod (Cambridge, USA). The obtained results demonstrate efficient acceleration of 3He ions to high energies in dedicated hydrogen–deuterium mixtures. Simultaneously, effective plasma heating is observed, as a result of the slowing-down of the fast 3He ions. The developed technique is not only limited to laboratory plasmas, but can also be applied to explain observations of energetic ions in space-plasma environments, in particular, 3He-rich solar flares.
6.
Faustin, J M; Graves, J P; Cooper, W A; Lanthaler, S; Villard, L; Pfefferlé, D; Geiger, J; Kazakov, Ye O; Eester, Van D
Modelling of advanced three-ion ICRF heating and fast ion generation scheme for tokamaks and stellarators Journal Article
In: Plasma Physics and Controlled Fusion, vol. 59, no. 8, pp. 084001, 2017.
Abstract | Links | BibTeX | Tags: fast particles, heating, ion cyclotron resonance, neoclassical transport, stellarator
@article{faustin-2017,
title = {Modelling of advanced three-ion ICRF heating and fast ion generation scheme for tokamaks and stellarators},
author = {J M Faustin and J P Graves and W A Cooper and S Lanthaler and L Villard and D Pfefferl\'{e} and J Geiger and Ye O Kazakov and Van D Eester},
doi = {10.1088/1361-6587/aa72a4},
year = {2017},
date = {2017-06-13},
journal = {Plasma Physics and Controlled Fusion},
volume = {59},
number = {8},
pages = {084001},
abstract = {Absorption of ion-cyclotron range of frequencies waves at the fundamental resonance is an efficient source of plasma heating and fast ion generation in tokamaks and stellarators. This heating method is planned to be exploited as a fast ion source in the Wendelstein 7-X stellarator. The work presented here assesses the possibility of using the newly developed three-ion species scheme (Kazakov et al (2015) Nucl. Fusion 55 032001) in tokamak and stellarator plasmas, which could offer the capability of generating more energetic ions than the traditional minority heating scheme with moderate input power. Using the SCENIC code, it is found that fast ions in the MeV range of energy can be produced in JET-like plasmas. The RF-induced particle pinch is seen to strongly impact the fast ion pressure profile in particular. Our results show that in typical high-density W7-X plasmas, the three-ion species scheme generates more energetic ions than the more traditional minority heating scheme, which makes three-ion scenario promising for fast-ion confinement studies in W7-X.},
keywords = {fast particles, heating, ion cyclotron resonance, neoclassical transport, stellarator},
pubstate = {published},
tppubtype = {article}
}
Absorption of ion-cyclotron range of frequencies waves at the fundamental resonance is an efficient source of plasma heating and fast ion generation in tokamaks and stellarators. This heating method is planned to be exploited as a fast ion source in the Wendelstein 7-X stellarator. The work presented here assesses the possibility of using the newly developed three-ion species scheme (Kazakov et al (2015) Nucl. Fusion 55 032001) in tokamak and stellarator plasmas, which could offer the capability of generating more energetic ions than the traditional minority heating scheme with moderate input power. Using the SCENIC code, it is found that fast ions in the MeV range of energy can be produced in JET-like plasmas. The RF-induced particle pinch is seen to strongly impact the fast ion pressure profile in particular. Our results show that in typical high-density W7-X plasmas, the three-ion species scheme generates more energetic ions than the more traditional minority heating scheme, which makes three-ion scenario promising for fast-ion confinement studies in W7-X.
2016
5.
Faustin, J M; Cooper, W A; Graves, J P; Pfefferlé, D; Geiger, J
Fast particle loss channels in Wendelstein 7-X Journal Article
In: Nuclear Fusion, vol. 56, no. 9, pp. 092006, 2016.
Abstract | Links | BibTeX | Tags: fast particles, heating, ion cyclotron resonance, MHD equilibrium, neoclassical transport, neutral beam injection, stellarator
@article{faustin-2016a,
title = {Fast particle loss channels in Wendelstein 7-X},
author = {J M Faustin and W A Cooper and J P Graves and D Pfefferl\'{e} and J Geiger},
url = {https://iopscience.iop.org/article/10.1088/0029-5515/56/9/092006},
doi = {10.1088/0029-5515/56/9/092006},
year = {2016},
date = {2016-07-29},
journal = {Nuclear Fusion},
volume = {56},
number = {9},
pages = {092006},
abstract = {One of the main goals of Wendelstein 7-X (W7-X) is to demonstrate the fast particle confinement properties of the quasi-isodynamic stellarator concept. Fast particle populations will be produced either by Neutral Beam Injection (NBI) or by minority Ion Cyclotron Resonant Heating (ICRH). A fraction of these particles are expected to be lost (even without collisions), despite the optimisation procedure used for the W7-X design. Confinement properties of NBI particles in W7-X were presented in the paper of Drevlak et al (2014 Nucl. Fusion 54 073002). A detailed study is presented here where the loss patterns of an NBI population are described. In particular, focussing on a high-mirror equilibrium, the confinement of fast ions with varying energy injection is studied under collisional conditions. It is found that collisions are not only responsible for classical transport losses but also enhance drift induced losses caused by trapped particles. Moreover, an asymmetry is found in the toroidal position of particle losses which can be explained by local variation in the equilibrium field. The effects of a neoclassically resolved radial electric field are also investigated. Fast particle confinement is significantly improved by the associated ExB drift. In particular, an increasing radial electric field helps to reduce and even stop the losses due to the 3D equilibrium structure for times comparable to slowing down time.},
keywords = {fast particles, heating, ion cyclotron resonance, MHD equilibrium, neoclassical transport, neutral beam injection, stellarator},
pubstate = {published},
tppubtype = {article}
}
One of the main goals of Wendelstein 7-X (W7-X) is to demonstrate the fast particle confinement properties of the quasi-isodynamic stellarator concept. Fast particle populations will be produced either by Neutral Beam Injection (NBI) or by minority Ion Cyclotron Resonant Heating (ICRH). A fraction of these particles are expected to be lost (even without collisions), despite the optimisation procedure used for the W7-X design. Confinement properties of NBI particles in W7-X were presented in the paper of Drevlak et al (2014 Nucl. Fusion 54 073002). A detailed study is presented here where the loss patterns of an NBI population are described. In particular, focussing on a high-mirror equilibrium, the confinement of fast ions with varying energy injection is studied under collisional conditions. It is found that collisions are not only responsible for classical transport losses but also enhance drift induced losses caused by trapped particles. Moreover, an asymmetry is found in the toroidal position of particle losses which can be explained by local variation in the equilibrium field. The effects of a neoclassically resolved radial electric field are also investigated. Fast particle confinement is significantly improved by the associated ExB drift. In particular, an increasing radial electric field helps to reduce and even stop the losses due to the 3D equilibrium structure for times comparable to slowing down time.
4.
Faustin, J M; Cooper, W A; Graves, J P; Pfefferlé, D; Geiger, J
ICRH induced particle losses in Wendelstein 7-X Journal Article
In: Plasma Physics and Controlled Fusion, vol. 58, no. 7, pp. 074004, 2016.
Abstract | Links | BibTeX | Tags: fast particles, ion cyclotron resonance, MHD equilibrium, neutral beam injection, stellarator, VENUS-LEVIS
@article{faustin-2016b,
title = {ICRH induced particle losses in Wendelstein 7-X},
author = {J M Faustin and W A Cooper and J P Graves and D Pfefferl\'{e} and J Geiger},
url = {https://iopscience.iop.org/article/10.1088/0741-3335/58/7/074004},
doi = {10.1088/0741-3335/58/7/074004},
year = {2016},
date = {2016-05-31},
journal = {Plasma Physics and Controlled Fusion},
volume = {58},
number = {7},
pages = {074004},
abstract = {Fast ions in W7-X will be produced either by neutral beam injection (NBI) or by ion-cyclotron resonant heating (ICRH). The latter presents the advantage of depositing power locally and does not suffer from core accessibility issues (Drevlak et al 2014 Nucl. Fusion 54 073002). This work assesses the possibility of using ICRH as a fast ion source in W7-X relevant conditions. The SCENIC package is used to resolve the full wave propagation and absorption in a three-dimensional plasma equilibrium. The source of the ion-cyclotron range of frequency (ICRF) wave is modelled in this work by an antenna formulation allowing its localisation in both the poloidal and toroidal directions. The actual antenna dimension and localization is therefore approximated with good agreement. The local wave deposition breaks the five-fold periodicity of W7-X. It appears that generation of fast ions is hindered by high collisionality and significant particle losses. The particle trapping mechanism induced by ICRH is found to enhance drift induced losses caused by the finite orbit width of trapped particles. The inclusion of a neoclassically resolved radial electric field is also investigated and shows a significant reduction of particle losses.},
keywords = {fast particles, ion cyclotron resonance, MHD equilibrium, neutral beam injection, stellarator, VENUS-LEVIS},
pubstate = {published},
tppubtype = {article}
}
Fast ions in W7-X will be produced either by neutral beam injection (NBI) or by ion-cyclotron resonant heating (ICRH). The latter presents the advantage of depositing power locally and does not suffer from core accessibility issues (Drevlak et al 2014 Nucl. Fusion 54 073002). This work assesses the possibility of using ICRH as a fast ion source in W7-X relevant conditions. The SCENIC package is used to resolve the full wave propagation and absorption in a three-dimensional plasma equilibrium. The source of the ion-cyclotron range of frequency (ICRF) wave is modelled in this work by an antenna formulation allowing its localisation in both the poloidal and toroidal directions. The actual antenna dimension and localization is therefore approximated with good agreement. The local wave deposition breaks the five-fold periodicity of W7-X. It appears that generation of fast ions is hindered by high collisionality and significant particle losses. The particle trapping mechanism induced by ICRH is found to enhance drift induced losses caused by the finite orbit width of trapped particles. The inclusion of a neoclassically resolved radial electric field is also investigated and shows a significant reduction of particle losses.
3.
Faustin, J. M.; Graves, J. P.; Cooper, W. A.; Geiger, J.; Pfefferlé, D.
Modelling of ICRF Fast Ion Generation in 2D and 3D Plasma Configurations Proceedings Article
In: 43rd European Physical Society Conference on Plasma Physics, EPS 2016, 2016.
BibTeX | Tags: fast particles, ion cyclotron resonance, stellarator, tokamak
@inproceedings{faustinModellingICRFFast2016,
title = {Modelling of ICRF Fast Ion Generation in 2D and 3D Plasma Configurations},
author = {J. M. Faustin and J. P. Graves and W. A. Cooper and J. Geiger and D. Pfefferl\'{e}},
year = {2016},
date = {2016-01-01},
urldate = {2016-01-01},
booktitle = {43rd European Physical Society Conference on Plasma Physics, EPS 2016},
keywords = {fast particles, ion cyclotron resonance, stellarator, tokamak},
pubstate = {published},
tppubtype = {inproceedings}
}
2015
2.
Faustin, J M; Cooper, W A; Geiger, J; Graves, J P; Pfefferlé, D
Applications of the SCENIC code package to the minority ion-cyclotron heating in Wendelstein 7-X plasmas Proceedings Article
In: AIP Conference Proceedings, pp. 060003, 2015.
Abstract | Links | BibTeX | Tags: fast particles, ion cyclotron resonance, stellarator, VENUS-LEVIS
@inproceedings{faustin-2015,
title = {Applications of the SCENIC code package to the minority ion-cyclotron heating in Wendelstein 7-X plasmas},
author = {J M Faustin and W A Cooper and J Geiger and J P Graves and D Pfefferl\'{e}},
doi = {10.1063/1.4936501},
year = {2015},
date = {2015-12-10},
booktitle = {AIP Conference Proceedings},
journal = {AIP Conference Proceedings},
volume = {1689},
number = {1},
pages = {060003},
abstract = {We present SCENIC simulations of a W7X 4He plasma with 1% H minority and with an antenna model close to the design foreseen for the W7X ICRF antenna [1, 2]. A high mirror and a standard equilibrium are considered. The injected wave frequency is fixed at 33.8 MHz and 39.6MHz respectively and only fundamental minority heating is considered. Included in this calculation is a new realistic model of the antenna, where it is found that the localization of the antenna geometry tends to break the five-fold periodicity of the system. We assess the heat transfer through the toroidal periods via Coulomb collisions.},
keywords = {fast particles, ion cyclotron resonance, stellarator, VENUS-LEVIS},
pubstate = {published},
tppubtype = {inproceedings}
}
We present SCENIC simulations of a W7X 4He plasma with 1% H minority and with an antenna model close to the design foreseen for the W7X ICRF antenna [1, 2]. A high mirror and a standard equilibrium are considered. The injected wave frequency is fixed at 33.8 MHz and 39.6MHz respectively and only fundamental minority heating is considered. Included in this calculation is a new realistic model of the antenna, where it is found that the localization of the antenna geometry tends to break the five-fold periodicity of the system. We assess the heat transfer through the toroidal periods via Coulomb collisions.
2014
1.
Faustin, J M; Cooper, W A; Graves, J P; Pfefferlé, D
Modeling of ion-cyclotron resonant heating in Wendelstein 7-X equilibrium Proceedings Article
In: Journal of Physics: Conference Series, pp. 012006, 2014.
Abstract | Links | BibTeX | Tags: confinement, fast particles, ion cyclotron resonance, neoclassical transport, stellarator, VENUS-LEVIS
@inproceedings{faustin-2014,
title = {Modeling of ion-cyclotron resonant heating in Wendelstein 7-X equilibrium},
author = {J M Faustin and W A Cooper and J P Graves and D Pfefferl\'{e}},
url = {http://stacks.iop.org/1742-6596/561/i=1/a=012006},
doi = {10.1088/1742-6596/561/1/012006},
year = {2014},
date = {2014-11-27},
booktitle = {Journal of Physics: Conference Series},
journal = {Journal of Physics: Conference Series},
volume = {561},
number = {1},
pages = {012006},
abstract = {W7X stellarator 3D equilibrium has been computed with the equilibrium code ANIMEC (Anisotropic Neumann Inverse Moments Equilibrium Code). This equilibrium was used to model ICRH minority heating in 4He(H) plasma with the 3D full-wave code LEMan (Low frequency ElectroMagnetic wave propagation). The coupled power spatial distribution is shown for different resonance positions within the range of frequencies foreseen for the ICRH antenna. It is found that for the high mirror equilibrium examined, the antenna frequency can be chosen to optimise the power deposition in the plasma core while limiting the absorption at the edge.},
keywords = {confinement, fast particles, ion cyclotron resonance, neoclassical transport, stellarator, VENUS-LEVIS},
pubstate = {published},
tppubtype = {inproceedings}
}
W7X stellarator 3D equilibrium has been computed with the equilibrium code ANIMEC (Anisotropic Neumann Inverse Moments Equilibrium Code). This equilibrium was used to model ICRH minority heating in 4He(H) plasma with the 3D full-wave code LEMan (Low frequency ElectroMagnetic wave propagation). The coupled power spatial distribution is shown for different resonance positions within the range of frequencies foreseen for the ICRH antenna. It is found that for the high mirror equilibrium examined, the antenna frequency can be chosen to optimise the power deposition in the plasma core while limiting the absorption at the edge.